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PostPosted: October 7, 2016, 5:15 pm 
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I am looking at building a middie with a Triumph triple engine. I would like to have differential motion intact so no solid or welded diff. Originally, I was thinking of either connecting the bike output directly to diff input (I already have Miata parts laying in the shop) or hacking it up for a chain drive by removing the ring gear. The later is a lot of extra custom work to get the oiling right and the former leaves no room for gearing changes. The max speed is 77. This got me thinking about using a transmission from a FWD car. Use the stock subframe and suspension. Mount the motorcycle output directly to the transmission input with a custom made giubo. The benefit here is direct drive in 4th, OD in 5th, and reverse. I can live without reverse but other than hacking the case up, I think this is reasonable doable. I just want to make sure that I am not completely missing something. Also, if there any reason I couldn't do this with an auto? I know that there is a history of racers using powerglides with clutches instead of torque converters. I would just have to figure out how to force the gear I want. Thanks. I would have asked this one the grassroots motorsports board but I want it to be a little bit of secret.


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PostPosted: October 7, 2016, 7:01 pm 
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Joined: June 15, 2010, 8:29 am
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Location: Duxbury, MA USA
2 transmissions in series? Maybe I am confused...

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PostPosted: October 8, 2016, 3:00 am 
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Most bicycles and trucks do this. Motorcycle engines ( most anyway ) already have a reduction in front of the transmission and then another reduction in the chain, so they sort of have three but you can only change the gears or ratios in the middle one. You can have as many as you want. You get to lose a little power and efficiency with every one of them.

Wether or not this is a good idea is another thing. If you use a bike engine with a dry clutch, maybe you can take the power right off the crank which helps with ratios and might be simpler. There are also high performance bike engines used in snow mobiles and water craft which don't have transmissions either. None of this is really easy though.

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PostPosted: October 8, 2016, 10:18 am 
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Location: Cornholio OR "Where the magic happens"
Driving a diff with a chain or belt is not that hard.

You need a can or cover for the diff and seals on the axles to keep the lube in.
Then some plates to hold large sealed bearings to support the diff.
And replace the ring gear with a sprocket for belt or chain.

I have thought about this for a long time, wanting to build a motorcycle trike with reduced unsprung weight.

Im sure Im not the only one who is a member of both forums but I won't blab.....

Modern cycle motors with unitized transmissions will be difficult at the least to separate.

I was thinking of using a lighter diff & axles like from the rear of a Pilot or AWD Subie both of which are FWD biased AWD.

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PostPosted: October 9, 2016, 3:04 pm 
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Direct coupling and 2wd? The VW 02M might be worth looking at.
The input shaft doesn't use a pilot bearing so that's a benefit.
5th and 6th are decent ratios, you should be able to remove the entire 1-4 gear cluster to save weight and you keep reverse.
A giubo between the bike output and the trans input would take care of minor misalignments, mounting them together might be difficult.

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PostPosted: October 9, 2016, 7:49 pm 
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There were some guys trying to do something similar with I think a hayabusa engine in a miata, using the miata transmission. They gutted the bike transmission and ran a jackshaft through the case with an automotive flywheel and clutch. They had some pretty bad driveability issues that they tracked down to the slop between the primary reduction gears. If you're keeping the bike clutch, you might not run into that issue though.
Kristian

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PostPosted: October 9, 2016, 8:31 pm 
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Good info gang. I will start fooling around with this soon and let you know how it goes.


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PostPosted: October 10, 2016, 11:19 am 
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Don't know if this is of help, but here's my $.02.. Experience has led me to avoid chain-driven cars at all costs.. too many issues with chain stretch, dry chains, heat, and chain breakage.. some have ok success with a chain-bath setup, but those can be tough to fab.. (not that it can't be done) ...I've lost several fun off road riding days because of motorcycle-powered buggy chain reliability issues.. sucks to build the thing and have a stupid chain be the car's Achilles heel.. :cry:

Using 'car' gears to shift a BEC.. for a short time I had a T5 inline in a former BEC project (I could shift at the bike box or through the T5).. I found the car tranny's gears were too far apart to be fun/effective with the bike engine.. after a short time I reverted to just using the bike box to shift (paddle shifted), even though I had the ability to use the traditional H-pattern gearshift-- used that only when reverse was needed, which of course was rare.. (vibration issues eventually had me pull the T5, and I didn't miss it)

If you're still interested in a car tranny, I didn't go down this road, but I thought an old-school VW trans might work if you go front/mid engine (bike) and RWD.. You'd eliminate the VW clutch bits and just use the bike's clutch.. coupling it would be work, but doable.. this puts some weight on the rear axle (ideally in a good way), IRS, reverse, and shifts like a 'car'.. Even if you learn you don't use it (the VW box) to shift (you just use the bike's tranny for that), it still incorporates reverse and IRS, albeit with a weight penalty..

Keep us updated- and don't forget to take pics :wink:


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PostPosted: December 4, 2016, 8:17 pm 
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ccrunner wrote:
If you're still interested in a car tranny, I didn't go down this road, but I thought an old-school VW trans might work if you go front/mid engine (bike) and RWD.. You'd eliminate the VW clutch bits and just use the bike's clutch.. coupling it would be work, but doable.. this puts some weight on the rear axle (ideally in a good way), IRS, reverse, and shifts like a 'car'.. Even if you learn you don't use it (the VW box) to shift (you just use the bike's tranny for that), it still incorporates reverse and IRS, albeit with a weight penalty..
Hope you don't mind if I resurrect this old thread, but your comment caught my eye, so I went out to the shop to take a few measurements.

First I crawled under the back of a 1981 Vanagon someone gave me years ago. The engine is conveniently removed, so I slid a tape measure in there and found out the input shaft is 6" from the top of the box. That's the same as the Hewland Mk9 in my vintage sports racer (VW IRS case).

I also have two motorcycle engines...a 1980 Honda CB750 that is about 7.5" from the bottom of the sump to the output shaft, and an '05 GSXR 1000 that's 8" from the bottom its dry sump pan to the output shaft. In either case the transaxle would have to be raised ~3" and the shafts would have to be coupled, but for a street car application these factors, and the the weight increase, would be tolerable if it will work.

Off to the googles... ;)

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PostPosted: December 6, 2016, 11:58 am 
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While we're commenting on this thread, I guess I could add a pic of our Quaife reverse box / diff coupled to a CBR1000RR -
Image

Solves all the issues, however at a significant cost $$$$$.
Check out the build log for more details - viewtopic.php?f=36&t=17633&start=30

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PostPosted: December 8, 2016, 1:10 am 
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Nice! Is that the powertech unit?


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PostPosted: December 10, 2016, 12:23 am 
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It's a Quaife QBA11R gear drive / reverse box / LSD / all in one / bring your checkbook unit.
They have them in a few different styles, the one we chose pretty much lends itself to a middy.
https://shop.quaife.co.uk/motorcycle-engined-cars

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PostPosted: December 10, 2016, 1:19 am 
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Yeah if memory serves they were, or are, around $3000, not counting the axles.

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PostPosted: December 10, 2016, 2:14 am 
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Closer to double that by the time you have it in your hand with the stub axles.

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