Equipment Question.

I had another driver trainer ask me a question and I hope you all can answer it for me. I got two different answers on Facebook.

What is a "fifth wheel stop block"?

Interesting question for this forum. Fifth wheel stop blocks (aka; pinned fifth wheel) prevent the fifth wheel from pivoting up and down. This is primarily used for frameless and quarter-frame dump trailer operation. The trailer is designed with an integrated pivot point allowing it to articulate during the dumping operation. If the fifth wheel is allowed to pivot along with the trailer, it greatly increases the risk of a roll-over event during the dump operation. When under this type of trailer, an unblocked fifth wheel would also cause horribly poor ride quality for the driver, creating a herky-jerky motion during stops and starts. Many fifth wheels are designed for un-blocked and blocked operation enabling greater flexibility in tractor utilization (ex: construction company tractor used both for frameless dumps, flatbeds, fixed frame dumps and lowboy operation).

Frameless dump trailer