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fubar. check some 70's kawasakis. kr750?


Ken
 

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It was used on a lot of bikes in early 70's.
You keep constant chain tension if links are correct length, or, you can set up for rise, squat and anything in between.
It should work even better with modern dampers.
Only real issue is extra weight and a lot of pivots to wear
 

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So you could set it up so there's negligable wheelbase change throughout wheel travel.

Height of the frame attachment points has an effect on how the chassis "sees" power. Notice the modern one has longer arms on the birdgage. Off the top of my head I'd say higher the top frame attachment point is the less wheelie prone the bike.

The modern bike, assuming the shock's mounted how I think it is, the shock isn't loaded by accel/decel forces. The old bike the shocks are actually more loaded by accel than they would be in a conventional setup.

It's basically a four-bar no different than a dirt late model or a pro stock drag car. Only thing limits what you can do on a bike is that any change that makes traction under power causes it to unload on decel. i.e. can't get near as radical as you can w/a car.
 

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I think one of the big advantages of this type of swingarm is you can arrange the bars such that the theoretical pivot coincides with the drive sprocket center.

Ever notice that on modern high hp sport bikes they try to get the swingarm pivot as close to the drive sprocket as possible. I forget the geometry involved, but I know when the SA pivot gets too far away from the drive sprocket the 100+ hp transmitted through the chain starts have strange effects on the suspension behavour.

With this four link setup you can adjust it so the theoretical "working" pivot is basically forward of the drive sprocket or concentric with the drive sprocket, thereby using more of the power to turn the wheel rather than "wrap up" the suspension. Cant' be done on a conventional swingarm because of the way the chain has to go "through" the plane of the swingarm.

But evidently the downside to this setup is greater than the upside because you rarely see it used in GP racing where they can certainly afford to engineer it any way they want.
JohnnyB
 

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Look up Mert Lauwel's Harley dirt tracker, and later the Lauwel Leader mountain bike he made. He did it a long time ago and it never really caught on. I remember seeing him at a mountain bike race with a bunch of suits that had invested but had no idea who he was. You know, promo tshirts over the button down shirt. We stopped by for autographs and the suits seemed perplexed, Mert just smiled because it had happened a ton over that weekend.
 

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Bimota SB3(4?) the swingarm pivoted on the same axis as the countershaft.

Other thing with this setup, more latitude in locating engine vertically than w/conventional swingarm.
 

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Yep, seems like I do remember a Bimoto that came up with some strange way to pivot the SA on the same axis as the countershaft.

Somewhere in one of my books ...Tony Foale I think, it's all explained so a normal person can understand it.

JohnnyB
 
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