5th Wheel to Gooseneck Adapters

Learjet wrote:

avvidclif1 wrote:

NMDriver wrote:
It takes x amount of force on the pin to move/stop/turn the trailer. That does not change, no matter what hitch you use. When that amount of force is felt the trailer responds. The mechanism to transmit that force to the pin does not add nor subtract from the force required. The stress ON THE PIN and FRAME is the same with all hitches. Get the adapter that meets your tow weight requirements.

Did you skip physics in high school? Study the operation of a lever.

Ditto....^^^^

x3

There is a significant increase in fore/aft rotational torque about the pin box, due to the significant increase in length of lever below the pin box. The pin box to hitch jaw distance with just the king pin is less than 2 inches. The pin box to gooseneck ball distance is about a foot and half.

Try loosening a very tight nut or bolt with a socket and one of those limited space, extra short handle ratchets. Odds are, you won't be able to get it loose at all. Now try the loosening it with the socket on an 18" long breaker bar. Odds are, you can do it with one hand.

That's what's happening to the pin box, and the trailer's frame the pin box is attached to, when using a gooseneck adapter on a fifth wheel.

Using the ratchet handle example above, even if you throw your whole body weight into it, you're only putting 150-300 lbs of force on the lever. Now imagine the effects of that same lever length, but with 5,000, 10,000, 15,000 lbs of force behind it (the weight of the trailer), chucking back and forth on bad roads, pushing on the back of the truck during hard braking, etc etc. You can see where the force on that lever wants to try to rip the trailer frame apart...

Add to that increase in force, the fact that RV trailers are built very light and cheap, with just barely enough frame strength to hold the thing together under normal usage.

Gooseneck adapters are not one of the better ideas that have come around, for fifth wheel RV's anyways.