Anticept Posted September 4, 2016 Report Share Posted September 4, 2016 We had some gouges and cracks in our aluminium piping welded before on our CTs. Well, I was replacing a leaky segment of hose and it looked like someone had tried this before with some seriously sharp instruments (aircraft was purchased used, and just before it was bought, the hose change was done), leaving a really deep gouge. I found out our welder guy is out on a job for at least a week in another city. And, where this pipe was located, I would have to remove a bunch of stuff to get to the clamps. We were considering using JB weld, but it's not exactly a kosher thing. Maybe it would work fine, but I really don't like using it in aircraft because there are better things. I was searching around for ways of fixing cracks that might be adaptable to fixing gouges, and I saw something that I hadn't thought about in a while. Brazing! Now disclaimer: I SUCK at welding. I was probably the slowest person in my class and never got past the basics (granted, we were using oxy-acetaline welding, which I understand is very hard, but still). I wasn't sure how this would turn out. Ran to the store, grabbed some aluminum brazing rod, a propane torch, flux, and came back. Had water ready in case I set something on fire! . (actually aluminum brazing needs to be quenched to draw out and help remove the flux, but anyways) Couple of youtube videos later, I used a wire wheel to clean the area, threw on flux, lit the torch and went to work. Because brazing uses a lower heat, I didn't need to remove anything from the aircraft, I just had to make sure I didn't melt anything nearby, so I strung up hoses and such out of the way and keep the flame at a focused point. First try was meh. Filed most of it away. Tried again... not bad. Can still see some of the pitting from the gouge. Third try... CRAP too much heat and a bunch of my filler ran right down the pipe and onto the floor. Applied solder wick to soak up the aluminium and start over. Fourth try... ohhhh that's almost got it! Little more heat, couple light touches, and some filing... wow that's the best hot metal job I've ever done larger than electronics! Saw a couple more gouges on the other pipe and thought "I'll try it". Nailed it first try! Photos: First photo is the first job I did. I just noticed I didn't wipe off the shavings but anyways, it's passable. I didn't measure the first one with the caliper before I got to work, and I wish I did, it would have been a great way to make sure I don't dig into the pipe, but it's less than a hundredth difference than measuring 90 degrees rotated, so it should be pretty good! Second one is the second job. You can slightly see where it's just a little built up. I did measure that one before I started. When I was finished, I had increased the diameter by less than 2 hundredths of an inch. Both of these are quite smooth to the touch. I'll hit them with emery cloth before closing up, but it should turn out pretty darn nice! Total cost came to about $50, and the torch I can use for other projects too! Link to comment Share on other sites More sharing options...
Roger Lee Posted September 4, 2016 Report Share Posted September 4, 2016 Hi Corey, Why did you worry about some scratches? Either they wouldn't affect anything or you could have just smoothed them over. Why did you fill them? Link to comment Share on other sites More sharing options...
Anticept Posted September 4, 2016 Author Report Share Posted September 4, 2016 They weren't "scratches". They were very deep, and were letting coolant leak by little by little. I could sink my fingernail into them. Thought they were cracks at first. The second brazing wasn't something I would have gone out to buy tools for, but since I had torch and rod in hand, I figured I would hit it anyways. Link to comment Share on other sites More sharing options...
Runtoeat Posted September 4, 2016 Report Share Posted September 4, 2016 Corey, it would be interesting to see if JB Weld would have worked here. Worst that would happen is one would see a leak come back and then the plan would be to use your newly developed skills for brazing. I have seen gauges made which result in persistent leaks. Whenever I have a hose removed, I make sure I'm there to oversee this or do it myself - making sure no tools are used - LIKE FLAT BLADED SCREWDRIVERS! Link to comment Share on other sites More sharing options...
Anticept Posted September 4, 2016 Author Report Share Posted September 4, 2016 Using tools are fine as long as they have rounded edges. Using an old awl and grinding a rounded "spoon" into it is perfect for helping to unstick sticky rubber. Link to comment Share on other sites More sharing options...
BravoFoxtrot Posted September 4, 2016 Report Share Posted September 4, 2016 Interesting. I had not previously heard of brazing aluminum with a propane torch. Thanks for the information. Link to comment Share on other sites More sharing options...
Anticept Posted September 4, 2016 Author Report Share Posted September 4, 2016 HTS 2000 brazing rod is crazy. Link to comment Share on other sites More sharing options...
Tom Baker Posted September 4, 2016 Report Share Posted September 4, 2016 Corey, it would be interesting to see if JB Weld would have worked here. Worst that would happen is one would see a leak come back and then the plan would be to use your newly developed skills for brazing. I have seen gauges made which result in persistent leaks. Whenever I have a hose removed, I make sure I'm there to oversee this or do it myself - making sure no tools are used - LIKE FLAT BLADED SCREWDRIVERS! From what I have heard if you use JB Weld first it is almost impossible to repair by welding after due to the contamination. I'm not sure, but I think the same would apply to brazing. Link to comment Share on other sites More sharing options...
Anticept Posted September 4, 2016 Author Report Share Posted September 4, 2016 That's correct. Once brazed, you cannot weld the same area. It's even said in 43.13-1b. The brazing alloy is the wrong alloy for welding. It's basically a very hot form of soldering, but bonds better. Brazing is nice for low and medium stress repairs, but welding is still the best for high stress areas. Welding aluminium is hard though! The reason I chose to braze this, is I can't normally destroy the part while learning. It's still far too cold of a process. Link to comment Share on other sites More sharing options...
Runtoeat Posted September 5, 2016 Report Share Posted September 5, 2016 Would silver solder work in this application? Link to comment Share on other sites More sharing options...
Tom Baker Posted September 5, 2016 Report Share Posted September 5, 2016 I don't think it will work with aluminum. Link to comment Share on other sites More sharing options...
Anticept Posted September 5, 2016 Author Report Share Posted September 5, 2016 Would silver solder work in this application? I try to use like alloys with like alloys unless I understand otherwise. When the wrong alloys are mixed, they might bond just fine, but fail down the road. I don't think aluminium and silver react weirdly, but nor am I sure if they bond. Aluminum brazing rod can be found at your local home improvement store and melts at around 600-900 degrees F. I think this piping melts at around 1200-1400. Link to comment Share on other sites More sharing options...
Tom Baker Posted September 5, 2016 Report Share Posted September 5, 2016 That's correct. Once brazed, you cannot weld the same area. It's even said in 43.13-1b. The brazing alloy is the wrong alloy for welding. It's basically a very hot form of soldering, but bonds better. Brazing is nice for low and medium stress repairs, but welding is still the best for high stress areas. Welding aluminium is hard though! The reason I chose to braze this, is I can't normally destroy the part while learning. It's still far too cold of a process. Don't think for a moment that you can't destroy the part with a propane torch. You can anneal the hardness without knowing, and it can get hot enough for the aluminum to melt and disappear. Link to comment Share on other sites More sharing options...
Anticept Posted September 5, 2016 Author Report Share Posted September 5, 2016 Don't think for a moment that you can't destroy the part with a propane torch. You can anneal the hardness without knowing, and it can get hot enough for the aluminum to melt and disappear. Definately! That's one of the important rules to consider when hotworking! Link to comment Share on other sites More sharing options...
Runtoeat Posted September 6, 2016 Report Share Posted September 6, 2016 Good information - forgot about the low temp aluminum rod being available. I've actually got a piece of the Rotax aluminum coolant tube to practice on. Might be a good project this winter to play with this. Link to comment Share on other sites More sharing options...
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