</font><font color="blue" class="small">( Actually thinking about this now it helps to explain the Weight Distibuting affect of a WD hitch. We are reversing the pivoting (teetering) of tongue weight. Connection (hitch) sits higher and transfers that weight to the front tires on the tow vehicle and the rear tires on the trailer.
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IMO, a WD hitch does not work because of the height of the connection, since it uses the same receiver mounting point on the vehicle, and the location of the hitch ball is adjustable up and down to match the specific vehicle. Otherwise, your description is accurate. IMO, it is actually the torsion bars, and their shape that makes a WD hitch work. The torsion bars are shaped like an "L" lying on its side, i.e. _____|
The short leg of that L is attached to the vehicle (actually to the hitch) while the long leg is attached to the trailer. The trailer ball (and consequently the tongue weight) is attached near the short leg. The long legs go back underneath the trailer tongue and attach to the trailer tongue via chains. When tongue weight is applied, it pushes down on the short leg, which tries to change (increase) the angle and distance of the torsion bars in relation to the trailer tongue. The rear attaching chains prevent this from happening -- so, this downward force is transferred back to the short leg of the L -- where it pushes the top of that short leg forward, transferring that force to the vehicle's frame and onto the front wheels...
It is possible to actually lift the rear of the tow vehicle with a WD hitch and trailer, decreasing traction and braking on the rear. That's why chains are used on the rear of long legs on the hitch's torsion bars -- to provide for adjustment. These chains are used to adjust for different loads (and consequently different tongue weights) on the trailer -- by connecting with a different link of the chain. All this sounds more complicated than it really is -- yet it's difficult to explain without pictures or hands-on experience. Bottom line is that it is the upright, short leg of the L-shaped torsion bar that tries to tilt forward under load, which transfers the weight from the trailer tongue to the frame and onto the front wheels of the tow vehicle.
Try to visualize this 'L" moving down toward the bottom of the screen: _______| Yet, the left end of the long leg is fixed, pivoting, and you see how this force is transferred to the short leg. That short leg is connected to the receiver (and frame) on the tow vehicle by a butt joint, so this force is transferred on to the front wheels. The torsion bars essentially bridge the connection between the vehicle and the trailer. Note also that WD hitches come with different torsion bars based upon the anticipated weight of the trailer and load. Common sizes are 7 or 7.5K, 10K, 12.5K, etc.
BTW, I use an inexpensive Hidden Hitch WD hitch to pull up to around 5,000 lbs behind a Dodge Dakota. Trailer is a tandem with 3500 lb axles and electric brakes. Truck is a Dakota Quad Cab with a 4.7L V8, rated for pulling 5,800 lbs. (Dakotas are rated up to 7,000 lbs based on engine, cab, axle, and 2WD or 4WD). Before this truck/trailer/hitch combo, I was pulling with a 1500 Ram and an F-150 before that. I don't need to haul huge loads (have smaller tractors), but I do tow for long distances. For example, last summer I did a trip to the Midwest where I put over 2500 miles on the trailer. I make fairly regular 900 mile one way (1800 round trip) pulls between Massachusetts and Tennessee...
The Hidden Hitch WD hitch cost under $300 and was one of the best investments I've ever made....
JMHO, your mileage may vary!
Here's a longer, more detailed explanation of how WDs work:
Mr Truck page on WDs
