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PJ1 (part1)

A mountain bike based on the geo of Petes existing bike, a Trek 8500.
35mm seattube with internal sleeve (31.6 seatpost). Columbus Life tubing mostly but with a Reynolds downtube.

Although bike will be built with rigid forks, they’re suspension corrected. The frame is a pretty big and with the long forks, the downtube length was bigger than anything Columbus could do.

PJ1 mock up

PJ1 Geometry

headtube and seattube

Theres’s an external sleeve on the bottom of the seattube (tube at the top of the pic) for some additional strength. Also some nice turned down headtube reinforcements (tube at the top of the pic). It’s a 1.1mm headtube so with these reinforcements it should be plenty strong enough!

tubes cut and mitred

Here we have all the main tubes cut and mitred. The chainstays have been bent but are still to be cut and the seatstays will be bent and cut once the main triangle is together and the chainstays are on.

seattube ready to braze

BB and seattube in the jig all fluxed up and ready to be brazed. This is one of the first operations that get done. I finish this joint as much as I can before doing the rest of the frame as the BB junction is one of the hardest joints to get into to clean up once it’s all together. The seattube is aligned after this process to make sure the BB and seattube are perpendicular.

H2O boss detail

This is the seattube and the downtube. I do as much of the braze-ons before building as possible. There’s no chance of the frame shifting out of alignment if we do it pre-braze. It’s also much easier to get into the tubes and do the drilling and stuff.
The tube at the top is the downtube and it’s got 2 sets H2O bosses (1 underneath) and a set of crudguard bosses. These have been installed and have been cleaned up. The bottom pic is the seattube. It’s just come out of the soak tank and is still all gunged up with flux residue.

H2O boss detail

Here’s pic of the seattube all cleaned up. You can also see the BB join in this pic.

all the images from this build are available in the PJ1 flickr set

posted by steven - January 10th, 2008