Hi
I'm contemplating converting to BEC, but as ever wnt to do this Lo-Cost!!
Rather than buy an expensive reversing gearbox has anyone any advice/experience in using a stripped out rear wheel drive box(leaving in the reverse gear) say Escort Mk11 type 3 etc. I know there's a weight penalty and a certain amount of power loss, but as I have 3 boxes seems a god idea...
Any thoughts?

Sevaun

Hi

Assuming you're still going hillclimbing with it, then the question is why?
You don't need reverse fitted at all for speed events.
(though it can make some paddocks a PITA!)

As you'll be in Sports Libre with a BEC engined locost, weight's going to be the holy grail and anything that adds that is to avoided at all costs?

That's before you look at gearing.
There's a very nicley engineered 1100 single seater that's BEC to Hewland and its beautifully done.
But even the owner questions the worth of it, as although the gearings spot on it's heavy compared to the bike box and chain drive approach.

Keep it simple, keep it light?

I guess it could be done. Better with a box that you can remove the bell housing from.

The difficulty would be connecting the output from the bike engine to the input to the box.

The benefit of this aproach would be the lack of need of a 3.14 diff. You could use 3rd for sprinting acceleration then change to 4th for a) more relaxed cruising and b) ultimate top speed.

The cheapest, easiest, lightest and most efficient route would be not to bother.

Will be a pain in the a*** and definitely not lo-cost. Easiest way is the starter motor trick. In effect a starter motor that reverses the car. Looks comical and is a bit agricultural but it works with a minimal weight penalty.

(my description is not the best, imagine sticking your car in reverse and trying to start the engine, the car will kangaroo backwards)

quote:

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Originally posted by smart51
I guess it could be done. Better with a box that you can remove the bell housing from.


The benefit of this aproach would be the lack of need of a 3.14 diff. You could use 3rd for sprinting acceleration then change to 4th for a) more relaxed cruising and b) ultimate top speed.

An interesting concept - running the final drive from the Bike Engine gearbox through the rwd gearbox in theory gives you 24 gears (or 30 if rwd box is 5 speed)
+ 6 speeds in reverse!!


Sevaun

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paulf - 25/6/08 at 12:37 PM

I considered this using a stripped out type 9 box.It would be possible to make a new bearing housing and adaptor to fit in place of the clutch plate and i considered using reverse , 4 and 5th gears but the problem would be the input shaft is not capable of handling the torque output of the bike engine when in low gears.Although the bike engine has low torque output it is multiplied by the gear ratio and would be a lot more than the type 9 is designed to take through the input shaft.
Paul.

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fatfranky - 25/6/08 at 01:33 PM

This is exactly what i had considered doing

quote:

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Originally posted by paulf
I considered this using a stripped out type 9 box.It would be possible to make a new bearing housing and adaptor to fit in place of the clutch plate and i considered using reverse , 4 and 5th gears

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But I hadn't banked on this bit

quote:

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Originally posted by paulf
but the problem would be the input shaft is not capable of handling the torque output of the bike engine when in low gears.Although the bike engine has low torque output it is multiplied by the gear ratio and would be a lot more than the type 9 is designed to take through the input shaft.
Paul.

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Is there another solution in which you could cannibalise a production gearbox for it's gears, bearings and/or shafts and somehow utilise them in a small fairly light High/Low/Reverse gearbox.

My intention would not be to change gears in this box on the move but more to select the "range" that you want before setting off, e.g. Cruising, sport or reverse so perhaps syncromesh would not be required either

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sucksqueezebangblow - 25/6/08 at 04:04 PM

I'm pretty sure someone told me that a reverse box is effectively a small diff with the drive going in through one output flange (1) and out through the other output flange (2) such that when the input flange is free to turn the output flange (2) rotates one way but if the input flange is locked the output flange (2)rotates the other way. If this is correct it may be a solution to seek out a small diff for the purpose and fit it with some means of locking the input flange, perhaps a small disc and caliper?

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James - 25/6/08 at 04:19 PM

Might be worth a u2u to Ned as a friend of his has a BEC Striker(?) with a Type9 or somesuch to do the reverse.

Seems crazy to me!

Just seems the wrong way to do it to me.

If I was attempting it with my car (which has a chassis mounted diff' ) I'd try and do it with a starter motor driving a gear fitted between the prop and the diff' flange.
Obviously there'd be some playing around to do to get the pair of gears to work!

All the best,
James

[Edited on 25/6/08 by James]

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