enginehistory.org

[avasko]

What was the Most Important development in Piston Aero Engine?

To start, let's exclude Optto for inventing the concept at least
I can think of many significant improvements made in pison aero engines. You might think of sodium salts inside exhaust valves. or maybe silver-plated lead bearings. Maybe Wright's power recovery turbines (PRT's) or maybe forged cyli heads. How about forged cylinder heads or coming up the mix of glycol and water for cooling or ADI for higher power. And then there's sleeved valves. Although I have two choices in mind, it will be interesting to first see what other gear-heads think.

[kmccutcheon]

Three suggestions:
1) One-piece master rod;
2) Superchargers
3) Tetraethly lead
_________________
Kimble D. McCutcheon

[rwahlgren]

Is this question just for large airline, transport type radial engines?
Not in any particular order of importance.
1 What came to mind first is the low tension ignition system.
2 Turbo chargers.
3 Fully machined cooling fins.
4 bifilar damper.
5 Quality spark plugs.
6 Pressure injection carburetors.
7 Special steel alloys

[sithomas]

In addition to the good suggestions above, I would add
a) Reduction gear, particularly the Farman type
b) main bearings with indium
c) dual plug cylinders
d) oil improvements over time
e) dampers probably deserve a second mention. Without them, the max continuous rpm of radials would have been around 1900. Furthermore the multi-row radials would be more difficult to balance even at that speed.

[avasko]

I guess I think of the big, round engines most as in my career I never came in contact with anything smaller than an R-985 in a Twin Beech. However the developments on the big ones did filter down to the HO community. Liquid cooled engines became pretty much exitinct when the P-51 and F-82 were retired.
I think that there is no doubt that the muse of lead in the fuel gave the single largest jump in power. You can see it now in the down rating of the big engines on 100LL. What they will do when even that is withdrawn is anyones guess.
There are, I think three important items not mentioned.
1. Higher revs possible only by items already listed.
2. Cowlin and cowl flaps. Look at the small air inlet on the CV-440 for a great example.
3. Cylinder baffling. Try to imagine a Wasp Major without cylinder baffles

[rwahlgren]

I had just mentioned ADI, but looks like it is posted above.

[avasko]

Most contributors seem to agree that improvements in AVGAS is a major contributor to increases in power.
If you want to dig deep into the histort of AVGAS, the website listed below has more information on EVERYTHING related to it. Covers all the maqjor countries including Germany, Romania and Japan. Specic info on major engines and boost in power with higher grade fuel and report on aircraft showing the ionrease infighter performance due to the higher power.
Some historical tibits too. Wright 1903 Flyer engine ran on 32-octane fuel. They have the exact spect/composition on viintage 1910 fuel fgound when they found drums of fuel preserved from the tragic Scott Antarctic Expedition. Stuff on German and Japenese very interesting
historyofavgas.com
HISTORY OF AVGAS - COMPOSITION & MANUFACTURE
History of aviation gasoline 1903-2003
A history of the chemical composition and manufacturing refinery processes of aviation gasoline (Avgas) from 1903 to 2003. A retrospective review of the chemical composition of Aviation Gasoline (Avgas) used in Australia from 1903 to 2003. The review has been done using modern analytical laboratory techniques, assessment of the refining process or data from published literature. Because Australia imported Avgas, the review also includes overseas production methods used and the chemical composition during this period.
The history of Aviation gasoline covers Australia, USA, UK, Russia, Japan, Germany, Italy, Rumania, Middle East, Caribbean West Indies, and East Indies. It also covers World War I, the interwar years, World War II, Korean War, Vietnam War and First Iraq War. It includes a timeline of world events including aviation and world aviation speed records to place the era in context.
It contains 41 chapters each dealing with significant aspects of aviation gasoline. The information has been amassed over 40+ years and has been an enticing journey which may explain the quest to find the composition of aviation gasoline ? Now almost the ?Forgotten Aviation Fuel?.
I hope these efforts have captured the information for others to use before it is lost to antiquity.
As a PS, try this one, Grade 150 fuel was widely adopted in European operation snd gave a sustancial inreases over the 100/130 grade. You can lose yourself lookingat the Source References. In there was references to Grade160 which is new to me.
wwiiaircraftperformance.org/150grade/150-grade-fuel.html
100/150 GRADE FUEL
Initial Testing and Proposals

[mksmith]

I would venture to say dynamic counterweights as they allowed much higher power engines to become practical.
_________________
Mike Smith

[avasko]

A good item to add to the list. I am sure the Liberty engines of WW-1 could have used them. There is an article on-line on AEHS covering the Liberty's vibration problems. But there were plenty of others too.
As a techie, I changed engines, fixed the on wing, ran them (all were airliners) but if I saw a dynamic damper, it was during a cylinder change and not much of a view. In A&P school, I did tear down a B series R-2800 but have no memory of actually noticing anything significant about the dampers and crankshaft (again, another AEHS article covers the problems P&W had with different orders of vibration).