finlay
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| posted on 21/1/08 at 08:44 AM |
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twin engine - what Diff set up ?
hello there
i m trying to find out some info on what diff set up you would need for a mid twin bike engined car - MK1 Golf (thinking of next project)
i know z cars have built one and some of the grass trackers run them but i m struggling to find any info or pictures on them
can any one pass on links to companys/fabricators etc also some pictures would be great to
i thought of the easy option of just having 2 sierra diffs side by side linked together by the inside outputshafts, what do you think ?
much appriciated
Finlay
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iank
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| posted on 21/1/08 at 09:17 AM |
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Do a search on NS Dev's posts. He's doing a twin engined grasser and has posted information on how he will be driving the wheels.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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Puk
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| posted on 21/1/08 at 10:09 AM |
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Interesting project! On the Z-car twin engined Ultima there engines are not linked mechanically. One drives the front diff and one drives the rear
one. There was some mention of an electronic link but you'll need to check their site for any further details. I'd be interested to hear
how it drives on track.
Before you judge a guy, walk a mile in his shoes. Then when you judge him, you're a mile a way and you've nicked his shoes.
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jkarran
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| posted on 21/1/08 at 11:47 AM |
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Twin diffs will leave you with very short shafts or very wide track (for a MK1). You will probably also sruggle to get prop shaft alignment on the RHS
engine unless you locate it forward of the LHS one (practically in the drivers seat in a MK1). Twin diffs would also mean you couldn't (and
wouldn't want to $$$) run an ATB.
Have you considered a transverse install with twin chain drives to a layshaft above the diff then a third chain dropping down to the diff?
Tensioning/maintaining them would be a royal PITA though.
jk
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Bob C
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| posted on 21/1/08 at 12:37 PM |
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I don't think you want a diff for sharing engine power. The action of a diff is to ensure equal torque on the 2 "axle" shafts. If
these were connected to the 2 engines, consider what happens at peak torque revs - one engine will produce more torque than the other (maybe only 1%)
so the other will move down from its peak torque revs - to where it has even less torque - so it will stop & then get driven backwards by the
winning engine.....
Has to be direct connection surely???
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NigeEss
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| posted on 21/1/08 at 12:42 PM |
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I've heard of a 2in-1out gear unit for rwd setups. Prob a Quaife unit.
The twin engined 4WD Zcars tiger is as Puk mentions, no mechanical link. Front
engine bolts directly to the diff flange and a prop to the rear.
The engines are linked electronically through a pair of Motec ECU's with data from
ABS rings, steering etc.
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NS Dev
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| posted on 21/1/08 at 01:29 PM |
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On my grasser the two engines are linked by chain directly onto a countershaft, which I made from some steel billet and hollow bar.............
 
Fiat bootspace Dec 07
Obviously I need no diff, just rear wheels locked together.
If you look at the bottom of the photo you will see two ally bearing blocks bolted to the tube frame, each of which carries 2 30mm bore sealed
bearings spaced 40mm apart. These support the short extender shafts you can see, which I made up with EN24t cups which slip over the std Aprilia
output sprockets. Welded to the other end will be a 630 chain 16 tooth sprocket, which will then drive down and forwards to each end of that huge
shaft you can see in the blue industrial bearings. This carries a 38 tooth 630 sprocket at each end, bolted on by 8 M10 bolts, and is recessed inside
each of those large cups, to carry a 108mm porsche turbo/2wd cossie gkn lobro joint. Its drilled and tapped for the joint to bolt in and end up flush
with the end of the shaft, helping to maximise drive shaft length (which is still only 11.5" on the short side)
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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NS Dev
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| posted on 21/1/08 at 01:32 PM |
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PS obviously one engine is not installed in the photo above.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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NS Dev
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| posted on 21/1/08 at 01:39 PM |
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Alternative layout, as employed by Endaf Evans in his old growler class 7 car and his pug before that, was to run a countershaft behind the engines,
drive it with a short simplex chain from each engine, then drive forward to the "diff" (i.e. spool) using twin chains (though these are prob
not a good idea, a single very high spec chain being more reliable and easier to keep tensioned)
 
growler 1
also, the short chains have no reduction ratio, and on a run that short, get red hot very fast!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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finlay
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| posted on 21/1/08 at 02:22 PM |
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quote:
Originally posted by NigeEss
I've heard of a 2in-1out gear unit for rwd setups. Prob a Quaife unit.
The twin engined 4WD Zcars tiger is as Puk mentions, no mechanical link. Front
engine bolts directly to the diff flange and a prop to the rear.
The engines are linked electronically through a pair of Motec ECU's with data from
ABS rings, steering etc.
yea!
thats what im after a 2 in 1 out, any more info on this ?
although i have been advised to go down the chain route, something to think about
cheers
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finlay
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| posted on 21/1/08 at 02:42 PM |
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quote:
Originally posted by jkarran
Twin diffs will leave you with very short shafts or very wide track (for a MK1). You will probably also sruggle to get prop shaft alignment on the RHS
engine unless you locate it forward of the LHS one (practically in the drivers seat in a MK1). Twin diffs would also mean you couldn't (and
wouldn't want to $$$) run an ATB.
Have you considered a transverse install with twin chain drives to a layshaft above the diff then a third chain dropping down to the diff?
Tensioning/maintaining them would be a royal PITA though.
jk
thanks JK
yea i ve thought about a transverse install with twin chain drives to a shaft above the diff then a third chain dropping down to the diff, it just
seems like alot of moving parts, i was trying to avoid that, the ideal for me would be a 2 in 1 out gearbox of some kind linked to the diff input
shaft
cheers
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finlay
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| posted on 21/1/08 at 02:49 PM |
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quote:
Originally posted by NS Dev
On my grasser the two engines are linked by chain directly onto a countershaft, which I made from some steel billet and hollow bar.............
Fiat bootspace Dec 07
Obviously I need no diff, just rear wheels locked together.
If you look at the bottom of the photo you will see two ally bearing blocks bolted to the tube frame, each of which carries 2 30mm bore sealed
bearings spaced 40mm apart. These support the short extender shafts you can see, which I made up with EN24t cups which slip over the std Aprilia
output sprockets. Welded to the other end will be a 630 chain 16 tooth sprocket, which will then drive down and forwards to each end of that huge
shaft you can see in the blue industrial bearings. This carries a 38 tooth 630 sprocket at each end, bolted on by 8 M10 bolts, and is recessed inside
each of those large cups, to carry a 108mm porsche turbo/2wd cossie gkn lobro joint. Its drilled and tapped for the joint to bolt in and end up flush
with the end of the shaft, helping to maximise drive shaft length (which is still only 11.5" on the short side)
thanks NS Dev for the pics, much apriciated, that will be some machine once its finished and the fact that you dont use a diff means you will have no
problem sliding the rear out lol however i am building mine for the road and will need a diff to get round corners safley lolbut lots of good ideas,
some more food for thought
thanks again
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finlay
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| posted on 21/1/08 at 05:54 PM |
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just a thought i ve just had, are chain drives road legal ?
cheers
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Howlor
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| posted on 21/1/08 at 06:41 PM |
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Yup no probs.
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iank
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| posted on 21/1/08 at 06:50 PM |
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quote:
Originally posted by Howlor
Yup no probs.
So long as no-one can get bodyparts trapped in it without removing guard/panels. I doubt they'd let you get away with exposed chains.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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snapper
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| posted on 21/1/08 at 10:27 PM |
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on a single engine Z cars use the guts of a LSD with the crown wheel replaced with a chain sprocket. you could run this to the idler shaft that
connects the two engines
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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ChrisGamlin
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| posted on 21/1/08 at 10:27 PM |
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There's some info / pics of the Z Cars transfer box on Tim's website
here.
I won't comment further, best do a search on here for twin engine installs for my thoughts on them 
[Edited on 21/1/08 by ChrisGamlin]
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NS Dev
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| posted on 21/1/08 at 10:34 PM |
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heh heh lol!!
Sorry chris, but I still insist that one of these would be fun, whatever you reckon, its faster than with one engine!!!!!........................
Ebay twin mille special linky
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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thomas4age
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| posted on 22/1/08 at 12:16 AM |
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well all that talk about not making difference in performance.... blah blah just do it for the sound then.
side by side mounted busa's in hillcimb car (says sr8 but it's not a radical)
http://video.google.com/videoplay?docid=-6111370037003719934
grtz Thomas
If Lucas made guns, Wars wouldn't start either.
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NS Dev
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| posted on 22/1/08 at 08:04 AM |
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quote:
Originally posted by finlay
quote:
Originally posted by NS Dev
On my grasser the two engines are linked by chain directly onto a countershaft, which I made from some steel billet and hollow bar.............
Fiat bootspace Dec 07
Obviously I need no diff, just rear wheels locked together.
If you look at the bottom of the photo you will see two ally bearing blocks bolted to the tube frame, each of which carries 2 30mm bore sealed
bearings spaced 40mm apart. These support the short extender shafts you can see, which I made up with EN24t cups which slip over the std Aprilia
output sprockets. Welded to the other end will be a 630 chain 16 tooth sprocket, which will then drive down and forwards to each end of that huge
shaft you can see in the blue industrial bearings. This carries a 38 tooth 630 sprocket at each end, bolted on by 8 M10 bolts, and is recessed inside
each of those large cups, to carry a 108mm porsche turbo/2wd cossie gkn lobro joint. Its drilled and tapped for the joint to bolt in and end up flush
with the end of the shaft, helping to maximise drive shaft length (which is still only 11.5" on the short side)
thanks NS Dev for the pics, much apriciated, that will be some machine once its finished and the fact that you dont use a diff means you will have no
problem sliding the rear out lol however i am building mine for the road and will need a diff to get round corners safley lolbut lots of good ideas,
some more food for thought
thanks again
PS I can't say from my oen experience, but my neighbour and fellow petrolhead has an old Opel Kadett GTE (rwd, b series) which he has got a 350hp
vauxhall 16v turbo lump in, and due to traction problems and lack of lsd, plus an impending santa pod showdown, he welded the diff up in.
He is now using it on the road and says he has no problems at all with the welded diff, other than heavy steering when maneuvering.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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finlay
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| posted on 22/1/08 at 08:33 AM |
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thanks ChrisGamlin for the link, thats the kind of transfer box i had in mind, but i was doing some deep thinking last night and had the skrible pad
and pencil out and i must confess after reading some of the posts and skribbling away i m swaying towards chain drive set up plus i noticed that
quaife do a LSD with a sprocket attatched, i wonder if they could moddify it and weld another sprocket on ???
i will try and post up some of the sketches to see what you all think
cheers
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NS Dev
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| posted on 22/1/08 at 01:20 PM |
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make your own chain driven diff, it is very easy if you have access to a lathe or somebody with one.
My **** **** internet connection at work just timed out after typing a huge reply to this one, so u2u me if you want the info and I will do it
again.
Need less to say you can have a chain driven, viscous limited slip, twin input flange diff for less than £200 if you diy it.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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ChrisGamlin
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| posted on 22/1/08 at 06:01 PM |
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quote:
Originally posted by NS Dev
heh heh lol!!
Sorry chris, but I still insist that one of these would be fun, whatever you reckon, its faster than with one engine!!!!!........................
Ebay twin mille special linky
Yep wouldn't disagree with that at all, it would be great fun and would be significantly quicker than a single engine'd version, but
grassers do away with a lot of the pitfalls I feel you need to overcome in a road / trackday car, primarily they don't need a rear diff which
makes transferring the power to the rear wheels a whole heap easier, and secondly they only need to run for a few miles between servicing 
[Edited on 22/1/08 by ChrisGamlin]
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iank
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| posted on 22/1/08 at 06:39 PM |
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quote:
Originally posted by NS Dev
heh heh lol!!
Sorry chris, but I still insist that one of these would be fun, whatever you reckon, its faster than with one engine!!!!!........................
Ebay twin mille special linky
Any idea what tyres are on that? Since Colway have gone bankrupt (again!) I need to rethink the tyres I was planning for the buggy.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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akumabito
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| posted on 22/1/08 at 09:10 PM |
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quote:
Originally posted by NS Dev
make your own chain driven diff, it is very easy if you have access to a lathe or somebody with one.
My **** **** internet connection at work just timed out after typing a huge reply to this one, so u2u me if you want the info and I will do it
again.
Need less to say you can have a chain driven, viscous limited slip, twin input flange diff for less than £200 if you diy it.
If you'll PM him with the story, you might as well post it here! I'd like to read it..
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