Truss Fork Tubing for my 36er

[Alex Clark]

I'm in the process of designing a 36er for myself. I have a built a few frames, and two forks, and would like to plan a truss fork for the 36er. For the sake of clarity, I am considering a truss fork with dual crown design and not the Oddity squid style fork with multiple blades meeting at the crown. My hang up currently is tubing diameter. I've decided that for the main tubes .049 or .058 would be best for my brazing abilities and safety. My questions for the forum are:

1) What is an appropriate diameter of tubing for an off-road truss fork? 5/8? 3/4? I'm in the high 250lb+ range, and I am short for a 36er at 6'. I mention this because I think that I will have little weight on the front end given my reach.

2) If I am using a dual-crown truss design should I use the same diameter for all four tubes, or larger for the main and smaller for the supporting struts that end at the upper crown?

3) Finally, my reason for wanting a truss fork aside from cool factor is that a 36" wheel would create a large lever under braking or front wheel impact. I like the idea of spreading load across two crowns instead of one. Is this valid? Should I instead be using large diameter tubing and using only two legs?

Any thoughts on the matter of truss forks are welcome.

Thanks,
Alex Clark

[Rody]

Alex,

For your weight, length of the axle to crown, and relative experience level, I would encourage a conservative approach to tubing selection.

May I suggest .875 x .058 for the main blades and .75 x .049 for the truss blades...this would give you plenty of material for the intended length/leverage and provide enough wall thickness that inconsistencies with the torch would not be detrimental.

After successfully building and riding, you could then go with lighter gauge tubes as your experience increases.

Best wishes and please share pics of your progress,

Rody