kingpin

Yes it doesn and has happened..

 

It happens rarely in bad crashes, but I've seen more fifthwheels ripped off the frame of the truck than I have broken kingpins, its a pretty tough lil bugger.

 

I've never dealt with dollys, but I assume they have to have safety chains because they probably fall under the same laws as any other bumper pull trailer.

 

One of the main reasons dolleys have safety chains is because of the pintle hitch they use to hook to the front trailer or vehicle. Think about all the force on that pintle hitch with the weight of the dolley, trailer, and load then figure in the movement forces. You can see why safety chains are required. The pintle hitches break more often than the kingpins. The pintle hitches are cast iron or steel where as the king pins usually start out of solid bar stock and are machined to spec then heat treated to increase the hardness. I have personally seen a king pin break from a guy backing into it very hard, but I have a feeling he had hit it hard many times before.

 

Ive never seen a kingpin break off but have seen cracks around them which would have resulted in a break. Most times they are hard to see because of all the grease on the plate.

You all do know, that when hooking up your safety chains to your utility trailer or boat, to make sure they are long enough so you can cross them under the tongue that way if something fails, the chains will cradle the tongue (if its still there).?