S/G repair back plate crack

[darryljs]

When I took the S/G apart to clean and replace brushes, I saw that the back plate was cracked . I was looking to get another one,but couldn't find one. So, instead of buying a new S/G, I thought I would try to fix this one. I have included pics (I know you people like pics), to show what I did (no, I don't have a welder to weld aluminum, yet ). I cleaned the plate and crack,then V grooved both sides. I used a product called Q-BOND (supposed to be better than J-WELD) to fill in the cracks. It dries rock hard in about 10 seconds. I then smoothed flush and made a plate from 1/8" thick aluminum, drilled and tapped 1/4" hole all the way through both plates (had them clamped together). Put Locktite on a short 1/4" bolt and tighten. I drilled the hole for the end plate bolt, which I will install with a star washer (thinner than a lock washer, because of the 1/8" plate. Don't know if it will work, but you don't know till you try.

[Sam Mac]

Hope it works but I would have had that TIG welded.

[darryljs]

Originally Posted by Sam Mac

Hope it works but I would have had that TIG welded.

TIG weld would work but I've seen cast aluminum crack along side the weld, so I 'll try this. I got this S/G for free for the 125 I'm rebuilding and it was in deplorable condition, almost junk. This is more or less an experiment.

[CADplans]

Originally Posted by darryljs

TIG weld would work but I've seen cast aluminum crack along side the weld, so I 'll try this. I got this S/G for free for the 125 I'm rebuilding and it was in deplorable condition, almost junk. This is more or less an experiment.

Adhesives typically only have strength in compression, or shear, not in tension,

Any bending or misalignment of the bonded joint, and you will be back where you started, hence, the sam mac recommendation of welding.

Actually, the stick product they sell at gun shows and flea markets that can be applied with a torch (propane, mapp, etc,,,,) does a pretty good job,,,

This would be a better application than their demonstration of sealing a hole in a beer can.

How do you get a hole on a beer can, anyways!!??

[mortten]

Can opener

[DoubleO7]

Might want to take the 1/8" plate off, rough up the surfaces and reinstall using that Q-Bond stuff. Really slather it on and fill the edges with it.

But like you said it is an experiment. Results would never be known if you do not try it, right?

[Steve149]

Originally Posted by CADplans

How do you get a hole on a beer can, anyways!!??

If you have friends like I do they poke a small hole just above the beer in the can with a pocket knife then stand back and watch it squirt out all over my chest when I take a drink...God I hate that!!!!

[darryljs]

Originally Posted by CADplans

Adhesives typically only have strength in compression, or shear, not in tension,

Any bending or misalignment of the bonded joint, and you will be back where you started, hence, the sam mac recommendation of welding.

Actually, the stick product they sell at gun shows and flea markets that can be applied with a torch (propane, mapp, etc,,,,) does a pretty good job,,,

This would be a better application than their demonstration of sealing a hole in a beer can.

How do you get a hole on a beer can, anyways!!??

I understand the strength in compression, or shear, that is why I put the 1/8" plate on (for the tension), to help with support. The back plate is mostly for support of the S/G back end. The way Q-Bond is applied wouldn't seal a hole in that beer can. You fill the crack with a powder, then drip on the super glue like adhesive. You get powder for plastic and a different powder for metal.