Serious rocket science. I'm a try this on HD/B heads... very cool idea!!!!
Should work pretty well on twin-cam heads(they are gigantic).
Gotta go see the welder with one of my stock sets. Thanks Tom.
I never even considered the possibility of retrofitting that to an existing engine. Now that you have me thinking about it, the mechanics may not be that hard to pull off, especially working with an air cooled head where you don't have water jackets to work around. I think a fast revving, short stroke engine would see the most benefit from this, but any engine should see a nice bump in torque by getting the fuel burned faster. Considering I've always heard of gas engines have efficiency ratings in the 30-35% range, topping 50% is simply astounding.
The biggest challenge I would see to putting this on a HD/Buell would be in managing the fuel requirements of the spark chamber. I could see trying to just fire a tiny injector on the same trigger pulse as the main injector, but then any tuning would require swapping to different sized injectors. I don't know that you could even find off the shelf injectors of the appropriate size. Otherwise you would need to find a way to control 4 fuel injectors. Sounds ambitious to me. If you do it, you must share!
A person, and a design concept: Harry Ricardo (one of my engineering heroes) Stratified charge Engines, for lean burn technology. The Co-generational aspect of using a turbo-powered generator probably gets the biggest boost in system efficiency. The Carnot efficiency limits how much you can get from a direct-expnsion heat engine, but if you can put in a "bottoming cycle" setup to extract power from the exhaust heat, that's where the action is. Combined cycle power plants can have pretty high overall efficiencies, but thermodynamic limits will get you in the end
Skip the "convert mechanical spinning energy into electric power, then back again".
Just add the spinning power through reduction gearing right back into the crank.
The Allison v-1710 ( 1710 Cu. Inch) engine sent the energy recovered by an exhaust turbine back into the engine through the starter drive. With the high RPM of the turbine geared down to appropriate speeds. An engine that originally put out 1000 hp, and 1700 with 150+ Octane equiv. fuel, had more that 3000 with turbo-compounding.
It lacks the storage mode that makes it attractive for the race teams, but for continuous power, hard to beat.
Also hard to make reliable, if your engine was a dog to begin with. the Wright R-3350 brought down more B-29s than enemy fire. That's with regular turbocharging. So "parts recovery turbine" was appropriate for an engine famous for leaking oil and catching on fire.
The 3350 was not a dog, it was just pushed into production too quickly and the engine mounting design of the B-29 just aggravated it. It became reliable enough to power Lockheed Constellation airliners (with turbo-compounding) and not too mention the great Douglas Skyraider. Not as reliable as the R2800, but that was as good as a big radial got. Which is not that great by modern standards.
Drove my minivan to work today - the "pooper", my two-tone brown '90 Voyager with a factory 2.5 turbo engine. On the way home, the belts started SCREAMING. Pulled off, dug through the van...not a damn thing in there. I use it mainly to get my mountain bike to where I ride in warm weather (it's actually a pretty rare, fully-restored toy car). Tried using a swiss army knife file on the spinning belts to remove glazing, no joy.
Climbed back in for a noisy ride home and my coffee mug was there.
Killed the engine and went to spill some coffee on the belts.
Fired it up...SILENT. Freakin' COFFEE quieted down the screeching belts!!
The initial design work was done by the genius who designed the R-2600. But he was taken off the R-3350 project to work on a troublesome experimental engine project that ended up being canceled. ( Part of the government Hyper engine program. None of them succeeded. )
With him gone, they basically cheaped out on the design, with major changes like running the front cylinder's exhaust out the front of the heads, instead of behind. It's more work to run all the exhaust pipes to the rear. You have to snake them between the rear cylinders, and use heat shields, change the baffles for cooling air flow, etc. But it means the cooling air for the whole engine doesn't first have to go past red hot exhaust pipes.
The English on some models of radial aircraft, ran the exhaust to a collector that they made into the front lip of the cowling. So you are pulling cooling air past a glowing hot rim into the engine... Clever, but dumb.
As the years passed, they kept improving the engine, putting in the features the original designer had drawn, until they eventually were making it the way it was supposed to be in the first place. But that took until mid-to-late 1945. ( they started in 1937 )
Naturally, the R-3350 had cooling problems. You are correct that the cowl flap & cooling design of the B-29 was a major contributor. Open the flaps to cool the engine, and the increased drag slowed the plane down, so you needed more throttle to keep up with the formation, making more heat..... And in the Rush to make war time production, many things got made that were flawed, or not developed enough, under orders to Make More and the heck with fixing the problems.
The Sherman Tank, which in it's Firefly Brit version with a bigger gun, could go toe to toe with a Panzer, just couldn't with the stock American spec gun. But they wouldn't slow production to make it better. A lot of guys died during the war as the result of that kind of decision.
back to the R-3350.
Curtis Wright was a top heavy organization, run by bean counters. ( sound familiar? ) They put the main R-3350 factory close to NYC where they had to compete for labor with the ship building industry. And weren't paying well either. When they had a 100% failure rate on the early models in the reduction gearing, it turned out the gang drill used in production was making bad parts and the saga continued with the company basically not caring about putting out crap as long as they got paid. ( The opinion of many people, then and now )
Dodge built a plant to make the R-3350 to meet demand for the B-29, and their engines were much more reliable, just because of workmanship and Quality Control.
Both the B-29 and the R-3350 were pushed into service before they were ready. Certainly the two together had a synergistic bad mojo issue. Both had serious problems that were not solved until after the war, a bit late.
Yeah, the Skyraider, and a generation of prop transport planes, successfully used the R-3350. But that was post war, and the failure rate was still higher than would be considered normal.
Of course, it's direct competition, the P&W R-4360, was an even more complex beast, and also had a higher failure rate than airlines wanted.
The Real Difference between the B-29 & DC-7/Constellation service, according to some, is because the Airlines had very experienced engineers who babied the engines, and better cooling systems.
I stand by the Dog comment in WW2 service, A LOT of B-29s were lost because of engine fires, but the engine did become successful later.
Thanks for the input, Aesquire. When I comment on aircraft lore, I'm usually too lazy to research, so I'm depending on the part of my brain dedicated to useless information that I started filling up when I was a small boy. I don't have any trouble believing that CW's quality control was part of the issue. I think I remember that the Brewster Buffalo (yuck) was so badly put together that there was a Congressional investigation. Agree about the cooling flaps, too. I think the change of strategy to concentrate on low-level fire bombing helped with that as much as anything. OTOH, for a brilliant example of how to package an air-cooled engine right, see the FW-190. Mechanical art. Your question about designing something with room to grow kind of highlights the overall point: those large engines were pushing the very limit of what piston aircraft engine technology could deliver. I'm not sure we could do much better now even with computerized machines and electronic engine controls.
The warbird guys are often using the later Transport plane versions of the engines for reliability and more power. Often just certain parts.
The famous R-2800 "C" model used forged heads, and those close spaced cooling fins were cut by gang saws following templates. The improved cooling of the forged heads allowed a lot more power. So you see "wrong" heads on a lot of war birds and most racers.
Curtis Wright was one of those places where they had some bright guys but then they left or lost positions, and the glory days stalled out.
The engine division had a bunch of the smart ones leave & go form Pratt & Whitney. Don Berlin designed the P-36, then P-40, but left because the bean counters wouldn't let him fix the problems, and work on the the next generation airplane.
The American fighters can be divided up to before the battle of Britain & after. ( summer 1940 ) The battle taught that we needed self sealing fuel tanks and armor around the oil tank and pilot. The Pre-war airplanes, P-38, 39, 40, all suffered from the extra weight of armor added after original design. ( the P-38 less, but it had it's own issues )
The Original P-47 was to be a small, heavily armed fighter using the V-12 Allison. The most compact air frame around the most powerful, streamlined engine. After the Battle of Britain, Republic figured out it would be no better than the P-40, so why bother? And got the Air Corps to modify the contract to the P-47-B, using the new R-2800 engine and a full intercooled turbocharger setup. Why was the P-47 so big? Under the pilot, and filling most of the back of the plane were BIG pipes, some the size of your body, pumping air, for the intake, intercooler, and pressurized air back through the intecoolers, forward to the engine, into the engines's gear driven supercharger... The turbo lived on the belly of the plane, and the cooling air for the intercoolers exited doors often in the American Star & Bars logo. Yeah, 2 intercoolers. And a bigger turbo than in a B-17. ( Bigger engine )
I would have sworn, before today, that only one photo of the Xp-47 existed, and I could not find it on the net. After a half hour of stubborn searching, I found... a different photo! One I'd never seen before.
I don't think any fighter airplanes, or bombers, went into service that had not been ordered before Dec. 1941. Even the P-61 Black Widow had been ordered long before first flight.
The F6F Hellcat was only ordered in the summer of 1941, and was in combat by 1943, making it probably the late comer in American fighters, and it shows, with one the highest kill ratios.
Oddly, the airplane with the highest kill ratio in WW2 in American service was not the Mustang, or the Lightning. It was the late war version of the F4F Wildcat, the FM-2 made by GM, that was used on the little "jeep" carriers in both theaters, and most famously in the Battle of the Atlantic, against U-boats. When the Jeep carriers were used in the invasion of France etc. The Wildcats scored 22-1 kill against Me-109s & FW-190s...But no one noticed until the 21st century when they were digging through the statistics of the war. Completely unexpected.
The Buffalo was a total dog in U.S. service. The landing gear was weak, and when armor and self sealing tanks were added, the extra weight didn't do it any good. It didn't do well in the Pacific, with One kill against the Zero, ( and that pilot was shot down right after that by a swarm of Zeros ) But... In Finnish service, the earlier, lighter model, fared well against the Russians and Germans. ( then again, Finnish snipers and troops did really well against everyone, so skill and cojones count )