Last updated: 7/19/2018
Big, Old Lycoming Engines
(The XR-7755, XH-2470, etc.)
(and a tribute to my late Dad)
R.J.Ribando, Copyright 1998, 2018 All Rights Reserved
This photo from early April 1929 and taken at the
My father began
working at Lycoming right out of high school in 1926, but left six months after
this photo was taken to begin study toward a B.S. in Mechanical Engineering at
The Lycoming XH-2470 in its test cell. The twelve cylinder
O-1230 was developed by Lycoming during the 1930's using $500,000 of its own
funds. When its output was deemed insufficient, the engine was stacked and
became the H-configured, 24-cylinder engine seen here in about 1940.† The XH-2470 flew in prototype form in the Vultee
XP-54 . The Paul E. Garber Preservation,
Restoration and Storage Facility in
Red Maxwell and Paul Cervinsky taking a break - next to, at 5000 hp., the biggest reciprocating aircraft engine ever made. This maintenance stand (with the steps that Red is perched on removed) could easily be the same one seen in the recent Smithsonian photo below. Red's "Red Baron" headgear is reported to have been a personal fetish - not an OSHA requirement.†
Experimental Engineering (where the engine was tested) staff poses with Lycoming XR-7755 sometime in 1946. Your correspondent's father is seen in the third row in the white shirt and tie, just to the left of the engine.
Row 1: Paul Butters, Phil Walkes, William Jopson, Jim Page, Ruth Moon Bruchlacher, Kay Wertman Metz, Mary Lib Cawkins, Lois Miller Lloyd, Dorothy Riddell, "Emy" Engler
Row 2: Warren Walters, Bill Lorimer, Charlie Bird, "Woody" Carson, Bucky Hessler, Oscar Woolever, Art Moyer, Alemose, Clarence Brooks, Clark, Andy Taylor, William "Red" Rathburn
Row 3: Roy Dockey, Bill Ribando, Charlie Motter, Gus Goyne, Lee Herman
For a group shot of the design team (including Clarence Wiegman, the chief engineer, who lived across the street from our family home) plus extensive specifications, click here.
Lycoming XR-7755 installed in its test cell. Your correspondent remembers how as a kid his father, on a quiet evening, could open a window and tell whether a 4 or 6-cylinder engine for which he was responsible was still running - in the test cells nearly two miles away. I can only imagine what this 36-cylinder behemoth sounded like!
With the cylinders four deep, air cooling was not an option, but providing liquid cooling to all 36 cylinders proved a plumbing challenge. PHOTOS OF THE THEN-NEARLY-COMPLETE X-7 RESTORATION!
Here's what's on the other side of that wall in the previous photo - the dynamometer room. My father is seen between the two units. The 5000 hp. engines were gone by the time I was old enough to go into the plant with my Dad occasionally on a weekend, but you can imagine the impression these dynamometers, which were still there, would make on a 5 or 6 year old kid!
The XR-7755 was being developed to power what
eventually became the Convair B-36 "Peacemaker"
bomber. The B-36 was originally designed for attacks on
The one surviving XR-7755 (of the two built) was recently restored at the old Paul E. Garber Preservation, Restoration and Storage Facility of the Smithsonian Institution in Suitland, MD. The inscription below it read: "Lycoming XR-7755-3 Engine - 1946. At the time this engine was developed, this liquid-cooled radial engine was the most powerful reciprocating aircraft power plant in the world. To achieve a design goal of high takeoff power and low fuel consumption for long range flights, it was equipped with 2-speed contra-rotating propellers and a unique mechanism for adjusting the valve timing and ignition timing while the engine was running. The XR-7755 was never tested in flight. Rating: 5000 hp at 2600 rpm."
At the new Stephen F. Udvar-Hazy
Lycoming old timers report that when they delivered the other engine to the program office at Wright-Patterson AFB, they were directed to "dump it on the ground." That engine is presumed to have been scrapped before making it into the AF museum's engine collection.
†My father seen in test cell control room (probably in the 1950's) and with his slide rule near his right hand - ready for action! (How many calculators last for 70 years?!) To the general aviation community "Powered by Lycoming" means what it does today because of people like my father who designed, built or tested engines "as if you are going to fly it yourself!"
(right)† Centenarians think itís pretty trendy to be "on the 'Net," so here's my mother boarding a Lockheed Constellation for Genoa, Italy in 1954 (she died 60 years later). She was on her way to visit my father, who had been sent from Lycoming to help the Piaggio Company set up testing facilities and procedures for the Lycoming engines they were building under license. You can tell it's a "Connie" and not a "Super Connie" by the round windows.
One of the
"perks" for Lycoming engineers was the possibility of a summer job
for offspring who were in engineering school themselves. During the summer of
1965 I worked with the engineers testing a multi-fuel diesel engine (the other
engines pictured here are "spark ignition" (Otto cycle)) under
development for the U.S. Army's Gama Goat articulated
vehicle. Most of the tests were done in the test cells within the plant, but
occasionally I was allowed to go "on the road" with the technicians
in a prototype vehicle. The tests were conducted on a recently-completed
section of I-80 which was not yet open to the public. We were expressly
forbidden from going off-road, but were still able to get our "jollies."
The exhaust stack on the Gama Goat was ideally located so that while driving to
the Interstate, we could pull up next to a convertible (whose occupants were
probably listening to the Beach Boys) and then, when the light changed, blanket
its occupants in Diesel soot! The Gama Goat went into very limited production.
Its three cylinder engine was noisy, and the vehicle was a challenge to drive.
A few are still in the hands of National Guard units and some serve in
Photos of the XR-7755 Restoration at the Garber Center.†††
Comments? Please e-mail me at: rjr at Virginia dot edu
Berkowitz, Bruce D., "Monster Engines - Why the Roar of the Mighty Recips Was Silenced Forever," Air and Space/Smithsonian, Dec. 1997/January 1998, pp. 80-87.
White, Graham, "Allied Aircraft Piston Engines of World War II - History and Development of Frontline Aircraft Piston Engines Produced by Great Britain and the United States during World War II," Society of Automotive Engineers, Warrendale, PA, pp. 379-382.
Wilkenson, Paul H., "Aircraft Engines of the
World - 1948," Paul H. Wilkenson,
Dick, Ron and Patterson, Dan,
"American Eagles - A History of the
Genevro, George, "Power from the Past: The Largest Aircraft Piston Engine," Custom Planes, Feb. 1999, pp 60-61.
Underwood, Tony, Personal Communication, Dec. 13, 2000.
R., National Air and