"The Kid", my 20 year old, needs to make new tie rods and ball joints for
his racing four wheeler. We're trying to keep the weight down and would like
to use aluminum for the tie rod shafts. Is there an AL alloy that is more
resistant to bending from shock loads than the standard 6061?
Bad idea Karl. The load and shock clearly identifies steel as the lightest
choice. It may be possible to reduce weight a few grams by using a crhome,
vanadium, moly alloy and making them smaller, but the standard material is
already a heat treated alloy.
Our plan B is chrome moly thinwall tubing with welded in plugs to cut the
threads for the ball joints. needs to be at least 3/4 tubing cause the ball
joint thread is 1/2x 20.
He's thinking solid AL 3/4" round is stronger/lighter than a steel
weldament. Wrong? No way does he want a solid 3/4 steel shaft. We couldn't
find 3/4 OD 3/8 ID steel shaft, plus its almost as heavy as solid.
The one that breaks uses 3/8x18 balljoint threads and 5/8 steel OD thickwall
tubing. The ball joint threaded shaft breaks off.
||Our plan B is chrome moly thinwall tubing with welded in plugs to cut the
||threads for the ball joints. needs to be at least 3/4 tubing cause the ball
||joint thread is 1/2x 20.
||He's thinking solid AL 3/4" round is stronger/lighter than a steel
||weldament. Wrong? No way does he want a solid 3/4 steel shaft. We couldn't
||find 3/4 OD 3/8 ID steel shaft, plus its almost as heavy as solid.
||The one that breaks uses 3/8x18 balljoint threads and 5/8 steel OD thickwall
||tubing. The ball joint threaded shaft breaks off.
Probably a stress riser where the threads start.
Are you using the best shafts/joints you can get?
Rex in Fort Worth
If you weld Chrome-moly, it must be annealed and then heat treated correctly
or you will end up with stress risers and embrittelment at the welds. I
don't think aluminum in any grade can cut it there. Please also keep in mind
that Alu will fatigue and fail eventually, especially when stressed.
I missed the beginning of this thread, but on the presumption that this is a
suspension or steering link on a race car, then aluminium tube is available
for this application set up with the correct ID to directly tap for heim
joints, sometimes it's even hex on the OD.. The tube is strong enough for
the application, in almost all cases, as it's primary target is dirt
modified racing and stuff like that - not subtle cars. they do use big
joints - 1/2" is probably the most common, if not 5/8" and 3/4". You can go
to split size ball joints, which have say a 3/8" hole and a 7/16" thread,
those are also common. The stress is actually caused by the jam nut, a
Jaguar sports racer from the 80's used a very clever attachment where a
small pinch bolt fixed the heim joint from rotating in the link, instead of
a jam nut, for the very reason of reducing stress.
One thing is that you never use a threaded ball joint on the suspension
member that is carrying the sprung load, they will not carry the weight of
the car very well, You often see insert ball joints there.