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billyzelsnack
02-08-2009, 03:44 PM
I'm taking another look at my servo brackets. I currently am using bolts as a pivots, but I'm not super happy with them from a clunkiness standpoint. What would be great is if it were possible to drill a hole ( in aluminum sheet ) and weld an aluminum rod into place to act as the pivot. The rod would have a hole drilled and tapped to hold the mating bearings/bracket in place.

Attached is a quick mockup of what I am thinking of.

I've done what might as well be considered zero welding in my life and I've heard that aluminum welding is quite a challenge. However I'm thinking this might actually no be as difficult a challenge because I can build a rig to hold everything in place.

Is this an insane plan? If not does anyone recommend what I would need to do this? Just the minimum of equipment to get this job done.

ScuD
02-08-2009, 04:02 PM
Anything can be done with enough practice. Brace it as best you can (c-clamps, custom jig, whatever you have handy) and consider drilling the hole after welding to minimize warping problems.

Adrenalynn
02-08-2009, 04:45 PM
It's doable, but not if you're not very experienced welding aluminum, or that sheet is REALLY thick. You'd just be tack-welding it anyway. And it doesn't braze for ____, don't bother trying. ;)

That said - do you have enough clearance to use an aluminum hub? I've been using them excessively lately for things like that. Then you can just bolt the sheet down. Something like: http://www.trossenrobotics.com/store/p/3380-Universal-Hub-6mm-pair-.aspx

billyzelsnack
02-08-2009, 11:17 PM
Using hubs would make it even larger than my bolt setup!

hmm. Maybe I could just get a torch and melt the two together? Though maybe that's what you meant by braze.

Adrenalynn
02-08-2009, 11:23 PM
That's all welding is.

robologist
02-08-2009, 11:41 PM
There's a really interesting rod made for welding aluminum, that I'd seen recommended by another robot builder/handyman. It's at Durafix.com (http://www.durafix.com/) and appears to be a really easy way to get to pieces firmly together or patch holes. Check the videos.

Quantum
02-09-2009, 12:31 AM
Ive done some welding and it was horrible. This is brazing and aluminum welding is an art. To do it good first requires the right torch along with the gases needed to do it. Brazing is good probably would work her since there is hardly and forces or wieght on the part. But its hard and takes tons of practice. Even regular steel weilding to do it rigth takes time to learn.

Find I a guy in your area to do it for your. My local weilder 25 bucks and its done. Drop it off in the mornig by lunch time its done.

Guys there are a ton of local shops that are slow and if its easy they can do it in a min or two they charge a small min price. totally worth it. And if you need several done it comes out to even cheaper.

Adrenalynn
02-09-2009, 12:48 AM
But if you want to learn it, not for one project, but for life, then by all means go for it. You're going to burn a lot of metal before you start getting worthwhile stuff.

I love TIG welding aluminum, especially thinner stuff. It requires a ton of concentration and a light deft touch. That said, even with years of practice, I still have a lot of burn-through. Argon Shielded MIG can also work on thin stuff, but is probably even more practice-intensive.

billyzelsnack
02-09-2009, 09:41 AM
Looks like that durafix stuff could work out pretty well..

YouTube - Durafix Aluminum Welding Rods

What sold me was that he was able to use it on the bottom of an aluminum can which is much thinner than the sheet I would use.

Someone in the youtube comments said they got something similar at Harbor Freight.

jes1510
02-09-2009, 09:45 AM
What about JB Weld? I've never used it for this stuff but it would be a cheap test.

robologist
02-09-2009, 02:53 PM
JB weld didn't work as advertised for me. I tried using it to make a square tube aluminum robot frame and the stuff just did not hold on the butt joints I'd clamped together to alow drying. I felt that some other epoxy would have been better. Wound up using corner braces with bolts.

Adrenalynn
02-09-2009, 03:30 PM
I've had mixed luck with JBWeld. I've used it to patch oil pans and cracked cylinder heads on 4x4's and it's been awesome. In my robotics experiences, it's invariably sucked eggs. Standard epoxies have been waaay better, and some of the newer metalic epoxy (like that from LockTite) have been insanely strong.

gdubb2
02-09-2009, 04:36 PM
I tried the brazing rod for Aluminum, It was a total meltdown. Now I always have my Al done by someone that really knows how. I've even got a very nice TIG setup, but I just can't seem to adapt to Al. It's definately a black art..

Gary

Adrenalynn
02-09-2009, 05:00 PM
That's my experience with brazing for aluminum too, Gary. Although I can MIG/TIG it fine (I use a Miller 350MPa [VS])