retromods
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| posted on 20/7/11 at 08:00 PM |
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diffs and direction of travel
hi
really struggling to get my head around this!
lets use a sierra as an example. engine up front, propshaft to diff.
now, IF i put the engine in the boot - prop and diff now pointing towards the front instead of down the car towards the boot..... would it have 5
reverse gears and 1 forward OR would it still drive the same 5 forward 1 reverse as the prop would still be rotating in a clockwise direction?!
cheers 
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Kev36
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| posted on 20/7/11 at 08:03 PM |
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it would depend if you wanted FWD or keep RWD ... i think
' A rich man is just a poor man ...with an awful lot of money..'
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retromods
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| posted on 20/7/11 at 08:05 PM |
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diff would still be on rear axle (cradle thing) it just points the other way now intentions of keeping it rwd
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eddie99
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| posted on 20/7/11 at 08:08 PM |
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It would be the wrong way around because you'd be changing orientation of engine as well, 180 degrees i think...
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blakep82
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| posted on 20/7/11 at 08:10 PM |
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erm, right, if you spun it round 180 degrees when looking from the top so the right output now drives the left wheel, then its 5 gears reverse, but if
you flip it over the other way, so like 180 degrees, when looking from the side, so the right output still drives the right wheel, then you should
still have 5 forward gears, BUT the crown wheel and pinion are designed to run 1 particular way, and if you run it constantly (effectively) in
reverse, then the gears won't last very long.
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BobM
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| posted on 20/7/11 at 08:11 PM |
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quote:
Originally posted by retromodsnow, IF i put the engine in the boot - prop and diff now pointing towards the front instead of down the
car towards the boot..... would it have 5 reverse gears and 1 forward OR would it still drive the same 5 forward 1 reverse as the prop would still be
rotating in a clockwise direction?!
I think you'd end up with 5 reverse gears.
Ultima use a Porsche transaxle which is similarly reversed but the other way round, i.e. engine is behind axle in Porsche but in front in Ultima. The
solution is to turn the diff/transaxle upside down. Just need to make sure that doesn't give you lubrication issues, you'd certainly need
to block off the breather and maybe create a new one on the new upper surface of the diff.
Not very Locost but very BEC 
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daniel mason
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| posted on 20/7/11 at 08:12 PM |
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or turn the diff upside down
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eddie99
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| posted on 20/7/11 at 08:12 PM |
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But to use the diff and prop like normally, you would have to spin its 180 degrees from its orientation in a RWD locost, no way of using diff etc..
with only 90 degrees
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garybee
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| posted on 20/7/11 at 08:13 PM |
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You'd have 5 reverse gears and the world's longest boot. Presumably that isn't what you actually intend on doing though,
what's your real plan?
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retromods
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| posted on 20/7/11 at 08:14 PM |
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90 degrees it is but yea it'll be all in reverse. ive seen kit cars with bike engines in the engine bay turned to the side, prop bolted to the
sprocket, this would be the engine facing the other way
is for a bike engine in the boot bolted to a sierra diff, no prop
[Edited on 20/7/11 by retromods]
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daniel mason
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| posted on 20/7/11 at 08:14 PM |
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the engine would be hanging way out back if the back axle is being driven. enigne-box-prop-diff
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retromods
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| posted on 20/7/11 at 08:20 PM |
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yea is for a bike engine in the boot, sprocket bolted to a sierra diff pointing the 'other' way instead of towards the engine bay (no
prop)
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daniel mason
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| posted on 20/7/11 at 09:10 PM |
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why not put the motor mid mounted in front of the back axle, and run the diff standard?
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mark chandler
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| posted on 20/7/11 at 09:34 PM |
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Range rovers have the same diffs in the front and rear, its does not hurt them going the wrong way !
In car this light a sierra diff would not care if inverted, just move the breather, that aside surely the chain would foul the engine casings if going
forward?
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austin man
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| posted on 20/7/11 at 09:36 PM |
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have a chain driven diff se MK Engineering he has done loads of rear engine bike configurations
Life is like a bowl of fruit, funny how all the weird looking ones are left alone
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Liam
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| posted on 20/7/11 at 09:50 PM |
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quote:
Originally posted by blakep82
erm, right, if you spun it round 180 degrees when looking from the top so the right output now drives the left wheel, then its 5 gears reverse, but if
you flip it over the other way, so like 180 degrees, when looking from the side, so the right output still drives the right wheel, then you should
still have 5 forward gears, BUT the crown wheel and pinion are designed to run 1 particular way, and if you run it constantly (effectively) in
reverse, then the gears won't last very long.
quote:
Originally posted by mark chandler
Range rovers have the same diffs in the front and rear, its does not hurt them going the wrong way !
In car this light a sierra diff would not care if inverted, just move the breather, that aside surely the chain would foul the engine casings if going
forward?
Upside down does not = going the wrong way. If all you do is flip a diff upside down it is still running 'forwards' even though
you've reversed the vehicle direction. The only time you make a diff run 'backwards' is when you're using a reverse rotation
engine - i.e. old Honda.
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mark chandler
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| posted on 20/7/11 at 09:59 PM |
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Okay, bad example, before it was outlawed peeps used to race landrover specials with the engine in the back, and flip the diff both ends in the casing
so it drove forwards.
The then changed the rules so the front of the engine block must be further forward of the centre line of the car so these became outlawed.
That aside on the overrun a diff is loaded the other way, on a car this light the diff should be fine, its just not conventional.
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retromods
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| posted on 21/7/11 at 05:07 AM |
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what about transfer boxes from a 4x4? tbh i dont even know if they have a diff in them but if they can go forward and reverse then it would also sort
the reverse gear out?
want to keep the car looking standard and try keep the rear seats, mid mounting would probably be easiest but needs to be half practical too
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Liam
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| posted on 21/7/11 at 06:53 AM |
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You could do what you want - have a bike engine mounted longitudinally behind the rear axle with a sprocket adaptor driving straight onto a diff.
You'd just need the diff to be up-side-down. You'd also need a long boot! A popular choice when doing a mid-bike-engine install is to have
the engine transverse with a chain driving a diff. Normally with the engine in front of the axle, of course, but you could have the engine behind,
again by flipping the diff.
Not sure what kind of car you're talking about here - if it's small and light I think you'll have problems fitting this installation
in and problems with horrible weight distribution. If it's a big car with a big boot I'd wonder if a bike engine is a good choice. Either
way, if you want to retain rear seats and standard looks, isn't the front a better place to stick an engine?
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Doctor Derek Doctors
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| posted on 21/7/11 at 08:59 AM |
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The best thing to do is go and get yourself a Technic Lego set with diffs and a little motor, we used this alot to work out how to put rear/midside
engined off-road trial vehicles together and make sure everything turned in the correct direction.
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zilspeed
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| posted on 21/7/11 at 09:39 AM |
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Pal of mine has a bike engined Clan.
Because of the rules, it must remain rear engined.
He uses a Blackbird engine with the output shaft pointing forwards bolted right up to a Sierra diff with the input pointing backwards.
Works fine.
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britishtrident
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| posted on 22/7/11 at 03:49 PM |
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The crownwheel and pinnions in the rear differential units of Austin Champs were prone to blow ups, because of the unusuall transmission layout
they turned in the reverse direction from which the gears were originally intended to. however it was a fairly highly loaded application.
But LR front diffs don't seem to suffer from the problem.
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