Rigids are right-swingarms suck. OK, that's one school of thought. There is the visual of a rigid-frame bike, sitting low to the ground, with an eye-pleasing line from the steering head to the rear axle that just looks right, as opposed to the sudden squared-off look of the frame, ending abruptly just past the transmission, at the swingarm pivot point. As they always say, beauty is in the eye of the beholder, and in our eyes, rigids just have that inherent beauty.
Wes White at Four Aces Cycle Supply in Pacoima, CA, shares this view. So when he purchased a clapped-out 1975 Harley-Davidson Shovelhead (in its stock swing- arm frame), he knew that a rigid was just a phone call away. That phone call was to V-Twin in New York for one of their weld-on hardtail rear sections. While the hardtail section was somewhere in the UPS system, Wes called Andy Janzen and Steve Uhl for some insight into cutting and welding the new rigid rear to the '75 H-D frame. Weld-on rear hardtail sections indicate that there will be some frame cutting involved before any welding can commence.
Before any cutting can start, the entire bike has to come completely apart so that the frame of the bike can be rotated in all directions for accurate cutting and the following welding of the new rigid rear section. With the exception of some minor setbacks while stripping the bike, the crew had it apart in a few hours. The teardown also revealed some strange assembly practices. For example, the front mounting bolts that fasten the transmission mounting plate to the frame were in upside-down. Whoever assembled the bike threaded the bolts in from the top of the plate, (providing no holding capacity at all), the bolts need to pass through the frame and then thread into the transmission plate. When Steve and Andy went to remove the wide glide frontend, there was a strange top-bearing nut that was too thin, which allowed the underside of the top tree to grind away the top of the top fork bearing race cup, due to the lack of the correct thickness of the bearing adjusting nut.
With the Shovel stripped down, it was time to make some sparks. Steve started by rough-cutting the rear section of the swingarm frame away from the front section. With the stock rear section out of the way, the front section was carefully trimmed a little at a time until the new rear section fit perfectly. The key to success is to trim and fit, trim and fit. Steve and Andy fitted the top frame tubes first and then moved south to the lower frame tubes, double-checking each and every dimension as they went to ensure a straight frame when finished. Dimensions were checked every way, side-to-side, top and bottom and level. Once the framerails looked and measured correct, they were tack-welded and then rechecked-only then was the rail finish welded.
Welding on a hardtail section to your frame is a major undertaking. It is best to have some help (as in a friend) who can add an extra set of eyes for alignment or help hold something in place while you tack weld or vice versa, you hold and they weld. If you think that your skills are not good enough to undertake this job, then take it to a reputable welding fabrication shop or your local bike shop.