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| Like big engines? Here's one for ya. (Page 1/2) |
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blackrams
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NOV 07, 10:45 AM
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Lycoming XR-7755, swap this into a Fiero and I'll be very impressed. 
https://en.wikipedia.org/wiki/Lycoming_XR-7755
The Lycoming XR-7755 was the largest piston aircraft engine ever built in the United States,[Note 1] with 36 cylinders totaling about 7,750 in³ (127 L) of displacement and a power output of 5,000 horsepower (3,700 kilowatts). It was originally intended to be used in the "European bomber" that eventually emerged as the Convair B-36. Only two examples were built before the project was terminated in 1946.
Design
The resulting design used nine banks of four cylinders each, arranged around a central crankshaft with each cylinder bank at a 40° angle to each adjacent bank, to form a four-row radial engine. Unlike most multi-row radials, which "spiral" the cylinders to allow cooling air to reach them, the R-7755 was water-cooled, and so each of the cylinder heads in a cylinder bank were in-line within a cooling jacket.
Each cylinder bank had a single overhead cam actuating the poppet valves. The camshaft included two sets of cams, one for full takeoff power, and another for economical cruise. The pilot could select between the two settings, which would shift the camshaft along its axis to bring the other set of cams over the valve stems. The design mounted some of the accessories on the "front side" of the camshafts, namely two magnetos and four distributors. The seventh camshaft was not used in this fashion, its location on the front of the engine was used to feed oil to the propeller reduction gearing.
The original XR-7755-1 design drove a single propeller, but even on the largest aircraft the propeller needed to absorb the power would have been ridiculously large. This led to a minor redesign that produced the XR-7755-3, using a new propeller gearing system driving a set of coaxial shafts to power a set of contra-rotating propellers. The propeller reduction gearing also had two speed settings to allow for a greater range of operating power than adjustable props alone could deliver. Another minor modification resulted in the XR-7755-5, the only change being the replacement of carburetors with a new fuel injection system.
General characteristics
Type: 36-cylinder turbosupercharged liquid-cooled "star" (9 banks at 40° angles, 4 cylinders in each bank) aircraft piston engine
Bore: 6.375 in (161.9 mm)
Stroke: 6.75 in (171 mm)
Displacement: 7,756.3 cu in (127.103 l)
Length: 121.35 in (3,082 mm)
Diameter: 61 in (1,500 mm)
Width: 60.5 in (1,540 mm)
Height: 61 in (1,500 mm)
Dry weight: 6,050 lb (2,740 kg)
Way more information available at the provided link.
Rams
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williegoat
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NOV 07, 11:05 AM
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That is certainly unique. I had never heard of it before.
I have always been a big fan of the R-4360.
from wikipedia:
| quote | | Each cylinder bank had a single overhead cam actuating the poppet valves. The camshaft included two sets of cams, one for full takeoff power, and another for economical cruise. The pilot could select between the two settings, which would shift the camshaft along its axis to bring the other set of cams over the valve stems. The design mounted some of the accessories on the "front side" of the camshafts, namely two magnetos and four distributors. The seventh camshaft was not used in this fashion, its location on the front of the engine was used to feed oil to the propeller reduction gearing. |
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[This message has been edited by williegoat (edited 11-07-2020).]
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MidEngineManiac
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NOV 07, 11:35 AM
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No Problem !
Build a nice engine stand, bolt it to the roof and air-boat that fiero ! 
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maryjane
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NOV 07, 11:38 AM
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I'm not sure 'aircraft engine' nomenclature is proper since none of the engines were ever installed in a single airplane. The closest they ever came was on a stationary test stand.
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williegoat
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NOV 07, 11:45 AM
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Raydar
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NOV 07, 11:54 AM
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Now that is a thing of beauty.
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theogre
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NOV 07, 11:54 PM
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blackrams
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NOV 08, 12:03 PM
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| quote | | The original XR-7755-1 design drove a single propeller, but even on the largest aircraft the propeller needed to absorb the power would have been ridiculously large. This led to a minor redesign that produced the XR-7755-3, using a new propeller gearing system driving a set of coaxial shafts to power a set of contra-rotating propellers. |
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Having no experience with counter rotating props, I'm interested in the aerodynamic flow as air passes through this blender. Is one prop more effective than the other? Are they the same size and pitch? Just curious. Tried doing a bit of research on it but have so far been unsuccessful.
Edited: To be clear, I do understand counter rotating props on aircraft with multiple engines with single props that turn different directions negating torque forces, I'm a bit confused about twin props on a single engine and how the aerodynamics of the air flow is effected. Compressibility between the two props, first prop compresses and then the second gets the same compressed air. 
Rams[This message has been edited by blackrams (edited 11-08-2020).]
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maryjane
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NOV 08, 12:33 PM
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| quote | Originally posted by blackrams:
Having no experience with counter rotating props, I'm interested in the aerodynamic flow as air passes through this blender. Is one prop more effective than the other? Are they the same size and pitch? Just curious. Tried doing a bit of research on it but have so far been unsuccessful.
Edited: To be clear, I do understand counter rotating props on aircraft with multiple engines with single props that turn different directions negating torque forces, I'm a bit confused about twin props on a single engine and how the aerodynamics of the air flow is effected. Compressibility between the two props, first prop compresses and then the second gets the same compressed air.
Rams
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Nomenclature--nomenclature--nomenclature!
1st of all, when speaking of 1 propeller on the same engine, on a multi engine aircraft, with direction of rotation being opposite to offset torque and wing load, 'counter rotating props' is correct nomenclature.
BUT, when speaking of 2 propellers on the same engine or gearbox, with each propeller rotating opposite of each other, the correct terminology is Contra-rotating.
"On most twin or multi-engine propeller driven aircraft, the propellers all turn in the same direction, usually clockwise when viewed from the rear of the aircraft. In a counter-rotating installation, the propellers on the right wing turn counter-clockwise while those on the left wing turn clockwise. The principle advantage of counter-rotation is to balance propeller torque effects thus eliminating any problems associated with a Critical Engine.
Counter-rotating should not be confused with contra-rotating which refers to two propellers on the same engine which spin in opposite directions."
In vertical flight capable aircraft, two sets of rotors on the same gearbox is correctly referred to as a Coaxial arrangement
https://www.sciencedirect.c...a-rotating-propeller[This message has been edited by maryjane (edited 11-08-2020).]
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Raydar
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NOV 08, 12:51 PM
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| quote | Originally posted by maryjane:
...
In vertical flight capable aircraft, two sets of rotors on the same gearbox is correctly referred to as a Coaxial arrangement
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I was thinking that I had seen some prototype helicopters with this sort of arrangement.
Ron... here's something that could make helicopter reliability even less certain. 
(There were even pics of some Sikorskys with this setup.)
 [This message has been edited by Raydar (edited 11-08-2020).]
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