Building a chassis

When I build a chassis I do it in 4 stages.....The first stage is to build the entire rear section from the front of the seat to the axle blocks including wheelie bar mounts and seat hoop. Then I mount the fuel tank and anything else that gets welded to the rear of the chassis. I take it off the jig and use a spreader bar on the axle blocks to spread the frame .375 then weld the entire thing up. Over the years I have found that if I don't spread the frame it pulls in .375 after welding. This is on my frames and yours may be different. I do it this way because I have found that most of the warpage occurs when welding the rear section. After it is all welded up I put it back in the jig but I do NOT clamp it down. Sometimes one side may be .020 or .030 higher than the other, If you clamp it down and weld on the front half, when you release it the chassis will twist back to where it was and cause a small twist.

Stage 2.....
After the rear half is welded I put it back in the jig and slide it all the way to the end and build the wheelie bars. This ensures me that the bars are perfectly square with the chassis. If the bars are off even a little bit it will cause the bike to pull one way or the other and we don't want that...After the bars are done I slide the rear section back on the jig and get ready for stage 3...

Stage 3.....
Now we're ready to make the front half of the chassis. I put the steering head in the fixture and position it for the wheelbase I want then clamp it down. I make and install all the tubes and side bars but I only tac them to the steering head. After they are all installed I remove the chassis from the jig and weld it up completely except for the steering head. When everything is welded ( except the steering head) I put the chassis back in the jig and install the pieces to make the backbone and side bars removable. I weld up as much of these as I can on the jig then remove the chassis once more and finish welding them up. Once everything is welded I cut the steering head loose and get ready for stage 4...

Stage 4.....
Once again I put the chassis in the jig but "DO NOT" clamp it down. I put the steering head in the fixture and fit it to the welded chassis then tac it in place. After it is tac welded in place I loosen the fixture and check to see that the steering head has not pulled one way or the other. If everything is ok I put the fixture back in place, tighten it up and weld as much of the frame as is possible on the jig then I check it one more time and if it is still ok I take it off and finish welding it up. After it has cooled I put it back in the jig and check it one last time. If everything is ok I go get a cup of my famous coffee and a cigarette then I lean on my anvil and admire my handy work........

It's a lot of work doing it this way but it ensures a good straight chassis and wheelie bar......I'm all tired now and need a break so I'm outta here...

Pup....