Old School Chopper Frame Fabrication - Knucklebuster

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Figure 2 Figure 2 shows the rough mockup for our particular project frame. In this case we've simply bolted up the motor, tranny and inner primary to check for clearances at the seat post and seat post cross member. Our 'motor' in this case is a plastic 'dummy' Evo made specifically for frame builders by Payr which is listed on our Links page. If you're interested, we're a dealer and can save you a couple of bucks on one of these if you don't already have the real thing. Figure 3 In this particular situation where we were using a thick cast aluminum inner primary we noticed that the bolt boss on the outside of the cover, opposite the pencil shown in the picture, could potentially rub against the lower rail. After rechecking this area in more detail we found that there would be slightly less than an eighth of an inch of clearance so we just barely ground down the extreme end of the boss by a little over a sixteenth of an inch. Wherever possible we try to maintain at least
an eighth of an inch clearance between components and frame members. An alternative would have been to make the frame a sixteenth of an inch narrower but in this case since there was only one point of potential interference it made more sense to just get out the grinder as the cast bolt boss was very thick. Before we get back on track and start on the down tube notches it may be important to reemphasize the importance of building a welding jig one piece at a time while we're also building our first frame. A good frame can be built without using a conventional welding jig and all types of temporary jigs and fixtures can be made using wood, clamps, spacers and cribbing but it is far easier to just go ahead and build even a rudimentary jig out of two by fours than it is to rely on stop-gap temporary lash-ups that have to be disassembled and reassembled as you progress through the fabrication process. A jig, even a crude one, is your third hand and believe me there will be times when you wished that you hand four hands when you're trying to hold together three parts at one time and getting some good accurate tack welds into place without everything moving around. To make the notches where the down tubes intersect the backbone (top tube) it's best to create some arrangement of temporary fixtures or use a jig to hold the backbone in its correct attitude as it would set on a finished frame. on our particular build the top tube slopes down towards the rear axle adjusters twenty four degrees from true horizontal. The height is determined by the length of the seat post, the slant angle of the seat post and the width of the lower rails. If you've welded up the upper frame section with the seat post and seat post cross member you can simply set this assembly in place and hold it at the proper angle. Place one of the bent lower rails in its correct position relative to the seat post cross member and let the down tube section lean in towards the top tube as shown in the pretty horrible snapshot of Figure 4. Figure 4
Page 1 and 2: Old School Chopper Frame Fabricatio
Page 3 and 4: 1. Steering head. Also called the s
Page 5 and 6: Figure Error! Bookmark not defined.
Page 11 and 12: Figure 11 This cross member sets th
Page 15 and 16: Figure 15 Figure 15 shows the end r
Page 17 and 18: Figure 17 There is a corresponding
Page 19 and 20: Figure 19 I call this area of the f
Page 21 and 22: Figure 23 The slope angle of the 'r
Page 23 and 24: In Figure 3 we can see the two tube
Page 25: Figure 1 shows the basic components
Page 29 and 30: Figure 6 In Figure 6 we've deepened
Page 31 and 32: Figure 2 if you look closely you ca
Page 33 and 34: angle finder. It explains is easy t
Page 35 and 36: Figure 6 In this shot I've propped-
Page 37 and 38: In case you're interested I messed
Page 39 and 40: Figure 3 Figure 3 depicts a plate t
Page 41 and 42: Figure 7 Figure 7 is another 'boxed
Page 43 and 44: Regardless of the style or type of
Page 45 and 46: Figure 13 At this point all you nee
Page 47 and 48: Figure 1 You'll no doubt realize th
Page 49 and 50: Figure 4 Actually the plate will be
Page 51 and 52: If you're building a frame without
Page 53 and 54: Figure 5 Now that the plates are in
Page 55 and 56: Figure 2 Clean the notch up slightl
Page 57 and 58: Figure 5 The frame in Figure 5 is o
Page 59 and 60: Figure 7 The tube in Figure 7 above
Page 62 and 63: We'll now begin doing the detail wo
Page 64 and 65: The charge has been removed from th
Page 66 and 67: Some people have reported problems
Page 68 and 69: Steering Necks For some unexplained
Page 70: Figure Error! Bookmark not defined.

Old School Chopper Frame Fabrication - Knucklebuster

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