Radial Vs. Piston
#11
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Joined APC: May 2008
Posts: 86
Yeah there have been some interesting engines along the way. during WW2 the lufwaffe had a bomber had engines that were actually 2 12 cylinder engines drivinga single gear box, 4 engines to drive 2 props. I think I saw an engine in a museum that was 3 banks of 8 big failure though. I have a book on the devlopment of different airplanes. There is a picture in there of a B-29 With ligued cooled engines engines built by Westinghouse By the way the cb16had some complex stuff it had a 2 stage supercharger and that engine was used on the DC6 it had a drive for a compressor to pressureise the cabin
#12
Excellent thread. The R-3350 Turbo Compound is a remarkably complex engine. I imagine that the significant advantage to the early jets was the ease of maintainence vs. the large Radials of the time. For those interested and in KC for any reason, go to the Airline History Museum - they are the Save a Connie folks. They have some 3350's out for examination, including a neat cut-away. The radials still have some utility - Air Tractor still manufactures an airplane that has a R1340 P&W (600hp+ I believe). One good person to get on this thread would be T-cart, who made his living with Ag Cats and Air Tractors - he would provide valuable insight into living with a radial on a day-to-day basis.
#13
#14
Those were technically called rotary engines (nothing to do with the mazda wankel rotary). The purpose was to use the engine itself as a flywheel to dampen vibrations...although the flywheel effect also provided plenty of precesion for the entire airplane when turning or pitching
#15
Those were technically called rotary engines (nothing to do with the mazda wankel rotary). The purpose was to use the engine itself as a flywheel to dampen vibrations...although the flywheel effect also provided plenty of precesion for the entire airplane when turning or pitching
#16
WWII bomber engines were some of the most complex engines ever manufactured including jet engines in the list. The part counts as well as tolerances were very high while reliability was a bit troublesome. The old saying goes if it's a radial and not leaking oil, something is wrong. This and the weight accounts for the reason they are no longer preferred over small turbines in large-prop installations. If you have the tooling required to produce the part tolerances large radials require you might as well make turbines, which is what the Germans started doing about this time. The reason large radials persisted to the end of the War is that turbines were not quite ready for battle and the War was too intense to allow their discontinuation.
My favorite is the Pratt Wasp Major with 28 cylinders as a working cutaway display at Southern Museum of Flight in Birmingham, Al but there are quite a few displays around. They were wonders of engineering at the time, and even now attract attention. There is a link lost between the piston and the jet in terms of appeal and advanced pistons were more approachable because they share technology with the earliest internal combustion engines.
Here is a great pdf article explaining how Wasp radials were balanced.
My favorite is the Pratt Wasp Major with 28 cylinders as a working cutaway display at Southern Museum of Flight in Birmingham, Al but there are quite a few displays around. They were wonders of engineering at the time, and even now attract attention. There is a link lost between the piston and the jet in terms of appeal and advanced pistons were more approachable because they share technology with the earliest internal combustion engines.
Here is a great pdf article explaining how Wasp radials were balanced.
Last edited by Cubdriver; 05-26-2008 at 11:24 AM.
#17
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Joined APC: May 2008
Posts: 86
I have loved Lodestars, and any variation of Lodestar for a long time - would love to see any pictures and hear stories about the beast - what a machine! Here is one of my favorite websites: http://homepage.ntlworld.com/m.zoeller/, a page devoted to large Lockheed twins.
#18
Round motors give you a shorter crankshaft which doesn't weigh as much and doesn't require as many bearings. The biggest non radial air cooled engine I can think of is 720 ci, after that you add a radiator and coolant. So the BHP per pound works out better. R2800 was probably the best around, bigger than that got too complex. There was talk of making a turbo-compound 4360 for about 5000 bhp.
#19
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Joined APC: May 2008
Posts: 86
My father said that the R2800 was considered efficent because it put out 1 hp for every pound that it weighed ( up to 2500hp and weighed 2500lbs ) The carb. for that engine weighed 75lbs and I can just about stick my thumb in the jets. It burns about 100gl an hr at cruise. The radial only has 1 set of main bearings per row of cylinders. Radial engines have a master rod that all of the other connecting rods join on to.
#20
Digging in deeper;
Notably, the fuel was mixed and sprayed into the center of the engine through a hollow crankshaft, and then into the cylinders through the piston itself, a single valve on the top of the piston let the mixture in when opened.The valves were counter balanced so that only a small force was needed to open them, and releasing the force closed the valve without any springs. The center of the engine is normally where the oil would be, and the fuel would wash it away. To fix this, the oil was mixed in liberal quantities with the fuel, and the engine spewed smoke due to burning oil. Castor oil was the lubricant of choice, its gum-forming tendency being irrelevant in a total-loss lubrication system. The result is that the engines threw a mist of unburnt fuel and castor oil; the pilot's scarf being used to wipe this from their goggles. Finally, the Gnôme had no throttle or carburetor. Since the fuel was being sprayed into the spinning engine, the motion alone was enough to mix the fuel fairly well.
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