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Old 01-29-2013, 05:17 AM   #3329
Beastly Gnarly
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Joined: May 2012
Location: VA
Oddometer: 1,630
Hopefully, this will not be a really vague question. I am looking to weld/braze an aluminum fork 'tang' and am scoping out what is needed. The fork is for a BMW /7 motorcycle and the tang is part of the brakes. Specifically, the tang stops the pad from rotating with the disc as the brakes are applied. Here is pic of the lower tang:

The maximum thickness is ~ 3/8" near the fork and tapers to 3/16" furthest away. The project involves taking a left fork leg and converting it into a right fork leg, i.e. making a mirror image. This involves cutting the tang off the left fork inside (nearest the disc) and welding/brazing it to the left front outside (which becomes the right front inside).

My equipment is not heavy duty, I have a Hobart handler 140 with 0.030" 5356 aluminum wire and argon gas. This welder is rated for 1/8" thickness. I also have (and am willing to try) brazing with HTS-2000 type aluinum/zinc using a sheet metal 'mold' to hold the pre-heated and tinned fork and tang in place. I am not a very experienced welder, but have done a bit of oxy-acetylene and some MIg. I have done a lot of brazing.

My questions are:
1. If I file/grind and bevel the fork and tang so there is a 1/8" thickness at the tang and fork pieces, which then increase to ~ 3/8", can a root pass be done with my 140 amp welder with ~ 200 deg F preheat? Or, will this approach likely result in a big mess without considerable skill due to the extra thickness and fork acting as a heat sink?

2. Presuming I can get the 1/8" thick root pass weld to get the tang in place, will adding material (i.e. additional passes) work with that small of a welder? Again, preheat is planned and beads would be applied over the previous weld in a multi-pass approach.

My main concern is that the fork leg is a big heat sink and even with pre-heating will pull heat from the weld. I can arrange the fork and piece on a welding table, and can pre-heat with a Mapp gas or propane. I intend to practice on some 6061 aluminum but those will be small flat pieces and nothing like a fork tube. Any constructive criticisms are welcome - along with tips on locating and recognizing a good weld shop - although this project is not beyond motivating me to buy a 225 amp spoolgun machine.

Stan_R80/7 screwed with this post 01-29-2013 at 05:42 AM
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