Continental XO-1430 Development
Part 8: 1 Jul 1936 to 31 Dec 1936
by Kimble D. McCutcheon
Published 19 Sep 2025; Revised 21 Sep 2025

2 Jul 1936. Continental engineer James. W Kinnucan met with Prescott at Wright Field and brought a metallurgical report on the single-cylinder test engine cylinder barrel failure that had occurred after 193 hrs. The failure was a circumferential crack near the second rib from the coolant jacket shrink ring. Kinnucan stated that some kind of chemical attack had been responsible as it was possible to pick a hole completely through the barrel; other surface portions were deeply pitted. Another impending failure was near the upper shrink ring. When the head had been removed, extensive electrolytic corrosion had occurred between the aluminum and steel. In one spot the erosion was 0.125" deep and about 0.375" high; the remaining material would have soon been compromised. Dr. J.B. Johnson of the Materials Branch suggested investigating spraying aluminum on the barrel outside surface, as well as the calorizing process, which coated the steel with an aluminum-iron alloy by heating it in a reducing atmosphere with finely-divided aluminum powder. Dr. Johnson further stated that electrolytic corrosion was a widespread problem for which the Materials Division was trying to find a remedy.

Kinnucan and Prescott discussed the spare crankshaft that was being built; its counterweights were slightly smaller than ones on the current test engine crankshaft. Neither party thought it worthwhile to revise the forging dies, but Kinnucan agreed to submit a Change Order and new drawing to reflect this change. This crankshaft was also to include the improved journal plugs. The new parts were also to be designed to accommodate the newly-designed damper at a later date.

Kinnucan stated that testing had suggested moving the camshaft oil holes from their present positions between the intake and exhaust cams to a position at the exhaust cam rear. This was expected to improve valve gear lubrication and exhaust valve stem cooling. Kinnucan requested use of MatCmd's torsiometer through Tuesday, 7 July, which was expected to be sufficient time to complete the torsiometer analysis; Prescott approved this request. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 21 Jul 1936 Memorandum Report E-57-57-285-44, Conference with Representative of Continental Aircraft Engine Company, 2 Jul 1936. 123 – 124.]

15 Jul 1936 Progress Report. A 5-hr single-cylinder engine endurance run was made under rated conditions. While the piston rings did not wear their appearance was not good. The piston had a crack extending up from one piston pin hole. The connecting rod bearing shell was worn and the big-end clearance was 0.010" instead of the nominal 0.006". The shell had sheared its locking pin and spun in the rod. There was no reason for this failure. Operating time on various parts at the period's end was as follows:

Drain holes in the XO-1430-1 starter and generator recesses were added. The accessory drive gears were carefully checked for tooth contour accuracy. The shaft centers were rechecked and it was determined that the gear teeth were functioning properly; while the backlash was small, there was no tip interference. After a 1:50 hr run-in at 2,200 rpm on a propeller load based on 600 hp at 3,000 rpm, the engine was stopped to investigate the considerable water in the blow-by. At 2,200 rpm and 50 bmep, blow-by was 73 ft³/hr.

The torsiometer was received from Wright Field and placed on the engine. The new Thermoid coupling had been completed and was used to replace the Fast coupling between the water brake and engine. (Thermoid was the trade name for a flexible coupling using laminated rubber/canvas discs to connect rotating shafts.) Forty-five torsiograph traces were taken from 600 to 2,800 rpm, generally at 50 rpm intervals. The run was not continued to 3,000 rpm because the oil pressure only read 45 psi at the reduction gear, and had suddenly dropped by 2 psi. The oil pump and new bushings were not defective.

The quill was changed to the original stiffer one and torsiographs were taken under conditions as nearly identical to the previous conditions as possible. During this run with a 2.8 inHgG at 3,012 rpm, 568 hp at 104.5 bmep was observed. At 2,800 rpm and 97 bmep blow-by was 12ft³/hr. A spacer under the oil pressure regulator spring increased the oil pressure by about 10 psi.

A complete inspection disclosed no defects. In view of water having been found in the oil, the oil cooler and heater were pressure-checked with air and steam, but no leaks were found. The Thermoid coupling greatly reduced clatter at low speeds and reduced the torsiograph amplitude as well. Total time was 108:25 hrs, 52:45 of which was under power and 55:50 motoring.

Engineering: After the Wright Field conference with Prescott where the reduction gear to gear shaft damper layouts were reviewed, all damper detail parts were released for manufacture. Details had also been completed on the revised oil pump and parts released. Layouts were made for revised crankshaft main and crankpin journal plugs. All spare parts castings were ordered and about 40 small items were complete and waiting inspection.

The torsiographs showed that the new quill reduced the frequency from 70 Hz to 65 Hz, which agreed with the original computations. This brings the 1.5-order harmonic resonance to 2,600 rpm instead of 2,800 rpm. The amplitude is 1/3 the original value, presumably due to the Thermoid coupling.

No additional replacement parts were required during this period.

Replacement Parts List Recapitulation:
Replacement Parts List Total dated 15 Jun 1936 = $1,668.73
Replacement Parts List Total dated 30 Jun 1936 = $1,703.38
Replacement Parts List Total dated 1 Jul 1936 = $0.00
Total Government Liability as of 15 Jul 1936, over and above the amount specified in the contract = $3,372.11
[RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 120 – 122.]

17 Jul 1936. Cross Reference No. 452.8 – Continental 1000 hp Engine
From: Chief, Engine Section – ALB:ML
To: General Electric Co.
Cross Reference from No.: 452.8 Superchargers

The only apparent advantage of installing two F-9 turbosuperchargers lay in the increased nozzle area and a corresponding efficiency increase due to utilizing more of the exhaust gases. This, however, would be partially offset by the fact that when using two F-9 turbosuperchargers in conjunction with the 1,000 hp engine, modifications would have to be made in the compressor in order to eliminate pulsations. The increased weight of this suggested installation would be virtually double the present F-10 type installation and would not increase the efficiency of the entire system in the same proportion. No action was to be taken on the drawing, but it was to be retained for future reference. [USNARA RG342 RD3285. 452.8 - Engines - 1000 Horsepower, 1929-30-31-32-33-34-36. E1K107.]

31 Jul 1936 Progress Report. Although the single-cylinder engine was assembled with the forked connecting rod, new big-end bearing shell, new piston and old rings, no running was accomplished during the period.

Torsiographs were obtained from the XO-1430-1 at 3,000 rpm and 750 hp with the new torsiometer. Scavenge pump investigation established that its capacity fell off markedly at high speed. However it was able to handle about 90% pressure pump capacity on either front or rear scavenge pump alone as when the pumps were on the engine. The XO-1430-1 was removed for inspection; no important changes were necessary. The engine was reassembled with accessory drive gears for running the engine in the same direction as prior runs. The special gears to drive the torsiometer were removed. The light quill shaft to the reduction gear was used.

After a 2-hr run-in to 3,000 rpm and 400 hp, the oil pressure was raised from 75 to 84 psi by placing washers under the pressure relief valve spring. A power increase to 3,000 rpm and 680 hp caused the I-beam mounting plates to overheat at the bottom without water in the exhaust pipes. Asbestos and aluminum radiation reflectors were installed and the temperature difference between the top and bottom flanges was decreased from 90°F to 40°F. Various exhaust pipe cooling methods were tried; copper tubing brazed to the elbow with water circulation was apparently effective. At this period's end, the following data was taken:

rpm = 3,010
bmep, observed = 157 psi
bmep, corrected = 162 psi
Boost = 12 inHgG
Spark Advance = 30°
Temperature, No. 1R Intake = 175°F
Temperature, No. 6R Intake = 180°F
Temperature, Oil-In = 147°F
Temperature, Oil-Out = 259°F
Temperature, Coolant-In = 230°F
Temperature, Coolant-Out = 242°F
Temperature, Average Spark Plug Gasket = 420°F
Temperature, I-Beam Mounting Plate, Top = 180°F
Temperature, I-Beam Mounting Plate, Bottom = 225°F
Crankcase Pressure = 0.7 inH₂O
bhp, observed = 850
bhp, corrected = 879
sfc = 0.637 lb/hp/hr

When this run completed the engine was removed for a complete tear-down inspection. Total time was now 123:56 hrs, 64:11 hrs of which was under power and 59.45 spent motoring.

Engineering: Layouts had been made for a new coolant pump using a packing-less seal like the one used on the single-cylinder engine. Layouts were made to investigate a new supercharger vent location in the rear accessory housing. Subassembly drawings showing the gear bushings in place in the various castings had been started. The spare parts orders were all in manufacturing. A new crankcase casting had been received and laid out by the Inspection Department with a view of correcting patterns to eliminate excess metal. Rough material, except the crankcase casting, had been received. The connecting rods were 80% complete. Gears, except reduction gears, were ready to have teeth cut. Small fasteners were complete. Bearings were promised by 15 August. Several parts, such as the rear accessory housing, crankshaft and oil plugs, were held up pending design modifications. Replacement parts used during this period were covered by attached sheets. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 125 – 132.]

8 Aug 1936. Prescott met at MatCmd with Kinnucan, who asked to borrow a fuel pressure regulator for XO-1430-1 engine tests; Prescott approved. The Stromberg NA-F7C carburetor purchased about one year prior gave indications of excessive pressure drop at 887 hp, which was the maximum output attained at that point. MatCmd's Mr. Hoffman recommended contacting Stromberg and arranging to exchange the NA-F7C for a later model that had been adapted to 1,000 hp without excessive pressure drop.

Kinnucan stated that the problem of oil vapor getting into the magneto breaker points had been remedied by a sleeve on the magneto coupling that sealed against the felt ring provided in the magneto. He said that the maximum power achieved to date was 887 uncorrected at 15 inHgG. The sfc was 0.61 lb/hp/hr, but Continental's efforts at mixture leaning were interrupted by the starter drive shaft bearing seizure. At inspection, all parts except the starter drive shaft bearing were in excellent condition. At 850 hp uncorrected, the required boost was 12 inHgG, sfc was 0.568 lb/hp/hr, crankcase blow-by was 73 ft³/hr and maximum spark plug temperature was 500°F.

The present leaky crankshaft had been shipped to the Ohio Crankshaft Company to have the main and crankpin journal bores trued up so that the new and improved oil plugs could be fitted in an effort to minimize oil leakage. The new crankshaft, which was being procured as a spare, was to have a revised oil passage drilling scheme to further improve oil sealing. Kinnucan stated that extreme difficulty had been experienced with water in the oil getting into the scavenge lines and flashing into vapor under the heat and reduced pressure, thus vapor-locking the scavenge pumps. The crankcase then filled with oil and the engine had to be stopped. During an investigation of this phenomenon all crankcase and cam box vents were opened to provide as free breathing as possible. This did no good until the exhaust pipe cooling water was shut off, at which time the water ingestion ceased. As a result of this discovery, the exhaust pipe cooling method was revised by brazing copper tubing around the exhaust elbow exteriors; the water or steam from this cooling loop then entered the exhaust pipe at a point distant from the cylinder ports. This scheme proved satisfactory and no further difficulty with the oil in the water was encountered.

Kinnucan said that the best spark plug results had been obtained with Champion spark plugs, but was unsure of the specific type; BG-157 plugs were currently in the engine. The Harrison Prestone coolers had functioned very well and Harrison's information on the coolers and their automatic temperature regulators would be forwarded to MatCmd.

Kinnucan requested constant speed propeller governor information, including diagrams of the oil system from the governor to the propeller hub, so that the new crankcase nose section could be provided with same; this matter was referred to the Aircraft Branch Propeller Unit. Continental was reluctant to take the oil required for propeller operation from the rear propeller shaft bearing as it was one of the engine's most heavily loaded bearings and should have its entire length devoted to its main function rather than sacrificing about 1" of its length to supply constant-speed propeller oil. Kinnucan wanted to omit the oil leads and grooves in this bearing; Prescott concurred. On 1 Sep 1936, Maj F.O. Carroll, the Engineering Section Acting Chief, sent Continental Air Corps Specification Nos. 29531 and 29532. Specification No. 29531, in addition to listing propeller shaft end requirements also included engine noses that facilitated interchangeable propeller controls among engines with the same shaft sizes. Specification No 29532 addressed propeller governor drives and accommodations for hydraulically controlled propellers; while still preliminary, Maj Carroll expected the standardization efforts would produce a complete specification in time for Continental's new shaft.[RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. Sep 1936 Letter, Maj F.O. Carroll to Continental Motors. 145.]

Kinnucan showed a revised coolant pump layout that incorporated a carbon-type coolant seal similar to the one used in MatCmd's single-cylinder test engine. He stated that this seal had functioned very well and would be satisfactory in the XO-1430-1. This pump layout had been submitted to the carbon seal manufacturer, which approved the design but wanted to install the packing in the pump at its plant. Kinnucan brought two supercharger seal vent layouts, one that opened at one side but drained from the space between the supercharger and accessory drive housings at the bottom; the other used a pressed-in or cast tube open to the atmosphere at one side. He wanted to know the reason for moving the vent from its present position at the accessory drive housing top when it appeared to be operating successfully. Prescott pointed out that the upward-pointing vent would fill with oil if the crankcase seal leaked and that oil would be drawn into the supercharger when the throttle was partially closed. Prescott stated that the desirable vent location was at the side where it would still function even if the oil seal was faulty.

Kinnucan asked about the status of the new parts contract that Continental had returned for revision after it priced the crankcase assembly at $27.00. Prescott said that the procurement authority had rewritten and transmitted a revised contract to the Contracting Office. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 11 Aug 1936 Memorandum Report E-57-285-45, Conference with Representative of Continental Aircraft Engine Company, 8 Aug 1936, on XO-1430-1 Engine. 142 – 145.]

XO-1430-1 Performance

15 Aug 1936 Progress Report. An inspection after the 850 hp run mentioned in the 31 Jul 1936 Progress Report revealed the piston rings slightly feathered, so they were replaced. The No. 6L cylinder wall was streaked, which was removed by hand-lapping. The No. 5R outer intake valve spring was broken. The engine was run-in for 5 hrs. Pistons and cylinders were in good condition. Run-in was continued to 12 inHgG intake manifold pressure and a mixture ratio curve made and spark advance setting checked. The intent during this run was to run with a 0.56 lb/hp/hr sfc. However, when the data was worked up, the sfc had not gone below 0.57 lb/hp/hr. Spark advance of 29° to 31° was found to be optimum. The corrected output for 3,000 rpm and 12 inHgG was 883 hp.

The throttle was opened to get 15 inHgG manifold pressure, where a flash reading was obtained showing 889 hp observed and 927 hp corrected. The oil pressure dropped by about 20 psi and the run was stopped. During this run at 12 inHgG, oil consumption taken at 5 minute intervals increased for the duration. During the last 0.25 hr of this 1.25 hr run, oil consumption increased from about 90 lb/hr to about 110 lb/hr.

The following data was obtained while running at 12 inHgG:

rpm = 3,012
bmep, observed = 156.7 psi
bmep, corrected = 163.5 psi
Boost = 12 inHgG
Spark Advance = 31°
Temperature, No. 1R Intake = 177°F
Temperature, No. 6R Intake = 177°F
Temperature, Carburetor Inlet Air = 84°F
Temperature, Coolant-In = 228°F
Temperature, Coolant-Out = 242°
Temperature, Oil-In = 148°F
Temperature, Oil-Out = 244°F
Coolant Flow, Right Bank, gpm = 81.3
Coolant Flow, Right Bank, gpm = 84.4
Oil Pressure, Front = 53 psi
Oil Pressure, Rear, 76 psi
Crankcase Blow-By = 79 ft³/hr
bhp, observed = 850
bhp, corrected = 887
sfc = 0.568 lb/hp/hr
Pressure Rise Through Impeller = 19.4 inHgG
Engine Air Flow = 6,720 lb/hr

This data provided encouragement that the O-1430-1 was capable of 1,000 hp.

The engine was removed from the test stand and disassembled to locate the oil pressure problem. Reduction gear bushing, Dwg #503605, was badly scored and starter bevel gear bushing, Dwg # 501007, was seized and badly scored; an investigation was under way to explain this failure. The high oil consumption was thought to be caused by crankshaft oil plug looseness. The crankshaft was sent to the Ohio Crankshaft Company to true up the holes prior to fitting the new, heaver oil plugs. Total engine time was then 134:58 hrs, with 73:14 hrs under it power and 61:44 hrs motoring.

Engineering: Details had been started on the new coolant pump. Subassembly drawings showing the gear bushings were continued. Studies had been made of various bevel gear fit-checking fixtures. Studies of various crankshaft oil seals continued. Spare parts were still being manufactured. The crankcase patterns were being changed to eliminate excess metal, and new castings were expected by 31 August. Most small items were complete. Intake valves were held up pending more single-cylinder runs. The rear accessory housing was held up pending a new supercharger shaft seal design release acceptable to MatCmd. The crankshaft was in work, but several details, such as crankshaft plugs, were delayed pending satisfactory design completion. Replacement parts cost and Government liability were covered by attached sheets. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 133 – 141, 146 – 154.]

31 Aug 1936 Progress Report. The single-cylinder test engine was not run during this period. A piston had been prepared with three separately-located compression rings and one vented oil ring. Tests were planned to determine the effects of several exhaust stacks from the XO-1430-1 setup to determine effects on cylinder performance.

Inspection of the XO-1430-1 after its partial oil pressure loss described in the last Progress Report indicated the rear reduction gear pinion bearing in conjunction with excess crankshaft leakage were likely causes. A list of parts and operations necessary to rebuild the engine were promised for the next Progress Report. A study and record of the reduction gear housing deflections and distortions were made for comparison with future inspections after more running. The crankshaft main and crankpin bores were made circular to within 0.0002" by lapping. Oil plug pattern modifications were made to secure heavier contact faces. The engine did not run during this period, but it was expected to have been repaired, rebuilt and ready for running by 14 Sep 1936.

Kwick-Way, Black & Decker and Hall valve seat surfacing tools were tried for touching up seats in the cylinder. The Kwick-Way was not acceptable, Black & Decker was moderately successful, and Hall, which held the most promise, had not been available for test.

Engineering: Details were completed on the new coolant pump and were to be released for manufacture. Studies of various crankshaft oil sealing methods continued. Sample test plugs were made to pressure test with hot oil several sealing schemes. The spare parts order was being manufactured except for the crankcase, reduction gear housing and accessory case, which were awaiting suitable castings from ALCOA. No additional replacement parts were used during this period.

[RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 155 – 157.]

1 – 2 Sep 1936. MatCmd civilian engineers Prescott and MatCmd civilian employee N.W. Lake visited Continental. MatCmd had learned that the XO-1430-1 crankcase was distorted so that the front and rear flanges were out of parallel by about 0.022". Investigation showed that the measurements had been misinterpreted and that only a 0.009" difference existed between the top and bottom front and rear crankcase flanges. This discrepancy was negligible. Details of the reduction gear housing diaphragm damage was discussed; Continental revealed that it had already rebored the diaphragm holes so that an oversize bearing set could bring the shaft centers into the correct locations. It appeared that no appreciable damage had been done either to the gear case or crankcase, and that these parts were satisfactory for further testing.

Lightening hole plugs in the existing crankshaft were discussed, as well as details of the proposed revised crankshaft with an improved lightening-hole plugging method. Continental had hand-lapped the lightening holes to be round and straight, and was fitting an entire new improved-design oil plug set. Several other oil plug designs had been laid out in an effort to overcome the present cast-magnesium oil plug leakage. The best plan included the use of steel tubing and stamped steel oil plugs with the sloping journal bore ends relieved a few thousandths so that a definite and uniform width would be left for the bearing operation within the lightening holes to insure these holes were round and straight. Crankshaft oil passages from the main journals to the crankpins were revised to accommodate the new oil plugs. Continental opined that the steel oil plugs would remain tight under all conditions, whereas much trouble had been experienced with the magnesium and aluminum parts due to different thermal expansion rates. In order to release the crankshaft and complete its fabrication, Prescott proposed that Continental send a drawing and change notice for MatCmd approval. Prescott also suggested that revised lightening hole plug drawings also be furnished.

Piston rings and piston setup were discussed; Tilley showed the latest piston ring setup comprising three compression rings and one slotted oil ring. MatCmd stated that the slotted oil ring might prove too severe, in which case conventional beveled oil rings could be used instead of the slotted oil rings. Continental was preparing to run single-cylinder tests on several piston/ring setups in order to determine the one most satisfactory.

A check on the supercharger impeller dynamic balance revealed that its static balance was incorrect. This imbalance was corrected to overcome the vibration that apparently had originated in the supercharger section. It was noticed that the supercharger entrance buckets were of unequal length; those on half of the impeller were about 0.125" higher than the rest. No attempt was made to straighten the entrance buckets. Continental was to notify GE in order that future impellers would be properly balanced.

Each time the engine had been disassembled, bearings close to the impeller shaft that served as an oil header were badly scratched, while bearings more remote from the impeller lacked this defect. Continental stated that a Cuno Company representative had decided that the current Cuno filters were only about 1/3 the necessary capacity. MatCmd test stands incorporated one or more large Cuno filters and full dependence was not placed on the engine-mounted Cuno filters. Continental stated that it had not understood this and complained that this procedure was unfair, if not dangerous, in view of the fact that no such precautions were taken with Air Corps aircraft engine installations. The MatCmd dynamometer laboratory was equipped with one Cuno filter at the main oil pump and a second in the pipe from the oil supply line to the oil tank. A third large Cuno filter was installed in the oil-out line from the scavenge pump to the oil tank, in addition to the Cuno filter in the engine assembly. The torque stand was equipped with a Cuno filter at the main oil pump and an auxiliary Cuno filter in each oil-out line from the scavenge pump to the oil tank, in addition to the Cuno filter that was part of the engine assembly. No such precautions were taken with aircraft installations, and complete dependency existed on the Cuno filters that were part of the engine. Service oil was received in drums and emptied into underground tanks, from which it was drawn by air pressure to fill Bowser pumps equipped with a 20-mesh finger strainer about 2" long and 0.5" in diameter. Thus, there was virtually no service oil supply filtering in addition to the Cuno filter installed in the engine. Continental did not know of the additional oil filtering in MatCmd test stands and had been operating with no filtering except that provided by the engine Cuno filter.

Continental thought it wise to determine the pressure drop through the engine-mounted filter at various oil flows, using oil viscosity that duplicated typical engine oiling conditions. Preliminarily, 70 psi was required to force 5 gph through the filter at 95°F. Further results were to be reported, but preliminary results indicated that during warm-up, all oil bypassed the Cuno filter; this condition was believed responsible for the bearing scratching. Continental thought that increasing the Cuno filter size or using some other filter type should be considered to reduce the Cuno pressure drop and bypassing large oil quantities directly into the engine oil system.

Kinnucan stated that several single-cylinder piston ring setups would be tested in preparation for XO-1430-1 installation. Tests to date on the XO-1430-1 seem to indicate excessive oil consumption that must be remedied before beginning 50-hr development test.

MatCmd was to advise Continental four days in advance of the engine mount plates being ready for test. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 4 Sep 1936 Memorandum Report E-57-285-46, Visit of Division Representatives to Continental Aircraft Engine Corporation, Detroit, Michigan on 1 – 2 Sep 1936. 196 – 199.]

15 Sep 1936 Progress Report. In view of the XO-1430-1's excessive oil consumption, a new piston with three separately-located compression rings and one vented oil ring were placed on test in the single-cylinder engine; the rings were not pinned during the run-in. Several bad blow-by periods were encountered but no damage resulted. The runs continued to contract output without further trouble. The exhaust system was changed to use a XO-1430-1 stack and provisions were made to get exhaust pipe pressure cards with the Farnborough indicator. As of 15 September the single cylinder engine part times were as follows:

Several different XO-1430-1 crankshaft plug fits were tried in a test rig using the newly designed cast magnesium plugs. It was found that plugs fitted 0.001" tight would loosen and could be pushed out by hand when heated to 200°F by circulating oil and cooled several times. Plugs that were 0.0005" loose at the start showed very little leakage at room temperature and none above 160°F. The crankshaft mains were fitted with plugs 0.0008" loose and the crankpins 0.0005" loose.

The crankcase was checked for alignment with the alignment bar in place; the front and rear mounting flanges were out of parallel a few thousandths. Connecting rod bearings showed some deterioration under the blade rods. An annular oil groove was made inside Nos. 4, 5 and 6 bearings; the other three were grooved in a similar location but extending only 45° either side of the parting line. Some of the valve seats were pitted; they were all resurfaced with a new grinder from the Cedar Rapids Engineering Company. Piston general appearance was generally good. Several ring locating pins were broken and were replaced. The supercharger impeller shaft ball bearing retainer in the accessory case was broken. The bearing was replaced by a new one with a different ball cage type. The supercharger impeller shaft nut was cracked between the rivet hole and base; it was replaced with a new nut whose hex was 0.25" larger. The impeller was checked for static balance and found out of balance. This was corrected by filing the edges of several scallops. The Dwg # 503679 gear on the accessory drive shaft was altered to prevent dirt from entering the bearing. Oil spreader grooves were placed on the thrust faces of all bronze bushings in the accessory case. The original Cuno oil filter was left out and replaced by a cover plate to permit the use of a much larger oil cleaner to reduce the pressure drop through the filter. The original engine unit was tested and the results plotted.

The starter and generator drive gear bushings that had turned in the reduction gear housing were replaced with new ones after the housing was re-bored. The gears were stoned and reused as their hardness was acceptable. The reduction gear bearing outside diameters were re-sized by plating and grinding to give a 0.0045" to 0.005" press fit. Oil spreader grooves were added to the bearings. Dwg #503605 bearing, which was badly scored, was replaced with a new one. Camshaft drive idler bushings were replaced to fit the re-bored case. The propeller shaft oil seal required to observe engine blow-by had worn and was replaced. On 14 September the engine was taken to the test house and set up on the dynamometer.

Engineering: Case assembly drawings showing various bushings in place were continued and were expected to be complete during September. Layouts and studies were being made to understand what accessory housing changes were necessary to accommodate a larger capacity Cuno oil filter. The crankcase, reduction gear housing and accessory case were the only spare parts not yet being fabricated; Continental was still awaiting acceptable castings from ALCOA, and the accessory case was held up pending a decision on the larger-capacity Cuno oil filter. The crankshaft had been rough-machined and was awaiting results on journal plug tests. Replacement parts and total Government liability for the period were covered by attached sheets. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 158 – 170.]

Gear Shaft Strengthening			Revised Piston Design

23 Sep 1936. Air Corps Inspector Robert Triggs wrote the MatCmd Engineering Section Chief about the O-1430-1 status. Inspection revealed that all parts were in excellent condition except the front and rear reduction gear housing bearings. These were burnished over a small area; Continental planned to continue using them and carefully watch their operation. Pistons were being modified to include vented oil control rings (Dwg #500601). This scheme had been checked in the single-cylinder engine by running 7.5 hrs up to 4.5 inHgG boost, after which it was disassembled and found in excellent condition. Another 2.5 hrs to 211 imep was followed by 3.5 hrs at 211 imep. Another inspection found everything in excellent condition. During this test oil was squirted through an orifice at the same pressure as in previous single-cylinder test when the piston and rings were the same as the current XO-1430-1. Single-cylinder oil consumption was halved by this setup. A Dwg #503537 gear shaft had broken and Dwg #500600 was being prepared with a fix to strengthen the gear shaft. Testing was expected to resume on 24 September. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 173 – 179.]

30 Sep 1936 Progress Report. Farnborough indicator cards were taken of various single-cylinder exhaust pipes at 3,000 rpm and 202 imep. No noticeable power change was observed with the various exhaust pipes, although the cards showed variation in maximum pressure and some cards showed small pressure differences when the intake valve opened. A piston was fitted with a new batch of American Hammered tapered-face rings with 0.055" gap. After a 10 hr run-in to 3,000 rpm and 211 imep, the unpinned rings were worn and feathered.

Exhaust Pressure Data

Since the XO-1430-1 had been running with what corresponded to ≤7.5 lb/hr oil consumption for the single-cylinder, an effort was made to determine single-cylinder oil consumption; no run exceeded 4 lb/hr. A piston of the type used in the XO-1430-1 was run-in using rings from the same batch as on the XO-1430-1 with the exception that the lower ring was changed from a 0.094" compression ring to a 0.188" oil drain ring. This groove was vented to the piston interior and compression rings were pinned. This setup was run-in, endurance-run for 3 hrs at 3,000 rpm and 211 imep and inspected. The rings were in good condition. Oil consumption was about 2 lb/hr. In view of these results, the XO-1430-1 pistons were modified, which cut its oil consumption in half. The indicator cards described above were again taken with this setup, which required about 2 hrs running at 3,000 rpm and 211 imep and eight stops; after these runs the ring surfaces were streaked, worn and feathered. As of 30 Sep 1936, single-cylinder component times were as follows:

The XO-1430-1 was run-in on propeller load up to 3,000 rpm and 550 hp, a process requiring 5 hrs. It was then removed for reduction gear section and accessory drive section inspection. Bearings looked good except for accessory shaft bushings, which were scratched. Extra oil grooves were added, a magneto coil replaced and the engine reassembled and set up for further tests. Lateral braces were added to the engine base and the run-in continued to 3,000 rpm and 870 hp. During this run the oil pressure fell off to 40 psi at the reduction gear housing. The lateral braces apparently had no effect on engine vibration. During run-in before the oil pressure loss, oil consumption was about 85 lb/hr, which was still excessive. The BG 157 spark plugs were replaced with new Champion M-11-A plugs because cylinders were misfiring.

Prestone Test Results

The engine was mounted on the dynamometer and run-in for 4:40 hrs up to 3,000 rpm with zero boost. The boost was then gradually increased until 10 inHgG and 800 hp was reached. Oil consumption readings were taken every 5 minutes for 30 minutes and consumption observed to be about 40 lb/hr. While running up to about 800 hp the engine started to miss and the oil pressure slowly dropped. During this period, several stops were caused by defective magneto operation; breaker points wore rapidly and unevenly, coils failed, brushes carrying primary current from the breaker assembly to the body wore at contact causing short circuits. The reduction gear back shaft bearing was in bad condition, necessitating regrinding its journal and replacing its bearing. This engine had 152:08 hrs total time, 86:14 hrs under power and 64:56 hrs motoring.

Continental sent a Prestone sample to the Detroit Testing Laboratory for examination. Spare parts required for Contract No. W-535-AC-9060 were being manufactured with the exception of the crankshaft, crankcase and reduction gear housing, which were to be completed in October.

Engineering: Routine drawing changes continued. An oiling diagram showing oil flow through the engine had been started. Replacement parts and Government liability for this period were attached. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 180 – 192.]

9 – 10 Oct 1936. In a Wright Field meeting with Prescott, Kinnucan brought test data covering a recent XO-1430-1 run that achieved 1,011 hp at 3,000 rpm. He suggested that the throttle position at 1,000 hp indicated that a slightly lower blower ratio could be used, which would probably result in a significant output increase from the reduced power to drive the supercharger and the increased engine power due to reduced charge temperature. A drawing had been made to increase the supercharger impeller pinion from 19 to 20 teeth for future testing. Test data showed that the full-power four-barrel carburetor drop was about 3.5 InHgG. Kinnucan thought this excessive and said that Chandler-Groves had proposed a carburetor with which the pressure drop would not exceed 0.8 inHgG. This might make it possible to again decrease the supercharger gear ratio and realize additional power.

Kinnucan stated that during this test a supercharger idler gear at the crankcase front end had failed, but the failure had caused no damage to other engine parts. A new gear was in process and was reinforced by insertion of a pressed-in tube; this was to be used until a redesigned gear was fabricated in which the stress at the failure point was reduced from about 18,000 psi to 6,000 psi.

The reduction gear secondary shaft bearings showed a peculiar wear in that excessive bearing pressure seemed to be transmitted to the bearings through a contact arc of about 180°. Examination of the secondary shaft detail drawings showed that protruding from the ends that formed the journals were thin and flexible, although amply strong from the bending standpoint when considered as a beam loaded by the two gear loads, which came on this shaft. However, the shaft was approximately 3" in diameter and had a 0.25" wall thickness; it was believed on examination that this shaft was distorted out-of-round in the loaded condition and that the effect caused excessive oil pressure loss at the unloaded bearing side and was somewhat of the effect of a self-intensifying brake across the entire loaded bearing side. Kinnucan stated that a test could be made and the distortion of this shaft under load investigating Kinnucan's proposed that the shaft was disturbed and out-or-round in the loaded condition and that this effect caused the excessive oil pressure loss at the unloaded bearing side and a portion of the effect of the unloaded bearing side. Kinnucan stated that a test would be made and the shaft dimensions and distortion be investigated. Prescott suggested that the shaft ends be reinforced by pressed-in flanges of considerable radial depth in order to prevent journal distortion under load.

Kinnucan stated that previous vibration troubles experienced at the engine supercharger end were traceable to the spring-type mount plate installed under the engine mount plate. For this reason, the engine was bolted down solid without a spring mount provision under the engine bed plate. However, this did not remedy the excessive vibration at the carburetor and it was pointed out that this may have been due to vertical engine flexing under bending imposed by the crankshaft main bearing loads. It was also pointed out that there might be some forward supercharger housing wall diaphragm flexing where it was attached to the secondary housing by an 8 – 9" circle bolt circle. Kinnucan stated that this would be possible to verify by the installation of a very simple brace from the carburetor to the intake manifold.

Kinnucan stated that the present engine dry weight was 1,205 lb but believed this would be somewhat reduced when all the casting sections had been reduced to the design thicknesses and all unnecessary weights eliminated. He stated that ALCOA had done a considerable amount of work on the crankcase in order to eliminate unnecessary weight due to sections being thicker than specified by the drawings. He showed a proposed accessory gear housing revision that permitted the use of two Cuno filters in parallel and also asked if MatCmd would favor experimental work with oil strainers of other designs; Kinnucan had in mind edge-wound strip strainer type which he believed could be designed into the same space as provided by the present Cuno filter and still not impose a pressure drop in excess or 3.0 to 5.0 psi. In view of the experimental work carried on showing the pressure drop through the present Cuno filter was so high that the oil bypass around the Cuno strainer was open most of the time, Prescott told Kinnucan MatCmd would favor investigating other oil strainer types.

Kinnucan showed drawings and samples of a revised crankshaft lightening hole plugging scheme and stated that the crankshaft to be fabricated on the recent spare parts order had been held up until a decision was reached in the oil plug design matter. They decided that the crankshaft should be provided with diagonally-drilled oil passages and the lightening-hole slanting ends relieved a few thousandths in order to provide a uniform-width band that could be reamed in a true circle. Kinnucan stated that there were two crankshaft oil plug designs that appeared to be worth investigating in connection with the new crankshaft design, and that both types would be made and tried during future testing to determine which type was most suitable.

Kinnucan inquired as to the provision for substituting new-design parts that were adapted to the inclusion of the crankshaft vibration damper. Prescott stated that a list of the new-design substitutions with a list of the parts that they superseded should be furnished to MatCmd and on this basis a MatCmd Engineering Order would be initiated to cover the substitution of these new-design parts for the present ones.

Kinnucan stated that Continental had just received an inquiry covering five Hyper No. 1 cylinders for spark plug testing. Continental desired to supply these cylinders with four different anti-rust treatments on the cylinder barrel outsides in order to prevent cylinder barrel rusting and erosion in service. The four treatments were tin plating, cadmium plating, aluminizing, and calorizing. Kinnucan asked about MatCmd's reaction to cadmium-silver bearings and stated that tests indicated that the friction coefficient was about 1/2 that of lead-bronze bearings and that the lead-bronze bearing frictional heat input would be greatly and that one danger of bearing deterioration, sweating the lead out of the bronze, would be materially reduced. Prescott said that MatCmd's tests indicated that lead began to sweat out of bearings in excess of 400°F. Kinnucan said that test results indicated that cadmium-silver bearing would operate successfully at temperatures in excess of 400°F. MatCmd was interested in tests covering bearing materials other than lead-bronze and proposed to test some experimental Satco bearings in the MatCmd single-cylinder test equipment. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 14 Oct 1936 Memorandum Report E-57-285-47, Conference with Representative of Continental Aircraft Engine Company, October 9 and 10, 1936, on XO-1430-1 Engine. 193 – 195.]

14 – 15 Oct 1936. Prescott traveled to Continental where he assisted in sorting out the reduction gear bearing troubles. When Kinnucan had last visited Wright Field, he brought up the secondary gear shaft stiffness (or lack thereof) and brought bearings removed from the engine after operation at 3,000 rpm and 1,011 hp; these bearings were excessively worn and exposed to excessive heat over a contact arc exceeding 180°. Distortion under load was blamed and Continental was tasked to investigate. On 15 October the shaft was set up in a compression testing machine with the bearings resting on carbon steel blocks; a load was applied at a gear's periphery. Calculations showed that that the load should have been 11,400 lb in order to give a bearing load equivalent to that in the engine at rated power and speed. At a 1,000 lb load, the hollow shaft flattened approximately 0.003", showing that at a very low load all the bearing clearance was used by the flattened shaft journal, and this flattening opened large passages that allowed oil to escape from the bearing on the unloaded side. At a 3,000 lb load, or about 30% of the actual engine load, the shaft end was 0.009" out-of-round, demonstrating the need for an immediate remedy. It was thought that fixing this defect would also improve the oil flow, which had been excessive and appeared to have caused by some defect at the reduction gear engine end. It was decided to install a spool-like stiffener at each shaft end and conduct further tests to demonstrate the improved shaft stiffness. Although the engine was being assembled, this shaft would not be installed until compression tests proved it had ample stiffness to withstand operational loads.

Prescott inspected parts being fabricated as spares to expedite 50-hr development testing. Among these were the crankcase halves, one of which after several attempts, was sufficiently close to drawing dimensions to be accepted and was being machined. The other half had been rejected 5 times, and the casting on hand was out a small amount due to core shifting between the bearing diaphragms. However, Prescott and Continental agreed that the discrepancies were not serious and would not jeopardize engine operation; it was decided to machine the case half. Continental was making arrangements in the pattern equipment to provide extensions to the offending cores so their positions could be accurately checked after having been set in the mold but prior to pouring the casting. All hoped this change would avoid core shifting in future crankcases. Both Continental and ALCOA had worked hard to reduce the casting wall metal content over drawing dimensions.

Prescott examined the rear accessory drive housing with special attention to flexibility in view of the excessive carburetor and carburetor elbow vibration, which were located at the engine rear. It was decided that three additional internal ribs would be added to stiffen the casting bearing bosses and add lateral stiffness to the entire casting. Continental had not yet ordered this casting, and these changes were to be incorporated in the casting to be machined as a spare part.

The blade connecting rods showed signs of incipient failure near the bearing shell tips. This was hard to explain, since it occurred on the unloaded bearing portions. However, it was observed that the entire affected portion was where the blade rod split operated. Prescott noticed that the edges and corners had been broken only very slightly and suggested that in the future these corners be stoned slightly in order to eliminate the possibility of a cutting edge, and also that the connecting rod bearing shells be slightly flattened at the upper and lower shell junctions; while this slight flat would not come in direct contact with the oiling system, it would fill with oil and form a spreader groove that would assist in lubricating that portion where the difficulty was being experienced. Other than this minor defect, the connecting rod and main bearing condition was excellent, suggesting that the current lubrication system was ample for lubricating all crankshaft bearings. RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 20 Oct 1936 Memorandum Report E-57-285-48, Conference at Continental Company on XO-1430-1 Engine. 216 – 218.]

15 Oct 1936 Progress Report. The single-cylinder engine got new American Hammered piston rings from the batch being used for XO-1430-1 testing. In order to reduce the need of an oil jet near the cylinder skirt, a hole was opened in the connecting rod bearing shell; this reduced the required jet pressure from 8 inHgG to 4 inHgG with the same 2.5 lb/hr oil consumption. The new rings were run in for 10 hrs without difficulty and a 2.5 hr run was made at 3,000 rpm and 211 imep; pistons and rings were in excellent condition. On 15 Oct 1936, running time on the single-cylinder parts was as follows:

XO-1430-1 reduction gear bearings were installed and parts cleaned, ignition wiring replaced and the engine reinstalled on the dynamometer. After a 3.5 hr run-in to 3,000 rpm and 650 hp, the nose section was removed for inspection. The reduction gear bearings showed some hard bearing but were in fair condition. The engine was reassembled and reinstalled on the dynamometer. The sub-base spring supports were replaced with steel solid spacers.

XO-1430-1 Oil Consumption

After a 1:40 hr run-in to 3,000 rpm, the engine was run for 2:29 hrs in excess of 500 bhp; 1:20 hrs of this run was above 900 hp, and the last 0.25 hr at 1,011 bhp. The graphic log shows results of a mixture ratio test made at 900 bhp. There was no power loss down to 0.54 lb/hp/hr and a 3.2% loss at 0.52 lb/hp/hr. Oil consumption was still higher than desired, suggesting further oil control investigation. Vibration at the carburetor continued to be severe with the sub-base solid mounting, but the engine was steadier at the front end and especially at lower speeds or when the engine misfired. During the run an auxiliary oil line was placed between the Cuno filter and nose section. This made but a slight change in the oil pressure drop from the Cuno filter to the front reduction gear bearing feed, probably due to the use of a 1/8" pipe fitting, the only available connection at the reduction gear housing. The engine was torn down for inspection, which revealed the basic engine, rear accessories and valve gear drives were in good condition. However, the reduction gear back shaft bearings were in very bad condition and the bolts holding the propeller shaft gear to the propeller shaft were all broken but one. Tests of the journal stiffness for this gear were made and it was determined that the deflection was excessive, which could account for the bearing failure. Means of stiffing these journals were under investigation. On 15 Oct 1936 the XO-1430-1 had 160:57 hrs total time, 0.25 hrs at 3,000 rpm and 1,000 hp, 93:53 hrs under power and 67:04 hrs motoring.

Data from the last XO-1430-1 run at 1,000 hp, was recorded in Reading No. 20, which appears as part of this Progress Report even though the engine did not run during this period.

Airflow = 7,900 lb/hr
Boost = 20 inHgG (About 0.5 inHgG More at Full Throttle)
Vacuum at Carburetor Out = 3.8 inHgG
Vacuum as Carburetor In = 4.8 inH20 = 3.5 inHgG
Coolant Flow, Right Bank = 83.2 gal/min
Coolant Flow, Left Bank = 88.4 gal/min
Temperature, Coolant In = 230°F
Temperature, Coolant Out = 245°F
Temperature, Oil In = 145°F
Temperature, Oil Out = 241°F
Temperature, Maximum Spark Plug Gasket = 535°F
Temperature, Intake at No. 1 Right and No. 6 Right = 170°F
Oil Pressure Into Engine Pump = 27 psi
Oil Pressure Ahead of Cuno Filter = 110 psi
Oil Pressure After Cuno Filter = 107 psi
Oil Pressure at Nose = 64 psi
Oil Pressure, Scavenge Out = 21 psi
Oil Pressure at Engine Rear = 93 psi
Oil Pressure, Right Cam Box Rear = 6 psi
Oil Pressure, Left Cam Box Rear = 14 psi
Blow-by = 143 ft³/hr
Air/Fuel Ratio = 12.57

Contract W-535-AC-9060: Of the 86 items on this contract, 30 were complete and had been accepted by the Air Corps Inspector. All other items were in work except the accessory housing, which had just been released for manufacture. This part was held up pending design changes. The crankshaft was promised 10 December, the reduction gears for 5 November, and all crankcases for 1 December. Continental expected this order to be 70% complete by 31 October and entirely complete by 10 December.

Engineering: The reduction gear back shaft static tests showed deflection under load. The shaft journal went out of round by 0.004" under 1/3 load. As the bearing clearance was supposed to be 0.003", this deflection accounted for the bearing troubles. A reinforcing plug was pressed into the shaft ends; further tests were to be made to determine its stiffening effectiveness. Accessory housing changes to increase stiffness had started. Replacement parts and total Government Liability for the period were attached. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 200 – 206.]

31 Oct 1936. Air Corps Inspector Robert Triggs reported on engine AC #34-298. The reinforced reduction gear jack shaft was tested for deflection of its bearing areas with hydraulic loads applied on the reduction gear, thus simulating operational loading. Very careful measurement indicated a maximum deflection of 0.0003" when full bearing loads were applied. This deflection being negligible, the engine was reassembled for further operation. Engine power was then brought up to over 800 bhp at 3,000 rpm for a period of 0.5 hr after which the reduction gear housing was disassembled for bearing inspection. Reduction gear pinion bearing, Dwg # 503605, was beginning to extrude lead between two of its longitudinal oil grooves. This bearing was to be replaced with one having a larger centrally-located circumferential groove similar to the jackshaft bearings.

The accessory drive shafts had tightened in their bushings on each side of the accessory drive shaft drive gears. These bushings were being replaced with new ones incorporating features that would give more satisfactory shaft oiling. Tests were also planned to determine if shaft deflection was occurring over its bearing areas when operating under load. Other than the two conditions noted above, the engine parts were in excellent condition. Repairs on the subject engine were being accomplished and test operations were expected to resume early during the first week of November. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 207.]

31 Oct 1936 Progress Report. Single-cylinder running continued with the same parts as at the end of the previous report. After 3 hrs at 3,270 rpm and 211 imep, there was bad blow-by, and the engine was taken apart for inspection. The piston rings looked distressed but not badly worn. The top ring was stuck with carbon and the third ring was broken about 1/2" from the gap. Single-cylinder component running times were as follows:

Reinforcing plugs were pressed into the XO-1430-1 reduction gear back shaft ends, and static tests showed negligible deflection under full load. The nose section bearings were replaced. Accessory drive shaft showed longitudinal cracks at the reduction gear end and was replaced. Static tests of this accessory shaft journal showed no deflection under full load, eliminating this part failure and associated bearings. The Scintilla DF magneto, No. 00268, loaned by Wright Field, was assembled to the engine and the engine was set up on the dynamometer and run for 3 hrs on propeller load up to half power at 3,000 rpm. The engine was then removed from the stand for nose section inspection; no defects were found. The bolts securing the gear to the propeller shaft were changed from eccentric-head type to concentric head type with screw driver slots. The propeller shaft counterbores were changed to accommodate the new bolts.

The engine was replaced on the dynamometer and run for 3 hrs up to 3,010 rpm and 893 hp; boost was 12 inHgG and the specific fuel consumption was 0.565 lb/hp/hr. The oil consumption was 36 lb/hr, a bit better than previous runs. Inspection after this run showed accessory drive bushings to be overheated. Small longitudinal cracks had appeared in the drive shaft. The reduction gear back shaft bearings were in excellent condition; apparently the journal stiffening had eliminated this bearing difficulty. This engine had 170:26 hrs total time, 1:46 hrs above 160 bmep, 101:51 hrs under power, and 68:35 hrs motoring.

Contract W-535-AC-9060: Of the 86 items on this contract, 54 were completed and accepted. The supercharger assembly being fabricated by General Electric had been rejected because of machining errors. GE had promised no completion date for the replacement. The cylinder head castings exhibited unacceptable porosity; of the four casting sets, none were acceptable. The crankshaft was promised for 10 December, the reduction gears for 10 November and the accessory housing pattern was being altered to provide additional ribbing; these castings were expected on 20 November.

Engineering: Revised accessory housing drawings were completed and released for pattern changes. New bolts were designed for attaching the propeller shaft to the reduction gear. The new bolts had a concentric head with a screw drive slot and usage to date indicated the new type would be satisfactory. Gauges were designed for all internal splines to facilitate checking new parts to insure interchangeability. Replacement parts with total Government liability were attached. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 208 – 215.]

10 – 11 Nov 1936. Tilley met Prescott at MatCmd to witness XO-1430-1 engine mount plate testing; these were to be tested not only up to the Transport and Bomber service limits, but the fasteners were carried to those obtained in the Pursuit group The mount plates withstood these loads satisfactorily. However, in the matter of fatigue due to vibration, the final design decision awaited satisfactory torque stand test completion.

Tilley inquired as to the procurement status for the five Hyper No. 1 cylinders and was informed that the proposal had been sent to Washington on 21 October and was expected back at any time; immediately upon receipt the Purchase Order would be forwarded to Continental. Tilley stated that MatCmd's understanding of the four proposed cylinder barrel corrosion prevention methods were incorrect; the five Hyper No. 1 cylinders were to be furnished with the same cadmium plating as the former cylinders, but that four O-1430 type cylinders being fabricated for Contract W-535-AC-8131 would be prepared for corrosion resistance by several different methods and their performance evaluated.

Tilley stated that XO-1430-1 vibration on the test stand was especially severe at the engine rear; this had already resulted in a supercharger inlet failure, which was attached to the carburetor elbow. The broken part was being replaced. Tilley enquired as to MatCmd's preferences for plugging the crankshaft journal bores and was told that that one method used Duprene (the original trademarked name for neoprene, a synthetic rubber developed by DuPont) rings to seal plugs; the other method involved stamped steel cups pressed in place. Naturally, MatCmd wanted three of each to be used as a test to determine the most effective.

General Electric had furnished supercharger drawings with inlet and housing dimension discrepancies. Assembly called for springing the inlet and housing castings in order to clamp the diffuser ring. Prescott thought this an undesirable situation and that the machining limits on these parts should be reduced to a value where excessive part strain was avoided during assembly. Tilley stated that difficulty had arisen, making it impossible to draw the joint between the inlet casting and housing tightly enough to prevent leakage.

Tilley showed a drawing of the accessory housing with new stiffening ribs added internally for tentative approval. Prescott thought the changes logical and that new Van Dykes should be furnished to MatCmd to update its files. Tilley stated that the cam housing being purchased on Contract W-535-AC-8131 specified unequal stud spacing for the bearing retainer at the housing cam drive end. An error had studs installed with uniform spacing and that interchangeability of this cam housing would be affected as far as the bearing retainer was concerned. Prescott suggested that an effort be made to install a special stud having oversized threads in the magnesium cam housing so that stud spacing could be restored to the standard position. Tilley agreed to study this and make a deviation request to MatCmd. Tilley was asked to furnish quotations on two pistons for the XO-1430-1 type cylinder giving a 7.5:1 compression ratio and two pistons giving an 8.75:1 ratio.

Tilley stated that the narrow gear that drove the valve mechanism and which was located on the reduction gear pinion had been ground 0.025" undersize by the gear manufacturer. The gear load magnitude was such that a 0.012" tooth height loss would not be serious and Continental thought it would be satisfactory. Prescott suggested sending a marked drawing and a request for deviation to MatCmd so that the gear could be officially approved. Failure of the supercharger drive gear train bearings and shafts at the XO-1430-1 reduction gear end was discussed. Tilley stated that it had been discovered that the doweling was insufficient between the reduction gear housing and the crankcase, and that bearing and shaft failures were caused by misalignment during normal engine operation. He suggested that it was desirable to eliminate the blind hole construction and open up one end of all bearing openings so that bearing alignment could be checked with the gear housing assembled on the crankcase. Under these conditions it would be necessary to use a plug to close these holes to prevent unbalanced or low oil pressure. MatCmd was in accord with the proposed changes. Tilley agreed to conduct studies and report the results.

Tilley requested verification fuel and oil consumption requirements for XO-1430-1 engine tests. He stated that Continental had implied from single-cylinder test that the maximum XO-1430-1 oil consumption was 0.025 lb/hp/hr and that desired fuel consumption during the 50-hr development test was 0.55 lb/hp/hr. Prescott said this was also the understanding of MatCmd, although the XO-1430-1 contract did not specifically state so. [USNARA RG342 P031177. 25 Nov 1936 Memorandum Report E-57-285-49, Conference with Representative of Continental Motors Corporation on XO-1430-1 Engines.]

15 Nov 1936 Progress Report. The single-cylinder engine was assembled with new piston rings duplicating the XO-1430-1 setup. A run was made at 3,000 rpm and 211 imep to get oil consumption data. The engine was disassembled and a rectangular-section drain groove added below the oil ring; this groove had oil drain holes into the piston interior. Oil consumption was checked under the same conditions as the first run, and revealed that without the oil drain groove, consumption was 2.35 lb/hr; with the oil drain groove it was1.34 lb/hr. This 43% reduction was extrapolated to indicate the XO-1430-1 oil consumption would be brought below 0.025 lb/bhp/hr. Single-cylinder parts time as of 15 Nov 1936 was as follows:

The XO-1430-1 was assembled with new accessory drive shaft bushings on each on each side of the gear at the reduction gear housing end. The oil pump assembly was replaced with one with a 37% larger capacity the pressure pump and a 25% larger scavenge pump. Also replaced were intake and exhaust gaskets, reduction gear pinion bearing and miscellaneous small parts. Many ribs adjacent to the through bolts in the supercharger intake casing were cracked. Several through bolts were not replaced because replacements were lacking. The reduction gear pinion bearing was replaced with a new one featuring a centrally-located annular oil groove instead of an axial oil spreader.

A check of the nose section alignment revealed that it was possible to assemble the nose case to the engine with 0.008" misalignment. This was due to wear on the large pilot resulting from numerous disassembly and assembly operations. This misalignment may have contributed to the trouble with these bearings and gears in the past. Additional dowels were provided between the nose section and crankcase to assure bearing alignment.

The engine was installed on the dynamometer and given a 2 hr run-in. During this run tests were made to determine the excessive carburetor vibration source. The mounting pedestal was braced transversely and the carburetor braced with three separate members, one from the inlet flange to the intake pipe, and two from each carburetor entrance flange side to the tachometer mount flanges on the cam housing. The side braces to the cam housing reduced the vibration but also broke the carburetor studs. It appeared the carburetor vibration source was crankcase deflection. (HA! Take note all ye separate-cylinder advocates!) To determine the transverse stiffness of the engine and mount, an 850 lb load was applied uniformly to the camshaft housing and produced the following deflections:

O-1430-1 Deflection Test Results

The wedges were driven between the floor and rear mounting table corners. Results of additional deflection tests were shown by curves. It was apparent that the principal deflection in the horizontal plane was in the engine mounting I-beam. A transverse plate from the engine rear to the point of attachment would greatly decrease engine-end deflection. Continental did not consider it wise to make extensive runs with the cracked supercharger casting. A new part was being obtained. The engine was removed from the stand and pistons removed for modification as described in the single-cylinder tests. Total engine time was 174:41 hrs, time above 160 bmep was 1:46 hrs, time under power was 105:06 hrs, and time motoring was 68:35 hrs.

Contract W-535-AC-9060: Of the 86 items, 70 were complete and accepted. New castings were on hand for the reduction gear housing and were to be machined as quickly as possible. Previous castings were rejected for porosity. The crankcase was promised for 1 December and the reduction gears for 20 November.

Engineering: Routine drawing changes continued. A special facing tool had been designed to face bushings and adapters for all bevel gears. This fixture was to ensure proper alignment and backlash. Studies were under way to determine the vibration magnitude at the engine rear. Layouts had been made to investigate several methods of doweling the reduction gear housing to the crankcase to ensure accessory drive shaft alignment. Tilley met with Prescott at Wright Field regarding various contract items, Hyper No. 1 cylinders, and the possibility of higher-compression pistons for the Hyper No. 2 cylinder. Tilley witnessed tests at Wright Field of the airplane type mounting plates for the XO-1430-1. Replacement parts and total Government liability for this period were attached. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 224 – 234.]

MatCmd felt that Continental could have pushed toward and early conclusion more diligently on a number of occasions but failed to do so. Continental management seemed unwilling to move ahead on its own initiative, delaying work until actual approved contracts were in its files. This attitude was believed to be responsible for at least a 1-year XO-1430-1 delivery delay. MatCmd felt that Continental should have taken the initiative in pushing this engine's development rather than playing it safe at every turn and by means of the delays thus introduced, causing itself losses by reason of the fixed expenses that went on regardless of whether the development was pushed. MatCmd believed that a somewhat healthier attitude was being taken by the Continental management, but in spite of this and the sincere engineering staff effort, the progress had not been as rapid as could have been wished. MatCmd realized that financial difficulties due to the depression hampered operations on this project, but MatCmd also felt that this development was sufficiently vital to Continental and to the Government, that considerably more diligence should have been exercised in pushing this project to a conclusion. [USNARA RG342 P031175. 17 Nov 1936 Memorandum Report E-57-285-50, XO-1430-1 Engine.]

21 Nov 1936. Triggs reported that the XO-1430-1 had been assembled with a new supercharger intake, Dwg #W4868049, replacing the one that had cracked in use. A 0.5" thick Duprene gasket was assembled between the carburetor elbow and the supercharger in an effort to stop carburetor vibration. Following run-in, power output was increased at atmospheric manifold pressure at 3,000 rpm. Carburetor vibration was not noticeably decreased. Various ideas were tried without effect. However the angular braces from the carburetor to the distributor would stop carburetor vibration until the carburetor flange studs sheared. In the future, the carburetor was to be mounted with a rubber sleeve connecting the carburetor elbow to the supercharger intake; this would permit further engine operation until the basic vibration cause could be remedied. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 219.]

25 Nov 1936. Triggs wrote that oil and Prestone temperature regulating devices had been used on the XO-1430-1 since the test program's beginning. Their performance was excellent and no repairs or replacement has been necessary. He thought the desired temperatures had been maintained more accurately than would have been possible with manual regulation. Both oil and coolant systems used Powers #10 temperature controllers in conjunction with Power diaphragm valves, made by the Powers Regulator Company, 2720 Greenview Avenue, Chicago, Illinois. For this test setup it was more convenient to install the temperature sensitive element in the line leaving the coolers rather than in the engine inlet lines. Oil and coolant temperatures at the engine were controlled by biasing the temperature settings to account for heat loss in the lines leading to the engine. This practice was advantageous as since the temperature sensing elements were undisturbed when the engine was removed and installed. The temperature regulating equipment was used in conjunction with Harrison Radiator Corporation, Lockport, New York radiators, Type HE21, Part No. 3106925. These were very small and compact. No leaks or other difficulties have developed during their use in the past 10 months, and their performance was guaranteed by the manufacturer. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 222.]

30 Nov 1936. The XO-1430-1 carburetor was mounted on a pedestal and connected to the engine via a rubber sleeve, thus eliminating all carburetor vibration and stopping the pendulum action on the supercharger inlet. Engine operation continued to obtain oil consumption data to check results of the vented annular groove under the piston oil control ring, which also had oil drain holes to the piston interior. Operation up to 14 inHgG boost indicated that oil consumption was approximately 36 lb/hr, a 4 lb/hr decrease.

When boost was increased to 16 inHgG, Prestone was ejected from the overflow tank outlet, terminating testing. The Prestone had enough water to boil at 250°F; the water present originated as condensation from the air pressure used to force Prestone into the engine cooling system from the Prestone storage tank, a condition that would be remedied. The engine was removed from the test stand for disassembly and inspection pending changes to the test stand cooling system.

Engine inspection revealed that cylinder No. 3R was lightly scored. There were cracks in the center main bearing support flanges of both crankcase halves. The steel backs of other main bearing shells indicated additional crankcase flange cracks. Further examination of these parts was planned after they were etched. Testing would resume with the new spare crankcase, pending design and pattern changes for a replacement crankcase. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 223.]

30 Nov 1936 Progress Report. The single-cylinder engine piston and cylinder were removed for inspection. The top ring was stuck for about 1/4 of its circumference due to carbon. The third ring was broken about 0.5" from the gap. Since the oil drain groove had been ineffective in the XO-1430-1, the piston was modified to increase the drain hole size behind the oil ring. A conference with the local American Hammered Piston Ring Company representative indicated that these drain holes should have as much area as the oil ring. The single-cylinder engine was reassembled with the same piston with this modification and a new third-groove ring.

After running in for 3.25 hrs, a 1.75-hr test run at 3,000 rpm and 211 imep to determine oil consumption, which was about 2.7 lb/hr. Inspection and further tests were to be made to explain this consumption increase over previous tests. During this test, a new cylinder coolant elbow with bosses for thermocouple connection produced readings consistent with prior tests. It was proposed to use the same setup on the XO-1430-1 to determine coolant temperature for each cylinder to guard against local overheating in future high-output runs. As of 30 Nov 1936, single-cylinder engine part times were as follows:

Oil Consumption Test Data

The cracked XO-1430-1 supercharger casting was replaced with a new one having reinforcing ribs at the outer edge. It was carefully assembled to avoid excessive pinch at the outer flange. A 0.5" Duprene gasket was replaced between the supercharger cover and carburetor elbow as a flexible, vibration-reducing carburetor mounting. The pistons were modified to add the oil drain groove below the oil ring. The engine was set up on the dynamometer and after a short run at light loads, it was clear that the Duprene gasket did not reduce carburetor vibration. The carburetor was connected to the supercharger inlet via a rubber duct and the carburetor separately supported by a floor-mounted pedestal; this eliminated the carburetor vibration. A 2 hr oil consumption run was conducted at 3,000 rpm and 0 – 8 inHgG manifold pressure. Essential data was presented on the graphic log sheet dated 11-23-36. Oil consumption was not uniform but seemed to be 39 lb/hr during the last 0.5 hrs of the run. This was a slight improvement over the previous run but not consistent with the single-cylinder results.

The engine was removed from the dynamometer to determine why oil consumption had not decreased. The cylinders, pistons and rings were in good condition; the connecting rods and crankcase were not disassembled. The engine was reassembled without modification and setup on the dynamometer. An oil consumption recheck attempted to substantially duplicate the pervious run. A graphic log dated 11-25-36 depicts this run. Oil consumption for the last 10 minutes was 33 lb/hr, which is slightly lower than the previous run. This test was re-run under the same condition except that the oil pressure was reduced to as low a value as was considered safe, values similar to those before the oil pump had been replaced. These data appear on the graphic log dated 11-25-36. These values were obtained with relatively low boost; when the boost was increased to 14 inHgG, oil consumption increased greatly. The coolant temperature also varied greatly, indicating that the Prestone was boiling.

The maximum power attained during these runs was just under 1,000 hp. The engine was removed from the dynamometer for tear-down inspection, which was incomplete at this report date. However, several crankcase main bearing bosses were cracked adjacent to the transverse bearing diaphragm, which would permit excessive leakage behind the main bearing shells. XO-1430-1 total time was 184:33 hrs, time above 160 bmep was 1:55 hrs, time under power was 114:13 hrs and time motoring was 70:20 hrs.

Contract W-535-AC-9060: Of the 86 contract items, 72 were complete and accepted. The crankcase and reduction gears were complete and were being inspected. The new supercharger assembly and crankshaft were promised for 15 December. The accessory housing casting was received and being machined. Continental had experienced difficulties getting usable castings for the reduction gear housings and cylinder heads. None had been free of porosity. ALCOA had been doing considerable work on these but as yet had been unable to duplicate the quality seen in the present castings.

Contract W-535-AC-9295 – PO 37-1680, Hyper No. 1 Cylinder Assemblies: The cylinder head patterns had been destroyed and new ones were being made; completion was promised for 5 December. Castings were promised 10 days after pattern receipt. Forgings were on hand for the barrels and jackets, and all small parts were released for manufacture.

Engineering: Routine drawing changes continued. Studies were under way to determine methods of loading the crankcase and measuring deflection as part of the vibration-reduction effort. Replacement parts and Government liability through 30 Nov 1936 were attached. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 235 – 246.]

7 Dec 1936. Triggs reported that the replacement crankcase fabrication would be completed on 7 December. The XO-1430-1 would then be assembled and test runs resumed, primarily to obtain additional oil consumption, pressure and distribution data. The broken crankcase was being etched, after which a thorough inspection of the crankcase halves was planned to locate cracks or distress at points other than the main bearing flange bearing bosses. Initial etching of the left half indicated a crack in the No. 2L cylinder pad extending toward the No. 3L pad.

Following the crankcase inspection, the halves were to be assembled with a line bar and a complete investigation of crankcase deflection and movement made using simulated loads. This data would be used in crankcase redesign. The connecting rods and caps showed signs of working, requiring No. 4 bearing replacement. Others were to be replaced when replacements were received. A new rear reduction gear housing casting was received to replace the porous previously-rejected one. After fabrication and acceptance, this housing was to be assembled to the engine and used with the torsional vibration damper. Engine operation was expected to resume on 10 December. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 244 – 247.]

10 Dec 1936. Continental's Reese, Gould, Tilley and Kinnucan met at Wright Field with Col Echols, Maj Page, Prescott, Snyder and Chenoweth. Col Echols said that a review of the XO-1430-1 engine situation indicated it would be approximately six months before its 50-hr development test would be complete, an a year before its 150-hr type test was complete. He thought that other engines of equal power would be available for flight at a much earlier date, which would make the XO-1430-1 of questionable utility. Tilley stated that he believed the 50-hr development test could be completed in 60 days; Col Echols stated that under this condition the XO-1430-1 would be of interest. Col Echols asked Tilley what he thought the XO-1430-1's power potential was and Tilley said he believed 1,200 hp, perhaps even 1,500 hp. Tilley stated that Continental's past development plan had been for the Government to pay for each step as it progressed, but Reese stated that this was not true and Continental had put a great deal of money into the project and would welcome an audit to show that the Government had not paid for all development to date. Col Echols directed Continental to draw up a plan showing what it proposed to do with this engine to make it of greater utility. [USNARA RG342 P031173. 12 Dec 1936 Memorandum Report E-57-285-51. Conference with Representatives of Continental Motors Corporation, December 10, 1936, on the O-1430-1 Engine.]

10 – 12 Dec 1936. Kinnucan traveled to Wright Field to meet with Prescott and produced Dwg SK84 showing proposed crankcase bearing web revision. He also brought a crankcase half for examination and discussion. The crankcase was cracked in one or more main bearing bores. Prescott thought this might be due to the large oil groove turned in the bearing shell exterior, the bearing bosses not being backed by ribs, and that a small fillet had been used. The proposed remedy consisted of increasing the fillet radius to about 1.25" and adding two ribs running from the bearing center to two stud bosses in the crankcase upper deck. In this connection it was also noted that the diaphragm thickness was but 0.312" at the bearing boss, tapering to 0.250" at the crankcase wall. This web thickness was to be increased to a uniform 0.312". In this way, it was believed that a slight core shift during pouring would not seriously affect the case strength.

Cracks were also discovered in the cylinder flange deck; to overcome this, the fillet radii under the deck were increased to about 0.625". In view of the extended operation of the engine using this crankcase and the rather minor failure nature, it was believed that these changes would prevent crack recurrence. The new crankcase, fabricated under Contract W-535-AC-9060, was installed in the engine for test continuation and plans were made to modify the patterns and immediately start fabrication of another crankcase so that a spare of improved design might be available in case the present one failed the 50-hr development test. The old case was X-rayed and photographed in MatCmd's Metallographic Laboratory. The casting was sound although it exhibited slight porosity indicators. Prescott cautioned Kinnucan that if the redesigned sections were too heavy, blow holes might appear during casting.

Crankcase and Reduction Gear Flaws

Kinnucan brought crankcase flaw photographs, along with a reduction gear photograph showing slight pitting that had occurred on the gear working face near the herringbone tooth vee centers. He did not think the pits were a failure but would be investigated for possible improvement in future gears.

Prescott said that the patterns suggested by MatCmd for the high-compression pistons being fabricated for MatCmd's single-cylinder engine should be revised for improved internal structure; the pattern was modified to provide an 8.75:1 compression ratio. Kinnucan observed that the proposed piston would interfere with the valves if the engine were mistimed. MatCmd planned using these pistons for a brief period during which the risk of mistiming would be eliminated. Thereafter, a 7.5:1 compression ratio would be achieved using a cylinder base shim.

Kinnucan and Prescott met with Mr. Vanvleck of the Cuno Engineering Corporation and discussed the oil pressure discrepancy between Cuno, Continental and MatCmd data. Vanvleck observed that Cuno data did not include the pressure drop in passages leading to and from the filter and suggested that Continental try to improve the passages to and from the Cuno filter chamber by eliminating sharp edges and using larger passages.

Kinnucan stated that Continental could not understand how the pistons and rings furnished to MatCmd for its single-cylinder test equipment were furnished with ring gaps of 0.020" in the standard 5.500" bore test rig; Continental fitted these with a 0.004" gap at the smallest cylinder bore location. MatCmd did not think this to be sufficient clearance and suggested that 0.010" to 0.015" gap was essential to prevent ring feathering and breakage. Kinnucan stated that Continental ring service tests concurred with the larger ring gap.

Continental had planned to conduct crankcase deflection tests on the old crankcase, but thought the results obtained would not be useful since much of the engine stiffness was also due to the engine mount plates and other parts. As a result, Continental had abandoned plans to do the deflection tests. Kinnucan showed a Harrison radiator tube for use with the Prestone/water heat exchangers. The tube was a type that may have been electrically plated onto a lead core after which the lead was melted and the tube tinned inside and out. Kinnucan opined the tubes were very rugged and had given satisfactory service.

Prescott suggested that Continental prepare preliminary sketches and rough estimates covering two larger engines, a 24-cylinder and a 30-cylinder using O-1430 type cylinders. Kinnucan stated that Continental was in a position to do this study since most XO-1430-1 engineering was complete, excepting those changes that testing suggested. He promised that such studies would be submitted in the near future in order that MatCmd might be informed of 2,000 to 3,000 hp engines using the Hyper No. 2 cylinder.

Prescott chastised Kinnucan that unnecessary delays with the single-cylinder engine and XO-1430-1 had made the engine about a year late and that this was the reason for the apparent Government loss of interest in the XO-1430-1 engine, even if its power could be increased. Prescott suggested that Continental seek commercial outlets for these higher-powered engines. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 19 Dec 1936 Memorandum Report E-57-285-52, Conference with Representative of Continental Motors Corporation on XO-1430-1 Engines. 249 – 252.]

13 Dec 1936. Triggs reported that the XO-1430-1 had been assembled with the replacement crankcase and run-in at 3,000 rpm for 5 hrs with power increasing to atmospheric manifold pressure (0 inHgG). It was then inspected and all parts found to be in good condition. The split oil control rings, which had been used for the first time, appeared to have functioned normally. The engine was to be reassembled and testing continued at 3,000 rpm and 12 inHgG, with oil consumption data collected. The split-type oil control ring setup was also being tested on the single-cylinder engine. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 248.]

15 Dec 1936 Progress Report. A complete new ring set of the same type used in the last report was assembled to the single-cylinder piston to recheck oil consumption. After a 10-hr run-in, the engine was operated at 3,000 rpm and 211 imep for 2:20 hrs. Oil consumption was 1.78 lb/hr, or nearly 1 lb/hr less than the previous run. The rings and cylinder were in good condition.

The engine was rebuilt with piston #36, which had the compression rings in individual grooves. The 0.188" oil ring groove was fitted with a single slotted oil ring. The rings were not pinned and the gap was set at 0.035" with the ring 4.5" from the cylinder crank end. After a 10-hr run-in the engine was operated for 1.5 hrs at 3,000 rpm and 211 imep, then 2:40 hrs at 3,300 rpm and 211 imep. After this run, the top ring was feathered and worn with a 0.017" gap increase. The second and third rings were in good condition, but the oil ring was feathered and worn with a 0.010" gap increase. The starting oil consumption was about 1 lb/hr and ending consumption was 2 lb/hr. Since the 3,300 rpm operation may have caused the ring wear, a new ring set was run-in for 9:45 hrs and then run 1:15 hrs at 3,000 rpm and 211 imep; the cylinder cracked about 4.5" from the crank end, terminating the run. Investigation showed that corrosion in the coolant jacket caused loss of section, which accounted for this failure. Study was started on the corrosive effect of ethylene glycol on stressed steel. As of 15 Dec 1936, single-cylinder engine part times were as follows:

Further XO-1430-1 inspection revealed no important failures beyond the crankcase main bearing bosses. The crankcase was cleaned, etched, and taken to Wright Field for X-ray inspection, which disclosed no further cracks but did show the casting were sound and free from internal defects. The engine was rebuilt with a new crankcase and new connecting rod bearings. The main and rod bearings were all equipped with a complete circumferential feed groove in the bearing center, as prior running had indicated this bearing type was in much better condition than partial-groove or no-groove bearings. Since the previous run's oil consumption had been too high, the pistons were equipped with two 0.094" bevel scraper rings with recesses on the lower faces instead of the single slotted oil ring.

After the previous run the coolant radiator was leak tested and found defective, which accounted for the previously-reported Prestone boiling. Tests of a Prestone sample showed that it boiled at 250°F. The radiator was returned to Harrison for redesign and repair. The engine was run-in for 4:25 hrs when the Prestone began to boil; the coolant radiator was again leaking. Mr. Holmes, Harrison Chief Engineer, examined the radiator and stated that the workmanship was defective; he furnished a new unit of the original style. As of 15 December, XO-1430-1 total time was 188:58 hrs, time above 160 bmep was 1:55 hrs, time under power was 117:33 hrs and time motoring was 71:30 hrs.

Contract W-535-AC-9060 – Hyper Spare Parts: Of the 87 contract items, 73 were complete and accepted. The supercharger, crankshaft, and all other items except the front reduction gear housing were promised for 30 December. A "sit-down" strike at ALCOA's Detroit Plant prevented crankcase pattern modification and procurement of aluminum castings. This was expected to delay endurance testing.

Contract W-535-AC-9295 PO 37-1680 – Hyper #1 Cylinder Assembly: A new cylinder head pattern had been completed and sample castings were promised from the ALCOA Cleveland Plant on 24 December. All other items were released for manufacture. Cylinder barrels and jackets were partially machined.

PO 37-2630 – Connecting Rod Assembly: Forgings had been ordered from Wyman-Gordon and were promised for 24 December. All other items were released for manufacture.

Engineering: Hyper #1 cylinder assembly drawings were revised to incorporate changes made during Hyper #2 cylinder development. New Hyper #1 connecting rod drawings were made; Van Dykes were to be forwarded to MatCmd. XO-1430-1 crankcase studies and layouts were made and discussed at Wright Field; when the revisions were complete, blueprints would be forwarded to MatCmd for formal approval. Pattern changes were held up due to the ALCOA Detroit Plant strike. Hyper #2 piston layouts to give 7.5:1 and 8.75:1 compression ratios were made and would be mailed to MatCmd for comment. Replacement parts and Government liability through 15 Dec 1936 were attached. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 253 – 259.]

19 Dec 1936. Tilley said that fabrication of a new, improved-design XO-1430-1 crankcase was held up by a labor dispute at the ALCOA Detroit plant; settlement did not appear to be in sight. Tilley thought that this might introduce a delay on the 50-hr development test. The previously-fabricated spare crankcase was installed but there was no assurance that it would pass the development test without repeating the previous failure since the main bearing boss construction was identical to the failed crankcase. While the previous failure was not serious, cracking of the metal backing the main bearing shells would prevent acceptance of the test even if actual engine failure did not occur. Snyder stated that the strike was also holding up certain projects of interest to the Public Works Administration, which was negotiating with the strikers in an attempt to release material required to continue the project. The strikers were negotiating through the Secretary of Labor for a favorable strike settlement. All hoped that the strikers would release the material in order to show their spirit of cooperation with the Government and that the crankcase patterns might be released in view of the vital nature of this work.

Tilley stated that layouts depicting 24- and 30-cylinder engines based on the XO-1430-1 cylinders were under way and would be submitted to MatCmd in the near future with a proposed program to develop a 2,000 to 3,000 hp engine. Cylinder barrel corrosion continued but MatCmd did not yet have a remedy. The XO-1430-1, as rebuilt with the new crankcase, had been operated to 3,000 rpm and 750 hp, using vented double-beveled oil rings. Tests indicated that oil consumption was too low and the engine was dismantled for modification that would slightly increase oil consumption; it was expected to again be operational on 21 December. Tilley also said that single-cylinder tests were being conducted on piston ring setups and that the results of these tests would be transmitted to MatCmd and incorporated in the XO-1430-1.

Tilley stated that more difficulty had been experienced with the XO-1430-1 Harrison coolant heat exchangers. Harrison was cooperating with finding a solution and opined that by reversing the connections so that coolant flowed through the tubes instead of around them would solve the problem. Bendix Products Corporation could furnish a four-barrel carburetor with only 50% of the pressure drop of the present carburetor. Gears would be available to operate the XO-1430-1 supercharger at a lower impeller speed, bringing about a power increase by reducing the supercharger drive power and charge temperature. Tilley inquired about using a new carburetor, but MatCmd wanted to keep the current one and save a new one for future development. Since the 3.5 inHgG carburetor pressure drop had included a slight amount of throttling necessary to hold the engine power to 1,000 hp, previous test results looked worse than they actually were. [RG342 RD1676 503-106 O-1430 Vol. 2 370101-371008. 4 Jan 1937 Memorandum Report E-57-285-54. Conference on 19 Dec 1936 between N.N. Tilley of Continental Motors Corporation and Messrs. Silas Snyder and F.L. Prescott of the Division regarding XO-1430-1 Engine and Tests. 12 – 14.]

31 Dec 1936. Triggs reported that the XO-1430-1 had completed 26 minutes of operation at 3,000 rpm and 1,000 hp. The oil consumption data taken during this run was disregarded when an oil leak was found at the oil cooler outlet. Air was also leaking into the supercharger at the rubber duct junction between the carburetor and supercharger. This air leak was sufficient to cause engine backfire due to the resulting lean mixture. The air leak was to be eliminated by replacing the rubber duct with metal bellows. Inspection disclosed slight lead extrusion from the bearing surfaces of Dwg #503604 – Bearing – Propeller shaft outer, and Dwg #503605 – Bearing – reduction gear pinion. These bearings will be replaced with new ones with large circumferential grooves, as with the other reduction gear bearings. Slight blade rod bearing pitting was attributed to improper bearing shell crush; the correct crush was to be determined at the next engine assembly. Further engine operation was delayed pending the arrival of replacement bearings from the Bohn Aluminum and Bronze Corporation, which had bearings in process despite labor difficulties it was experiencing. Bearing delivery was promised for 6 Jan 1937. While awaiting the replacement bearings, major XO-1430-1 parts measurements were being taken in compliance with Specification #28144, Section VI, Paragraph 2. The engine was expected to be ready for calibration on 9 Jan 1937. [RG342 RD1676 503-106 O-1430 Vol. 1 360225-361231. 260.]

31 Dec 1936 Progress Report. In view of indications that the ground cylinder bore had a wash-board effect in the XO-1430-1, a run was planned with the cylinder bore honed. Such was available having been honed at Micromatic Hone Company about a year previous and not being used because of the thin wall. This cylinder was assembled to the single-cylinder test engine and run-in; there was no change in run time from the previous report.

XO-1430-1 inspection showed cylinders, pistons and rings in good condition although looking differently than on prior inspections, probably due to less oil getting by the control rings. The engine was reassembled with the same two 0.094" bevel scraper rings with recessions on the lower faces as used for the previous run. The engine was set up on the dynamometer and run for 6:05 hrs up to 3,000 rpm and 8 inHgG where the power was 734 bhp. During the last 2 hrs of this run, oil consumption started at about 6 lb/hr and ended up at 15 lb/hr. The engine was removed from the dynamometer, disassembled and inspected for operational effects with the decreased oil consumption. The cylinders were slightly scored on grinder marks that ran lengthwise in the barrels. Apparently with the more severe scraping action there was not enough oil film to prevent metal-to-metal contact on grinder ridge marks. All cylinders were lapped by hand to improve the cylinder bore finish. The honing equipment was delayed by a week.

The engine was reassembled and reinstalled on the dynamometer and given a 4.5 hrs run-in to 3,000 rpm atmospheric intake manifold pressure and then 1.25 hr up to 6 inHgG intake manifold pressure. During this last period the oil consumption was about 9 lb/hr. The engine was again removed from the dynamometer and the cylinders inspected. The bores, pistons and rings were in excellent condition. These parts were reassembled without change. The supercharger impeller nut had loosened and a thicker washer was made so that the nut was tight when the pin holes were aligned. During the last run, the right distributor assembly was wrecked because of a screw that held the distributor arm in place on the shaft had broken at the safety wire hole, permitting the nut to back off. The distributor assembly was replaced by a new one.

The engine was mounted on the dynamometer and run up to 3,000 rpm and 16 inHgG intake manifold pressure, developing 958 hp. One cylinder showed high temperature at its spark plug gasket. After considerable investigation including removal and inspection of the offending cylinder, the trouble was traced to a defective spark plug gasket. The run continued to 17.5 inHgG intake manifold pressure where the power was 990 bhp. After 17 minutes at this output the run was stopped because the rubber connection between the carburetor and supercharger failed. After several temporary repair attempts the engine was removed from the dynamometer for inspection. During the previous runs a leak had developed in the oil scavenging system despite which the oil consumption was about 25 lb/hr.

Engine inspection showed two reduction gear bearings in perfect condition and two with rubbed spots. One of these spots was due to spreader grooves and the other due to insufficient oil feed. New bearings were being obtained to correct these deficiencies. One connecting rod bearing showed lead-bronze bearing loss on the side adjacent to the plain-rod split. Bearing crush and fit was being investigated. Complete measurements of all engine parts was being made with a view of conducting calibration runs, Contract Item #2, during the first week of January 1937. If these bearing troubles were eliminated after that run, Continental planned to start the endurance run. The pistons, cylinder and rings were in excellent condition after this last run.

Some delay had occurred in procuring the new crankcase main bearings, reduction gear bearings and other lead-bronze lined parts due to an incipient strike at the Bohn Aluminum Company, which had avoided an actual strike by taking inventory. Engine run time was as follows: Total time = 206:59 hrs, time above 160 bmep = 2:40 hrs, under power = 131:57 hrs and motoring time = 75:10 hrs.

Contract W-535-AC-9060 – Hyper Spare Parts: Of the 87 contract items 83 were completed and accepted. Supercharger and crankshaft delivery was promised for 10 Jan 1937. ALCOA Detroit employees went back to work on 21 Dec 1936. The crankcase pattern changes were complete, molds made and heat-treated casting of both crankcase halves, together with the front reduction gear housing were to be at Continental during January 1938.

Contract W-535-AC-9295 PO 37-1680 – Hyper #1 Cylinder Assembly: A sample cylinder head casting had been received and was being checked. All other items were in process and were to be completed before the cylinder heads. If suitable head castings could be obtained, the order should be completed by 31 Jan 1937.

PO 37-2630 – Connecting Rod Assembly: All items were being manufactured and were to be complete by 31 January.

Engineering: Crankcase drawings were revised to include additional rubbing and blueprints were forwarded to MatCmd for final approval. Piston layouts for the Hyper #2 cylinder to provide up to 8.75:1 compression ratio were being forwarded to MatCmd for comment and approval. Layouts for a larger engine using existing cylinders and valve train were under way. Studies on torsional characteristics, balance weights and overall dimensions or several engine types were being conducted. It was expected that sufficient work would have been accomplished to permit preliminary MatCmd conference during the first week of January 1937. Replacement parts with Government liability up to 31 Dec 1936 were attached. [RG342 RD1676 503-106 O-1430 Vol. 2 370101-371008. 1 – 6.]

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