--- Your position is that tongue weight is still right there where it always was, yet you cannot comment on what the scale in my previous example would read after a WD hitch was engaged.
Thomas, your post/scale becomes a fulcrum which supports the hitch head. The hitch head supports the rear end of the TV and the ball coupler of the TT.
The WD hitch, with bars 30" long and tensioned to a total of 2000#, produces a torque of 60,000 in-lb at the hitch head. This torque cannot be transmitted through the ball. The torque therefore is all transmitted to the TV.
The TV must balance the torque with an UP force on the front axle and an UP force on the rear axle. To calculate the forces we must know the relative values for the spring constants on the TV's axles. To make things simple, lets assume the spring constants are equal although we know they are not.
Given torque = 60000 in-lb, distance from hitch head to front axle = 195", distance from hitch head to rear axle = 65", and equal spring constants, we calculate a front axle load INCREASE of 277# and a rear axle load INCREASE of 92#. And, as always, the WD bar loads will cause a load INCREASE of 300# on the TT's axles.
So how have things changed? Well, several posts back, we started with a "tongue weight" of 900# sitting on the tongue jack. We now have replaced the tongue jack's UP force of 900# with
1) an UP force of 277# on the TV's front axle,
2) an UP force of 92# on the TV's rear axle,
3) an UP force of 300# on the TT's axles, AND
4) an UP force of 231# on the post supporting the hitch head,
giving a total of 900#
We have done nothing more than replace ONE support reaction (that of the tongue jack) with FOUR support reactions. None of the TT's weight has been moved and the portion of the TT's weight carried on the ball coupler has not changed one iota. We have distributed 900# of support reaction. We have not redistributed any mass.
Perhaps the reason this is so hard to grasp is due to the fact that normally in the analysis of structures the structural characteristics are fixed and the loads are moved around (redistributed). Changing the loads changes the support reactions. In the case of a WD hitch, the structural characteristics are changed. A large rotational spring is inserted to "bridge" across the ball coupler and a large torque is introduced into the system.
The WD hitch does not redistribute any weights. It does change the structural characteristics of the TV/TT connection so that, even without any changes of weight, the support (axles) reactions do change. That's the whole point. You can change the axle loads without performing any kind of "weight distribution". Too bad they didn't call it an Axle Load Distribution Hitch and maybe we could have avoided this whole discussion.
Ron
