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

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.

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.

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

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???

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.

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)

PS obviously one engine is not installed in the photo above.

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!

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.

---

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

---

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)

---

just a thought i ve just had, are chain drives road legal ?

cheers

Yup no probs.

quote:

---

Originally posted by Howlor
Yup no probs.

---

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

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]

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

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

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

---

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

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.

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

---

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

---

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.

---

quote:

---

Originally posted by thomas4age
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

---

quote:

---

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.

---