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Maybe this has come up before?

My BEC project is going to need to have the engine mounted at the rear, behind the axle.
I have not seen any bike engines that would allow the chain to be routed forward from the sprocket.

Body was originally designed for VW Bug power and not enough room behind the seat to convert to mid-engine.

Unless I find a way to invert the chain rotation I would end up with lots of reverse gears.
Also need a diff at the same time for the street.
Not seeing a handy way to do it using only chains.
Anyone know a light but reasonably strong gearset that can be used?
Needs to be helical cut too, a bike engine will already be loud.
I can fabricate a housing if need be.

First thought is a sprocket sharing an input shaft with a helical cut gear meshing with a ring gear on the diff.
Where to get the matching gears that can be mated up?
Need to be able to bolt them to flanges.
All the power gets transmitted through them so needs to be strong.

A shaft drive engine and "V" drive might work with the engine facing normally, still need a part source and light enough weight.

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If I must be a one-man PC free zone, so be it!

If you're using a VW transaxle, just reverse the diff like they do on Formula Vee racing cars.

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Stan
Dauntless Racing
You can have it fast, cheap and reliable -- choose any two!

With the sprocket replacing the crown wheel for chain drive I don't see that making a difference.
No input shaft to switch sides on.

Really want avoid using the VW trans at all if possible in order to cut weight.

Thinking there ought to be a smaller and lighter diff. available, Honda 600 or that three cylinder GM, whatever it was called.

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If I must be a one-man PC free zone, so be it!

You could mount an angle drive under the engine with a sprocket attached . That will kill two birds with one stone and convert to shaft drive going forward which will make coupling the driveline to the diff easier. Dozens of these are made for industrial applications ,there will be a choice of input/output ratios and obviously strength. Wheres my cigar?

Bob

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Mancave http://s1116.photobucket.com/user/mypic ... ow/mancave

Make a bearing Mount that attaches to the engine that let's you run a long ofset on the drive sprocket so you can bring the chain forward of the engine. Look at DP cars for their AWD 2 sprocket arangement to see what I mean. No reverse box required axle in front of engine.

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MG midget bodied Locostish car in progress

Ah...okay. I guess I read your comment about it having "VW Bug power" and presumed it was a rear-engine configuration, so you could skip the chain and use a coupler instead.

I see my mistake...

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Stan
Dauntless Racing
You can have it fast, cheap and reliable -- choose any two!

I have been working on this problem my self .
we do some VW based motorcycle engine builds .
every one we have done we do mid engine as long as it's not a cut down VW pan the Suzuki motor fits .
on some builds with like the triumph rocket motor we needed to counter rotate the drive shaft .
we did a simple gear to gear and this will counter rotate the shaft .

what motor are you thinking of using ?
what diff are you thinking of using ?

Late model Tundra front IFS diff, place the engine behind the longer shaft and run the chain (or belt) to the front of the engine instead of the rear.

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"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

Engine has not been decided yet, but looking for a "Deal" on 1000+cc water cooled.

Thinking of a small common diff, maybe GEO Metro?

Thought of the gear to gear right away, but what gears to use?
Lots of stress there so I doubt that V8 timing gears would live for long.
Briefly considered those for their ready availability.

I can make a gearbox once I determine parts.
Or is there a set-up currently available?

Extended output shaft or jackshaft is a possibility but seems like it would force raising the engine mounting.
Want to keep it low mounted for best center of gravity.

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If I must be a one-man PC free zone, so be it!

Like the GEO Metro trans I considered a top view would be helpful.
There have to be three shaft mounts there, one input and two axles.
One axle originally went to the long housing?
Seem weird.

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If I must be a one-man PC free zone, so be it!

It's a front diff, the long side originally went under the engine oil pan.

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"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

I should learn to explain better. ... The axles go left and right in the picture, the pinion is barely visible at the rear. You can just see the bolt holes on the pinion flange.
You're looking towards the rear of the car from this angle.

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"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

For a small, lightweight differential, how about looking at really small, lightweight vehicles like lawnmowers, golf carts or UTVs (off-road golf carts) for inspiration?

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Mike - Read my story at http://twinlakesseven.blogspot.com/

If you're not dead set against straight cut gears (you'll already have six sets of them, what's one more?), consider using a quick change rear end gearset. Ebay is lousy with them for not much money as they have a limited lifespan in their natural habitat and they get replaced regularly, but with a bike motor they'd be bullet proof. They were used in a custom gearbox on the "Angry Hamster" Z600 LeMons car a few years back to correct the rotation of a shaft drive bike engine.

I'm liking that Hamster gearbox.
I also have CNC tools and an EDM.

Will look at the QC gears.
Will also need to see about making a housing for a small diff.
At this point that seems likely to be GEO Metro unless something better is suggested.

Going to try to make some chassis measurements today.

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If I must be a one-man PC free zone, so be it!