View Full Version : Recip question

Lu Zuckerman
9th Nov 2002, 00:24
Since everyone on this thread is testing everyone else on their collective aviation knowledge I thought I would add my own two cents (Canadian).

What is the largest radial recip ever designed for use in an aircraft? They constructed several but the design never entered production.


big pistons forever
9th Nov 2002, 01:03
I think it was some marvel of British complexity, A post war W 24 cyl monster, made by Bristol ?

9th Nov 2002, 02:01
Lycoming or Continental - I forget which - came out with a 36 cylinder - 5000+ cu in monster back in the early fifties. I think it made it as far as the test bed. I've got a bit of info on it around here somewhere, in a book that Pratt and Whitney published on their 25th anniversary. Gotta see if I can find it.

9th Nov 2002, 02:53
Hmmm, 'twas Lycoming I think, but can't remember the displacement.
The Hiller museum in San Carlos California has a very nice cut-away rotating display of the P&W R4360...LOTS of moving parts.

From the guys that flew the Stratocruiser...used "nearly" as much oil as fuel...:rolleyes: :rolleyes:

9th Nov 2002, 08:15
I suspect that it was the Lycoming XR-7755-3.
This 5,000 hp engine was intended to power the Convair B-36.
NASM (http://www.enginehistory.org/nasm.htm)

9th Nov 2002, 18:34
5000 hp ? Pah, a mere stripling. :p

R-4360-20 7000hp, 7800 with injection.

Lu Zuckerman
9th Nov 2002, 19:18
To: Paper Tiger

5000 hp ? Pah, a mere stripling. 4360-20 7000 HP, 7200 with injection

Here are the only 4360 models listed on the R-4360 web site along with their respective power output. There is no –20 listed. I checked the air race mods for this engine and although it was used on several different aircraft in the air races there was no listing of a 7000 HP engine. Where did you get your info?

R-4360-4A: 3,000 hp (2236 kW) R-4360-4W: 3,000 hp (2236 kW) R-4360-35: 3,500 hp (2610 kW) R-4360-41: 3,500 hp (2610 kW) R-4360-59B: 3,500 hp (2610 kW) R-4360-63A: 3,800 hp (2834 kW)

I know that injection increases horsepower by increasing the volumetric efficiency of the engine but doubling the designed horsepower is a bit of a stretch. However I have been wrong before.

Although it was stated above that the XR-7755 was built to power the B-36 it was my understanding that it was built for a single seat fighter that resembled a P-47 on steroids. The engine was mounted behind the pilot much like the Aircobra. The aircraft was to be built in the Fisher Body Bomber plant in Cleveland, Ohio. On one test flight (before the cancellation of the program) the aircraft augured in and pushed the pilot or what remained of the pilot 30 some feet into the ground.


9th Nov 2002, 21:00
Oh dear :o On this C-119 page (http://www.geocities.com/pentagon/quarters/4980/boxcar.html) it says The C-119 had two R-4360-20 Pratt & Whitney engines. Each engine had 28 cylinders in four rows and seven banks, 56 spark plugs, 7 Magnetos, 4 seperate circular rotating cams, and an internal super-charger. At take off settings, together they developed 7000 HP (7800 water injected) delivered to, two Hamilton Standard, four paddle blade, 14 foot props. The Pratt & Whitney R-4360-20 was the most powerful internal combustion reciprocating engine ever built. Unfortunately while my eyes boggled at the 7000 hp figure, they missed the rather important word 'together !
Unusual way of quoting hp, but no excuse :rolleyes:

The dash 20 appears to be the military equivalent of the -CB2.

I shall spend the next 30 minutes in the penalty box.

10th Nov 2002, 01:43
PaperTiger is quite correct when he quotes the R-4360-20 being installed in the C-119.
Also fitted were -20WA's in the C-119C.

For Lu, there is a PDF file in the AHES site under P & W and search through R-4360, which lists all the various dash# and applications for R-4360

The Fisher a/c mentioned, the XP-75, utilised the so-called double Allison-V-3420-19 installed a la P39, P-63 behind the pilot and driving the propellor via a long extension shaft.
8 XP-75's ff 30-9-43, plus 5 P-75A's built.

The P-47 on steroids was the XP-72 fitted with an R-4360-13, 2 of which were built, ff 2-2-44.

Quotations from :United States Military Aircraft since 1909, by Gordon Swanborough & Peter M Bowers. Published by Putnam.
New Edition 1989
ISBN 0 85177 816 X

To clarify the Lycoming XR-7755-3.
This is a size in cubic inches, and not a horse power figure.

Excellent references to be found at :
AHES (http://www.enginehistory.org/engines.htm)


10th Nov 2002, 09:06
Some more figures re: the Lycoming XR-7755.
This 36 cylinder engine was destined to be the largest reciprocating engine ever built. The displacement was 7,755 cubic inches. When compared to Lycoming's largest production engine in production today which displaces 720 cubic inches, it was more than 10 times larger!

This huge engine was 10 feet long, 5 feet in diameter and weighed 6,050 pounds. It produced 5,000 HP at 2,600 RPM, and the target was 7,000. It used 580 GPH of av gas at the 5,000 HP rating.

There were nine overhead camshafts which could be shifted axially for METO power in one position and cruise at the other. Two great shafts emerged for coaxial propellers, and there was a two speed gear-change box between the crankshaft and the propeller shafts.

Development of the XR-7755 began at Lycoming in Williamsport in the summer of 1943. With the end of World War II in 1945, the military no longer had a need for an engine of this size, and development of the XR-7755 stopped at the prototype stage.

During those years, Lycoming put together a team, under the leadership of VP Engineering Clarence Wiegman, to develop this super-size engine.

The engine now resides at Silver Hill of the Smithsonian Institute.

(Special thanks to the editors of Lycorama newsletter)


Lycoming XR-7755
Date: 1943
Displacement: 7,755 cu. in. (127 liters)
Cylinders: 36
Bore and Stroke:: 6.4 in. (162 mm) x 6.8 in. (171 mm)
Weight: 6,050 lbs. (2,744 kg)
Horsepower: 5,000 hp (3,728 kw) at 44 in Hg.MP.
RPM: 2,600
4-cycle, 4 row radial, liquid cooled, 2 speed geared dual
rotation propeller drive with turbo-supercharger.

© The Aviation History On-Line Museum. 2000 All rights reserved.


10th Nov 2002, 10:07
How about the Napier Nomad. The Nomad was one the most advanced turbo compound engines. A liquid cooled opposed diesel engine coupled to an axial flow turbine. Thermal efficiency as high as 42%.

Type: Horizontal opposed compression ignition 2-stroke engine
Cylinders: flat 12 arrangement
Bore and stroke: 6 x 7.375 in
Swept volume: 2502 cu in ( 41.1 litre)
Compressions ratio: 3.5:1
Boost pressure: 89 psi
Revolution: 2050 crusing
HP range: 3030 cruising, 4100 take-off
Specific fuel consumption (lb/hp/h): 0.33
Weight, lbs: 3580

Not the heaviest but quite bulky and probably the most efficient aero-engine built to date. Unfortunately it was hideously complex as only a Napier engine could be :D:D

There's one in East Fortune Museum if your up that way

10th Nov 2002, 10:45
I believe the record holder was some Italian monster that never made it into an airframe. Unfortunately the book with the information is not accessable at the moment but I'll look into it.

11th Nov 2002, 22:52
Anyone know what the company spokesman said when it was realised that the jet turbine engine had been invented and these massively complicated piston engines were suddenly obsolete?

I think it was probably "******!":(


Lu Zuckerman
11th Nov 2002, 23:19
To: Shy Torque

Anyone know what the company spokesman said when it was realised that the jet turbine engine had been invented and these massively complicated piston engines were suddenly obsolete?

Having worked in the aerospace industry since 1955 I would think what went through the minds of the engineers at the recip. manufacturers was,”Job Security”. Most of the recip. manufacturers shifted gears and started to build jets.