WW2 Drone Engines 7

WWII Gunnery Target Engine Technical Analysis
Part 7. Conclusion
by Tom Fey
Published 19 Jun 2017; Revised 13 Nov 2018

Contents

Part 1. Background and General Configuration
Part 2. The Righter 2-GS-17 (O-15-1) in Detail
Part 3. The Righter O-15-3 Engine
Part 4. Performance and Efficiency Comparison between O-15-1 and O-15-3 Engines
Part 5. The O-45-1 and Kiekhaefer O-45-35
Part 6. Performance and Efficiency Comparison between O-45-1 and O-45-35 Engines
Part 7. Conclusion

Summary

While neither a manned nor armed aircraft, the WWII Radioplane gunnery drones served the training needs of the US Army and Navy to the tune of almost 15,000 sub-scale target aircraft during the war years. This summed production tally is greater than the Boeing B-17 Flying Fortress, Curtiss P-40 Warhawk, Grumman F6F Hellcat, or Lockheed P-38 Lightning. The technologies of their airframes, guidance, launch, and recovery systems, as well as their engines, are subjects worthy of study, admiration, and documentation for posterity. It is my hope this treatise does justice to the latter, and I thank all those that helped me with this task.

Acknowledgements

Special thanks to Ted Koch, Kevin Russen, and Laurie Videle who kindly photographed and measured their engines and parts, Kim McCutcheon who unearthed the type test reports, Sam Ferguson, Calum Douglas, and a dozen others that kindly responded to my numerous requests for photographs, documents, and measurements.

Full Tables

Table 7.1. Comparative Engine Data — Capacity, Volumes
(Dimensional Data Refers to Cylinders Unless "Engine" Appears)
Engine and Cylinder	Engine Swept Displacement (in³ (cc))	Bore (inches)	Stroke (inches)	Dynamic Stroke (inches)	Company Nominal Comp Ratio	Static Comp Ratio	Dynamic Comp Ratio	Clearance Volume (in³ (cc))	Static Volume (in³ (cc))	Dynamic Volume (in³ (cc))	Engine Dynamic Volume (in³ (cc))
0-15-1 Sand Cast #6212 Rectangular Port	16.9 (277)	2.25	2.125	1.42	6 to 1	5.5 to 1	4.0 to 1	1.89 (30.9)	10.3 (169)	7.5 (123)	15.0 (246)
0-15-1 Sand Cast H-6212 Round Port	16.9 (277)	2.25	2.125	1.42	6 to 1	5.5 to 1	4.0 to 1	1.89 (30.9)	10.3 (169)	7.5 (123)	15.0 (246)

0-15-3 Die Cast Rectangular Port	16.9 (277)	2.25	2.125	1.31	7 to 1	6.2 to 1	4.2 to 1	1.64 (26.8)	10.1 (165)	6.9 (112)	13.7 (225)
0-15-3 Die Cast Round Port	16.9 (277)	2.25	2.125	1.31	7 to 1	6.2 to 1	4.2 to 1	1.64 (26.8)	10.1 (165)	6.9 (112)	13.7 (225)

Kiekhaefer 0-45-1	45.6 (747 )	3.25	2.75	1.88	7 to 1	7.3 to 1	5.3 to 1	3.6 (59)	26.4 (433)	19.2 (314)	38.4 (629)
Righter 0-45-1	45.6 (747 )	3.25	2.75	1.88	7 to 1	7.3 to 1	5.3 to 1	3.6 (59)	26.4 (433)	19.2 (314)	38.4 (629)

0-45-35	45.6 (747 )	3.25	2.75	1.86	?	8.6 to 1	6.2 to 1	3.0 (49)	25.8 (423)	18.5 (302)	36.9 (605)

Table 7.2. Comparative Engine Data — Cooling Fin Area
(Dimensional Data Refers to Cylinders Unless "Engine" Appears)
Engine and Cylinder	Engine Cooling Fin Area (in²(ft²))	Cooling Fin Tip Gap (inches)	Cooling Fin Base Gap (inches)	Cooling Fin Tip Thickness (inches)	Typical Barrel Fin Depth (inches)	Outside Diameter (inches)	Exhaust Stack External Area (in²)	Weight (grams)
0-15-1 Sand Cast #6212 Rectangular Port	402.3 (2.79)	0.175	0.12	0.07	0.375	4.0	15.05	1247
0-15-1 Sand Cast H-6212 Round Port	402.3 (2.79)	?	?	?	?	?	?	?

0-15-3 Die Cast Rectangular Port	368.4 (2.56)	0.19	0.166	0.055	0.66	4.0	15.05	1056
0-15-3 Die Cast Round Port	?	0.185	?	0.055	?	?	15.05	1134

Kiekhaefer 0-45-1	614.4 (4.27)	0.18	0.12	Head=0.060 Body=0.065	0.64	5.0	2.8	2364
Righter 0-45-1	?	0.26	0.10	Head=0.098 Body=0.078	0.55	5.0	12.64	?

0-45-35	687.2 (4.77)	0.145	0.088	0.045	0.88	5.45	1.696	2370

Table 7.3. Comparative Engine Data — Induction and Transfer, Part 1
(Dimensional Data Refers to Cylinders Unless "Engine" Appears)
Engine and Cylinder	Engine Crankshaft Length (inches)*	Piston Ring Number and Thickness (inches)	Rear Case Inlet Port Area (in²)	Rear Case Inlet Port Arc (degrees)	Intake Transfer Trunk Dimensions (inches)	Cylinder Transfer Trunk Area (in²)	Rotary Valve Cut Out Area (in²)	Rotary Valve Cut Out (degrees)	Rotary Valve Diameter (inches)	Rotary Intake Open (° ABC)	Rotary Intake Open (° BTC)	Rotary Intake Close (° ATC)
0-15-1 Sand Cast #6212 Rectangular Port	15.5	2 x 0.151	2.48	90	1.375 x 0.61	0.836	1.68	60	4	55	125	30
0-15-1 Sand Cast H-6212 Round Port	15.5	2 x 0.151	2.48	90	1.375 x 0.61	0.836	1.68	60	4	55	125	30

0-15-3 Die Cast Rectangular Port	10.67	2 x 0.085	2.48	90	1.375 x 0.61	0.836	1.68	60	4	55	125	30
0-15-3 Die Cast Round Port	10.67	2 x 0.085	2.48	90	1.375 x 0.61	0.836	1.68	60	4	55	125	30

Kiekhaefer 0-45-1	14.0	2 x 0.092	3.156	87	(1.92 to 1.97) x 0.825	1.584	2.44	61	4.75	58	122	27
Righter 0-45-1	14.0	2 x 0.092	3.156	87	(1.92 to 1.97) x 0.825	1.584	2.44	61	4.75	58	122	27

0-45-35	13.5 (approximate)	3 x 0.085	4.41	100	(2.09 to 2.12) x 0.844	1.70	3.8	85	5	35	145	30

Table 7.4. Comparative Engine Data — Induction and Transfer, Part 2
(Dimensional Data Refers to Cylinders Unless "Engine" Appears)
Engine and Cylinder	Cylinder Transfer Port Area (in²)	Exhaust Port Area (in²)	Carb Deck Throat Diameter (inches)	Intake Duration (degrees)	Transfer and Exhaust Port Height Difference (inches)*	Exhaust Port Open (° ATC)	Transfer Port Open (° ATC)	Transfer Port Close (°ATC)	Exhaust Port Close (°ATC)	Exhaust Port close (°ABC)	Transfer Duration (degrees)	Exhaust Duration (degrees)	Exhaust Port Height (inches)	Exhaust Port Arc Width (inches)
0-15-1 Sand Cast #6212 Rectangular Port	0.984	0.932	1.175	155	0.12	107	122	247	258	78	125	151	0.58	0.402
0-15-1 Sand Cast H-6212 Round Port	0.61	0.61	1.175	155	0.12	107	122	247	258	78	125	151	0.438 dia. x 4	0.440 dia. x 4

0-15-3 Die Cast Rectangular Port	1.000	1.123	1.175	155	0.12	111	116	249	258	78	133	147	0.58	0.484
0-15-3 Die Cast Round Port	0.61	0.61	1.175	155	0.125	?	?	?	?	?	?	?	0.438 dia. x 4	0.604

Kiekhaefer 0-45-1	1.244	1.244	1.78	149	0.122	102	110	251	262	82	141	160	0.7 x 2 + 0.57 x 2	0.706 x 2 + 0.573 x 2
Righter 0-45-1	1.537	1.537	1.78	149	0.122	102	110	251	262	82	141	160	0.694 dia. x 4	0.699 x 4

0-45-35	1.27	1.27	2.26	180	0.19	93	112	248	257	77	136	164	0.7 x 2 + 0.58 x 2	0.706 x 2 + 0.583 x 2
* From Direct Cylinder Measurement

Table 7.5. Comparative Engine Data — Heat Rejection, Performance, SFC, Dimensions
(Dimensional Data Refers to Cylinders Unless "Engine" Appears)
Engine and Cylinder	Engine Fin Area (in²(ft²))	Fin Area per HP (in²)	Fin Area per HP (ft²)	Connecting Rod Length (inches)	Rod Length to Stroke Ratio	Rated HP @ RPM	Engine Torque (lb/ft)	Engine HP/Dynamic Volume	Best Fuel Consumption (gph)	Fuel Consumption (gal/hp/hr)	Engine Specific Fuel Consumption (lb/hp/hr)	Oil Ratio	Engine Dry Weight (lb)	Engine Specific Weight (hp/lb)	Engine Length (inches)	Engine Width with Plugs (inches)
0-15-1 Sand Cast #6212 Rectangular Port	402.3 (2.79)	61.8	0.43	4.25	2.00	6.25 @ 3800	8.6	0.40	1.60	0.26	1.30	8 to 1	25.5	0.25	16.5	19.5
0-15-1 Sand Cast H-6212 Round Port	402.3 (2.79)	61.8	0.43	4.25	2.00	6.6 @ 3800	9.1	0.43	1.60	0.24	1.40	8 to 1	25.5	0.26	16.5	19.5

0-15-3 Die Cast Rectangular Port	368.4 (2.56)	46	0.32	4.375	2.06	8.0 @ 3800	11.1	0.58	1.40	0.18	1.08	6 to 1	19.3	0.41	12.0	19.875
0-15-3 Die Cast Round Port	368.4 (2.56)	46	0.32	4.375	2.06	8.0 @ 3800	11.1	0.58	1.40	0.18	1.08	6 to 1	19.3	0.41	12.0	19.875

Kiekhaefer 0-45-1	614.4 (4.27)	30.7	0.20	5.0	1.82	20 @ 3650 (22 @ 4000)	28.8 (28.9)	0.52 (0.57)	3.20	0.15	0.90	6 to 1	34.5	0.64	16.375	24.0
Righter 0-45-1	?	?	?	5.0	1.82	20 @ 3650 (22 @ 4000)	28.8 (28.9)	0.52 (0.57)	3.20	0.15	0.90	6 to 1	34.5	0.64	16.375	24.0

0-45-35	687.2 (4.77)	9.8	0.14	5.0	1.82	35 @ 4250	43.3	0.95	5	0.14	0.88	6 to 1	35.0	1	14.625	23.312

References

1946 National Air Races, Cleveland, Ohio. Periscope Films. https://www.youtube.com/watch?v=m5jgGxLoxTE
Botzum, Richard A. Fifty Years of Target Drone Aircraft . Northrop Ventura Division, 1985.
Dunkin, James E. Dennymites, Drones, and More. Dugout Publications, 2008.
Engine Manual Righter 2-GS-17 Series 41 and 42. WRA 7228 Fort Monroe 2-3-43-1000. 3-Feb-43.
Handbook of Instructions with Parts Catalog for Radio Controlled Airplane Target AAF Type OQ-14 Naval Model TDD-3. Technical Order 28-10C-4. 20-May-45.
Operation and Maintenance O-15-1 Engine. Technical Order 02-80AA. 10-Nov-42.
Operation and Maintenance O-45-35 Engine with Parts List. AN-28-10C-9. Undated, likley 1945/1946.
Operation and Maintenance Instructions OQ-2A Airplane Target and Catapult. Technical Order 11-55AA. 1-May-43
OQ-3 Handbook of Instructions with Parts. AN-28-10C-2. 25-Sep-44.
OQ-3 Operation, Service, Overhaul, and Parts. AN-28-10C-2. 30-Jun-45.
OQ-3 Operation, Service, Overhaul, and Parts. Technical Order 28-10C-4 REVISION. 6-Mar-46
Parts Catalog OQ-2A Radioplane. Technical Order 02-80AA-4. 20-Feb-43.
Parts Catalog OQ-2A Radioplane. Technical Order 11-55AA-4. 25-Feb-43.
Righter 2-GS-17 Engine Instructions. Righter Manufacturing Corporation, Burbank, CA. Undated.
Walter H. Righter and Radioplane Website. http://www.ctie.monash.edu.au/hargrave/denny.html

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