Chucking?

richardcoxid.. You are correct about chucking. A software simulation using vector analysis is what an engineer would use to demonstrate it on a computer. It would take into account truck/trailer, speed, weight, harmonic/phase shift distribution, spring rate/dampening as well a leverage on the fifth wheel in three dimension which would be interesting to watch on a monitor. The vector sum would result in a back and forth movement of the truck. The pin box leverage on the truck is much different than a tow trailer which is the reason fifth wheel trailers call it chucking and tow trailers call it porpoiseing.
Chucking generally can not be compeltely limited unless the compenstion is very precise which is impracticle for all highways conditions and trailer/truck criticl dampening charactoristics. It can be minimized with some of the 5th wheel solutions like MorRide and TrailAir.