Question for Paul McBride, the General Aviation News engines expert: My grandfather, Russell Leuck, worked at Avco Lycoming Engines in 1943. I found a picture of him with a group of men with the XR-7755-3 (that’s how it’s labeled). My grandfather is pictured bottom row, third from right.
He was a self-taught mechanic and I never heard the full story of his role at Avco.
I was wondering if you would possibly have any thoughts in regards to how he would have been helping with this project?
Joy Hobbs
Answer from Paul, who retired after almost 40 years with Lycoming: Joy, thank you so much for your letter and picture from the past at Lycoming.
From looking at the photograph you sent, my best guess is that those in the picture are the engineers and the mechanics who actually ran the XR-7755 engine in the test stands.
I recognize some of the faces of those in this picture and, as a matter of fact, I had the privilege of actually working with some of these men during my years at Lycoming.
Again, it was so nice of you to write and send this information to me — this is what makes our lives so interesting.
A bit of history
The Lycoming XR-7755-3 is the largest, most powerful reciprocating aircraft engine in the world, with 36 cylinders and a power output of 5,000 horsepower.
During World War II, the U.S. Army Air Forces requested an engine with high takeoff power and low fuel consumption for a yet-to-be designed long-range bomber and transport. Lycoming began designing the engine in early 1944 and it was ready for testing by mid-1946. It featured nine dual-lobe overhead camshafts, which shifted axially for takeoff and cruising efficiency, and a two-speed, geared, dual-rotation propeller drive.
Lycoming built two XR-7755-3 prototypes. The company and the Army successfully tested them, but neither engine ever flew in an airframe.
The reliability of new gas turbine engines introduced after World War II made the XR-7755-3 obsolete before it could be fully developed.
The sole surviving engine is on display at the National Air and Space Museum’s Steven F. Udvar-Hazy Center in Chantilly, Virginia.
My father James B. Taylor was a tool and die man and worked on this engine. He always said that rumor was it was destined to be used on Hugh’s’ flying boat, but never made it in time. I can’t tell you any tech stuff, however he said that they were trying to develop a supercharger for it but the vacuum from the engine at high revaluations would be crack the blades on the supercharger. He said that the tolerances on the engine from front to back were extremely critical and that just small particles of grease between the cylinders would through the tolerances off.
For cid calculation “square the bore x stroke x .7854 x number cylinders”.
How’d you do?
That weird looking Lycoming was orig. designed as ME501/504. Somebody traded prints. Check it out!
Denny Werk
Formerly: Continental Motors (TTP)
Some of you may be engineers, designers or draughtsmen. I salute you.
Alas very few (er none) can write English (Her Majesty the late Queen Elizabeth II ‘s English.
Thank goodness for the barrier to contamination – The Atlantic Ocean. Pip! Pip!
If only. We are contaminated by instant communication and a cultural variation of Stockholm syndrome. Our youth have been denied the true cultures transference via the long march through the institutions. Europeans are now reduced to the same intellectual and innovation level, or lower, as the US.
Headline is misleading. Biggest AERO engine perhaps but industrial and marine piston engines are very often way way bigger
Kinda’ve a silly title. The largest piston engine(s) in the world are those built by the Engineer’s working for Wartsila – Sulzer in Finland and MAN B&W in Germany – the huge crosshead marine diesel/duaI fuel engines used primarily in huge marine vessels – containerships, tankers etc.
I was under the belief that the largest piston engine’s that were ever made belong to the external combination (steam engine) group of engines and they are static engines at leeuwarden and harlemleer in Holland and were built by John Harvey and Co, Hayle, Cornwall!
They have 12′ diameter cylinders!
Just google The World’s Largest Diesel Engine.
Your average mechanic uses a half-tonne chain block to take an engine out of a car.
A Marine Engineer used a 5 tonne crane to take a piston out of a large engine.
I have center punches and drifts I made from injector components from ships engines , the heaviest crank shaft we lifted out was 160 Tons
There is a bigger similar engine, the Zvezda M504. It is a 56 cylinder diesel engine with 6370 hp. A few of them have modified to run on methanol.
Timeline – You mention the engine was ready for testing by mid-1946. By that time GE had already developed their second jet engine, the first a Whittle design that was tested in the bombay of a B-24 with a tail pipe that went all the way out through the tail gunner’s location. Flight testing was done in Brownsville TX and the 24 was flown by PAA crews. PAA did all the overhauls on the radials for the Army and that became their first test facility. My dad was one of the pilots. That was about 1944 – 1955. I may have the dates in my dad’s log books, not sure. GE’s second engine the first axial flow was housed in a B-29 bomb bay and actually lowered out into the slip stream to do the operational tests at altitude. The flying test lab was moved to Schenectady, NY (the home of GE) in about 1945 or very early 1946.
It’s a very interesting concept, though I don’t know how practical. I’m guessing it’s very high demand: weight, fuel, oil/coolant, and maintenance. Mostly, it would have been too late to make a difference in WW2. This setup, driving two shafts through middle of same engine may of been very useful later in developing jet engines.
“Bubba’s tabaccy, shoot’in irons and auto parts – how can we help you?”
“Hi, I need a head gasket for a Wärtsilä RT-flex96C, the 14 cylinder model, 107,389 horsepower, you got one?”
“Lemme go look” (Banjo music on hold.)
“Nope, but we do have two rebuilt long blocks in stock, any color preference?”
I’ll be danged – I have a what looks like Look or Life magazine open to a picture of that engine hanging on my office wall. The brochure says it has 3000HP…
As piston engines go, it’s just a tiddler compared to giant 2 stroke marine diesels. So NOT the biggest piston engine by a long shot.
This engine was liquid cooled, and was supercharged at a 6:1 ratio.
Piston engines paved way for gas turbine engines, truely automotives called mother of aviation, salute to Engineers and mechanics who worked hard for the development as per the requirements with limited resources.
The title is poor: “The men who built the largest piston engine in the world.”
How much larger is it than a super-tanker engine? This aero engine could probably fit inside the swept volume of a super-tanker engine.
This might have been the largest AIRCRAFT piston engine, but it is hardly close to being a really big piston engine. For that you have to look at marine diesel engines. Specifically, the Wärtsilä RT-flex96C, which has 14 cylinders, produces 107,389 Horsepower, and more than 7,000,000 Newton Meters (5.2 Million ft-lb) of torque. And it was actually built and installed in the Emma Maersk, the world’s largest container ship when it was launched in 2006 as the world’s largest container ship.
While it’s listed as the “largest” ever built, what was the displacement in cubic inches ??
I read the story thru 3 times and did not find any mention of actual engine size, or it’s static weight.
It’s cubic inch displacement was 7755, in keeping with traditional recip engine model naming.
Did it have sleeve valves like the Bristol Centaurus?
This engine is rated at more HP than current railroad locomotive engines.!
It would be interesting to see what propeller could handle 5,000 HP, and the engine mounts to handle the torque.??
Appears the rows aren’t staggered for air cooling.
The description mentions a two speed dual-rotation prop drive, so I would suspect that it would spin two contra-rotating propellers like the big four engine Russian propeller-driven bombers that use turbine engines.
The engine was designed for dual, contra-rotating propellers.
Many marine engines are considerably larger piston engines. And while this engine was built for aircraft use it was never fitted to an aircraft so therefore it is not an aircraft engine, it is however a masterpiece of aeronautical engineering design and manufacture.
What amazing engineering for the times without are computers and engineers of today !!! I remember using a slide rulers 📏 🤣
SLIDE RILES. !!!!!!!,. MY dad used that for ACCURATE calculations —- teach didn’t like that, called it cheating!
Praise the Lord
My husband had those pictures in a brochure
Very unusual configuration, not a typical corn cob, and appears to be water cooled. No mention of it being turbo or super charged?
That’s probably a given.
Aviation engine, not “In the world”
They must have used some form of forced induction to assist in the 5k hp mark, won’t be surprised to see water methanol injection or nitrous oxide using 100/130 or better?