Casting Repair

[TripleTrophy]

It seems I carry too much in the trunk of my motorcycle. I have broken my second luggage rack, a two (actually three) piece casting of what I assume is some grade of aluminum. Both have broken at the same point, the forward bolt hole. I have to conclude that a) I carry too much - capacity is only 11 lbs, less than my laptop and bag, b) railroad tracks have to be taken slower and c) it was a bad design to begin with, confirmed by the Yahoo Triumph Trophy group.

So, last time I broke it, about 4 years ago, it was $255 Cdn. Ouch! Since then, I have acquired a welder or two. Perhaps it can be repaired? Part of the fun of having a welder is doing things most people (not you guys though) can't. Pics of the broken part are attached.

[TripleTrophy]

I took a crack at it this weekend. Filed down the edges to give me some semblance of a vee, then took the TIG welder (Diversion) to it. Running at maximum amps, the material welded easier than I anticipated.

Is this typical with casting vs. structural (rolled/drawn) pieces?

The first side I had not cleared back the paint from the edge of the V. That seemed to lead to some porosity (pic 61 looks particularly ugly), so I filed it off on the second bracket. Welds look a bit better, but still somewhat porous. I left the bolt hole intact, but am beginning to wonder about that. Would I have been better drilling it out, then cleaning and filling?

[TripleTrophy]

Sorry for the three part (so far) post. Easier to attach pictures this way.

I ended up filing things down and fitting together. Things look better filed

However, aligning by eye does not seem to have worked. There is enough play in the pieces before welding that one side is out about 1/16", while the other is a good 1/8" out. So now I am thinking of cutting one or both back apart and starting over, but only after I make a jig to hold it. Either that or open up the mounting holes and live with a crooked rack.

Question, how dimensionally stable is aluminum through the welding process? I know with steel, I would probably end up bending things.

Also, in order to improve the design, i am thinking about filing both sides of the gap between the two pieces to a V and welding it. My thinking is this should be a stronger design than the original, which seems to always crack at the bolt. A bit of filing, some black paint, it should look good. Hopefully it will support it's original 11 pound declared capacity. (Saving grace is I rode about 30 km. with the luggage rack in two, with the lap top inside, and did not lose anything.) Otherwise, it is fork out the cash for a new one.

I still have a concern that this is not an aluminum casting, or not something that is readily welded.

[youfoundtheking]

Question, how dimensionally stable is aluminum through the welding process? I know with steel, I would probably end up bending things.

I cant answer any of your other questions, but aluminum has a higher thermal expansion than steel, but its offset by the greater thermal conductivity, so its ends up very close to steel in stability.

[TripleTrophy]

Well, net result was I was not successful, although I did learn a lot. I did not get all the parts aligned close enough for the finished product to fit properly, or more importantly, fit to my satisfaction. I did learn some things however:

- Dirty aluminum castings are prone to porosity.
- Paint (I suspect the castings were powder coated) needs to be cleared well back of the weld.
- My second attempt at welding it, after I cut it apart and filed out most of the original welds, worked much better.

So, a failure in achieving the repair I wanted, but a success in learning something. And, I am crazy enough to try it again.

[Portable Welder]

Clean all the paint away and vee groove down close to the threads and if its a hole weld it solid and drill out afterwards.

Build up around the area, adding more material than what was originally there will easily fix the problem.