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Airfoiling the tail to counter tourque

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#11 Rick65


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Posted 24 October 2017 - 12:02 AM

Is the following correct?

Merlin, crank rotates clockwise, prop counter clockwise when viewed from the front, wants to swing to left on take off when viewed from cockpit

Griffon, crank rotates counter clockwise, prop clockwise when viewed from the front, wants to swing to right on take off when viewed from cockpit


Based on the following


Vintage Wings of Canada Merlin engined Spitfire XVI

“Ease the power in sloooowly. It is not visible to the spectators, but that big propeller will give some remarkable asymmetric forces on the take off roll and, with a max power take-off, you will need full right deflection of both aileron and rudder to keep it straight.”


Regarding the options with spur gears.

Unlike the Mosquito which had both props rotating the same direction, the Hornet had props that rotated in opposite directions.

Both Hornet  Merlin engines rotated the usual direction but one had an additional shaft in the reduction gear to reverse the direction of prop rotation.

#12 GregP


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Posted 24 October 2017 - 05:38 PM

The Merlin prop does rotate counterclockwise when viewed from the front and does require right rudder when taking off or climbing. You are correct about the crankshaft. Her's an animation: https://www.youtube....h?v=CEBA9kWDAyA


The Griffon prorp does rotate the other way, and I would suspect the crankshaft does, too, but don't know for sure as I have never been able to play with a Griffon being rebuilt. But it makes perfect sense as a Griffon was based on the Merlin. It DID use a hollow crankshaft to lubricate the main bearings.


The standard right-turn Allison rotates the same as the Merlin. Just as an aside, when you hear about a left turn or right turn Allison or Merlin, the "left" and "right" indicate the prop as viewed from the cockpit, not from the front, and certainly not the crankshaft.

#13 Kutscha


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Posted 24 October 2017 - 08:03 PM

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.


Vees For Victory! The Story of the Allison V-1710

#14 GregP


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Posted 25 October 2017 - 05:42 PM

Funny, Kutscha, bit if you're assembling an Allison from scratch, it doesn't take any more effort to build a left turn or a right turn. But if you have a right turn and want a left turn, it as a major undertaking requiring almost complete disassembly of the engine. Actually, you wouldn't have to disassemble the accessory case.


By the way, thanks again for finding that drawing of the Bf 109E tail airfoil. I would probably not have checked since a reference said it started with the F.

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