sgraber
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| posted on 27/1/04 at 06:46 PM |
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Why won't this idea work?
 
Crazy drivetrain idea
Pardon the simplistic rendering. Hopefully you get the idea.
I'm talking about rotating a transverse FWD powerplant 90d so that it becomes longitudinal and then running driveshafts off the differential to
front and rear differentials.
I'm sure I've seen FWD transverse units where the c/g was close to being on top of the half-shafts. You could conceivably get the engine
mass close to the centerline...
- Will the shafts rotate the wrong direction?
- Will be ratios be unusable?
- Other problems?
Graber
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timf
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| posted on 27/1/04 at 07:03 PM |
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steve the biggest problem would be sourcing front and rear diffs.
since the fwd box contains the final drive already it would be nexessary to get almost a 1:1 diff.
ford had something similar to what you gave drawn with the rs200 but this had specialieced gearbox for the car etc
tim
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Donners90
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| posted on 27/1/04 at 07:24 PM |
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Although not necessarily relevant to kit cars, it is possible to do this on a Land/Rangerover. I believe it is done by swapping the front and rear
axles and mounting them upside down. This way the wheels end up turning in the correct direction. Doing this means that the chassis remains relatively
unmodified. There are plenty of people who have done it, but I can't find any articles on the web.
With regards a kit car, taking the drivetrain out of a 4x4 car and turning the diffs upside down may work too.
Anyone else with a thought on this?
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JoelP
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| posted on 27/1/04 at 08:07 PM |
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its an ok idea, the front and back diffs would have to turn opposite directions, but if you got the lowest common ratios possible, used large wheels
and skipped 1st gear it would be ok, except on fast roads.
actually, with a 3 to 1 raito it would top out around 50mph, assuming a donor top speed of 150.
so, as tim says, its down to finding 2 suitable diffs. in the past people have said diffs arent happy being run upside down, so i dunno...
a good plan though if someone does work out how to make it work!!
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Peteff
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| posted on 27/1/04 at 08:15 PM |
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You would have to lock the front wheel drive diff to get power to both the others all the time as well.
yours, Pete.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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JoelP
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| posted on 27/1/04 at 08:20 PM |
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do you mean the new front diff or the original diff in the FWD gearbox? cos i thought all 4x4s had 3 diffs all in?
[thick]me[/thick]
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Alan B
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| posted on 27/1/04 at 08:26 PM |
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Steve, it's done a lot around here already...the double reduction of two final drives is used to good effect...they fit huge wheels (for ground
clearance) and take advantage of the low gearing.....in order to make.........hunting buggies for the swamps....
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Alan B
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| posted on 27/1/04 at 08:28 PM |
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Oh yeah, I forgot.....On of my neighbours teaches auto shop class at the local high school..they built one using one of the GM FWD V6's...
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sgraber
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| posted on 27/1/04 at 09:46 PM |
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Ahh yes, my next project. A swamp buggy... for the Arizona Desert...
So for a streetable car all I really need are some custom 1:1 ratio reverse rotation diffs and I'm golden? Might as well make them LSD while
were at it.
No problem!!! 
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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Alan B
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| posted on 27/1/04 at 10:03 PM |
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Quaife can do that no problem....just remember to bring a fat chequebook...
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GTAddict
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| posted on 27/1/04 at 10:21 PM |
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Yes, it will work, but I would guess you would get a poor handling car because the torque bias of a 'standard' left/right diff is 50/50.
Hence, your mid-engined beast will act more like a front driver with lots of weight at the back... not a good combo. Most front engined 4WD cars
tend to split between 33/67 and 50/50. I wouldn't like to try the math for a mid-engine setup - but the Lamborghini Diablo VT was 4WD - must be
loads of info on that.
However, if you can find a supplier to replace the diff in your chosen box with a torque biasing LSD with ratios to your design, then that solves that
problem.
I would guess your next problem is coping with the output torque in the driveshafts, which are now effectively at least twice as long between final
drive output and wheel. Torque reversals down the drivetrain to the centre diff might make the car feel very 'shunty' (new word!) and
unstable.
Of course, all pure speculation. 
Get the supplier to make a 1:1 final drive with torque-biasing LSD for your chosen combo, and then you are talking. Steal a pair of rear diffs and
driveshafts from two dead Subaru Imprezas - and nick the complete set of hubs and brakes from one one them while you're there - and you got
yourself a serious project going on... Especially if you can find the engine/tranny from a Lancia Thema 8.32. Four-wheel drive mid-engined car with
Ferrari V8 power, anyone?
Mark.
[Edited on 27/1/04 by GTAddict]
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rontyler
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| posted on 28/1/04 at 01:17 AM |
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Steve,
If you can find the right bits, as others have suggested, I think it could be interesting.
The only opinion I really have is that AWD is worthless unless the vehicle is traction challenged, ie wet roads or LOADS of torque. If you
talk'n small displacement 4cyl. (or equiv.), then I don't believe you'll "gain more than you lose" due to the weight
penalty.
--rt
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Rorty
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| posted on 29/1/04 at 05:34 AM |
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If you swapped the engine around the other way, at least you'd be driving the front and rear diffs the "correct" way.
I did a vaguely similar thing, though used a duplex chain drive for the transfer drive in an inline RV8/Renault 4WD car. The front diff was out of a
Passat (along with the hubs, struts et al), and fitted the front of the (Super (1303S)) Beetle beautifully.
I had to sit in the car for about 10 minutes after I turned the engine off: I would get sort of....erm..."caught" on the steering wheel,
if you know what I mean!
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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ned
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| posted on 29/1/04 at 10:40 AM |
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Rorty,
Your suggestion of turning the engine round is a good one, you could then use a sierra 4x4 as a donor for example. the difficulty i see (please
correct me if wrong) is that you then run into problems with the gearbox being in the wrong place and the you'd need to sort out a remote
gearchange mechanism. the gearbox being at the back would make i recon for a very long rear end too.
It should bea n easy conversion though, just extend the front prop and shorten the rear one i guess. the difs would all be spinning the right way.
A thought I had. would it be possible to use any porsche/vw difs or gearboxes as with the engine in a beetle/911 in front of the engine it would spin
the right way if front gearboxed with a torque tube, not sure how you'd work the transfer box!
Also, some honda engines spin the wrong way, could this be utilised with standard eg sierra front + rear difs which could then spin the right way?
Ned.
beware, I've got yellow skin
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internetautomart
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| posted on 2/2/04 at 12:29 AM |
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try this for some interesting ideas
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Rorty
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| posted on 2/2/04 at 06:59 AM |
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I should clarify my last post. With the RV8/Renault setup, the whole ensemble was inline (with the transaxle at the back) and the transfer drive came
out the left side of the trans and ran the prop to the front diff.
Sgrabber's FWD setup swapped around, shouldn't be a problem length wise.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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