semi trailer upper coupler and king pin strength 1

[Les53]

SAE J 133 is unclear about load "C" in the only indication that it is fully reversing is the double arrow in fig 2. I assume that a fully reversed load being more severe is the correct load case.
Are canadian stds. similar?
Is the research being done at Penn State/Army/USDOT on king pin loads going to force a change in the SAE standard?

 

[icrman]

I am suprised that throughout the years there haven't been alot more failures of those king pins. They may take a load fine, but they just plain "look" too small. They use the same size pin to pull large lowboys with 150,000 plus pound machines on them.

 

[zeusfaber]

"They use the same size pin to pull large lowboys with 150,000 plus pound machines on them"

They often do, but they probably shouldn't.

ISO standards (337 and 4086) allow for two sizes of kingpin - 2" for ordinary jobs and 3.5" for heavy haulage.

I'm quite surprised at how many big trailers come with small pins.

A.

 

[rmw]

Actually, the drive shaft is the weak link in the chain. The drive shaft will twist in two long before a king pin will fail.

BTW, I have seen upper couplers designed to provide for interchanging 2" and 3.5" pins, but have never seen anyone do it.

rmw

 

[zeusfaber]

rmw,

I agree that the kingpin probably isn't the weak point.

For everyday loading, I see what you mean about the drive shaft.

In an accident case, I believe it's not unknown for the bolts that hold the fifth wheel onto the rails on the tractor to be the weak link.

A.