I'm in the process of building a road legal bike engined Seicento. The engine is gonna be in the back driving the rear wheels via a diff. To keep costs to a minimum I'm using the Seicento diff out of a 1108 FIRE engine gearbox. The question is how do I go about mounting it and making sure its all centred and secure enough?

My intention was just to drill holes in the crown gear and bolt the sprocket to it. 3 problems with that:

1: The crown gear is only 165mm diameter including the helical cut teeth. THe sprocket mounting holes are on a 160mm PCD and are 10mm diameter. Obviously this isnt great.

2: I've been told that the crown gear is likely to be made of tool steel and therefore a b***h to drill.

3: The sprocket doesn't centre on the crown wheel at all, so the chance of me gettign it centred by hand is pretty much impossible. Is any off centre-ness likely to break the chain with ecentric motion, or will it just be a bit less efficient?

So what should I do? An adaptor plate seems like a good idea but still leaves me with 2 of the three problems unless I get it professionally machined.

Any advice much appreciated! :-)

PS I don't have easy access to a lathe or milling machine.

flak monkey can help with lathe or milling machine some 1 off stuff his name is David give him a pm mite be worth your while

Cheers. Will U2U him and see what he suggests. What do other people do to mount sprockets on Sierra diffs?

By far the easiest way is to remove the crown, then send the diff away to somebody like B&C express who will make a sprocket to match the bolt pattern and diameter - it wasn't expensive..


James

Interesting,
I am considering front engined, when I get a minute


http://www.locostbuilders.co.uk/viewthread.php?tid=114476

I looked at front engined but my engine of choice is a V-twin. And fitting it sideways didnt solve any of the problems.

There is a blade engined seicento floating around Fiatforum somewhere. Ran the output of the bike engine straight into the car gearbox input shaft. Was lethally fast in a straight line ubt the engine was that far forward it completely ruined the handling :-(

I'll keep an eye on yours though, looks like a good concept...

I was thinking Aprillia V twin in the front, still looking for the right car.
Once I have one, between other jobs I review the possibility of this, If it wont work, then rear eng it will have to be, or not!

I sawe the blade one, it had been lengthened in the wings I think?, not my bag, I want something standard and pick up off existing mounts
Cheers

[Edited on 24/8/09 by ReMan]

Yeah bear in mind a V twin is very long so you either need it sideways, which means you need a very short rwd diff. Or you need a very long engine bay.

The honda V twin I have is about 650mm long, and to avoid having it silly high it needs to sit in front of the diff.

Rear eng has been done a lot for grass trackers as I understand it but all are little more than spaceframes with a seicento or cinq shell dropped on the top. I'm aiming for something a bit more civilised.

the blade one was lengthened. I reckon you could fit an inline 4 in where the original fiat engine sits and chain drive it to a diff. The blade one was so long because it retained the car gearbox as well so had a huge gear selection to chose from.