I stopped by Anvil the other day to pick up a 130mm indexed dummy axle (luckily I got out before laying down the plastic for a new fixture, damn them nice tools!!). We got to talking, which is always very educational for me, and Don kindly set me up with a couple of his custom seat tube collars. I always feel like a total dumbass when talking to him or anyone that knows so much more about framebuilding and tooling than I do (which is most everyone…). But one of the cooler things in his shop was actually a restored VW truck….it is absolutely SICK!
The seat tube collars are made by him on the lathe from 4130 (1.25″ x 0.058″) on the lathe and slotted with a 1/8″ end mill. Because I’ve had a couple bikes have seat post slippage issues from my too-narrow slot made with a die-grinder and abrasive disc, I thought…”I can do that!” So alas, i ordered up an end mill set from ENCO (about time, eh?) and did it myself. The below pic is an externally butted seat post for the cross bike I’m building, but I’ll definitely be using Anvil’s collars on the next couple of bikes.
The Anvil collars are sweet, especially for someone like me who doesn’t have access to a lathe. They’re lighter than using an external sleeve, like I’ve been using on previous builds, and no there’s no brazing needed. Just a quick fusion pass around the seat tube to connect the collar and you’re done. The top tube and seat stays should split the difference of the fusion pass on the seat tube – half above the collar, half below or thereabouts. That way that collar gets the backup it needs since the fusion weld isn’t very structurally strong. I used a Paragon collar on my fatbike (MC9) and they’re really nice but too short for my liking. They are also made of stainless steel and don’t come with a slot. The Anvil’s are longer overall (3″) but have a much shorter step (0.2″) and include an aluminum shim to use with a 27.2 post. The longest PMW’s are 2″ with a 1/2″ step and are thicker-walled to fit a 27.2 post, so no need for a shim. The only thing that may be tricky is lining up the pre-milled slot along the centerline of the tube before laying down the fusion pass. But I figure if you weld the BB first, use an angle finder and tack it after that, no problem.