So, I've got one of my spare XS1100's blocked up so that I can build the front end on it before moving the finished unit over to the Flying Breadpan.
Do I measure trail using the fork cenerline or the headstock centerline? Then, once thats figured, I want less trail, right? By how much? Lets say its 8 inches right now, is moving it down to 4 inches of trail too far?
The swingarm pivot point for the front end, can it be bronze bushings or does it need to be needle cage bearings?
The measurement for trail is taken from the centerline of the steering stem, near as i remember. Trail on the average UJM is in the 5-6" range, afaik. In theory trail should be brought down to within 1-2" to impart the 'power steering' characteristics. I built my front end utilising a set of custom bearing blocks that 'slide' on the swinging arm in a range of 1", adjustable from 1" to 2" of trail.
My home-designed and fabricated setup is somewhat bass-ackwards, and a little more complicated, from what is normally done, but it works. I used neither caged needle bearings or bronze bushings. The bearing blocks have three sets of replaceable linear ball bearing units press-fit into place. I used the above wisdom in terms of trail parameters in the design of it, and the bearing choice on the advice of the machine shop doing my machining of the blocks FWIW.. if someone more learnered than i, thinks i am wrong on this, PLEASE, stand up and let it be known. If i'm doing something unsafe in terms of measurements, it is better i am the only one making the error - but i have been happy with 1" trail for three years 🙂
"This is the reason for building the 3 piece swingarm, to keep it square so i could flat-deck the rear portion of the swingarm for a set of sliding bearing-block shoes bolted in position, which in turn are the downtube pivot-points. This allows for limited adjustment in trail."
I like the adjustable pivot point idea. Got any close up photo's of that part?
Originally written by Lunatic on 12/11/2007 8:22 PM
I like the adjustable pivot point idea. Got any close up photo's of that part?
Sorry, I don't. Only the long range photo above, and a few other on my photo site like that. It's basically a bearing block, secured to the swinging arm with a pair of 12mm allen head bolts, and adjustable in the range that the bolts can slide in the groove machined into each bearing block base. The allen head bolts are secured into the swinging arm itself. I took the idea from commercial bearing blocks used for tension adjustment of industrial conveyer belts.
My photo site (reachable through my sig link) might give you a better idea of how i put it together.
Also take a look at this website for further insight on leading link theory and design.
http://www.sidestrider.com/leadingfork.html
