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Joined: 12/11/2001 From: Taylortown,
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The casting material used in the die castings of model engines has a high zinc content so the aluminum will fill out all the little intricate details of the casting design.
Aluminum castings with a high zinc content do not lend themselves to being the most weldable of metals. What the welder experiences is, that to get the metal hot enough to get any penetration, you will be within a hair breath of the whole thing melting into a puddle or at least a hole melting in it. The solution to this problem is to use a low melting point "solder type weld metal" which, as a result, does not have the strength of the original metal.
In the case of the previously mentioned Saito 150 and 180 cylinder castings, you can not just weld or solder the broken piece back on. The area would have to be welded up and re-machined with the original broken off piece not being used as such.
Most of our model engines are die castings. Some of the low production and one-off racing engines may have sand cast crankcases. These would typically be of a more weldable (356 prime) alloy with only 2.5% zinc and be much stronger with 2.5% copper.
I'm sure this will spark up some counter points from some metallurgical weld engineer and the discussion is welcome.
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Attended the CutFinger Institute of DirtNap University for years but never did graduate....
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Joined: 1/23/2006 From: New Milford,
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I hope that something like this will work. When looking into aluminum repair, I found this site. http://www.aluminumrepair.com/aluminum_repair.asp It says it only needs about 735f for the rod to flow, and since I didn't break of any pieces, I'm hopefull. I watched a video of them brazing a butt joint, and then beating the heck out of it with a hammer, and it looked pretty strong. I'll go talk to a guy today and see what he thinks.
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Joined: 12/11/2001 From: Taylortown,
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There's a catch-22 The aluminum rods cost $65 for a 1 pound starter pack and then you need a torch. They say Mapp Gas but from my experience, the Mapp Gas torch has too broad of a flame for this application. You will need a small acetylene torch.
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Attended the CutFinger Institute of DirtNap University for years but never did graduate....
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Joined: 1/23/2006 From: New Milford,
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I'm hopeing the guy I'm going to see today is familiar with this stuff, and can do the job. We'll see. I can always buy the new jug if it doesn't pan out.
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Joined: 12/2/2001 From: Colonial Beach,
VA, USA Status: offline
Jim, I put the custom TurboHeaders on the TS .90 today and ran two 10 oz tanks through it, good news and good news, the pressure taps worked out perfectly and the rpm with a Bolly 13.5x6 is 9,750, 1,650 rpm idle is doable, kinda lumpy but it doesn't quit. Good job and Thanks for indulging me.
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"I have gone faster backwards, upside down and on fire than most people have gone at all" Don Garlits
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Joined: 2/13/2006 From: Maybee, MI, USA Status: offline
Rex,
Just don't get it to hot, the temperature difference from the rod to the base material is usually only about 50 degree's. Soak your part in alcohol or some sort of degreaser for a while then let dry out. I have tried a few of these repair rods, and for something like this , it might be worth the effort.
Andy
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I go out , I crash , I fix ..... Club Saito member #590
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Joined: 1/23/2006 From: New Milford,
CT, USA Status: offline
According to the website. the HTS-2000 rods flow at about 735 degrees, and aluminum melts at 1200+. I watched the videos and I'm tempted to spend the $65 whether I repair this or not. I do a lot of stuff with aluminum, and it looks like this stuff would come in handy.
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Joined: 3/14/2006 From: Gowen, MI, USA Status: offline
I used some of this a while back, it is touchy but i used it on my small boat motor and it's still holding today. I broke the choke mount off and it gets a fair amount of vibration to boot but like i said its still there. you want to clean the aluminum good before useing the stick. It was not the best looking job i ever did but it worked.
< Message edited by waterloged -- 6/3/2008 9:58:47 PM >
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