Land Pride RCR1560 brush mower problem.

As the title says I am having a problem with my RCR 1560 mower. This is the second time that the rear tail whee has fallen off. It wants to keep breaking the weld at the area where the pivot pin is welded to the yoke that holds the wheel/tire assembly. The last time I welded it I thought I had a good hot penetrating weld. Has anyone else had this type of problem? This time it broke when I hit a bump where the pavement and gravel road come together. The mower was in the raised transport position at the time. I put some washers on the shaft last time to keep the pin from being able to move up and down so much. It almost seems that when I hit a bump the pin is able to move too much, and the weight of the wheel assembly acts as a sort of hammer to break the weld. Is there supposed to be a spring around the pin to absorb the shock?
I'm getting tired of having to tear it apart to weld it. Any help would be appreciated.


Bob