C-band dish what type of aluminum?

mr3p

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I may need to repair a pair of the support ribs on my 10' KTI dish which bent at the mount point. There is no good way to get it into a square tube roller so I think if I heat it up a torch I should be able to bend it back to normal curve using a form made from a normal rib. I was then thinking about welding a couple of strips of aluminum on each side for extra support but I wasn't sure if it was 6061 or 7075 aluminum, the latter isn't really weldable. The junctions of the support ribs and connected so I'm guessing it has to be 6061 although somewhere long long ago I thought I recalled reading "Aircraft aluminum" in a flyer or manual which I realize doesn't specify. Reinforcing with steel isn't a great option as that just asking for corrosion. Lastly I could change mount so it has 2 connection points instead of 1 but that involves drilling more holes in the support ribs which I prefer to avoid.
 
I may need to repair a pair of the support ribs on my 10' KTI dish which bent at the mount point. There is no good way to get it into a square tube roller so I think if I heat it up a torch I should be able to bend it back to normal curve using a form made from a normal rib. I was then thinking about welding a couple of strips of aluminum on each side for extra support but I wasn't sure if it was 6061 or 7075 aluminum, the latter isn't really weldable. The junctions of the support ribs and connected so I'm guessing it has to be 6061 although somewhere long long ago I thought I recalled reading "Aircraft aluminum" in a flyer or manual which I realize doesn't specify. Reinforcing with steel isn't a great option as that just asking for corrosion. Lastly I could change mount so it has 2 connection points instead of 1 but that involves drilling more holes in the support ribs which I prefer to avoid.
Same dish as a Sami. They are Aircraft grade T-5 aluminum
 
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Thanks, I'm assuming that means 6061 T5? Any idea if you can weld T6 to T5 and if welding "undoes" the heat treatment? We successful MacGuyver'd a rectangular tube bender with wood dowels and clamps to restore the the normal dish arc without having to remove the mesh or heating it up with a torch. I'm considering my options for stiffening up the section where the reflector attaches to the mount and welding on an extra strip of aluminum is an option.
 
If you mig dissimalar alloys your weld will never be as strong as matching them.
Use the correct filler and gas. Because alum. has such a high heat soak you will definitely have to use large gauge wire and preheat the area to be welded. Using your everyday mig welder is only going to give mediocre results.
Do not clamp the parts gorilla tight. Looser is better. There will be a lot of uneven expansion and contraction. Rigid clamping invites cracks. Aluminum is fun. But sure is a bear. Preheat to weld, post heat to cool.
One designed with the flexibility to specifically weld alum. is the only way to get optimal, mechanically solid results.
Tig. The way to go. Sorry. It is. Not saying with enough experience a mig will get the job done.
Don't expect to pull one out with argon, feed a roll of wire in it and get factory beads.
Did the factory use mig or tig? Do you see stacked dimes or 'cow patties'?
You're not dealing with aircraft here. And I'm sure the factory didn't weld with a gas cloud. Maybe.
Asking a dedicated welding supplier for alloy suggestions and methods would be the best bet.
You will get a sort of a squint if you mention you're mixing alloys though.
I think I'm a pretty good fabricator and welder until I see someone who does it every day of work life behind a shield.
 
Thanks Arlo, incredibly useful info. I consulted a welder friend of mine who I know has experience welding Aluminum but didn't get into specifics yet. As this is all new to me, isn't T5 and T6 essentially the same alloy? I'll post a couple of pictures of the existing Aluminum joints and the bent rail after restoring arc but here is what it looked like prior to disassembly. The bulges in the back wall are completely gone and the only thing that cracked is the paint. The bolt hole where it bent somehow does not appear to be cracked or damaged. Instead of welding on Aluminum, another consideration is to weld a piece of steel to the mount so that the mount bolts to rail in 3 places and not just 1.

bent rail.jpg
rail.jpg
 
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