Author Topic: Thorks article in MXA  (Read 5844 times)

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Offline Michael Moore

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Thorks article in MXA
« on: January 31, 2014, 08:50:31 am »
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

Offline Michael Moore

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Re: Thorks article in MXA
« Reply #1 on: February 02, 2014, 04:26:34 pm »
It looks like that article was in the October 1979 issue, should anyone have that falling readily to hand.

cheers,
Michael

Offline Michael Moore

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Re: Thorks article in MXA
« Reply #2 on: March 01, 2014, 09:20:45 am »
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

Offline Tahitian_Red

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Re: Thorks article in MXA
« Reply #3 on: March 01, 2014, 10:52:16 am »
Anyone ever see a set on a bike, at the track? 
The "Factory Novice"
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Offline firko

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Re: Thorks article in MXA
« Reply #4 on: March 01, 2014, 11:58:09 am »
They're very similar to my Swenco forks.             
                                                                                                   
'68 Yamaha DT1 enduro, '69 Yamaha 'DT1 from Hell' '69 DT1'Dunger from Hell, '69 Cheney Yamaha 360, 70 Maico 350 (2 off), '68 Hindall Ducati 250, Hindall RT2MX, Hindall YZ250a , Cycle Factory RT2MX flat tracker, Yamaha 1T250J, Maico 250 trials, '71, Boyd and Stellings TM400, Shell OW72,750 Yamaha

Offline FourstrokeForever

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Re: Thorks article in MXA
« Reply #5 on: March 01, 2014, 12:35:29 pm »
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....
Arrogance.....A way of life for the those that having nothing further to learn.

Offline firko

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Re: Thorks article in MXA
« Reply #6 on: March 01, 2014, 12:38:23 pm »
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.
'68 Yamaha DT1 enduro, '69 Yamaha 'DT1 from Hell' '69 DT1'Dunger from Hell, '69 Cheney Yamaha 360, 70 Maico 350 (2 off), '68 Hindall Ducati 250, Hindall RT2MX, Hindall YZ250a , Cycle Factory RT2MX flat tracker, Yamaha 1T250J, Maico 250 trials, '71, Boyd and Stellings TM400, Shell OW72,750 Yamaha

Offline FourstrokeForever

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Re: Thorks article in MXA
« Reply #7 on: March 01, 2014, 01:31:38 pm »
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?
Arrogance.....A way of life for the those that having nothing further to learn.

Offline firko

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Re: Thorks article in MXA
« Reply #8 on: March 01, 2014, 01:45:49 pm »
Quote

 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. 
'68 Yamaha DT1 enduro, '69 Yamaha 'DT1 from Hell' '69 DT1'Dunger from Hell, '69 Cheney Yamaha 360, 70 Maico 350 (2 off), '68 Hindall Ducati 250, Hindall RT2MX, Hindall YZ250a , Cycle Factory RT2MX flat tracker, Yamaha 1T250J, Maico 250 trials, '71, Boyd and Stellings TM400, Shell OW72,750 Yamaha

Offline FourstrokeForever

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Re: Thorks article in MXA
« Reply #9 on: March 01, 2014, 01:52:26 pm »
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  ::)
Arrogance.....A way of life for the those that having nothing further to learn.

Offline jerry

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Re: Thorks article in MXA
« Reply #10 on: March 01, 2014, 02:55:38 pm »
I think De Coster ran them in a couple of GP's on the works RN. Honda had a go also. J

Offline Michael Moore

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Re: Thorks article in MXA
« Reply #11 on: March 01, 2014, 05:13:04 pm »
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

Offline Michael Moore

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Re: Thorks article in MXA
« Reply #12 on: March 03, 2014, 11:31:02 am »
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

Offline Rusty

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Re: Thorks article in MXA
« Reply #13 on: March 07, 2014, 07:50:44 am »
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
Poke that bone back in and wrap it up tight sport - I am racing the second moto.