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Post by pipe welder on Mar 25, 2012 10:50:42 GMT -5
Here's a photo of Yvon DuHamel's Kawasaki 750 in '74.  Does anyone know the story behind this swingarm design? |
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Post by lc on Mar 25, 2012 11:19:40 GMT -5
Affectionately identified as "FUBAR" by the press. I believe H2Rtuner once posted the history in a thread at KTW years back.  With some effort in a search you may find it.  J |
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Post by Walms on Mar 25, 2012 11:39:01 GMT -5
Same idea as a 4-link used in car drag racing... In cars, it is useful as the differential doesn't rotate under load and it plants the tires better....
Not sure if required on a chain drive for that reason but it sure would be beefie for wheel deflection! I like it!
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Post by sooperarthur on Mar 25, 2012 16:02:40 GMT -5
There was some kind of handling issue with that set up I think. I remember seeing a motocross bike with that setup on it too. Or maybe it was too many parts with not enough benefit. ?
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Post by Walms on Mar 25, 2012 18:11:42 GMT -5
You'd need To use ball bearings on the pivots to get the required rigidity.
Bronze bushings would not be the way to go... Not sure what they did on Yvon's bike.
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Post by pipe welder on Mar 25, 2012 18:13:55 GMT -5
It looks like a lot of un-sprung weight and I don't see the rotation benefit.
Maybe it was just perceived to be more rigid than the two arm swing arm.
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Post by lc on Mar 25, 2012 18:54:08 GMT -5
As I recall the design intent was there was supposed to be some sort of anti squat tendency when on the power. It didn't work as planned.
If you post your question (addressed at 'tuner) over at Kawi2strokes I'm sure 'tuner will chime in with the full story.
J
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Post by Walms on Mar 26, 2012 6:14:21 GMT -5
As I recall the design intent was there was supposed to be some sort of anti squat tendency when on the power. It didn't work as planned. J I could see it helping the hop of a shaft drive bike, but I can't see how it would do anything for anti squat? Did they just have their fingers crossed? ;D |
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Post by lc on Mar 26, 2012 13:11:17 GMT -5
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Post by Walms on Mar 26, 2012 19:52:57 GMT -5
If you look close at some of those pics, I think that the pivots are closer together at the front then they are the rear... They probably did their best to make the links look parallel to throw off the competition... ;D Parallel links would make the axle pivot the same as a single swingarm. An un-parallel 4 link would allow you to set it up so that there was an artificial pivot point of the axle over the counter shaft, keeping the chain at the same tension through the full travel of the suspension. I'm still struggling with why this would prevent a bike from doing a wheelie though... |
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Post by sooperarthur on Mar 26, 2012 23:07:15 GMT -5
I think the torque produced from the rear wheel would force the top link forwards/down and the bottom link downwards/rearward. which, well in my head would plant the front wheel.
Or is it the simulated pivot point at the c/s to eliminate chain tension and suspension preloading on acceleration. With that said, look how loose that chain is!
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Post by Walms on Mar 27, 2012 4:43:18 GMT -5
So I suppose if the torque caused the rear of the bike to standup or be neutral, there would be less weight transfer...
I've never rode a bike with struts in the rear... When in place, do they have a big effect on reducing wheelies?
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Post by zambia on Mar 27, 2012 7:28:43 GMT -5
So I suppose if the torque caused the rear of the bike to standup or be neutral, there would be less weight transfer... I've never rode a bike with struts in the rear... When in place, do they have a big effect on reducing wheelies? My buddy used struts on his street drag H2. It helped keep the front wheel down, but the rear went up in smoke. He used to run a big Avon on the back and reduce the air pressure to 15lbs or something. |
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Post by bababa3wheeeeeeee on Apr 6, 2012 20:47:17 GMT -5
"The concept was to create a swing arm setup that didn't move the rear axle from loose to tight to loose on chain tension, and to make for a much more stabile rear suspension operation, like a car suspension works a tire straight up and down, without deflection. The parallelogram was somewhat successful, but considerably heavier than what was desired.
Japanese manufacturers came up with something much better soon after the FUBAR program was scrapped by the U.S. engineers, the single (mono) shock and braced swing arm, aiding suspension, but not chain tension issues. Most of the Team motocross bikes with conventional single swing arms, were fitted with Cancilla chain tensioners, and that took care of the chain issues for them.
The most unique of these parallelogram frame setups were the two H2R ones built for testing in late 1973. One was a short chassis, the other was patterned after the longer Talladega chassis.
I know of only one chassis set that got out of Kawasaki R&D. I would hope there are a couple of them out in the private sector today, be nice to see another one.
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-Dave Ray
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Post by sbs on Feb 3, 2013 17:38:21 GMT -5
Mert Lawwill [fairly recently] did an H-D street-tracker using that same FUBAR set-up - having, of course, no issues with locating multiple fat H2R/KR pipes - which was one of the major bugs with the Kawasaki effort.
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With some effort in a search you may find it. 
