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Thread: Race chassis

  1. #1246
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    28th November 2013 - 21:58
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    Dawes Jaguar
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    Thanks everyone, I think I'll probably give it a go. As an apprentice I used various brazing methods from hearth/forge, town gas and air to OA, but that was a long time ago. Also used a carbon-arc "torch" to build a racer back in the 80s.
    Bloke in the local gas suppliers said he's heard that oxygen consumption is much higher, but, still worth trying, I think.
    Baby TIG on the wishlist, too.

    Back to actual chassis (chasses?), I posted this scan on ESE for the crank picture but I thought the bolt in bracing was interesting and the apparent lack of support for the SA pivot a bit puzzling...
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  2. #1247
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    13th June 2010 - 17:47
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    Obviously stiff enough...I'd pick that there's some cancelling of at least vertical loads at the pivot with the lower shock mount apparently sharing the pivot pin.
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  3. #1248
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    12th February 2004 - 10:29
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    bucket FZR/MB100
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    Wheel exerts upward force on swingarm which is resisted by suspension strut. Swingarm pivots about suspension strut connection point exerting downward force on swingarm pivot. Suspension struts under compression through bellcrank compress shock therefore also exerting a downward force of swingarm pivot. At rest all downward force on swingarm pivot is balanced by upward force on bellcrank pivot.

    Looks to me like suspension compression forces result in an extension force in the frame between the swingarm pivot and the bellcrank pivot. With the geometry of the various bits this results in a force trying to rotate the bellcrank pivot about the swingarm pivot.

    Without the usual pivots at the lower end the forces on the swingarm pivot and bearings will be a lot less.

    Or have I got it all wrong?

  4. #1249
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    25th March 2004 - 17:22
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    Sounds good. As long as you don't have to lean the bike over for any reason.
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

  5. #1250
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    20th April 2011 - 08:45
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    Quote Originally Posted by F5 Dave View Post
    Sounds good. As long as you don't have to lean the bike over for any reason.
    A reason might be that a racing track has more corners than straights, and for negotiating corners without leaning over you'd need more wheels...

  6. #1251
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    2nd July 2013 - 11:52
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    Click image for larger version. 

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ID:	331418i never made to the last bucket meet but out the blue someone made this 50 frame and turned up with it , my brother said it went ok for its first time out , looks like some shorter forks would suit it , would be hard work on a kart track
    i'm over buckets

  7. #1252
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    25th March 2004 - 17:22
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    Yeah the guy brought it in from Holland, sort of Kreidler rotary valve replica with a Derbi type barrel and presumably replica frame. He said it flowed around the corners nicely. With that rake and seating position I would think that was just riding a small bike for the first time in 20yrs.
    Was pretty cool though.
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

  8. #1253
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    13th June 2010 - 17:47
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    Quote Originally Posted by F5 Dave View Post
    Yeah the guy brought it in from Holland, sort of Kreidler rotary valve replica with a Derbi type barrel and presumably replica frame. He said it flowed around the corners nicely. With that rake and seating position I would think that was just riding a small bike for the first time in 20yrs.
    Was pretty cool though.
    Well that story answers the question I had as to where the fairing came from....Someone needs to get a mould off it quick.
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  9. #1254
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    2nd July 2013 - 11:52
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    Quote Originally Posted by Grumph View Post
    Well that story answers the question I had as to where the fairing came from....Someone needs to get a mould off it quick.
    just about looks like my gt50 fairing
    i'm over buckets

  10. #1255
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    25th March 2004 - 17:22
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    In the same way a GSXR1000 fairing does. Put yer glasses on Scotty.
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

  11. #1256
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    2nd July 2013 - 11:52
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    Click image for larger version. 

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ID:	331423my last bucket build number 20
    i'm over buckets

  12. #1257
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    2nd July 2013 - 11:52
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    Quote Originally Posted by F5 Dave View Post
    In the same way a GSXR1000 fairing does. Put yer glasses on Scotty.
    if you say so prity boy
    i'm over buckets

  13. #1258
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    2nd July 2013 - 11:52
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    Click image for larger version. 

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ID:	331425gsxr1000 fairing lol
    i'm over buckets

  14. #1259
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    20th April 2011 - 08:45
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    Quote Originally Posted by mr bucketracer View Post
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    someone made this 50 frame and turned up with it , my brother said it went ok for its first time out , looks like some shorter forks would suit it , would be hard work on a kart track
    Quote Originally Posted by F5 Dave View Post
    Yeah the guy brought it in from Holland, sort of Kreidler rotary valve replica with a Derbi type barrel and presumably replica frame. He said it flowed around the corners nicely.
    Flowing nicely compared to what? A Harley-Davidson? Going by the rake angle there can't have been much difference.
    The frame itself does indeed look like a copy of a Van Veen Keidler, a very desirable veteran. I estimate that of the maybe 60 or 80 original Van Veen racers that were ever built, only 200 or so are still around .
    And Bucketracer is right about the forks: shortening them by about 150 mm would give the bike a more genuine look. It would also improve the handling, but still not nearly enough for a kart track. You would have to shorten the wheelbase another 100 mm and move the rider 200 mm forward in order to stand a chance.

    In Europe we run classic 50 cc racers and the new Freetech-50 class simultaneously in order to make up the numbers and split the track costs.
    The classics are lower and lighter than the Freetech bikes that are mostly built around a Honda RS125 chassis with tires twice as wide as the classics have.
    On the straights the classics can hold their own but when a corner comes up, the Freetech bikes outbrake them and ride circles around them. And this is on long, flowing classic circuits. On kart tracks the classic guys won't even bother to turn up.

    Click image for larger version. 

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    Yours truly with a Van Veen Kreidler, some time (about an century) ago.

  15. #1260
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    25th March 2004 - 17:22
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    Quote Originally Posted by mr bucketracer View Post
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ID:	331425gsairing lol
    The GT fairing does look cool, but itsabout twice the height. The Kreidler one looks like the belly of a dolphin.
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

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