Welding on an aluminum forging

By sspeedstreet Date 01-20-2007 20:36

Hi. I'm glad I found this forum. Should have come to mind to check the AWS as I studied metallurgy in college. I found the jewelry industry more fun so that's where I am now (30 years later).

I'm working on a modification for my hobby car. I'd like to upgrade the front spindles (steering knuckles) and there is nothing available aftermarket. There is, however, one from another car that is pretty close for geometry. It's an aluminum forging and would need an upper ball joint boss in an area where there is nothing now. The added part would be approximately 2" x 3" x 1" thick.

First, if properly done, is this advisable?

Pre-heat I assume. Post heat treat? Is the alloy of the base part critical? If so how do I identify it?

I'd appreciate any thoughts you can send my way.

Neil Fischer

By aevald

Date 01-23-2007 04:38

Hello Neil, I have one thing to say, DON'T DO IT. In this case you are looking at a high-stress part and even if you could determine exactly the grade of material that you are working with, the likelyhood of being able to add the necessary ball joint mounting perch to this spindle assembly and then be able to return this casting to it's original strength and reliability are remote. Anyone attempting to do this for you would likely be setting themselves up for a liability that they really shouldn't. Aluminum can be a rather fickle material to work with when compared to other materials, especially when you are dealing with heat-treated materials. Just my $.02 good luck and regards, aevald

By GRoberts (***)

Date 01-23-2007 05:42

I'd have to agree with the first post. I would venture to say that the forging is probably a heat treatable or cold worked alloy in order to gain strength. Welding will cut the strength significantly in both the weld and heat affected zone. Fatigue properties on welded aluminum are not very good. So even if it holds to start with, it probably wouldn't last long.

By jwright650 (*****)

Date 01-23-2007 11:41 Edited 01-23-2007 11:46

Neil,
Is it possible to remake the part by machining a new piece out of a better material?

BTW, what do you have for a hobby car?

Here is a modified spindle from a 1970 camaro, I am installing C5 corvette brakes and had to move the attachment points outward for the calipers to clear those C5 rotors.

In that picture, I haven't removed the broken off backing plate bolts. They get drilled out and tapped to accept 1/2x13 grade 8 bolts for the caliper brackets.

By sspeedstreet Date 01-23-2007 17:55

Thanks for the replies. The fatigue life was what I was afraid of.

The car is a 1988 Fiero GT. The suspension was unique to that one year. The front spindles were designed to accept a bearing cartrige that was used on only that car for that year. GM no longer stocks them and the one aftermarket unit has reliability issues.

I had toyed with making a cast poymer model of the part I want, have it scanned, digitized and then CNC'd but the cost would be prohibitive. I guess that leaves me with constructing one from mild steel.

Again, thanks for the advice.

Neil