[Andy]

If you know any mechanical engineers(with a PE) or a metallurgist, it would be worth taking it to them to see what they think caused the failure. A fracture would constitute a failure of the part due to a stress concentration in a particular area caused by a void in the material(small piece missing), or an area that wasn't radiused correctly. Where it fractured at would have rough jagged edges on the outer border. If the ball failed in necking, you would see what appears to be an elongation/thinning of the area where the fracture would be. If the part was designed incorrectly and the defective part illustated that the portion of the design that was incorrect caused the failure, then you could have a valid case for a lawsuit against the manufacturer.

In my opinon it sounds like it failed due to not meeting the rating for which it was given and it wasn't radiused correctly.

A question, where the ball meets the shank, was there a smooth radius there? Or did it look like the ball was cut on the bottom and affixed to the shank with no radius? The reason I ask is that if it had a radiused edge, the stress would be significantly lower than it would be with out it.

Its good to know that he is alright. Sorry to be long winded, but as an engineer when I see problems like this, I try to use the stuff from the books to come up with a reasonable answer why it could have happened.

Oh, one more thing. Most of the time, when something like a trailerball, winch cable, rope....anything that is load rated is desgined by an engineer or company, a factor of safety is usually incorperated. For instance, if the trailerball was rated at 10,000 lbs, but had a factor of safety of 1.5, then the maxium load it should be able to withstand would be 15,000 lbs. This is done primarily to protect the customer. Most people don't know exactly how much things weigh they they are towing/lifting, but they have a general idea. Its better to build a product with some extra capacity than build it with only the rating that is stamped on it.