Gettin' Jiggy

The frame building jig is still coming together.  Lori at RT Machining in Ballard is working on the pieces that need to be machined to center the bottom bracket, head tube, and seat tube.

The main triangle in the jig.  A rear axle spacer will be added to the rear of the main jig backbone, aligning the rear dropouts at the appropriate distance for brazing.

Centering the head tube in the jig with two conical pieces machined to be threaded onto a piece of M8 threaded rod.

The seat post center had to be machined to fit inside the seat tube cluster, rather than using a wedge, as the top of the seat lug isn't cut square to the seat tube.

The bottom bracket center block, ready to be machined down to the thickness required to hold it off the jig by the necessary amount to center it.  Threaded rod will be inserted into its center, then the last of the conical wedges will be threaded on the outside to center it.

Milestone

This weekend saw a milestone in build #0, that being the first time the main triangle had been fitted together.  Since the dimensions I knew were that the top and seat tubes were 585mm center to center, these were the ones I laid out first on my plywood template.  Once these were cut to length and fitted, the fixed angle of the bottom bracket between the seat tube and down tube revealed the length to cut the down tube at the head tube junction.

Main triangle tubes fitted together for the first time.

Each lug required grinding down the inside surface where it mates with the appropriate tube.  Early on, my reluctance to remove too much material led me to follow a procedure that was like, grind, test, grind, test, grind, test, before finally arriving at a good fit.  By the last lug, this was more grind, grind, grind, test, grind, ok.  It feels good to be learning and getting the hang of it.

I cut each of the copes using a tube angle jig that worked with a 1/2" drill motor and a hole saw arbor that a buddy loaned me.  I cut the correct end of each tube, indicated by a bit of paint at the end to cut, as the thicker butted section is longer at one end than the other.  This is especially important on the seat tube, as it's only butted at the bottom bracket end and requires no cutting to fit into the seat lug.

Drill motor and downtube in angle cutting jig. 

Once the tubes were able to be fit through the lugs, I marked each tube's cutline with a Sharpie and scribe by laying the tubes on the template and setting each tube on its centerline.  These marks can be seen on the sides of the tube in the picture below.  I also scratched a small file mark at the point of each lug so that the tubes could be placed into the cutting jig horizontally, as once one end is coped, the tube's orientation is established.

Preparing to cut the 60 degree cope in the downtube where it meets the headtube.

Finally, once each tube was cut, I fit it into the lug and ground the end flush with the lug.  The remaining tasks to complete prior to brazing the front triangle together are to cut the head tube to length and figure out how I'm going to hold it together and in alignment whilst brazing.

Bikegasm

I've always wanted to build myself a custom lugged steel bike frame.  A current gap in my employment as an IT professional, combined with just enough cash to get some parts, and some awesome encouragement from my Velomihottie (thanks, babe!) recently had me going from just thinking about this, to ordering a Columbus SL Tubeset with lugs and all the rest.

Uncut tubeset and lugs roughly laid out on my template board.

Upon receipt of the package, I set out the tubes and lugs to see if the angles and sizes were roughly correct.

Once this was confirmed, I decided to start with the top tube/head tube junction, filing the lug and removing the burrs from the edges to fit it to the top tube.

The headtube/downtube lug sitting on the workbench.

The idea is to build a classic steel road frame with lively 74 degree angles like the steel racers I rode as a kid.  I plan on it being a size 58.5 center to center because this is the only way to get that size, and that's my size according to Greg LeMond's formula of taking one's inseam and multiplying it by 0.65. It'll have enough clearance for fenders, and I'm still deciding whether it should have rack mounts as well.  I want it to be versatile, but at the same time, I'm a bit leery of cluttering the frame too much with braze ons.