Again, thanks all for the good input. I've managed to collect comparative info now on the most likely materials (coefficients of static and dynamic friction, tensile strength, compressive strength, hardness, etc.), and I can play those off against the cost of materials, and make a choice. Its not like I have to have the perfect material. If what I try doesn't work, I'll just make another set from the next material in line. It's not a life and death issue, just a hobby. I'm not making a product for sale, just playing around in my shop.
Hobot, I know Jim Schmidt did his homework before settling on Turcite A. It's a great choice, and I have nothing against it. I'm just curious what other possibilities there are, and I like experimenting and making my own stuff. I also take John's point about PEEK very seriously. It is one of the Cadillacs of engineering plastics, but quite expensive. I'm also quite aware that I could live with the stock arrangement. After all, I have for several decades. But I like trying to find improvements, even if it is "gilding the lily" or "making a silk purse out of a sow's ear." Your claim that a little slop in the fit makes no difference might be true for the sort of riding you do. I rarely take my Commando in romps through the cow pasture, or sliding around gravel roads, and for all I know the longer travel and loose fit you describe is great for that. I do have plenty of experience with the difference a well set up front end makes when riding close to the limit on pavement, particularly a bit bumpy pavement. I may not push it that hard any more, but I still like the idea that I've at least set the front end up to work as well as it can, given the small size of the stanchions compared to modern practice. If I really wanted to improve the handling as much as possible, I'd just fit a good set of modern forks, like comnoz and others have done. But for this bike, I'd rather see what I can do while still keeping the original appearance.
FWIW, Jim Schmidt was doing stuff like this back in the '80s. For the front end of his monoshock racer, he replaced the stanchions with slightly larger OD 4130 tubes, made his own fork yokes to fit, made his own cartridge dampers using rear shock internals (Fox, I think), along with slider extensions that screwed in the top. I think he made his own top bushings, but I no longer remember what material. He also did a conversion on the lower bushing to fit PTFE/bronze inserts that could be adjusted by adding shims behind them. The forks worked quite well, but I eventually replaced them with Forcelle Italia 40 mm forks, just to get the larger tube size, and wider spacing for the wheels and rotors I wanted to use.
Ken
