anyone have any pics of a fixture/jig to keep everything lined up i need to narrow a banjo for a fed project with a banger motor not too worried about breaking it (80 hp at the most and real light) my thoughts were a big piece of Ibeam bolt the flange where the pinion bearing goes down to the beam then machine up a bar to go through the carrier housing of the ring gear and through the cut axle tubes make another bracket that keeps the wheel bearings parallel and flat to the face of the pinion bearing surface just thinking out loud what do you think thanks tk
Having just the bar going thru the carrier is enough. The issue now is about the ends and keeping them square. If you are using bearing ends then you machine a bisket that fits the ID of the bearing housing and the OD of the alignment bar. If you are using the roller bearing ends then you chuck the end on a lathe to check the bore and either turn or shim the alignment bar to match. Lightly tack weld (and lots of them)the end to the bell before heaveier tacks and then finnish welding. Two things, first mount the rear end into the chassie and weld the mounting brackets that way any warpage will not influence where the ends are and when you weld the ends - looking at the right side start at the 5 o'clock possistion weld clockwise and on the left side start at 7 o'clock and weld counter-clockwise.
Since you have a rear that is already true, build a stout jig as it is. Make some uprights out of thick steel that bolt to the backing plate flanges. When you cut the ends free and and remove the required length of tube, clamp in some solid square stock on two sides, the same thickness as the amount of tube removed and tighten down at the ends as well as a bar running through the from end to end. The fact that the tubes are tapered helps to keep them from warping as much or at all as a straight tubed rear, especially being welded at the flange and not in the middle of the tube.
Its not nessasary to build any jig fixture when one is not in production and when the lineup bar method is used throughout the raceing industry to shorten housings.
I've been thinking how to do it as well and one of the things i was thinking of was a threaded fixture bar that had the cone bearing on one end (fixed & true to the bar) slide that inside a bell so it seats to the race so now the bar is exactly where the axle should be, i'd have some threads on the other end so you can screw a lathe nut/axle bearing plug up inside your bearing house at the end of the tube. Then your bar will act as a clamp to seat the housing end and it will be true to the carrier bearing. I would make my bar from solid chrome moly as large as you can possibly manage.
I have done them both ways and the alignment bar is the best method. Most good shops have one or you can purchase one for the job. If this is a one time deal have it done at a shop. In the LA area it runs about $150 or less if you have everything cut and ready to go then about $75
I agee, however the OP is building a fed and making something on the fly to get the one time job done would be simple and easy. The through bar is good but the id. of the banjo tubes is small and a 1 1/2" is all the larger of a bar that would go through. You stated a one time job but mentioned machining some parts $$$. I would still use some small bar through to keep the ends tight but wouldn't rely on it to keep them square. As i mentioned earlier its the ends that are being welded, keeping those square is the main concern and building a jig/uprights off of it as it is now using the housing as a jig to make a jig is simple and a do it yourself thing in the shop for little $$.
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