December 21, 2007

Friday show and tell

Segmented forks (ie, the kind I build a lot of) have been a hot topic on Frameforum this week, and so I’m following a (newish) FF tradition and doing a “Friday show and tell”. This is oriented toward fellow framebuilders moreso than casual readers, so be warned that I’m skipping some of the more basic steps in the description.

First off, a little background. I’m building this fork for Steve Garro at Coconino Cycles, so it’s going on a bike for a customer of his, and I’m not involved with the frame or fork design process. Steve wants a 440mm long, 45mm rake, disc specific fork for a 180 pound rider doing all-around XC. Fair enough!

The dropouts are from Ceeway, in the UK. I buy these in huge batches because I use them a lot – and I’m happy to sell a set or two to anyone who wants to build a fork like this but doesn’t want to pay $20 worth of shipping to get them from the UK. The part number is LE13-1. There’s a version that will fit 25.4mm tubes as well (these are for 28.6mm) but I seldom use them. They are intended to be plugged in and brazed in place, but I simply cut the plugs off and weld them on, because it’s quicker for me to do. They’re cast, so the metal isn’t super happy about being welded, but it works well enough.

I mount the legs and steerer up in my spiffy Anvil fork fixture – the legs are 1.2/.7/.9mm double butted (with the thick section at the top) and are made for me by Fairing Industrial. Steerer tube is a True Temper MSRDLT OX platinum steerer tube that’s butted 1.6/1.1mm.

Next, I machine up some crown pieces on the mill. These ones are made from 1.125″x.049″ 4130 purchased from Wicks aircraft. The fixture I made to cut every crown section at a 15 degree angle. I can make 1″ pieces as well, by using a little shim shoved into the fixture. It’s certainly possible to make these by hand as well, but it’s a big waste of time for me, since I’ve got the milling machine. The crown pieces always require some deburring (as you can see) and a bit of hand mitering at the leg side to fit perfectly, but the total time required to finish them after they come out of the mill is probably