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So I was having a discussion the other day while watching the local b-ball team miss free throws. .. good game even though they lost.
What about using a transverse mounted fwd trans in back and adapting the trans input shaft onto a bevel gear with a driving gear mounted to the driveshaft output? Sure, sure, you'd be modifying the bellhousing, would probably trim some of it off. It still puts a clutch/bellhousing assembly on the engine so you don't save on footwell space but it moves the 75+ lbs of transmission to the rear of the vehicle. .. I'm thinking (?!?? ) you could maybe have a flat plate bearing carrier attach to the existing bellhousing mounting points and hold the end of the trans input shaft in place, a (driven) gear carrier flange splined onto the trans input and an attached housing to hold the driving gear in place, wouldn't even have to share the sump with the trans.
You wouldn't care where the driven gear sat on the spline as long as it had full engagement with the spline and the driving gear so the right angle drive could be assembled then bolted to the trans with an o ring seal on the inner side.
Gear size might be a problem since you don't want a reduction and would prefer a slight overdrive. .. makes for a big set of bevel cut gears to get the tooth contact desired and you'd actually want some sort of ratio just to keep face wear down.
Front engine/driveshaft/rear wheel drive requires a right angle gearset anyway, basically your just moving the power loss further up the supply chain. ..
The driveshaft should get a center support which could be mounted onto the interior of the tunnel easily enough.
Engine left or engine right orientation of the transmission would affect weight balance. .. seems like "engine right" orientation would make it easier to create the gear set in the smallest space in my opinion.
Engine choices become limited only by your ability to make a clutch housing with output shaft and transmission torque capacity.
I'm assuming that you would use the tunnel as a "torgue tube" of sorts but may need a guibo or similiar just to avoid vibrations from non parallel shaft alignment caused by engine or transmission rotation on their respective mounts.
The driveshaft would tend to wind up if you used a line-lock and slipped the clutch at the starting line so a full throttle launch might get interesting
Seems to me you could end up with a locost version of this http://www.xtrac.com/pdfs/1007%20-%20SUPERCAR%20TRANSVERSE%20SYNCHROMESH%20GEARBOX.pdf with the gearset preceding the diff.

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"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

What's the advantage over using the VW/Audi/Porsche longitudinal FWD units like are in the back of the Porsche 924/944?

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mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

Availability primarily though I wonder, it seems to me that by putting the angle drive at the higher shaft speed (and lower applied torque) you would reduce the side thrust and could use smaller gears than commonly used in a differential. Might even gain a small amount of efficiency. .. I dunno, the math would make my brain hurt I suspect.
The fairly common Honda cable shift trans, for example, is cheaply sourced and relatively strong as well as being comfortable at a high input shaft speeds, aftermarket gearsets, lsd's etc are widely available as well. Rotational direction is matched by the angle drive bolted to the remainder of the bellhousing and bob's your uncle, its off to the races.

I service and install right angle drives on a regular basis with keyed shaft slip on outputs. .. at far slower shaft speeds however, 55 fpm is a typical belt speed with 18" rollers spec'ed for 10k+ hours of service and they're heavy chunks (I can't remember the output but the input is 1750 rpm). There was a lot of beer and food about plus a dead chrysler in the driveway. ..

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

and probably single digit horsepower, industial gearboxes just aren't made for these kind of applications.

Very true, though there are a few in the 12-16 hp range, thats why I posed the question in the "in theory" section.
200ft/lbs flywheel torque thru a 3-1 first gear means that applied torque is 600 at the pinion gear. .. ahead of the transmission means a higher rotational speed with smaller gear faces because of the lower force applied.
It seems to me that the limiting factor is surface speed of the gears so 108 mm (4 1/2") od to stay under 50m/sec at 8000 rpm (50 m/sec is a commonly quoted limit)(5400 engine rpm / 0.67 od gives a pinion rpm of 8060).
So an 78mm od or so driven gear and a 100mm driving gear. .. thats a lot bigger diameter than any pinion gears I've ever used. (assuming a 21.4mm 20 spline bore on the driven gear for a Honda trans)
Its easy enough to rebuild a pocket to hold a tapered roller and some shims in a flat bulkhead, I do that on occasion, but quite another, at least for my poor poor untrained mind , to create a carrier from whole cloth.

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

Just mount the engine transversely way up in the front to give more foot room or way far back to make for a better weight distribution and then run a chain thru the tunnel to drive the tranny then you don't need to right angle anything.

BTW I'm just pulling your chain.

_________________
mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

pulling my chain (snickersnicker). .. a lot easier than pushing a piece of string!

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

OldJack

More power to you!!!!!

Unfortunately, I can only be a cheerleader on this one. GO TEAM GO!!! I've beat my brains trying to adapt a fwd to a transverse rear transaxle. I know exactly where you are going and why you are going with it. The last thing I couldnt work out was getting the tranaxle reasonably centered in the frame. As a tip, some of the AWD transverse front engine setups have nice "90 deg" setups to get the power to the rear - would be a reasonable source for gears.

I hope you get further than I did. I eventually came to the conclusion that a 915 Porsche transaxle would make more sense.

You been talkin to TWWTFM again????

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JD, father of Quinn, Son of a... Build Log
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The AWd transmissions are what got me to thinking on the subject, the (easy to find) pic shows a mitsubishi trans. ..
as you can see the factory output to the rear of the vehicle is driven by what appears to be a fairly small diameter shaft.
Probably not designed to have full engine output applied to it (twin turbo v6 ) but after chopping 12-1500 lbs off the vehicle weight I find myself wondering; 1)could it handle it(?), 2)whats the internal assembly method (gear as part of shaft or ?) and 3)how hard would it be to come up with a new intermediate housing between the angle drive and the trans input shaft? I'm not so worried about centering the trans, having the bulk of it to the off side should help l-r balance and a small difference in shaft length on the rear isn't that big of a deal.


OTOH if you figured out a way to rotate the rear output to become a front output and clear the sump you could create a mid engine awd. ..

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"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

I've been following this and don't have much to add. It is a discussion, at least for me, that is purely academic. Interesting, but nothing I will use on my build.



Are you referring to the shaft(?) that is parallel to the main input of the transaxle in the lower RH quadrant driving the 90deg adapter? If that is a shaft and not a tube covering a smaller shaft inside, I look at it's size compared to the main input shaft which carries the full power from the engine. From that perspective, it looks like a close call to me. If it is a tube, then I really doubt it.

YMMV

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Chuck.

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I'm on my lunch break so I need to keep it short.

That's the exact transaxle I thought could be pillaged for parts.

I cant imagine that shaft not being able to carry full engine torque - Might have a torque proportioning thing internal but I didnt think so. Either way, your point is valid - I REALLY cant imagine it not being enough for a Locost. The low weight of the locost is only going to allow so much torque to the wheels before you just spin. The torque calculations are simple enough but I say Mitsubishi already did it and thats fine with me.

Somewhere I have a PDF shop manual or some cutaways of that transaxle - I will try to find them later.

I couldnt imagine the intermediate housing being that much of a deal (given a free waterjet, machining center, and being able to use the Mitsubishi 90 degree setup ) - not alot of stress unless you put the clutch in the housing. The torque of the motor isnt that much to deal with at that point - after it goes through 16:1 gear reduction a ring gear or cv can see - then its a different story. I had a race engineer who was going to help me tell me he didnt think it would be a big deal - machining time and matching splines the biggest problem - custom shafts are $$$, but it is in an area that I would not rule out welding - if you had to, splines can be popped off a clutch plate

I have built a torque tube transaxle type setup in the past - 944 transaxle to a different motor - spline coupler was oem. Driveshaft welded.

One other thing to consider - make sure you dont end up with 5 reverse gears. If you run into that, drop gears from a QC might be the ticket. Drop gears will also get the input shaft height where you want it. That's the problem with Porsche 944 - look how high the motor is mounted so it can be inline with the transaxle input. I'm sure if they didnt have to use Audi parts, they would have done something else.

I think it was somewhere around here, I started worrying about weight/complexity/and where my efforts should be. A Porsche 915 is a light transaxle with the correct rotation and input shaft height, relatively simple to connect to a torque tube (leaving lots of room in the interior), and as much weight as you want on the rear axle ( I think 60% is a benificial). But you are still left with a transaxle that's expensive to get the right gears in, doesnt shift particularly well, expensive LSD, and only 5 gears, and (in terms of a Lotus or Locost) its getting dangerously close to trying to make a zebra into a horse - if you are going that far, start with something closer


Anyway, I'll find that cross section veiw of the 90 degree when I get home.

pulled from a dsm website. ..




Apparently they come in a 22 spline and a 23 spline flavor with the split in 92 and a ratio change in 97.
so. ..
315 tq, 75% to be conservative about max capacity, so a (fairly) conservative 236 tq rating in a 3760 lb vehicle. ..

_________________
"There are times when a broken tool is better than a sound one, or a twisted personality more useful than a whole one.
For instance, a whole beer bottle isn't half the weapon that half a beer bottle is ..." Randall Garrett

I think that's an interesting unit. It looks close to 1:1, I wonder if it is? I wonder if it could be a help for some people with bike or snowmobile engines?

Are there any FWD transaxles that have bolt on bell housings?

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Use a rear transaxle from an early 60's Pontiac Tempest. May have been related to the Corvair transaxle.

Might be a bit hard to find these days...