OzVMX Forum
Clubroom => General Discussion => Topic started by: ba-02-xr on February 16, 2009, 08:11:56 am
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Was going through some old mags on the weekend & found some articles about the boysen link rear suspension. I remember the big deal the world made of this amazing but complex system. Does anybody know what ever hapened with the system. There were predictions that it would be on production bikes in a few years. But instead the manufactures went simplier eg PDS.
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(http://i323.photobucket.com/albums/nn458/mx250syd/MXA_feb08-AncientArtifactsweb_Page_.jpg)
" Chain Torque. It's a phrase that almost never crops up in conversation, unless you are talking to Horst Leitner or Eyvind Boyesen. Both men have spent a large percentage of the last 30 years trying to convince the motorcycle industry of the evils of chain torque.
The parallelogram Boyesen Link has been tested by everyone from Bob Hannah to Jo Jo Keller (who made the top five in an AMA 250 National on the bike) to Roger DeCoster - and always with rave reviews. However, it's confusing to look at the multiple linkage arms that replace the bike's normal swingarm pivot.
In action, the Boyesen Link produced four major effects:
(1) It reduced pitch changes (because the polar moment of inertia was reduced). (2) It improved rear wheel contact (because the shock absorber was not subject to outside forces).
(3) Suspension rise was lessened under varying throttle loads.
(4) It balanced out the chassis by reducing chain torque.
Unlike ATK and AMP Research designer Horst Leitner, Eyvind didn't want to start his own motorcycle company to get his anti-chain torque knowledge into the mainstream. He wanted a major manufacturer to license his design (most manufacturers have paid Boyesen royalties for his reed and porting designs). They never did. Not because it didn't work, but because the tooling and development costs were too expensive. As for Eyvind himself, the bike he races today has a Boyesen Link on it. "
http://www.motocrossactionmag.com/ME2/dirmod.asp?sid=&nm=&type=news&mod=News&mid=9A02E3B96F2A415ABC72CB5F516B4C10&tier=3&nid=D875899FB2D14E99826BBB1DEB2161C8
Scan the article and flash it up; I'd be interested in reading it.
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The article I was reading was in Trail & track. It said pretty much what your bit said but over 3 pages. There was also a article in ADB but it was pretty uninformative. Just interesting to see what happened to these ideas. Ha just had a thought. Would it be legal in a pre 90 class. That should open a can of worms.
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There is also a thread on it here : http://mxtrax.co.uk/boysie-link/forum/viewtopic/60/286159?siteid=6 (http://mxtrax.co.uk/boysie-link/forum/viewtopic/60/286159?siteid=6)
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The article I was reading was in Trail & track. It said pretty much what your bit said but over 3 pages. There was also a article in ADB but it was pretty uninformative. Just interesting to see what happened to these ideas. Ha just had a thought. Would it be legal in a pre 90 class. That should open a can of worms.
Its essentially a parallelogram arrangement. Even before LTR suspension became an issue the Yankee Corp, US importer of Ossa, work with an 'inventor' and made an Ossa with a parallelogram rear suspension. They claimed better rear suspension performance, probably because of the reduced 'chain torque' (it was known even back then with 4 inchs of travel and 18hp ::)). I think others have played with the parallelogram suspension. There are some engineering advantages of isolating the forces acting on the suspension. But there are other disadvantages such as weight and complexity.
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Interesting Bob Hannah fact, in 1986 Bob won the Unadilla 250GP riding a Boyesen link Factory Suzuki, rumored to have 14" ( 35cm +)rear wheel travel. It is my understanding that this was the only time Bob could race the Boyesen link, because of the production rule in the USA did not apply to a World GP.
In the past I have read a couple of articles from Ivan Boyesen. it seams the Japanese Companies did not like the high production cost.
Team Zundapp
Terry
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Its essentially a parallelogram arrangement. Even before LTR suspension became an issue the Yankee Corp, US importer of Ossa, work with an 'inventor' and made an Ossa with a parallelogram rear suspension. They claimed better rear suspension performance, probably because of the reduced 'chain torque' (it was known even back then with 4 inchs of travel and 18hp ::)). I think others have played with the parallelogram suspension. There are some engineering advantages of isolating the forces acting on the suspension. But there are other disadvantages such as weight and complexity.
I come across this pixie; nice bit of fabrication/engineering. This application addresses two Bultaco, Montesa et al issues of the period.
(http://i323.photobucket.com/albums/nn458/mx250syd/museomotos22wz0.jpg)
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That's what I was looking for Graeme. When this thread started I thought about the Bulto parallelogram (try to write that after a few cold 'uns) but couldn't find a pic so I didn't post.
That one might be a (very neat) home-built jobbie, 'cause I don't remember the Bulto set-up using a cross-over shaft.
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That's what I was looking for Graeme. When this thread started I thought about the Bulto parallelogram (try to write that after a few cold 'uns) but couldn't find a pic so I didn't post.
That one might be a (very neat) home-built jobbie, 'cause I don't remember the Bulto set-up using a cross-over shaft.
Nice work isn't it Tim. I would love to try one just to see if there is a discernible difference. For the same reason I would love to try the new BMW.
I think this Bully is unnecessarily complex (and unnecessary additional weight). The same thing could have been achieve by moving the parallelogram's pivot forward to make the c/shaft sprocket co-axis. But it is neat with the original frame intact and the parallelogram metal work added on. But results in a short(er) swing arm which I don't think is ideal. The other feature I find interesting is the heavier bottom s/arm and the fact that the rear wheel and the c/shaft sprocket are not in the middle of the parallelogram, but equal distance. I'll have to think this through ::).
The other interesting feature is the additional hole on the rear wheel carrier. Looks like it's for adjustment.
Here's another.......
(http://i323.photobucket.com/albums/nn458/mx250syd/Dholda02.jpg)
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Graeme, rumour has that the new BM is crap. Apparently the front end leaves a LOT to be desired. BTW did you know the motor is made my Kymco? Yup, Chinese scooter makers.
I don't know about the parallelogram set-up. Of more importance, IMO, would be a floating rear brake. Most bikes when you use the rear brake lock the rear suspension (that's the reason for those nasty breaking whoops into a corner) a bike with a floating rear brake still has suspension under braking. It was tried on a few bikes (de Costers Suz) and then dropped. Dunno why.
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All this assumes there is a 'problem' with chain torque, most manufacturers seem to work with it or put the swingarm pivot as close to the countershaft as possible. These blokes probably don't want to know how moving the pivot point up or down(in relation to the output shaft) is used to dial in squat or anti squat by just about every 125/250/MotoGP/WSS/WSBK/AMA and Australian superbike teams ::)
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All this assumes there is a 'problem' with chain torque, most manufacturers seem to work with it or put the swingarm pivot as close to the countershaft as possible. These blokes probably don't want to know how moving the pivot point up or down(in relation to the output shaft) is used to dial in squat or anti squat by just about every 125/250/MotoGP/WSS/WSBK/AMA and Australian superbike teams ::)
Apparently chain torque is an issue which can be minimized by careful c/sprocket location rather than eliminated. I believe it was the root cause for Suzuki at the GP500 level for years. Some frames come with an adjustab;e pivot for this reason.
Here another........
(http://i323.photobucket.com/albums/nn458/mx250syd/NSUBMW1.jpg)
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He he how many R series Beemers around with a chain drive? ;D
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This is why i like this forum. I didn't know this type of linkage existed. Fascinating stuff!
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This is why i like this forum. I didn't know this type of linkage existed. Fascinating stuff!
We aim to please ::)
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Drag cars have had a similar set and achieved the same results .
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If adjusted correctly , would it not stop the weelbase getting longer and shorter during suspension travel ?If you coupled it with a ribi frunt the bike wouls stay the same length at all times?
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All this assumes there is a 'problem' with chain torque, most manufacturers seem to work with it or put the swingarm pivot as close to the countershaft as possible. These blokes probably don't want to know how moving the pivot point up or down(in relation to the output shaft) is used to dial in squat or anti squat by just about every 125/250/MotoGP/WSS/WSBK/AMA and Australian superbike teams ::)
It's a point and I'd forgotten about it. Yup when you give it the berries the swinging arm tries to pull down and under the bike, locking the suspension. This trick is used extensively by trials riders.
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Hey Mates !!!!
The guy that did the development work for Yankee/Ossa was Joe Bolger.He later had a company Joe Bolger Products that sold specialty tools and made some engine mounts for foreign cars that used different mounting holes than originally.They were used when mounting holes were damaged in collisions instead of replacing or welding up the engine blocks.This info. may help if someone wants to do some more research on the subject.
Good Luck.
Bill Davis Texas Vintage Racing Club & Honorary VMXWA
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Bolger is (was?) a seriously clever bloke. Especially when he sued Suz and won.
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The guy that did the development work for Yankee/Ossa was Joe Bolger.
Yeah that name rings bells. I described him as an inventor but I remember the article describing him as having a background in lateral thinking and development.
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(http://hem.passagen.se/ossa/vanceeaton/Bolgersuspension350rt.jpg)
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This has turned very intereseting & informative. Any outher strange rear suspension set ups people can remember.
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How about the jack shaft idea on this CR125 Honda ? I read somewhere that Maico tested a similar set-up on one of their works-bikes .