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Thread: Brazing tutorial

  1. #1
    ecoli Guest

    Default Brazing tutorial

    Since there's been a few requests for this, I decided to post up a brazing tutorial. Pics will follow when I get a chance.

    As a warning/precaution: brazing can be dangerous and hazardous to your health. Breathing in galvanic fumes may lead to galvanic poisoning also known as metal fume fever. Make sure to work in a well ventilated area. Also, remember you are working with a very hot flame and molten metal. Work over non-flammable surfaces and make sure you have water nearby should something start on fire! Basically, be safe kiddies!

    First, you need some supplies. Most of this can be obtained from your local hardware store or welding supply store.

    Brazing torch head - I prefer the more expensive Bernz-O-Matic automatic torch head. Finer control of the flame and no extra fiddling with starting it up, just push a button. Make sure it's one that's compatible with MAPP gas.

    MAPP gas - in the yellow container. They've recently introduced a "new" MAPP gas. Works just as well as the old stuff

    Brakeline - available from any automotive store. 99.9% of the time I use 3/16" brakeline, even for supers. 1/4" can be used for very large builds, but it generally looks too bulky.

    Braze and flux - forget the cheapo brazing rods at HD, Can Tire. If you're using a MAPP only set-up, they require way too much time to heat up and only work really well with a hotter set-up (i.e., with O2). I go with Harris Safety Silv 45 and the matching stay silv white flux. Low melting point and extremely easy to work with. The 45 refers to the silver content, so if you can't find this exact brand, ask the welding supply store if they have something similar (mention you're working with a MAPP only set-up, so you need a high silver content braze). Safety Silv is not cheap, but it's 6 of one, 1/2 a dozen of the other. If you go for the cheaper rods and use an oxygen based set-up, you'll spend the difference you saved on O2 bottles. I prefer the simplicity of a one bottle set-up.

    The above are the bare essentials you'll need to start brazing. On top of this, you're going to need sandpaper, pliers, clamps, welding magnets, tubing bender, tube cutter, tape measure, Dremel, drill, etc. Most of which you likely have if you've been in r/c for a while.

    Building the tuber:

    First thing you need is a plan. If this is your first tuber, I suggest something quite simple without a lot of compound bends. You can either draw it out yourself, or base it on an existing rig. If I'm basing my design on an existing 1:1 rig, I look for a good profile shot and then enlarge it to the size I need for my build. To do this, simply enlarge it until the tires in the photo are about the same size as the tires you have planned for your axles (5" for 2.2, 7" for supers usually).

    Once I have the design in place, I start by making the main structural components. You can usually tell what parts are the main structure after looking at your drawing/photo for a while. Get the brakeline ready by sanding off the galvanized coating with about 120 grit sandpaper (avoid the brakeline with the black coating, commonly sold at NAPA. It's good as brakeline, but the coating is a pain to remove). The brakeline will go from dull to a slight shine. No need to sand too hard, the coating is relatively thin.

    Start by marking off the initial lengths you need and making any necessary bends. At this point, it is very important that you ensure lengths are right and it's square. If it's off by a little bit, this throws the rest of your build off, and it gets worse the further out you go. Yes, you can still run an off-centered tuber, but it looks like crap!

    So bend and cut (tubing cutter or Dremel cutoff wheel) your brakeline. To create a strong joint, you'll want to fishmouth the ends of the brakeline where they meet. A 90 degree angle is the easiest, and one you might want to practice first. I generally use a 3/16" chainsaw file, but you can use a dremel stone or angle grinder too. The two pieces should butt up to each other with very little space in the joint. A tiny bit is ok, as the braze will fill it in.

    Next step is to hold the pieces together using your welding magnets. Then, apply a small amount of flux all around the joint. Fire up your torch and apply heat. The braze is ready to apply when the flux melts and turns clear. Apply a small amount of braze, turn off the torch, and allow it to cool down. It does get simple after a while, but definitely requires practice to know when to apply the braze, how much, etc.

    Now just braze up the rest of the tuber. Once completed, you'll need to break out the sandpaper or Dremel flapwheel and sand down the joints to remove the rough edges and leftover flux. Once this is done, hit it with some metal primer paint and then whatever finishing paint colour you want. Alternatively, you can get it powder coated or anodized.

    The above are just the basics. There are, of course, a lot more principles when it comes to building the tubers (link placement, shock placement, bracing, etc.). This should get you started though.

    Good luck, have fun, don't burn your house down!

    Chris

  2. #2
    Join Date
    Mar 2015
    Posts
    28

    Default

    Hi Chris (or anyone else that can assist)
    I am brazing successfully but I am having trouble ensuring my work is square. I am brazing brass tubing so welding magnets wont hold it in place. Is there an easy way to ensure work is sitting square before brazing and ensuring it doesn't move during brazing? Also when you are brazing what do you do your brazing on, in other words what material do you lay your tubing on that can take the heat and doesn't move itself affecting the brass tubing to be brazed. I am think of making jigs that I can lay down ensuring work is butted together at the fish mouth and doesn't move but before I do so does anybody else use jigs that may suit my requirements. Any assistance would be appreciated.
    Thanks
    Shane
    Thanks

  3. #3
    Join Date
    Jan 2014
    Posts
    36

    Default

    I use a couple of these to hold things in place. One might work, but 2 are better and can hold each piece separately.

    http://www.amazon.com/SE-MZ101-Helpi...s=helper+hands

  4. #4
    Join Date
    Mar 2015
    Posts
    28

    Default

    Hi Thanks for that and they are pretty cheap as well.
    Thanks

  5. #5
    Join Date
    Mar 2015
    Posts
    28

    Default

    Having seen a few you tube videos I am going to have a go at making my own helping hands with various clamps, if it turns out I will post it.
    Thanks

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