Rear wheel and rear disc brake mounts

I drilled the hole for the rear wheel in the 40x20 tubing using a cheap stepped cone drill.  This worked very well, much better than a standard drill which leaves a ragged hole in 1.5mm steel.  I have an M12 clearance, 17mm spacer inside the tube to prevent it being crushed when the wheel nut and bolt is tightened.

With the wheel fitted, I measured for the brake mount.  I made an IS caliper mount using information from this excellent site:

http://www.peterverdone.com/disc-brake-mounting-systems/

 Cutting out the recess where the caliper protrudes was the most challenging part of the build so far.  I couldn't get an angle grinder into the recess and a Dremel was too flimsy.  It took me a long time with a hacksaw and a file - the end result is functional but ugly.

Drivetrain test

I have an old 9-speed drivetrain from another bike - today I installed it to check the chainline and clearances. 

I found that I had to shorten the drive side dropout tab in order to mount the wheel with the mech installed.  I also had to add a washer to the mech as the hanger was too thin (5mm) and the chain was hitting the screw.  After this it was all fine.

Front frame assembly and welding

I've spent the last couple of weekends welding the front frame.  I have no jig, so I've had to align the various pieces using careful measurement, magnets and temporary spacers TIG tacked on. 

As usual, the distortions from welding have required a certain amount of bending and adjustment after welding, but I'm very happy with the final alignment and rigidity.

The front boom / BB mount and the 40x20 cross pieces are still too long and need to be trimmed.  I will also add brake mounts at some point - I'm still not sure if I will use a disc or v-brake as I had the wheels built to be able to use either.

So that's why there's a guard on an angle grinder....

Flap disc abrasive on an angle grinder that I had been too lazy to replace the guard on.  Silly chicken.

New wheels from Germany

The wheels arrived.  I had them built by Ginkgo in Germany, as the single sided hub and suitable 406 rims are impossible to source in the UK.  I've added 50mm Schwalbe Big Apple tyres - these are heavy, but will be the python's only suspension.

https://www.ginkgo-veloteile.de/ginkgoshop/en/home/

Front frame sides welded

I'm very happy with the way the side pieces welded.  After cooling, they are exactly the same.

Front frame pieces cut in the mitre saw

Today I measured, cut and prepped the 30x10, 40x40 and 40x20 for the front frame.