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Twin engines- transmissions?


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I'm in the design phase of a salt lake racer that will sport twin engines side-by-side. Now, would both these engines have its own tranny going to a rear axle with two diffs? Or would it be more like this pic? How was this done on some of the multi-engined racers in the past?

Twin.jpg

Any help would be appreciated. Thanks for your time.

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You could use two transmissions but they should be sync' together somehow so as to change gears at the same time. Running through one tranny was also done, generally with one engine in front connected to the front of the crank shaft of the rear engine with a flex joint. (Generally two sprockets side by side connected by a double row chain wrapped around both sprockets)

The one transmission thing is a more logical design because it simplifies things while the torque buildup on a SLR car is slow enough to allow a race prepared automatic to put up with the additional horsepower of two engines.

Many SLR cars only have two speeds anyway.

As for two differentials.... I don't think that was ever done! It couldn't work unless one gear set was removed. You only need one set anyway, so a show-car like the Invader probably had two rear axle tubes welded together with one differential gear set allowing for the slippage between left and right wheels while the other differential was solid.

Many early 60's Dragsters didn't even use a transmission. Most just had a clutch and an in-and-out box for idling at the line.

A couple of early dragsters used two axles to solve the problem of coupling by running one narrowed axle behind the wider wheel set. This allowed the axles to be mounted very close together. ("Jack the Bear" is what I think it was called) The builder later said it would have worked better if the two axles had been mounted on a common "Bogie" pivot. Unfortunately, the way it was built, the front end tended to lift when it accelerated which lifted the forward drive axle slightly unloading the wheels which would spin even faster creating a huge amount of rubber smoke.... ;)

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Thanks Jairus. So I will build something more like the picture then. The shot above is a WIP shot of the 1:1 show car Twin Mill. A full size version of the old Hot Wheels car.

Twin3.jpg

Edited by Jantrix
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Just out of curiosity, why side by side in a land speed car? That's gotta be more drag than two engines in line.

Excellent question! Why indeed? Answer- no idea! I've just always wanted to do a side by side engined vehicle. Too much Krass and Bernie growing up, I expect.

Ron, thanks for the links, much appreciated.

Edited by Jantrix
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Excellent question! Why indeed? Answer- no idea! I've just always wanted to do a side by side engined vehicle. Too much Krass and Bernie growing up, I expect...

Eh. Cool enough. I love the Twin Mill, BTW. Do you have any magazine articles on it? It was in Street Rodder a few years ago.

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Thanks Jairus. So I will build something more like the picture then. The shot above is a WIP shot of the 1:1 show car Twin Mill. A full size version of the old Hot Wheels car.

Twin3.jpg

Actually tandem twins are generally coupled together by triple-row sprockets, one on nose shaft of rear engine (double-or-triple woodruff-keyed and shaft hardened!) and one behind flywheel of front engine, on a flange. The sprockets are coupled together tandem-style, with a 6-row roller chain, master-linked at where they meet. (sprocket-length, no idler) Tom McMullen coupled his together like this, in his English Ford "Chevy-Two" that he drove on the street. (!)

Tommy Ivo, in his Twin Buick rail, went the same route as Eddie "the Thrill" Hill. Both diggers were twins, but the flywheels were replaced with large spur gears, turning a suspended third gear in the center. (the 'up' motion of the right hand engine meshed with the center gear, which meshed on the other side with the down side of the left engine) The in-and-out box was operated by a twin-disc dog clutch, and turned a Halibrand quick change rear with the ring gear 'flopped' to the right-hand "passenger" side.

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How did Mickey Thompson hook-up his 4 engine Challenger LSR?

The engines on one side hooked up to the front, the other side to the rear. It was a pair of double inline setups. There has been every possible combo of engines, drivelines, and hook-ups devised over the years. Ray Keech had three Liberty airplane engines all driving the rear axle direct drive! 81 litres and a push start! on the sands of Daytona! Anything can be devised or imagined would probably have a real world counterpart.

Andy

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