4X4Dodger wrote:
Let me clarify that when I wrote about the distance between the pivot point and the AXLES I mean the TRAILER axles NOT the tow vehicle axles. It is this distance that truly affects how a trailer tows. I question whether the distance from pivot to TV axle has any great affect at all. This is a weight issue.
One reason that the axle distance matters is overhang on the rear. The greater the overhang beyond the rear axles the more the Airflow works against the sides of the trailer...with a longer lever arm than if the axles were farther to the rear. This would cause sway.
Lets use your example. Lets place the wheels on the trailer all the way at the rear like on a tractor trailer combo. Looking at the pivot point on a 5th wheel trailer and a conventional hitch or a pintle hitch. Now lets place lateral force against the pivot point on the 5th wheel hitch and lateral force at the pivot point on the conventional hitch. That wind force that you speek of works forward of the trailer axles as well. Difference is with a 5th wheel hitch, that leverage I spoke of earlier doesn't have as great an effect on the pivot point on the 5th wheel hitch as it does on the conventional merely because there is virtually no leverage at the pivot point because the pivot point on a 5th wheel hitch is directly over the center line of the rear axle. With a conventional hitch that force exerted by the wind forward of the axle (on TT) has a compound effect because of the leverage created by the distance of the pivot point behind the rear axle (on TV).
Now, if you will. Move the trailer axles to about 2/3 the distance form the pivot point like on many TT's. That wind again that you spoke of has a multiple effect in that it works against you in one direction as a passing vehicle begins to pass and pushes against the back of the trailer aft of the center line of the axles. As the passing vehicle reaches the trailer axle center line it begins to work in the opposite direction as it continues to push against the side of the trailer, once past the axles, that push is opposite it was before it "crossed" the center line of the trailer axles. This is where "sway" begins to occur. Again only because of the leverage created by the distance of the pivot point behind the center line of the rear axle of the TV.
That lateral force is eliminated with a 5th wheel hitch setup. The placement of the hitch directly over the center line of the TV rear axle makes it so that there is absolutely no leverage on the TV. Not so with a conventional hitch, again.., that lateral force against the hitch is working against the TV in as much as it has leverage to move the TV by the later force working against the hitch. The longer the distance behind the center line of the rear axle of the TV the greater the leverage. Can you see it? I hope I was able to explain what I am trying to get across.
Now with the traditional friction sway control, if the friction is overcome problems can begin. With the "premium" hitches (and this is where the firestorm begins) the pivot point is "changed." I'm not an engineer so I can't and wont attempt to explain the math. The only one I can explain is the Pull Right where the pivot point is literally and physically moved forward to the center line of the rear axle (or as near as possible).
Either way, tested by an independent organization or not. You can't ignore the physics of it. With the friction type of control, if you make it "harder" for the trailer to pivot. It accomplishes what it designed to do, create tension so as not to allow it to pivot so easily. With the "engineered" type, the possibility of sway is engineered out.
The question you ask about it masking a bad setup. I'm sure beyond a doubt that there are setups out there like that where someone maybe happy as a lark (with there sway control) all the while they are a ticking time bomb. I am equally sure that there are folks out there that need a sway control of some type (and are without) that are an accident waiting to happen. And there are those that have it that perhaps don't need it and so on and so forth. You get the idea!
