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Triple Bushings
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Posted by: MACE---------------------
Jer, you've mentioned triple bushings as the only good thing on Ohlins fork and "blinging" on WPs. I've not found any further discussion. Why are triple bushings "the cat's pajamas"? How are they configured?
I guess the configuration I'm envisioning would be more prone to "jamming" under fork deflection than a normal two point support.
Still waiting for the rolling element fork, BTW :D
Posted by: Jeremy Wilkey---------------------
Mace,
I'm quite the "hammer" today as I cannot find any photos of the design...
I will and post them here.. ITs really quite simple..
Imagine a fork Tube Counteboared 3-4 inches into the tube to except a third bushing. A long AL tube on WP Ohlins use a folded sheet, seperates the bushes..
THe seperate bushings provide more length between centers and with better aliment seems to prevent harshness dude to slap downs, or square edges, rather than transmiting the laod to the bars. ITs quite a bite more tricky taking them apart and putting them together however. I've found its actually best to push the tubes apart form the top rather than "hammer them" like a normal fork.. The constanct force seems to do less dammage.
Br,
Jer
Pictures to follow...
Posted by: MACE---------------------
So the there are two female bushings... <insert cheap shot joke here>
Pros:- Wider spread of male and female bushings will reduce cocking of the tube in the bore - especially at full extension. This will make less friction on slap downs.
- Wider spread of male and female bushings will reduce surface normal forces on bushing faces due to wider couple. This will make less friction all the time.
Cons:- Both the male and female tube lengths must increase to make up for the distance between female bushings. This adds weight
- When the tubes are in a deflected state (not straight) the third bushing will increase the bushing friction as it tries to resist the tube deflection.
I think I like the increased distance between top and bottom bushing but don't like the third bushing. Some sort of mechanism to allow the bushings to seek alignment to the tube would be good too (like a spherical ball).
Please build my forks with an extended bushing spacer and leave out the third bushing...
:D
Posted by: Heat---------------------
Just for arguments sake.....
1. Is there enough overlap of upper and lower tubes that more length isn`t required to use a 3rd bushing?
2. Would the 3rd bushing give enough increased bearing surface that the friction felt by the rider would be less because it would be spread out over a larger bearing surface?
Was it Thede that was working on a fork using bearings instead of bushings? Maybe it was Elmer of FMF I read about working on this.
Posted by: SFO---------------------
I keep thinking about linear bearings used on CNC machine tool ways.
Talk about low friction with high lateral loading...
Posted by: WhiPit---------------------
Mace,
You have to try the forks to appreciate the difference. I think in this case, a picture would be worth a thousand words - but let me try. Imagine in the two bearing (bushing) design, you have your upper (on the chrome tube) bearing and the lower (behind the seal) bearing. When the fork is into the travel, there is a space between these two bearings. This is where a good portion of your fork flex is going to be noticed - because there is no support in this area.
Now, throw a bearing in between the two "standard" bearings and you get more support for the chrome tube. Thusly, you keep the inner and outer tubes in a better alignment. Less flex is the result and as Jer noted, you'll feel this most in extreme situations like slap-down landings. The systems is works everywhere, better than a standard two-bearing system. But, the example of the slap-down is a nice, easy way to get the point across.
Believe me - it's a better system. One extra bearing is the only weight gain. It costs more to manufacture, because of the extra machining that's required, the extra bearing and the aluminum spacer sleeve. But it's well worth it. If you get a chance to ride either a bike with 2002 SXS forks, or a 2003 KTM - do it!
Is there more friction caused by the extra bearing? Technically.....probably. But the benefits FAR out weigh any extra friction that you might think you feel.
And, no, the tube lengths are not increased to accomodate the third bushing - all those dimensions are the same.
Definitly, try it before you jump to any negative conclusions. Any other thoughts, Jer?
Posted by: KTM-Lew---------------------
I tend to believe if you keep the tubes in better alignment with three bushings, the fricton should go down, compared to the two bushing design. 
Now my head hurts....
Posted by: WhiPit---------------------
Lew, in not-so-many words, you hit my point exactly!
Posted by: Jeremy Wilkey---------------------
Guys,
One thing that really impressed me was the WP factory R & D testing of the tube and bushing design.. The Dyno had a jig setup that tested forks in a real world speed, loading postion, etc. They ahve spent alot of time working to make sure the combotnation works best.
Something else to consider Mace is that maybe the design is to gurantee that all the bending occurs above that point.. ??? Tube flex is something that I really wish I could know more about. What cool software do you have in that War chest that migh sheed some light on us?
BR,
Jer
Posted by: Jeremy Wilkey---------------------
BTW..
I think you where talking abouyt Gill at Works Performance. Hey built the forks that had extranal stablolizers, and linear bearings.. It was in Dirtbike If I recal..
BR,
Jer
Posted by: JTT---------------------
Heat, Cannondale uses a roller bearing arrangement in their bicycle forks. I am sure this is not the arrangement you were thinking of, but interesting to check out just the same. It work well from a "stiction" point of view but is complex and somewhat difficult to maintain though.
http://www.cannondale.com/bikes/inn...inics/headshok/
Posted by: Jeremy Wilkey---------------------
Forking understament of the year.. BTW it was very cool just don't ever take one appart and change postions of the "sheets"
BR,
Jer
Posted by: Jeremy Wilkey---------------------
Well the Suspension Gods may look down at me for such "blasphemy" but here is a picture of a 01 Ohlins "triplebushing" The 02 is actually way better with its longer single busings.. The better name for the Ohlins unit would Quadrouple bushing.. But thats a whole diferent Joke... Take this one to the den Mace..
Posted by: DEGBERT---------------------
Jeremy,
How much better do you think the stock 03's will be in comparsion to the 00-02 forks? Do you think the new stock WP forks will finally out do the stock KYB forks? Just curioues, since I'm thinking about buying a new 03 200SX.
Posted by: Jeremy Wilkey---------------------
DEGBERT,
I've had the pleaseure of working on these babies for the last 6 months and they have exceeded my exspections on all accounts. The major damping issuse are not changed however the added avantage of improved basic mechanics is a pure joy to work with.
BR,
Jer
Posted by: DEGBERT---------------------
Why would KTM not address the damping issuses, it's no secrect that the stock KTM suspension is... shall we say a couple steps behind the Jap. stuff. I just read a mag test on the prototype 200SX, the bike had the works WP forks and got great reviews. Why would KTM not use the same active and passive valve configurations as they do on the works forks. Is it a manufactureing/cost issue? I lot of people make their bike buying decisions based on the mag. shotouts and KTM comes up short every year in the suspension department. I sure hope KTM comes out on top this year.
Posted by: WhiPit---------------------
Jer didn't say that the forks are the same as '00-'02 in every way EXCEPT for the triple bushing............the settings have been improved in a big way for 2003 production - that's from a very close and reliable source. Plus, the bikes are already getting good reviews - especially for suspension - in the Euro mags.
Posted by: DEGBERT---------------------
WhiPit
I'm just fishin for any inside info on the 03 WP suspension.
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