Two Engines Back Driving One Differential.

[cajunfj40]

To calculate, you can find equations in googleable papers on hybrid power-split transmissions, or look up torque summing drives.

Do note that automotive differentials are not meant for continuous significant speed differential. They have only thrust washers - flat bushings - for the spider and side gears.

You might be able to creatively misuse some planetary gearsets, or rob a mechanical skid-steer loader to get a combining drive.

Apologies for terseness, home from work with something, and about out of think.

[cRiPpLe_rOoStEr]

Originally Posted by seifrob

Or like ZIL 135, one engine transmission combo for each side, no interconnection between wheels, but road.

While this is great to operate on loose terrain, where the effect of an open differential is not so desirable, a similar approach in a road vehicle able to operate at higher speeds would require some way to emulate the presence of a differential, and then the clutch system similar to those 2-wheel tiller tractors seems to be the easiest approach.

[Angel And The Wolf]

Originally Posted by cajunfj40

Do note that automotive differentials are not meant for continuous significant speed differential.

Yes, I would probably have to create something similar to a differential, but with proper bearings.

[Angel And The Wolf]

Originally Posted by cRiPpLe_rOoStEr

While this is great to operate on loose terrain, where the effect of an open differential is not so desirable, a similar approach in a road vehicle able to operate at higher speeds would require some way to emulate the presence of a differential, and then the clutch system similar to those 2-wheel tiller tractors seems to be the easiest approach.

To get back to my original question:

[Angel And The Wolf]

Wikipedia seems to indicate an averaging of the ratios. If that were so, I'd have 19 different ratios, though, some are so close as make the shift useless.

1/1 13.990
1/2 11.765
1/3 10.720
1/4 10.065
1/5 9.625
2/2 9.540
2/3 8.495
2/4 7.840
3/3 7.450
2/5 7.400
1/locked 6.995
3/4 6.795
3/5 6.355
4/5 5.700
5/5 5.260
2/locked 4.770
3/locked 3.725
4/locked 3.070
5/locked 2.630

[Isaac Zackary]

I think a CVT type transmission, like a hydraulic CVT, would make more sense. If I were to make a two engine vehicle, I'd make one that would run near peak efficiency while cruising at highway speed, and the other for use only during acceleration. That way I wouldn't have a large engine running far from peak efficiency just so it can have enough power to accelerate quickly. But I don't thing that would work with your differential idea.

[cRiPpLe_rOoStEr]

Not sure if I understood correctly now. But anyway, maybe you should try to consider the final output as the arithmetic mean between the different gears.

[jakobnev]

You seem to be forgetting that the same torque has to applied to both half-shafts. It makes no sense for the engines to use different gears, if the higher gear gives enough torque, then both engines could just be in the higher gear.

[Angel And The Wolf]

Yeah, it's just a crazy mind exercise.nobody needs that many gears.
In fact, knocking the too close ratios and the shifts requiring back shifts on one transmission leaves 10 up shifts, including two ultra high cruising ratios:
Easiest
Shift
Patern
1/1 13.990
1/2 11.765
------------(Not Used) 1/3 10.720
------------(Not Used) 1/4 10.065
------------(Not Used) 1/5 9.625
2/2 9.540
2/3 8.495
------------(Not Used) 2/4 7.840
3/3 7.450
------------(Not Used) 2/5 7.400
------------(Not Used) 1/locked 6.995
3/4 6.795
3/5 6.355
------------(Not Used) 4/4 5.25
4/5 5.700
------------(Not Used) 5/5 5.260
------------(Not Used) 2/locked 4.770
------------(Not Used) 3/locked 3.725
4/locked 3.070
5/locked 2.630

[Angel And The Wolf]

Just have to come up with a durable continuous use differential design.