Old School Chopper Frame Fabrication - Knucklebuster

Figure 12
In Figure 12 we see another common alignment problem where one of the adjuster plates has been welded into the frame
without being perfectly square and plumb with its opposite counterpart. In this case the rear axle will always be crooked no
matter how it's 'adjusted'.
Ninety percent of all mass produced frames we've worked on over the past couple of years have had the plates installed with
a combination of these two common adjuster alignment problems which is why we want to point this problem out at the onset
of this article. It also is the reason that we don't provide 'standard' templates for axle plates.
If you're having a problem on a stock or aftermarket bike with the chain or belt not tracking properly the first place to look is
at the alignment of the adjuster plates relative to the transmission sprocket or pulley and the location of the adjuster slots
relative to one another.
I strongly suggest that you not cut your plates or adjuster boxes until your frame is almost completely tacked together and
you can use your tubes, as they are, to make a template from. You will do doubt find that one side of the frame tubing is ever
so slightly different than the opposite side and for this reason you'll probably have to make two different templates (or one
oversized) to make your plates exactly match the angles that your rear tubes ended up being bent. The objective of course is
to keep the axle hole or slot exactly the same even if the two plates themselves are slightly different in dimensions and
angles.
In addition to aligning the adjuster slots as seen in a 'profile' view its also vitally important that the plates be perfectly parallel
when viewed form the top or bottom or from the front or rear and not only should they be parallel to one another but also
aligned in the same plane as the chain or belt as it leaves the transmission drive sprocket or pulley and it goes without saying
that the rear and front axles should be aligned as well.
How accurately these components are aligned is subject to debate but in general most builders agree that if the front and rear
wheel are within an eighth to a quarter of an inch the bike will track properly. The drive sprockets or pulley's however require
much more precision and if you're off by more than a twentieth of an inch (0.05") you'll probably have some long-term
problems.
To make the template for the axle plate I'll usually just use a piece of cardboard and 'scribe' around the frame tubes freehand
as shown in figure 13 below.