09
Aug
12

Eight Tubes, Part 6: Put A Fork In It…

Check “build fork” off the list. It’s done.

And the damn thing looks pretty good.

Last time out, I had finished brazing up the crown and steering tube and had just finished trimming the fork legs to length. What has left to do was to set up the tubes in the jig and to braze it up, Easy, right?

It was a little trickier than that.

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The thing that took the most care was the set up. I had built a fairly simple jig out of angle iron and an old front hub. It is a fairly rudimentary piece of equipment but, with some patience and my kick-ass angle finder, it got the job done.

First, I had to double check to make sure that the jig that I had built was actually square. Turns out that it wasn’t – it had a small twist in it. I found that out by putting the level/angle finder across each end of the jig and comparing the angles. If things are parallel, the angles should match. They didn’t. A couple of shims under one end fixed that problem.

Second, slipping the tubes into the jig, the fork legs and crown have to be parallel with each other fore and aft. (Fork legs, of course, aren’t parallel with each other when viewed head on). Resting the level/angle finder across both legs, the angles (if the work table isn’t dead level) should match when measured at the fork crown, the fork ends, the middle of the leg, and on each end of the jig itself. In other words, you are checking to see if there is a twist your set up,

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Third, you have to orient the legs fore and aft so that the you get the appropriate amount of rake. This is measured by the angle formed by the steering tube and the fork legs. Again, I used the level/angle finder to measure this. The tricky part was taking into account the fact that the fork legs are tapered, meaning that I had to put a small shim under the angle finder to correct for the taper. The rake on this particular fork is supposed to be 7 degrees.

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Confused? Bored? Look at the pretty girl; that’s what she’s there for.

Anyway, after about an hour of futzing with the set up, I lit the torch and had at it.

It turned out pretty good. Getting good strong joints with no gaps or voids and solid penetration is important on a fork; the joints are highly stressed and if they fail the resulting accident can kill you. I think that I did the deed. Put it this way; I’ll be happy to ride on it.

Putting the dropout gauges on the fork shows that the dropouts are parallel and that he fork legs are the same length. Sliding a wheel into place shows that the lateral alignment is good.

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Most importantly, it looks cool.

Big thanks to bike guru Slippery Pete Czapiewski for cutting the crown race. The dude has skills (and tools).

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2 Responses to “Eight Tubes, Part 6: Put A Fork In It…”


    • August 9, 2012 at 11:24 am

      That’s a really good solution. Are you a wood worker? If so, mucho respect. I tried it and wasn’t terribly good at it – it takes a lighter touch and different approach than I have. The tools are very cool, however. I picked up that digital inclinometer from Beall Tools, a woodworking shop. They have some really neat lathe mandrels and a gizmo that turns fancy fountain pen bodies. They turned my order around very quickly too.


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