On Mon, 12 Apr 2004 15:14:28 GMT, "Karl Townsend"
wrote:

||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