Help out the new guy - reverse box for bike engine

[suparuss]

hello to y'all.
im looking for experience in the reverse gearbox's available for bike engines. my situation at the moment is ive just about finished building my own from scratch, using the guts from a ford escort gearbox and heavily modifying the shafts (trying to head the cheap as chips direction), it is looking pretty damn good. but, since im designing the whole car from scratch and will be totally unique (hopefully) im now concidering using more readilly available parts so as to keep remanufacturing options open. now seems to be a very good time to start building kit cars for a living. so back to the point- the car will be mid engined so i was thinking of the martin keenan engineering one, but im not sure how it works, does the electric motor actually move the car backwards?!? are there any other options out there specifically for mid bike engined cars?


Cheers.

Russ.

[smeagol]

AFIK the MK uses an electric reverse (start motor style). Other options are a Quaife reverse box. The latter is more expensive but is designed for this application.
Hope that helps.

[GreenV8S]

I remember seeing a company called "R & D" who specialise in bike-engined transmissions, at the Autosports show. They had reverse boxes on display there.

[suparuss]

cheers,
the quaife one tiger uses, which looks pretty sturdy but the one ive seen is propshaft type with flanges not really intended for mid engined cars, but is cheaper than i expected, only 495 + vat, id rather pay the extra pennies than have an electric motor move the car. problem then though is that the sprocket on the engine is a good four inches above the flange on the sierra diff, anyone ever mounted a diff upside down??
and they are too close together to use a prop shaft.
any idea if they are available direct from quaife or would i have to go through tiger?


Thanks again,

Russ.

[moomin]

Hi Russ,

I'm busy working on the reverse system on my car at the moment. I'm trying to visualise what your problem is, or what you are trying to do? Can you enlighten me?

I have removed the mechanical reverse from car, and am swapping to an electric one.

moom

[suparuss]

hi moomin, im just trying to find the best way of sorting the reverse out, having just about finished constructing my own reverse box i have decided to use something that i wouldnt have to spend 8 months building again if i ever need to replace it. not that ive wasted my time building since ive learned a lot in the process. im not too keen on the idea of the electric ones, but ive never witnessed one in action so its not really an educated decision to avoid them, but i would also like to avoid using a chain in the drive system, since youre going to be pulling around twice the weight the chain would usually be pulling.
so this leaves a "straight through" shaft type box which would require a straight line from the shaft the sprocket is usually on to the flange on the rear diff, but to do this my sump will be about 2 inch from the floor, with the sump ground clearance at 100mm, which is about what i would like, the offset between the two is about 60mm. so ideally i could do with a reverse box with a minimum of this offset between its imput and output shafts, anything over that can be compensated with latteral adjustments.

hope you understand! i almost do and sorry for rambling on.

cheers,

Russ.

[moomin]

Hi Russ,

Right, I'm with you now, sorry if I was being a bit dense.

Hmmm, that sounds tricky as I understand you have a mid-engined application and therefore use of propshafts is a no go.
I have a reverse gearbox for sale at the moment, but I don't know of any which have an offset input and output flange like you require. I am not totally up to speed with the internals, but I believe that the normal forward on the box is as straight through as possible for a good reason (i.e. vibration, loss, etc.).

I have heard of people who have gone directly from a reverse box into a diff with just a universal joint between the two.

Erm, that doesn't help much does it

Moomin

[suparuss]

well, thanks any way. i may well end up going for chain drive. what about mounting the diff upside down? i just checked in cad and it actually puts the flange bang on vertically, the engine would be way off to the passenger side, but it leaves plenty of room near the floor to put the fuel tank behind the drivers seat. i think ill have to have a good look at the rear diff when i order the running gear to make sure there wont be any probs but that may be the answer.
ps- if youve still got the reverse box in a few weeks i may take it off your hands, looks like a nice piece of kit!


>> Edited by suparuss on Tuesday 18th March 17:33

[chrisx666]

If you turn the diff upside down will you not be in reverse already? The reversebox would need to be in reverse all the time, unless the engine rotation is already wrong, then it would be OK. This is confusing..

[suparuss]

youre right, it would be going backwards. im thinking a bit too far outside of the box.