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Old 10-05-2012, 07:14 AM   #23
Beastly Adventurer
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Joined: Aug 2012
Location: The Dutch swamp
Oddometer: 1,053
Originally Posted by adventure950 View Post
Hi Prutser, when I did the calculations regarding the driveshaft length and the amount of travel tha Maximum on a 100mm extension was theoretically 260mm doing ( a rough bit of working out 244 at 50mm extension) really would be the maximum travel so to achieve 248 you need to be carefull your not pushing two areas too far. Firstly the uj will be running very tight at those angles, and even though these are extremes if the shaft is revolving at any speed the wear and stress on the joint will be very high. Also the internal dimensions of the shaft tube mixed up with the offset pivot between the uj and the swing arm pivot mean the more extreme the angle the closer the shaft gets to the edge of the internal area of the tube which in turn puts pressure on the UJ and swing arm pivots. This clearance I believe runs out before the above measurements. Which would indicate your drive shaft could well be rubbing on the internal metal of the tube. Both these factors are part of the reason why HPN run a maximum of 240 travel on a 100mm extension and take into account they also machine the internal area of the tube as well as machine part of the the bevel box cup end of the shaft to lighten and reduce the diameter of the shaft which may give them a slight advantage over the standard sizes. I wanted to go a bit safer again and so reduced that travel to 234mm travel in real terms but doubt it would ever get beyond 230. I am not being critical here at all just hope you are aware of the problems that may be encountered and ( i hope are not a problem for you) if your informed you can prevent a failure of the components or damage to your bike or even worse yourself. Jake.
Thank you Jake,

I'm am aware of those things and using the thin drive shaft.(not the one with the demper)
When I measured the clearance there was still enough room. And not to much (extra) stress on the u joints.
The shock I'm using is even shorter than what I could actually fit on the bike.
I have measured a lot of those swingarms and checked the clearances. Al the bikes had a different amount of travel before something would touch on the inside or the u-joint would be under to much stress.

At the moment I'm putting a bike together with the same length swing arm. And this one will never be able to make the same wheel travel because of the swing and shaft combi...!

I think I was just lucky with the shaft and the swingarm combination i'm using.

What I did do is give the bike more sag. To keep the monolever from jacking(lifting) until the shock is fully extended.

But thanks again for all the data. That might be helpful to a lot of us.

Thanks, Bas
BMW R100'91/R80'93/R75/6 R80ST'83/R65GS'87/GasGasTXT300/DouglasW20-1920

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