sscguy
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| posted on 10/12/04 at 04:43 AM |
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BEC Differential/Drivetrain choices?
Hey all, I'm a bit new to all this, so apologies if I'm out of line with a question that's been asked 1000000000 times. I've
been researching this whole bike-engined car thing, specifically in a Locost chassis, and one of the biggest things I've had trouble with is
figuring out how exactly to transfer the power to the rear wheels. I've seen some of the Quaife units, though they're expensive. I
don't want to run the chain directly to a rear axle, as that'd be equivalently like a locked diff all of the time.
My examples are limited, being on the wrong side of the big pond, and I thought you fellas would be able to draw from a bigger pool of knowledge. Do
you all have any preferences or suggestions?
Thanks in advance 
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Rorty
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| posted on 10/12/04 at 05:26 AM |
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quote:
Originally posted by sscguy
I don't want to run the chain directly to a rear axle, as that'd be equivalently like a locked diff all of the time.
It would function OK as long as you didn't weld the diff up or fit a spool or Detroit Locker etc. It's just a case of replacing the crown
wheel (or ring gear as you would probably know it) with a sprocket.
I presume you're talking about mid-mounting the engine? If so, there have been several threads on this topic here, including one recently which
touched on mounting a Golf (Rabbit to you) or Torsen diff in ecentric bearings.
Have a bit of a dredge through the BEC forum and you'll come across it.
If you want to put the engine in the front, then that's the way most BECs are tackled. You simply bolt a UJ flange onto the engine's
output shaft in place of the primary sprocket and then run a prop shaft to a rer live or IRS diff.
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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alister667
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| posted on 10/12/04 at 08:09 AM |
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He mentions in his post a 'locost chassis' so I'm assuming it's a standard front engined layout. If so, all we do is run a
(modified) propshaft down the transmission tunnel to a 'normal' car diff. The drive is taken off the bike engine from the shaft that
drives the chain sprocket. It (the sprocket) is removed and an adaptor is fitted that allows the front of the prop shaft to be bolted on.
The propshaft is modified by altering it's length to fit and fitting a 'slider' to the front to allow for movement. Most also
feature a carrier bearing towards the front of the transmission tunnel.
The diff at the back can take many forms. For a standard locost the rear (live) axel from a ford escort is used - I'm not sure what you could
use in the states, mabye a MazdaMX-5 (are these called a Miata across the pond?). Some folks like a limited slip for sideways action, but I have an
open diff and it works fine. Pay attention to the drive ratio of the diff as it will have a large bearing on how easy your car cruises at (say)
55mph. Get it wrong and you could be sitting at 8,000rpm at 55 - very buzzy and not very relaxing!
All the best
Ali
http://members.lycos.co.uk/alister667/
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alister667
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| posted on 10/12/04 at 08:24 AM |
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Oh, apologies Rorty, I didn't read the last paragraph of your post and assumed you'd concentrated only on a mid-engined layout!
Also sscguy if you want more info on this sort of stuff, follow the 'search' link and stick in 'sprocket adaptor'
there'll be pics and lot's more discussion.
http://members.lycos.co.uk/alister667/
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Rorty
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| posted on 10/12/04 at 12:12 PM |
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quote:
Originally posted by alister667
Oh, apologies Rorty...
That's all right. Us Dungannon men can be a bit quick. 
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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chrisf
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| posted on 10/12/04 at 02:10 PM |
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SSCguy:
You need to get a diff from an Merkur XR4Ti. This is similar to the Sierra, though it has a 7.5" diff, not the 7". The 5-speed version
came with the 3.62 ratio and the auto had the lower gearing many of the BEC builders in the UK use.
With the Miata bit, you will top out at 80 mph. Plus, it is shaped funny. I bought my diff from low mileage car for $30
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sscguy
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| posted on 10/12/04 at 02:36 PM |
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That's excellent, thanks all for the help  :thumbs up:
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The Shootist
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 posted on 10/12/04 at 04:46 PM |
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My plan..
I plan to find a Subaru SVX rearend 3.545 ratio and LSD. The Subie has a long input snout, which means a shorter drive shaft.
The drive shaft length can be a problem in the fact that the crittical speed of the shaft is based on a length verses diameter ratio. Many european
Locosts use a reversing box, and/or a 2 piece driveshaft. With the SVX unit the long snout should keep the DS length below critical speed for a sanely
sized shaft dia.
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alister667
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| posted on 10/12/04 at 05:33 PM |
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quote:
Originally posted by Rorty
quote:
Originally posted by alister667
Oh, apologies Rorty...
That's all right. Us Dungannon men can be a bit quick.
***warning off topic***
Holy flip! Another Tyroneainian! Ahh you can take the man out of Dungannon, but you can't take Dungannon out of the man etc etc!
Where abouts were from originally?
I'm out past the Moy - Annaghmore direction.
http://members.lycos.co.uk/alister667/
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Rorty
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| posted on 10/12/04 at 11:25 PM |
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quote:
Originally posted by alister667
quote:
Originally posted by Rorty
quote:
Originally posted by alister667
Oh, apologies Rorty...
That's all right. Us Dungannon men can be a bit quick.
***warning off topic***
Holy flip! Another Tyroneainian! Ahh you can take the man out of Dungannon, but you can't take Dungannon out of the man etc etc!
Where abouts were from originally?
I'm out past the Moy - Annaghmore direction.
I grew up in Dungannon, but lived across the road from you (Mullenakill) for years before leaving those green shores. 
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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alister667
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| posted on 11/12/04 at 10:20 AM |
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quote:
Originally posted by Rorty
quote:
Originally posted by alister667
quote:
Originally posted by Rorty
quote:
Originally posted by alister667
Oh, apologies Rorty...
That's all right. Us Dungannon men can be a bit quick.
***warning off topic***
Holy flip! Another Tyroneainian! Ahh you can take the man out of Dungannon, but you can't take Dungannon out of the man etc etc!
Where abouts were from originally?
I'm out past the Moy - Annaghmore direction.
I grew up in Dungannon, but lived across the road from you (Mullenakill) for years before leaving those green shores.
Left? My God how could you leave weather like this behind <looks out window> soaking wet roads, leaden skies, monkey's out searching for
thier brass bits.
You must be mad
All the best
Ali
http://members.lycos.co.uk/alister667/
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