Fan Housing Crack Welding

[1982911SCTarga]

The fan housing on my project cabriolet was cracked in two places at the point where the lower two spokes meet the center ring that the alternator mounts to. My theory is that overtightening the fan belt stresses the fan housing at the lower spokes. The cracks weren't bad, but I was afraid of buttoning everything back up and then worrying about possible damage later from fan blades-fan housing contact at some point down the road if the cracks worsened.

I contacted a local welding guy that I found from a Craigslist ad, who does a lot of TIG welding work for local bicycle enthusiasts. After describing what I needed done -- including the fact that we were working with magnesium, he said he would give it a shot. However, he said I would need to provide some magnesium for additional welding filler material.

This had me scratching my head for awhile, because to me, it was like asking if I had any spare platinum laying around. Then I realized that a couple years back I had bought a trashed targa top for parts (mostly for the latches and trim pieces). A targa top's frame is magnesium. Anyway, this morning I took the fan housing and a rear frame piece of the targa parts top to the welder's shop.

Using a hacksaw, we cut a section of the targa frame piece to act as a magnesium filler rod. We cleaned the filler piece up with a file and welder dude went to work with his Hobart TIG unit. Bottom line: The housing is solid again.

While I was there, I had him repair a cracked weld on my cab's catalytic converter pipe. I could have done this in my own shop with my MIG, but I figured he could lay a prettier bead than I could.

Total cost for both welding jobs: $60. Not too shabby. If any of you local guys want this guy's contact info, let me know.

Brian

[deshetlr]

Any pictures?

[johntyboy]

Hi that weld will need to be heat treated or there will be a good chance it will crack again. Try 170 deg C for 16 hours. It can be treated for a shorter time but you need an oven that can reach about 300 + DegC.

kind regards John

[1982911SCTarga]

Interesting. According to this sample chapter (read down a bit for the background info and chart), the heat treatment time for a magnesium casting is 500 degrees F for an hour.

Brian

[stevemfr]

Wow!

Sample chapter. You da search king