OzVMX Forum
Clubroom => General Discussion => Topic started by: Michael Moore on January 31, 2014, 08:50:31 am
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I've found some photos on the web of Rich Thorwaldson's "Thorks" leading link forks. Motocross Action magazine (MXA) appears to have done a test on them about 1979. I don't have an exact date for that issue of the magazine.
If anyone has a copy of that I'd very much appreciate getting a clear scan of the article.
cheers,
Michael
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It looks like that article was in the October 1979 issue, should anyone have that falling readily to hand.
cheers,
Michael
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I hate paying collector's prices for a magazine just to get one article, but in this case I'm glad I did.
http://www.eurospares.com/graphics/chassis/MXA197910Thorks.pdf
I found the comments very interesting, and I wonder how many sets were sold. I suspect there was a lot of sales resistance of the "I'm a sheep, no wait, I mean racer, I don't want anything that looks different from what everyone else is using" type.
:)
The comments on the lack of flex seem spot on to me. I've been in ruts with vintage teleforks where turning the handlebars didn't seem to result in much turning down at the wheel in the rut. 4 pounds lighter than the comparable teleforks is a pretty fair savings.
cheers,
Michael
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Anyone ever see a set on a bike, at the track?
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They're very similar to my Swenco forks.
(http://i1112.photobucket.com/albums/k495/firko2/swencoleadinglink_zps836d8e93.jpg) (http://s1112.photobucket.com/user/firko2/media/swencoleadinglink_zps836d8e93.jpg.html)
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WoW :D Those Swenco's look pretty trick. I was toying around with the idea of putting a set of leading link forks on my B44 and did put the feelers out for a set off a Greeves or similar, but had no luck.
I like the idea of having nealry zero flex and no diving under brakes....
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I'm intending to put the Swenco's on my DT1 when I get a chance. I have a vision of turning it into a desert sled circa 1970.
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Cool....reads like you've got a full build list this year then Mark....
I like the alloy bottom loop on the Swenco's. Probably doesn't weigh any less than the ChroMo set up but it looks more rigid. I wonder if there is more flex in the Swenco's compared to other leading links because of the conventional type clamps used?
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like the alloy bottom loop on the Swenco's. Probably doesn't weigh any less than the ChroMo set up but it looks more rigid. I wonder if there is more flex in the Swenco's compared to other leading links because of the conventional type clamps used?
No idea TBM, I got them in a swap deal with a mate . He'd bought them for a Hodaka project but got the wrong ones, these are for medium sized bikes like my DT1. I don't really know much about leading link forlks and have only ever ridden on bike, a Greeves, fitted with them. As far as projects for the year, I'm not sure if I'll get to half of them but I live in hope.
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As far as projects for the year, I'm not sure if I'll get to half of them but I live in hope.
A man has to have hope.....otherwise the only outcome will be failure ::)
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I think De Coster ran them in a couple of GP's on the works RN. Honda had a go also. J
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I like the alloy bottom loop on the Swenco's. Probably doesn't weigh any less than the ChroMo set up but it looks more rigid. I wonder if there is more flex in the Swenco's compared to other leading links because of the conventional type clamps used?
I suspect they aren't as stiff as the tubular steel links on the Thorks. Aluminum is 1/3 as stiff as steel, and the metal in the middle of a solid section doesn't do much work. Also, a closed box is stiffer than an open "U" channel is and resists torsional loads much better. Aluminum has 1/3 the weight, but that solid aluminum bar will weigh about 4.75X the steel tube. Aluminum needs to have larger sections to have an advantage over steel. An aluminum tube of about 1.1" OD x .187" wall will have similar stiffness to the 1x.062" steel tube and about the same weight.
A 1.05" OD solid round of aluminum has about equal stiffness as a 1" x .062" steel tube
The Swencos have a small stanchion, designed to slip into the stock clamps, and those small forks are often not very well clamped, as anyone who has fallen down and had to straddle the front wheel to twist the handlebars back perpendicular to the wheel can attest. If they are welded up there's no slippage. On John Cronshaw's very fast and successful Goldstar VRR bike he's gone to fabricated steel clamps welded directly to the telefork stanchions for less weight and greater stiffness.
http://www.eurospares.com/graphics/chassis/CronshawBSAweldedfork.jpg
DeCoster/Honda used the Ribi forks, which are much more complicated (and expensive) than the normal LLFs like the Thorks. You can find some Ribi patent documents in that folder on my website.
cheers,
Michael
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I found a side-view photo of a small Honda with Thorks on it in "Design and Tuning for Motocross" by Gianatsis. It shows the pivot/axle relationship
http://www.eurospares.com/graphics/chassis/HPFHondaThorksD&TforMX.pdf
cheers,
Michael
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I think De Coster ran them in a couple of GP's on the works RN. Honda had a go also. J
Those were the Ribi forks - not Thorks