Fork building sequence?

General Discussion
1

Thinking about building my first fork - unicrown for mini velo, thru axle, disc brake. I am interested in hearing what sequence folks use. In particular, anticipating distortion of one fork leg following tig welding brake tab. Would love to hear what steps/sequence is best practice. Considering using blades like this: UNICROWN FORK BLADE OVAL. — BICYCLE FABRICATION SUPPLY

Thanks for any input, Daniel

2

For a segmented fork I follow this order after I’ve cut everything to size. I’d guess the method is the same except for the welding the dropouts.

  • braze/weld dropouts
  • tack cross members to fork leg
  • tack cross member to steerer
  • confirm alignment
  • if significantly out of alignment I’ll make adjustments
  • if close to aligned, perform weld sequence based on correcting small issues.
    • when welding that both parts ends of the cross member and contribute to something being in/out of alignment.
  • let the fork cool completely. re-check alignment. cold-set if necessary.
  • attach disc tab.

My tacking sequence is maybe overkill but I do the following in this order

  1. 12:00
  2. 6:00
  3. 1:30
  4. 7:30
  5. 4:30
  6. 10:30

This way, if I did something really bad, I can use the 1:30 - 4:30 | 7:30 - 10:30 sections to really pull something back into alignment. It also helps to make the weld look pretty from the front.

For welding a disc-brake tab similar to this, I tack using this sequence:

  1. Top edge
  2. Bottom edge
  3. 2-4 more small tacks if needed.

And the weld sequence is like lug nuts.

The reason I tack the top + bottom is to help prevent the corners from melting away when I run a full bead.

If you’re able to control your heat decently you should be able to minimize distortion by following a “lug nut” welding sequence.

Setting up a couple of tests to identify how things are going to distort will really help you. (FWIW, I never did that and I don’t seem to learn from that 1 mistake . . . ever.)

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3

Thanks for sharing this. It looks solid. From your description, you don’t experience significant bending/bowing of the fork leg when you weld the disc tab to the back of the fork leg. Or at least not to the extent that dropout alignment is affected. Is this correct? Thanks, Daniel

4

Yeah that’s correct. Unless you’re really cooking the tube, I think it’s far more likely that the disc tab will pull one to one side or another due when the welds cool.

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