sean951
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| posted on 7/9/05 at 10:23 PM |
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BEC midi diff
i know that people have made their own bec diffs out of front wheel drive diffs. my question is can the same be done using a diff fom a rear wheel
drive car. is the mating to the crown wheel different? is it a matter of finding some way of holding the diff unit in the car? any feedback would be
greatly appreciated.
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kb58
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| posted on 7/9/05 at 10:31 PM |
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It's virtually the same part. You'll still have the same issues though, how to lubricate it, how to attache the sprocket, etc.
Or, spend $1000-1200 for a Quaife sealed unit... which are based on Fiesta or Civic axles.
[Edited on 9/7/05 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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sean951
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| posted on 7/9/05 at 10:38 PM |
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that was a fast responce , and thats what i wanted to know, thanks. im not to crazy about spending $1200 on the quaife sealed unit just yet, i
consider it a last resort if i cant make anything work. im wondering if anyone has used a diff from a rwd rear end in their BEC. maybe they can chime
in.
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kb58
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| posted on 8/9/05 at 12:02 AM |
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Search around in this very forum; there were a couple threads on this recently, about making a cup that goes over a car's diff to make it a
stand-alone component.
Keep in mind the $1200 Quaife part looks much more reasonable once you factor in the Quaife LSD in it, which is about $800-900 by itself.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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sean951
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| posted on 8/9/05 at 12:30 AM |
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that is a very good point, it is quite a value when you put it that way. but cost is a big issue in my build, as im sure it is with many. so if there
is a cheaper way in doing something, i have to explore that option first. if i can make my own diff set-up for less than $500 and still has limited
slip, i will do it. i know that the factory limited slip from a car is not as good as the Quaife unit. but i have to put things in relative terms,
when it all comes down to it, im trying to building a fun, inexpensive car. other than autocross, im not planing on going competitive, i wouldnt even
know what class the car would fit in. so i have to select every part with that goal in mind.
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chrisf
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| posted on 8/9/05 at 01:48 AM |
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Sean:
Have a look at the 26 spline GM LSDs. These can be yanked from the scrappers for very cheap. You'll have to research this a bit to see what
vehicles they came in.
Honestly, I would look at these because they are a true Torsen. But like KB says, it will need
a cup machined to keep the bits slippery. Try PMing Sven. He's researched this quite a bit.
Alternatively--and since you are on a budget here--have you considered running the bike engine parallel to a regular car diff (like those BMW bits
folks have been talking about) and running a chain directly to the nose. Mike in the 3 wheel section did this to his Abarth and has some good pics of
what he did. I can't imagine it cost him more than $100. But I'm sure it weighed much more as well.
--HTH, Chris
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Chris Clarke
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| posted on 8/9/05 at 02:56 AM |
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I was going to recommend the Torsen also, it is a very good diff for these types of cars, and I think is used more than the Quaife in production (I
haven't looked into Quaifes much). I think they perform basically the same, except that the Quaife have a preload on them, so it will still act
as a lsd if you lift one wheel, whereas the Torsen will act as an open diff. Correct me if I am wrong on the Quaife.
Torsens are used in some Miata's, you can also use all the driveline parts from them, stub axles, CV's, driveshafts, uprights, hubs, etc.
Seeing as you are in the states, they shouldnt be too expensive for the whole rear end. In fact, the Miata would make a really good donor car for a
midi.
Here is an ebay bid for the torsen from a Miata, it could be a little expensive if you arent getting a donor. You can see the support bearing on the
unit.
Miata Torsen
You can seal and drive it the same way as previously mentioned.
I dont know anything about the GM unit, except you could get the Torsen in some 4th gen Camaros.
[Edited on 8/9/05 by Chris Clarke]
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sean951
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| posted on 8/9/05 at 11:13 AM |
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i have considered picking up a miata at a local auction for parts. ill have to u2u Sven to see what he has to say. i actually emailed Micke asking
about the upside down car diff. this is by far the easiest and cheapest way. but it is heavy, and i would rather run the engine the same way its
mounted in the bike, for oil surge issues. this is not possible with the car diff. but im still considering it.
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kb58
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| posted on 8/9/05 at 02:03 PM |
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quote:
Originally posted by Chris Clarke
I was going to recommend the Torsen also, it is a very good diff for these types of cars, and I think is used more than the Quaife in production (I
haven't looked into Quaifes much).
[Edited on 8/9/05 by Chris Clarke]
AFAIK, "Torsen" diffs are manufactured by Quaife.
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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kb58
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| posted on 8/9/05 at 02:06 PM |
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quote:
Originally posted by chrisf
Alternatively--and since you are on a budget here--have you considered running the bike engine parallel to a regular car diff (like those BMW bits
folks have been talking about) and running a chain directly to the nose.
--HTH, Chris
I wonder how this lasts. Automobile diffs aren't intended to have a big side load (from the sprocket/chain) on the pinion bearing so I'd
expect it to fail quickly. Of course if "quickly" means 10,000hrs instead of 50,000hrs, who cares...
Edit: I should have added that it may be tough to get the gearing right. By having an automotive diff in the picture, there's another 3:1
"ish" gear reduction ratio that'll mess with things. I haven't worked it out, but just bringing this up in case you're
really going to do it. Make sure to run through all the numbers first or it could be an unpleasent surprise to find your car has a top speed of
52mph...
[Edited on 9/8/05 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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MikeR
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| posted on 8/9/05 at 06:37 PM |
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But .......... if you've got a sproket at both ends (ie bike gearbox and diff) surely you can get different numbers of teeth to sort out the
gearing somewhat.
And bear in mind this is exactly what the current lot of bec's do (although via a prop shaft which just gives 1:1 ratio.
Could you add nother bearing to the other side of the diff to help support the sproket ? Surely that would help extend the diff life.
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Chris Clarke
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| posted on 12/9/05 at 08:30 PM |
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quote:
Originally posted by kb58
Edit: I should have added that it may be tough to get the gearing right. By having an automotive diff in the picture, there's another 3:1
"ish" gear reduction ratio that'll mess with things. I haven't worked it out, but just bringing this up in case you're
really going to do it. Make sure to run through all the numbers first or it could be an unpleasent surprise to find your car has a top speed of
52mph...
Our FSAE car has a Kawasaki ZX6R in it, it redlines at 13500 rpm. We run 13" tires with a loaded radius of 9.81" (Goodyear Eagles 20.0 x
6.5-13).
With our final sprocket ratio of 3.462 (45/13 teeth) and the individual gear ratios of:
1 -- 2.923
2 -- 2.063
3 -- 1.632
4 -- 1.381
5 -- 1.217
6 -- 1.083
Primary: 2.023
We have the following top speeds in each gear.
1 -- 61.9 km/h
2 -- 87.8 km/h
3 -- 111.0 km/h
4 -- 131.1 km/h
5 -- 148.7 km/h
6 -- 167.1 km/h
So top speed would be about 104 mph.
To get a top speed of 135 mph you would need a sprocket ratio closer to 2.69, which would be 35/13.
Here are the speeds for each gear with a 2.69 sprocket ratio.
1 -- 79.6 km/h
2 -- 112.9 km/h
3 -- 142.7 km/h
4 -- 168.6 km/h
5 -- 191.2 km/h
6 -- 214.9 km/h
I imagine that the gear ratios would be lower numerically for a larger displacement bike engine, as there is more torque and the redlines are lower.
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Rorty
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| posted on 13/9/05 at 07:03 AM |
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quote:
Originally posted by kb58
AFAIK, "Torsen" diffs are manufactured by Quaife.
Torsen diffs are made by Torsen Traction. They are a superior item compared to a Quaiffe ATB.
The nose bearing in just about any diff will adequately cope with the loads imposed by a bike engine. The relative loads wouldn't even be close.
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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RallyHarry
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| posted on 13/9/05 at 09:34 AM |
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eh, what ?
"Torsen" is short for >>torque sensitive<< and could be manufactured by anyone (with the right skills :-)
Mazda Miata(MX5) has a lovely torsen diff, dunno about the weight though ...
Cheers
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Rorty
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| posted on 13/9/05 at 01:13 PM |
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quote:
Originally posted by RallyHarry
"Torsen" is short for >>torque sensitive<< and could be manufactured by anyone (with the right skills :-)
Mazda Miata(MX5) has a lovely torsen diff, dunno about the weight though ...
Cheers
Zexel Torsen patented the Torsen diff in the early eighties, producing the Torsen T1 and have produced them for, or licenced them to, IIRC, twelve car
manufacturers including Mazda.
They derived their name from TORque SENsing. I think they're now Jap owned.
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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Syd Bridge
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| posted on 13/9/05 at 03:12 PM |
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Not to take this too far off topic, or upset anyone's i'net surfing skills, but....
Torsen diffs were invented by a one Vernon Gleasman, and the initial manufacturing rights and first units were made by Gleason Works in Rochester, New
York. Gleasons still make them, to fit a number of cars, and a few to fit Sierra 7" will be available soon exclusively from a certain person of
Australian birth!Still gotta find a source of sensibly priced cwp's. They dont cost £150 to make, but sell for £450+. Maybe another job for
Gleasons!
Gleasons also cut gears for many race and rally teams, from FF to Indycars and F1.
The patent has run out, but because the internals are difficult to cut, and need special machines(in gearcutters terms) few are tempted to make them.
[Edited on 13/9/05 by Syd Bridge]
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chriscook
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| posted on 15/9/05 at 04:55 PM |
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There's no problem with the reduciton you get in the chain drive as you won't have the reduction from the diff as you are driving the
crownwheel not the pinion.
Chris
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