arrybradbury
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posted on 22/1/07 at 08:21 PM |
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BEC drivechain
I'm sure i've seen before, but a search hasn't thrown anything up, a BEC driven through 2 UJ's to a sierra diff. Does anyone
know who this is or where the topic is? I can't remember whether this was thought of as good or whether it had any flaws!
Thanks in advance
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ChrisGamlin
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posted on 22/1/07 at 09:10 PM |
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What car are you planning installing into? If its a front engine'd RWD car such as a Locost then virtually everyone uses this method, although
you'll need a centre bearing in the middle because the distance between the engine and diff is too much to use a single piece propshaft with a
UJ either end
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arrybradbury
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posted on 22/1/07 at 09:46 PM |
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I'm sure the one it was mounted in was a middie with just 2 UJ's between the sprocket adaptor and the diff.....
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RallyHarry
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posted on 22/1/07 at 09:55 PM |
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Yeh, I remember that also.
Was a year ago (and a half?) I beleive ...
Cheers
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mark chandler
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posted on 22/1/07 at 09:57 PM |
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In a middy a short prop is okay so this may be correct.
The length of the prop from sprocket to diff is quite long, a single prop will be liable to aggressive vibrations and will try and destroy itself
unless balanced perfectly. You will be hard pushed to get someone to make a single piece prop from 2" tube, they would maybe if you are lucky
make one from 3" tube as this would be stronger.
Not a good idea really, its a lot of metal at 5000 rpm threatening to take you leg out if it fails.
Regards Mark
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pathfinder
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posted on 22/1/07 at 10:24 PM |
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dunno who's car it is tho Image deleted by owner
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ChrisGamlin
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posted on 22/1/07 at 10:29 PM |
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I think someone once calculated that to make a single piece prop that was suitable for a front engine'd RWD BEC, it would need to be something
like 5" diameter. Its not the balancing as such, its the resonant frequency of a tube of that length thats the issue, so it will always be
likely to fail at a certain RPM regardless of how well its balanced.
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indykid
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posted on 22/1/07 at 10:30 PM |
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it was spunky.
from what i remember from seing it at newark, it was a bike engine, could well have been a blackbird, with a prop that was little more than 2
uj's, think they were bolted back to back, onto the sierra diff
afaik, he sold it some time last year, maybe the year before, but he still post pretty regularly
tom
[Edited on 22/1/07 by indykid]
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pathfinder
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posted on 22/1/07 at 10:30 PM |
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pic is of a Honda VTR in a midtec Spyder
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arrybradbury
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posted on 22/1/07 at 10:39 PM |
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I found it, but just after someone had done it on here, thanks guys, that was the pic i was looking for. So is that configuration still in one piece
and a suitable method for a BEC middie to avoid complication/cost of a chain drive?
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russbost
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posted on 22/1/07 at 10:54 PM |
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Spire did something very similar with a ZX12 in the Spire Gt, I think theirs was a single U/J with a sliding joint IIRC.
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NS Dev
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posted on 23/1/07 at 09:14 AM |
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to be honest you could do that in a variety of ways. If you want the engine that close then you could just make an adaptor to go onto the sierra
pinion flange that takes a rubber drive donut, then get a sprocket manufacturer (Talon Engineering) to make you up a flange to bolt to the engine side
of the donut, and which pushes onto the bike output spline as usual.
They quoted me £15 for that sort of item (basically a blank sprocket with 4 or 6 holes in it)
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
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JoelP
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posted on 23/1/07 at 07:55 PM |
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that 2 u/j method is fine IMHO, the middle piece essentially IS a prop. If you imagine the bolted flanges being a short piece of tubing etc...
And if it did fail, at least its not beside you!
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Peteff
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posted on 23/1/07 at 08:33 PM |
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I often thought (bit risky, causes headaches)
If you could get your engine to one side of the diff flange or above it you could use sprockets and a short loop of chain. If you got used different
size sprockets you could then vary the gearing so you don't depend on manufacturer ratios.
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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tks
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posted on 25/1/07 at 08:41 AM |
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no
the problem can be / is balance..
because its centered on the bolts and thats never as perfect as a straight tube wich is balanced
TKs
The above comments are always meant to be from the above persons perspective.
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wheezy
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posted on 5/2/07 at 11:57 AM |
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I got mine manufactured with 2 UJ's and a sliding tube in the middle. Overall length between the engine sprocket and diff flange is about 8
inches.
Dave
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