Old School Chopper Frame Fabrication - Knucklebuster

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This assembly actually represents about 70% of the overall chassis tubing and while it may not look like much in this
condition it represents a tremendous amount of work and very few do it yourself builders get this far on their first project.
If you don’t have a tubing bender you can probably find a chassis or welding fabrication shop somewhere near your locality
to bend the wishbones. You can also try posting a message on one or more of the motorcycle forums and you might find
somebody near your location who has a bender and who'd be willing to help you out. I do not recommend that you attempt to
make these bends with a hydraulic pipe or conduit bender and if you try to heat the pipe and bend it by hand the radius will
be to small and the tube will probably flatten anyway.
If all else fails and you can’t find anybody to make these bends you may be able to successfully accomplish the task by using
a 1” thick-wall (rigid) conduit bender with a long extension handle as the outside diameter of 1" rigid electrical conduit is
very nearly the same as the O.D. of 1.25” ERW tubing.
Part 2
Before we go much further we need to decide what style of connection we want to make between the backbone or top tube
and the seat post. There are three joints that are commonly used. The first, seen in Figure 3 is probably the most common and
the one I personally prefer as it allows easy access for running wiring inside the tube. It seals off the seat post to water
intrusion yet the open end of the top tube is naturally sloped to drain.