P-38 engines left/righ

[Staga]

Was the change in propeller rotation in left and right engine made by reduction gears or by modifying the whole engine running "backwards" like some websites suggests ?
Gotta admit latter sounds a bit strange...

[mora]

It runs backwards. Yes it sounds strange but that's how it was done. That of course creates a little bit of problems in the spare parts department.

[Staga]

Are you sure about that?

When installed in a twin-engine P-38, it was paired with a left-hand drive V-1710-55 engine to counteract the effect of torque. The only difference between the two engines was the direction of propeller-shaft rotation.

Taken from USAF museum:
http://www.wpafb.af.mil/museum/engines/eng1.htm

[Delirium]

I seem to remember there was some constant annoying engine problems with the #1 or left hand engine on some of the p38s.

This is a good question for Slack, I remember him posting something on it some years ago.

[GtoRA2]

I though for sure it was just a reduction gear change. I can check Vees for Victory tonight on this.

[Angus]

You'd need another crankshaft, but what else? Pistons just go up and down, so do valves, the Crankshaft is the boss of which direction.


Opps  Camshaft.....

Whaddever, need to know better what the english terms are for these parts. Hope you know what I mean though

[justin_g]

Another feature of the V-1710 design was the ability to turn the propeller either clockwise, or counter-clockwise, by simply assembling the engine with the crankshaft turned end-for-end, installing an idler gear in the drive train to the supercharger and accessories, and having a starter turning the proper direction. The ignition wiring and firing order were also arranged to accommodate the direction of rotation.

Thats from an article written by Daniel D. Whitney - Author, Vees For Victory! The Story of the Allison V-1710

[icemaw]

Originally posted by Angus
You'd need another crankshaft, but what else? Pistons just go up and down, so do valves, the Crankshaft is the boss of which direction.


Opps  Camshaft.....

Whaddever, need to know better what the english terms are for these parts. Hope you know what I mean though

 Most any reciprocating engine will run is either direction. You would need a different cam, firing order and starter. Possibly a different crankshaft.

[Wolfala]

I forget which engine it is on the market today, for civilian use atleast - but I believe it was accomplished by some clever use of the magneto. As for the 38 - lord knows.

[Bodhi]

Has not been a problem for us to change any of our Allisons around.

[joeblogs]

Remember, Allison got into the business of liquid cooled aircarft engines by making them for airships...

-blogs

Originally posted by Staga
Was the change in propeller rotation in left and right engine made by reduction gears or by modifying the whole engine running "backwards" like some websites suggests ?
Gotta admit latter sounds a bit strange...

[GScholz]

Well, some engines are designed to operate in only one direction. The DB's for instance had slightly different stroke and compression ratios on the two cylinder banks to help counteract torque, i.e. the pistons were pushing more on the crank from one direction of the inverted-V than the other, thereby creating a counter force to the torque generated at the crank.

[Staga]

Some engines have also a crankshaft moved a bitt offset from the centerline of the cylinder block; the angle between piston and connection rod stays smaller at the firing stroke = there's smaller forces affecting the piston sideways = less friction = less wear.

[Captain Virgil Hilts]

The Allison V1710 uses a crankshaft that may be installed in the block either way. To reverse rotation, you swap the crankshaft end for end, rewire the magnetos for a different firing order, and add an idler gear to the accessory drive. It was not necessary to change the camshafts. This is good since the Allison is a double overhead cam engine with four valves per cylinder operated by roller rocker arms. Changing cams is a nightmare unless you are highly skilled or intimately familiar with the system. The Allison V1710 was extremely advanced for its time, because Allison started out as a company that was focused on racing and custom engineeering.

It was desireable for the engine to turn backwards in order to create completely opposite torque from the other engine. Remember that the engine is mounted solid to the airframe, so if it ran in the same direction and simply reversed prop rotation, zero net torque would not be possible. Both engines would be exerting the same force on the airframe.

The problems were a result of problems in the early gearboxes which did not operate properly when rotation was reversed.

[MiloMorai]

Originally posted by GScholz
Well, some engines are designed to operate in only one direction. The DB's for instance had slightly different stroke and compression ratios on the two cylinder banks to help counteract torque, i.e. the pistons were pushing more on the crank from one direction of the inverted-V than the other, thereby creating a counter force to the torque generated at the crank.

Never  seen a different stroke stated, though the cr left/right had ~0.2 difference.

Do you have a source for different strokes?