X Full Timer---5th Wheel Virgin
Full timed in a 33 travel Trailer for three years. Hated towing that thing even with my Dodge 3500. Found the road is calling me again... Bought a 2011 F250 Crew Cab 4x4, 8' Bed. Truck was a goose ...
Forum Discussion
You know, my dear old schoolteacher Mom used to tell me, "If you find yourself driving down the road and everyone else is coming at you, at some point you have to consider that you might be driving the wrong way."
Your hammer analogy isn't all that bad - EXCEPT the constant is the force transferred from the tow vehicle at its attachment point at a given rate of acceleration. If it takes 2000 lbs of horizontal force to move the trailer at a given acceleration (regardless of the hitch type), the difference in the force applied to the pinbox-to-frame junction is a function of the length of the moment arm between the hitch attachment point and the pinbox-to-frame juncture. If that distance is 24" in the case of the gooseneck ball and 8" in the case of the 5th wheel kingpin, then the resultant moment will be 3 times greater with the gooseneck (2000 lbs x 2 ft = 4000 lb-ft) than it will with the 5th wheel hitch (2000 lbs x .66667 ft = 1333.3 lb-ft). The force required for the truck to accelerate the 5th wheel at a given rate of acceleration doesn't change - it's always F = M x A.
If you don't believe me, then how about the following excerpt from the instructions of one gooseneck adapter manufacturer (emphasis mine):
In actuality, since the load plates of the 5th wheel hitch and pinbox prevent rotation, the force transmitted to the trailer with a 5th wheel hitch isn't a torque but a shear force of 2000 lbs in the example above. For simplification, I treated the 5th wheel hitch arrangement the same as the gooseneck adapter.
Rusty
Your hammer analogy isn't all that bad - EXCEPT the constant is the force transferred from the tow vehicle at its attachment point at a given rate of acceleration. If it takes 2000 lbs of horizontal force to move the trailer at a given acceleration (regardless of the hitch type), the difference in the force applied to the pinbox-to-frame junction is a function of the length of the moment arm between the hitch attachment point and the pinbox-to-frame juncture. If that distance is 24" in the case of the gooseneck ball and 8" in the case of the 5th wheel kingpin, then the resultant moment will be 3 times greater with the gooseneck (2000 lbs x 2 ft = 4000 lb-ft) than it will with the 5th wheel hitch (2000 lbs x .66667 ft = 1333.3 lb-ft). The force required for the truck to accelerate the 5th wheel at a given rate of acceleration doesn't change - it's always F = M x A.
If you don't believe me, then how about the following excerpt from the instructions of one gooseneck adapter manufacturer (emphasis mine):
A word of caution is in order about the use of the Cody Coupler! Because of its design, additional pressure may be placed on the "King Pin" of the trailer it is mounted on. This is a result of the leveraging action involved. Because of this, we feel it is wise to mention several steps that should be taken by the owner of such a rig. These are "common sense" suggestions that could and should apply to any type of trailer hook-up.
REGULARLY INSPECT THE INSTALLATION OF THE COUPLER
Make certain the "King Pin" is securely attached to the Pin Box. Occasionally, additional reinforcement might be advisable.
AVOID THE "POP-A-WHEELY SYNDROME"
Smooth, even starts and stops are always better than the jerky motion.
TRAILER BRAKES SHOULD ALWAYS BE IN GOOD WORKING ORDER!
And properly hooked up.
In actuality, since the load plates of the 5th wheel hitch and pinbox prevent rotation, the force transmitted to the trailer with a 5th wheel hitch isn't a torque but a shear force of 2000 lbs in the example above. For simplification, I treated the 5th wheel hitch arrangement the same as the gooseneck adapter.
Rusty
