Repairing aluminium casting

DXN · Jul 13, 2013

I have a problem on my 4-wheeler. I think it backfired, due to bad tune and low battery. When it did It broke part of the casing. This is where a shaft rides that holds an idler gear to the flywheel. A case is pretty expensive, dose any one have any advice on how to repair cast aluminum.
This is not mine but its broke the same way, dose anyone know a machine shop around North Central Texas that can handle this kind of repair.

Cofe · Jul 13, 2013

Re: Repairing aluminium casting

Find a good Weldor who can weld aluminum with a tig. I would do it for you, but I live purdy far away.

DXN · Jul 13, 2013

Re: Repairing aluminium casting

If I built up the are around it with brazing rods do you think it would hold? There are no clearance issues. Where the wall is 1/4" thick I could make it 1/2 or more to make up for the weaker brazing. If it lasted a year or so id be happy

Cofe · Jul 13, 2013

Re: Repairing aluminium casting

DXN said:
If I built up the are around it with brazing rods do you think it would hold? There are no clearance issues. Where the wall is 1/4" thick I could make it 1/2 or more to make up for the weaker brazing. If it lasted a year or so id be happy

Do not attempt to braze aluminum. Brass will not stick to aluminum. There is JB weld for aluminum, but it is bound break again in an area that is subject to stress. The right way is to clean all the oil off broke area and tig weld to build it up, and then drill the proper hole size for it looks like a bearing or bushing in the pictures.

Tim Frank · Jul 13, 2013

Re: Repairing aluminium casting

^^^^ that.... or buy the new casting.

DXN · Jul 14, 2013

Re: Repairing aluminium casting

They make aluminum brazing rods. I have herd people say they had good luck with them. But I suspect it is highly dependent on the alloy I've got some old lawnmower engines I'm going to experiment on. I'll share my results.

...but the damage on the 4 wheeler was worse than the picture I posted, After inspecting I wont be attempting to repair it. If my wife can pull-start it I will just go without electric start. The case is 1,400 from the dealer, and if I have to replace the case I'm not putting it back together without a full rebuild so its gonna cost even more.

gm280 · Jul 14, 2013

Re: Repairing aluminium casting

What ever you decide to do, please don't do a shotty repair job and then pawn it off on an unsuspecting customer. The world has too many of those folks now. Do the job right with correct repair techniques.

DXN · Jul 14, 2013

Re: Repairing aluminium casting

I don't do shotty work

. That's why I'm not repairing it, the way it broke I could never get the shaft "true" again. There's nothing left to find center.

I'm not one of those guys that will replace a rod bearing that's knocking and sell it!

DXN said:
I'm not putting it back together without a full rebuild so its gonna cost even more.

MTboatguy · Jul 14, 2013

Re: Repairing aluminium casting

By time you get through looking for, or fixing it yourself, you will have enough time and money invested to purchase a good used one, I would take a scan at ebay and see what you can find, I had to purchase a couple things for my quad and found them for a tenth of the price they cost new.

rbh · Jul 14, 2013

Re: Repairing aluminium casting

Don't mess with it, replace it.
There is a ton of torque transferred around the inside of those cases, idler or not.

DXN · Jul 14, 2013

Re: Repairing aluminium casting

I found one for 325 I'm just hoping its still there Friday...Please still be there Friday!

bruceb58 · Jul 14, 2013

Re: Repairing aluminium casting

Aluminum brazing would have been a hack job.

DXN · Jul 15, 2013

Re: Repairing aluminium casting

Kinda what I was thinking, but I figured It would get me through till I needed to go through the motor and I could save for a NEW case

I'm still gonna experiment with the lawnmower engines. I've see videos of people fixing cast aluminum with brazing, but none stress testing the repairs. So I'm gonna knock some fins off and knock a hole in the block. Then Ill take a hammer to it and see. < I'm trying to come up with something more scientific lol.

The_Kid · Jul 17, 2013

Re: Repairing aluminium casting

DXN said:
I'm still gonna experiment with the lawnmower engines. I've see videos of people fixing cast aluminum with brazing, but none stress testing the repairs. So I'm gonna knock some fins off and knock a hole in the block. Then Ill take a hammer to it and see. < I'm trying to come up with something more scientific lol.

I haven't used the aluminum brazing rods on cast but I have tested them on aluminum flat stock. I used some I picked up at Harbor Freight and wanted to do a break test to see how strong the joint was. I just used a couple lengths of 1/8 flat stock I had sitting around. I did a "T" joint with no beveling. On the side 1 I didn't have enough heat so the bead is pretty poor, but side 2 came out better with the torch cranked up.

After it cooled I did a bend test. Here are the first and second bends and the result when it finally did break.

It took 4+ bends back and forth before the original flat stock broke. The only place the brazing let loose was at the end between the green lines where I didn't apply enough heat from the propane torch to let the rod penetrate the base metal.

Now, a word of warning. Not enough heat and you get a weak repair. To much heat and you'll melt what you are trying to repair.

bruceb58 · Jul 17, 2013

Re: Repairing aluminium casting

If I TIG'd those pieces, I can guarantee it would have taken a lot more than 4 bends to make the joint fail.

The_Kid · Jul 18, 2013

Re: Repairing aluminium casting

bruceb58 said:
If I TIG'd those pieces, I can guarantee it would have taken a lot more than 4 bends to make the joint fail.

Please read my entire post. The joint didn't fail. What broke was the 1/8" aluminum bar, and it broke above the joint. Yes there was a portion of the joint that failed because I didn't apply enough heat. This was my first time I had used the aluminum rods, and like any new welding procedure there is a learning curve. I'm sure the first time you TIG'd something it came out perfect.

The OP asked if brazing rods would be strong enough to repair it. As my pictures show the brazing rod deposit is stronger than the base aluminum.

Tim Frank · Jul 18, 2013

Re: Repairing aluminium casting

The_Kid said:
I haven't used the aluminum brazing rods on cast but I have tested them on aluminum flat stock.

<italics, bold type, and underscore by me>

You might want to re-read the thread title....

The_Kid · Jul 18, 2013

Re: Repairing aluminium casting

Originally Posted by The_Kid
I haven't used the aluminum brazing rods on cast but I have tested them on aluminum flat stock.

Tim Frank said:
<italics, bold type, and underscore by me>

You might want to re-read the thread title....

You might want to do some research on aluminum brazing rods. Most of the ones out there like Alumaloy, Alumaweld, Alumarod, Durafix, Aladdin 3 in 1, and HTS-2000 are designed to be used on all aluminum alloys whether extruded or cast. Some of them such as HTS-2000 can be used on magnesium aluminum mixtures, zinc, die cast, pot metal, copper, bronze, Nickel, Titanium and galvanized parts.

bruceb58 · Jul 18, 2013

Re: Repairing aluminium casting

Aluminum brazing rods are a hack fix if you don't have a TIG welder. And if you fail to do a good job with the brazing rod, you have the zinc from the rod all over the place so a real welder may not be able to repair it with a TIG.

Actually, the first time I TIGd something it did come out great! Of course I was a pretty good gas and MIG welder before that.

For the OP, even TIG would have been tough. Brazing rods impossible.

A better test for the brazing rod break test is to do a butt joint. Then you will actually see how poor the joint is.

Tim Frank · Jul 18, 2013

Re: Repairing aluminium casting

The_Kid said:
You might want to do some research on aluminum brazing rods. Most of the ones out there like Alumaloy, Alumaweld, Alumarod, Durafix, Aladdin 3 in 1, and HTS-2000 are designed to be used on all aluminum alloys whether extruded or cast. Some of them such as HTS-2000 can be used on magnesium aluminum mixtures, zinc, die cast, pot metal, copper, bronze, Nickel, Titanium and galvanized parts.

If you have actually used brazing rods to do the repair that the OP is contemplating, I apologise for my lighthearted comment.
My extremely limited welding experience has shown me that welding anything that has been cast is at least three parts witchcraft....

I don't even try at this point in my learning curve. (the gurus in here might say that I am missing out on a lot of fun, but I am also missing out on a lot of aggravation....a trade-off that at this point works for me).
From what you posted it looked to me like you were comparing "apples with oranges".

I may have misinterpreted what you meant when you said

I haven't used the aluminum brazing rods on cast

For some reason I thought you meant that you hadn't used the aluminum brazing rods on cast. Go figure.

Repairing aluminium casting

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