Rear frame welding

The design of the rear frame has changed from the original plan.  I decided to have a crosspiece so that the part of the frame under the seat is now in the centre line of the bike.  This adds a bit of weight, but should increase rigidity (twisting) and make mounting the pivot and the seat easier.

When welding, the crosspiece distorted, leaving the two long pieces not parallel.  This was expected.  My plan was to bend the long section by hand / vise using my body weight.  This did not work as the tubing is too strong (on reflection, a good thing).  I therefore welded some dummy beads on the outside of the tube to deliberately distort it in the direction needed.  I used low power and needed 4 beads before the desired distortion occurred.  Pretty pleased that I managed to figure this out.

Tomorrow, I plan to lay out the bike in a parallel frame to finalise the angle and length to cut the rear frame end to mount the pivot plate.  I will also use the opportunity to think about a seat position and mounting.