Originally Posted by atvtinker
You need to move your fulcrum point further to the back or "load" to see the point made about air bags. Because your axles are so far back in a truck, the airbags tend to lift both the truck and the trailer tongue point making the "effort " part of your drawing require less effort. The taller the fulcrum and the closer to the load it is, the less effort it takes to raise the load. More basic physics. The air bags "raise" the fulcrum point. This in turn shifts some of the weight back to the front of the vehicle. It also shifts some of the trailer weight back to the axles of the trailer something a WDH can't do. Think of the lever in the drawing as being broken closer to the load, the tongue of the trailer would rise. When not using a WDH, there is a second pivot now happens at the hitch itself. Just food for thought. Now granted a WDH does tie together the TV and TT and makes them more solid like a one-piece unit, but a airbag setup give you more flexibilty when it comes to movement. Personally, I think it a matter of preference on which one you use.
I see what you are saying about the location of the fulcrum point. But airbags do not change the amount of tongue weight pushing down on the hitch behind the fulcrum point. airbags may slightly decrease the "light front end" effect caused by the trailer weight, but not nearly as much as a weight distribution hitch. And you are wrong about the air bags distributing weight back onto the trailer axles more so than the WDH ( I believe you said a WDH doesnt not do that at all which is false). That's the whole benefit/point of a WDH and the torsion bars...It distributes the weight more evenly throughout the entire truck/trailer combo which lowers the effective tongue weight on the rear of the vehicle. Air bags do not do that, they simply do a better job supporting all the weight at the rear of the truck.
I'm confident there is a bit of benefit to be had on the front end by keeping the rear end higher instead of sagging. But that does not mean airbags are distributing the same amount of load onto the front end and throughout the trailer as a WDH. A proper WDH setup (adjusted correctly) will level the load by distributing more weight to the front end and to the trailers axles (thats what they are designed to do). An airbag setup will slightly help distribute (not as much as a WDH) as a byproduct of leveling the load and not allowing sag in the rear.
But they are not equal or interchangeable pieces of equipment. If you look at a properly adjusted WDH setup the truck will be level (or close to it) but will sit lower as a whole than a truck that is using airbags to support the rear end weight. That is because there is more load being distributed to the front end of the truck using a WDH.
Air bags are definitely better than not running anything, but they are NOT a sufficient replacement for a WDH setup for heavy loads IMO. They serve two different purposes....yet can be used in conjunction when needed. Keeping the load level is not the same as distributing the weight.
I promise I'm not making this stuff up