Hi all,

after a lengthy philosophical (i.e drunken) discussion yesterday, I thought I'd ask you, the great unwashed, this question.

Is it possble to attach a bike engine via the usual sproket adaptor directly to a diff, like a Sierra diff with out an intervening propshaft?

That is sprocket adaptor bolted to diff flange.

to make a compact mid-engined set-up.

I think it would work as both the engine and the diff would be bolted solid to the chassis.

Go on, shoot me down in flames!!!

Cheers

Chris

i remember asking this a couple of years ago. i think the general concensus was that it would be a bad idea. youd need something flexible between them as it would be difficult to ensure no movement occurs between engine and diff. due to chassi flex, slight play on moutings etc) if there is there would be a lot of stress on the shafts.
i think you could probably get away with an early typt cv joint which is made mostly of rubber and therefore can flex in all directions and would be quite compact. a single solid type cv joint is out because they only allow twist and bending, but not parralel movement.


Russ.

What if you would mount a flange on the diff that has, let's say 5, high strenght bolts with the same diameter as the notches in the sprocket,the bolts would replace the chain and there would be enough play to deal with flexing of the chassis.

another point tho is the shock when changing gear on a bike, if there is nothing to take it then the gearbox will take a right beating. needs a cush drive or something as well.

What about engine/cush drive/diff then?

I didn't think there'd be that much movement with the engine and the diff both bolted up solid.

Cheers

Chris

i think that the combo of engine movement and any slight inaccuracies in the mounts would ruin stuff in the end. But a simple cush or u/j in the middle would be perfect. Indeed, its been done many times.

Has It?

Show me!

(come on, you've nothing better to do)

Cheers

Chris

It has definitely been done before, but I don't have photos of it.
There are several options of adjoining the engine with the diff. I posted ages ago about using a readily available industrial PU star cush drive.
Lots of industrial equipment is cojoined using various couplers including wrapping a short length of duplex chain around the sprocket on the power supply and an identical sized one on the shaft (diff flange in this case). The double row chain allows for small amounts of mis-matched alignment, yet is very direct.

The Sylvia Stylus mid engine bike use a Sierra/Freelander differential with a cush drive.

And no you can not bolt the engine directly with the differential unless your chassis have been welded on a jig adn all teh mounts CNC machine sfrom the same datum.

Cheers