Blue Ox Sway Pro, how it functions against sway

[rexlion]

I've been reading about and looking at pictures of the Blue Ox Sway Pro. And I've read some of the recent threads here that discuss this hitch. Blue Ox describes the sway control as a "caster effect" but their advertising does not elucidate beyond that one descriptive phrase.

Near as I can figure it out, this caster effect is caused by the spring bar sockets being offset from the swivel point (the ball). On the other end of each bar, a chain runs upward to the trailer frame. If the trailer should sway to one side, the end of the bar on that side will travel farther along the frame in the direction of the trailer, and since the chain's length is fixed it causes the bar tension to climb, and all of this exerts a push on this side. Meanwhile the opposite (pull) is occurring on the other side. Do I understand this correctly so far?

Assuming I've stated the forces at work with reasonable accuracy, it seems to me that the push-pull forces continue to be exerted (albeit in a declining amount of force) as the trailer's angle to the tow vehicle once again approaches 180 degrees (i.e., straightens out).

The problem I see with this is the fact that an object in motion tends to stay in motion. Consider the pendulum: as it climbs to one side, the force of gravity exerts a downward pull and the pendulum slows, reverses course, and swings toward 'straight down'... but the pendulum does not stop there. It continues to arc upward in the opposite direction. Taking this example to the Sway Pro, it seems as though the trailer's motion back to 180 degrees has little or nothing stopping it from continuing its swing in the opposite direction. As the trailer sways the opposite way, the Sway Pro again exerts the push-pull force in an increasing measure until the TT's sideways momentum is stopped... and is again pushed & pulled in the other direction where it again has unchecked momentum to go beyond 180 degrees.

Without some dampening force (such as friction) to slow the momentum and avoid the pendulum effect, I don't see how the Sway Pro can truly be an effective anti-sway hitch. If someone has a different or better concept of the physics involved, I'm open to hear it (I'm not a mechanical engineer, unlike my son).

As for people's experiences while using the Blue Ox Sway Pro, I fully realize that most users are happy with it (but meanwhile, some users have experienced sway with it...and felt strongly that it was properly adjusted, too). I think that an analogy might be drawn to the many people who, over the years, have happily and successfully towed without any sway control whatsoever; in other words: it worked fine, right up until the one day when conditions were just right, and then (surprise!!) it didn't work.

Comments? Questions? Curse words? 😄

[rexlion]

Maybe it is a placebo effect. 😉

[Walaby]

gmw photos wrote:
Folks can argue all they want about the "how" or the "whether it should" work.

I have towed my travel trailer just on the ball. I have towed the same trailer behind the same truck with the blue ox hooked up, in all sorts of weather over 50K miles.

"It works". The trailer stays noticeably straighter behind the truck with the blue ox in place. For me, it's been well worth the money spent.

I agree... I can't explain the physics or engineering behind it, but I know it works. At the end of the day, that's all that matters to me.

Mike

[gmw_photos]

Folks can argue all they want about the "how" or the "whether it should" work.

I have towed my travel trailer just on the ball. I have towed the same trailer behind the same truck with the blue ox hooked up, in all sorts of weather over 50K miles.

"It works". The trailer stays noticeably straighter behind the truck with the blue ox in place. For me, it's been well worth the money spent.

[rexlion]

Lynnmor wrote:
I think you will find that it is not a true pendulum, in that there is spring pressure applied whenever the trailer is off the center line. This causes a self centering effect and the "pendulum" energy is dissipated with that spring compression....

When a trailer on a simple ball starts to sway, there is pressure (from the pull of the ball and the sideways friction of the tires) to swing back toward a straight line. But that pressure causes the TT to overshoot to the opposite direction. The compression of the springs works on the chains to give an even greater push. It seems like this greater push could enhance sway rather than dampen it.

The push in either scenario (on ball or with SwayPro) is weak if the TT is off by a small angle, and it grow stronger in either scenario as the angle increases. When the TT shoots back toward straight, what in either scenario is operating to slow the TT so it does not overshoot to the other side? Is a big pushback somehow going to stop the pendulum better than a small pushback? If we push an object harder, it should go farther... the opposite of what is desired in towing.

[drsteve]

A reasonably well balanced trailer with the proper amount of tongue weight will not sway unless an outside force acts upon it. The outside force gets it moving, the hitch dampens the motion, and the force is dissipated. They all work that way, more or less. Except a Hensley. Nobody agrees on how they work. 😉

[downtheroad]

I have a lot of experience towing trailers (5 of them). I have had the basic WDH with a sway bar, an Equal-i-zer brand hitch and a Reece Dual Cam Strait Line hitch.

I now have a Blue Ox SwayPro. Trailer is 10K gross. I'm not a physicist and I can't begin to figure out or explain how it works. But I can say that it absolutely does work....not a drop of sway. What I also noticed is there is very little if any feeling when a big rig passes us. No "bow wave" affect.

It's easy to set up and easy to use..Down side is that the hitch head is very heavy...much heavier that any of my previous set ups.

[Lynnmor]

I think you will find that it is not a true pendulum, in that there is spring pressure applied whenever the trailer is off the center line. This causes a self centering effect and the "pendulum" energy is dissipated with that spring compression.

I don't have one but have been reading mixed reviews that has kept me from buying one. I like the idea of eliminating the noisy, troublesome friction control of both the popular and inexpensive hitches.