Final drive choiсe for bike-engined car
Discussion
Hello, PHers!
I need a final drive for the transversally mounted bike engine (actually, engine itself and bike gearbox). Looked at Zcars-built mid-engined Minis and didn't like its chain-driven final drive: I want normal 'gear' final drive! But the final drive unit is indivisible from gearbox casing on all transversally-engined cars (Golfs, Astras, etc).
What would you recommend, gentlemen?
I need a final drive for the transversally mounted bike engine (actually, engine itself and bike gearbox). Looked at Zcars-built mid-engined Minis and didn't like its chain-driven final drive: I want normal 'gear' final drive! But the final drive unit is indivisible from gearbox casing on all transversally-engined cars (Golfs, Astras, etc).
What would you recommend, gentlemen?
Is the engine already fitted? is there a need for it to be transverse?
If not you will probably find the engine is no bigger inline as most bike engines and boxes are so compact they are almost square in footprint dimensions.
So what i'm saying is why dont you just couple it up inline to a Ford sierra diff with either a short prop or a cush drive of some sort? If your on a tight budget that would be how i would do it.
Ive seen the quaife setup in the back of a 205 and it looked really long and awkward, good for weight distribution but it looked so close to the seats infront! but also very expensive as youve pointed out.
Mike
If not you will probably find the engine is no bigger inline as most bike engines and boxes are so compact they are almost square in footprint dimensions.
So what i'm saying is why dont you just couple it up inline to a Ford sierra diff with either a short prop or a cush drive of some sort? If your on a tight budget that would be how i would do it.
Ive seen the quaife setup in the back of a 205 and it looked really long and awkward, good for weight distribution but it looked so close to the seats infront! but also very expensive as youve pointed out.
Mike
Engine is not mounted yet - first of all we want to weld the rollcage/engine+suspension subframe. More of that, the engine is not even chosen yet - most of bike units that we checked were ruined.
I suppose, that the engine has to be mounted transversally because of lack of space: think of a Daihatsu Charade with the engine behind the seats. I think, there's simply not enough space for the longitudally mounted inline-4, even small.
I suppose, that the engine has to be mounted transversally because of lack of space: think of a Daihatsu Charade with the engine behind the seats. I think, there's simply not enough space for the longitudally mounted inline-4, even small.
Hi KVas,
A few motorbikes (BMWs for example) transmit drive to the back wheel using a driveshaft instead of a chain.
Figured it would probably be easier to hook one of those up to a normal car differential, though obviously a bit academic now you've got a chain drive unit.
Seem to remember some custom trikes have used Reliant back axles with chain drive by cutting holes in the diff casing and hooking the chain up to a modified differential crownwheel.
Maybe you could do something similar with a Sierra diff, though not sure what you'd do about lubrication as it would no longer hold oil. Frequent applications of white grease like they use on chains perhaps?
A few motorbikes (BMWs for example) transmit drive to the back wheel using a driveshaft instead of a chain.
Figured it would probably be easier to hook one of those up to a normal car differential, though obviously a bit academic now you've got a chain drive unit.
Seem to remember some custom trikes have used Reliant back axles with chain drive by cutting holes in the diff casing and hooking the chain up to a modified differential crownwheel.
Maybe you could do something similar with a Sierra diff, though not sure what you'd do about lubrication as it would no longer hold oil. Frequent applications of white grease like they use on chains perhaps?
grahambell said:
Hi KVas,
Seem to remember some custom trikes have used Reliant back axles with chain drive by cutting holes in the diff casing and hooking the chain up to a modified differential crownwheel.
Maybe you could do something similar with a Sierra diff, though not sure what you'd do about lubrication as it would no longer hold oil. Frequent applications of white grease like they use on chains perhaps?
Not much point in trying to modify a diff. casing in this way with independent suspension, though. The only reason to do it on a trike is to retain the continuous beam axle.
Remember that what we commonly call a diff. casing is, in fact, a final drive casing which encloses both the differential unit (which has its own 'cage') and the crownwheel and pinion (rear wheel drive) or ring gear (front wheel drive) that gives the final drive ratio. The crownwheel or ring gear is usually a separate component to the diff cage and bolted to it by a ring of bolts. You don't 'modify' the crownwheel - you unbolt it, throw it in the bin, and bolt a suitable sprocket in its place!
If you accept that you're going to have to use an exposed chain drive (and AFAIK even the Quaiffe unit uses an enclosed multiplex chain to actually transmit the power), you might as well do what everyone does: get rid of the final drive casing altogether and use something like a Fiesta diff, in which the diff cage itself can be relatively easily made oil tight, chain driven to a sprocket in place of the crown wheel and the main bearings mounted in blocks either side and running in grease (fine for taper roller bearings, of course - that's how wheel hubs work).
Even diff. cages which are difficult to make oil-tight because they are relatively 'open' in construction can simply be enclosed with a lightweight 'tin can' to keep the oil in.
Wrong time of year now, 'cos the season's just finished, but I would have suggested nipping along to you next local sprint or speed hillclimb to have a nosey at the bike engined single seaters, if you want to see how it's done - this is a well established solution that's been used for many, many years.
You could always try ringing someone like Jedi, OMS or even Sylva (their new R1ot is BEC powered with a chain driven Fiesta diff) for advice and/or parts.
If all else fails, e-mail me off list and I'll scan some photos I have of the diff/chaindrive arrangement on various bike engined single seaters, for reference.
The only problem with chains is that they have limited lifespan and they need occasional adjustment for stretch, but there really isn't any other sensible solution for a mid transverse bike engine installation, period.
hi,
I am in the midle of converting a miny diff to chain drive it is not realy all that hard to do if you have acces to a lathe.
however on this diff you have to machean the teath of the crown weal as it makes up the bering mount point on one side of the diff. then you bolt the sprocket on in its place make up some bering carrers and a can to seal the diff with and hay presto you are done all I have left to do is finish my bering careres and make the can to seal the lot with.
blake
I am in the midle of converting a miny diff to chain drive it is not realy all that hard to do if you have acces to a lathe.
however on this diff you have to machean the teath of the crown weal as it makes up the bering mount point on one side of the diff. then you bolt the sprocket on in its place make up some bering carrers and a can to seal the diff with and hay presto you are done all I have left to do is finish my bering careres and make the can to seal the lot with.
blake
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