Andersen Weight Distributing Hitches

[rabbit]

I ain't no train driver but I find it pretty simple to visualize a vertical and a horizontal plane and forces acting primarily, substantially, mostly, totally in one or the other. I sense the argument with reference to the action of the Anderson tending to the horizontal and an adverb to be established.

jack

[Jim Bennett]

Originally Posted by rabbit

I prefer that you employ your anatomy in your explanations, Jim. Not that I don't see the humor but it's a lot funnier when you tip over.

jack

Mix me another cocktail. My preferred reason to fall over. :-)

[Byron Kinnaman]

Originally Posted by rabbit

I ain't no train driver but I find it pretty simple to visualize a vertical and a horizontal plane and forces acting primarily, substantially, mostly, totally in one or the other. I sense the argument with reference to the action of the Anderson tending to the horizontal and an adverb to be established.

jack

I've been trying to understand how the forces in vertical plane work for that WHD? hitch. As I see it the the restriction of the vertical movement would be caused by the friction between the ball and the coupler clamp. The tighter the chains are the more friction between the ball and coupler clamp. (the clamp is my word for lack of a better word, it's the part of the coupler that tightens down against the ball when you latch the coupler).

Also the tighter the chains the more presser applied to the ball tapered pin and friction sleeve. The pressure would increase at the bottom and top in opposite directions the tighter the chains. The chains pulling back and coupler pushing forward.

Anybody else have a better explanation?

[Jim Bennett]

Originally Posted by Byron Kinnaman

Anybody else have a better explanation?

Did you not see my explanation to Jack? I thought the Hitch on the backside 'splained it all.

[Byron Kinnaman]

Originally Posted by Jim Bennett

Did you not see my explanation to Jack? I thought the Hitch on the backside 'splained it all.

I think you need to look at where the forces are and the direction. As I see it as the chains are tightened the bottom of the ball (under the hitch, attached to plate) is pulled back forcing the coupler to apply forward force the to ball. You would have equal forces pushing on the top of the ball and pulling on the bottom of the ball. All the forces would be contained between the tongue, the coupler and ball. I don't see anyway those forces can be transferred to any other part of the tow vehicle. The only left is friction.

I'm surprised you don't understand vertical and horizontal planes. I'll explain. Side motion of the trailer around the ball would be on the horizontal plane. Up and down motion of trailer around the ball would be on the vertical plane.

[Byron Kinnaman]

I see one other possibility. With enough tension on the chains the friction between links might be able to provide some of the same characteristics as torsion bar. That's a bit of a reach.

[David78073]

I'm not sure why everyone is so worried about what force is applied to the ball and hitch on the rv... the weight is already there when you hook up the trailer, grease the hitch on the rv and move on. It's a round ball going into a round coupler... and I can't recall hearing from anyone they had to replace their hitch or coupler because it wore out. But then most people I know actually perform maintenance on their vehicles... let's see, grease the coupler and lube the release...

18 wheelers drive down the road putting a whole lot more weight on the hitch setup (granted it's a 5th wheel) and the only thing protecting those two surfaces is grease... and I dare so the vast majority of them drive a whole lot further than you in a years time. The whole time I drove truck, I only got the 5th wheel greased at regular oil changes, 15k miles +/-. Never having replaced a 5th wheel plate because it wore out.

WDH takes the trailer and spans the load more evenly from front to back so you don't have a "heavy" spot at the hitch point. That causes the front wheels of the tow vehicle to become less in contact with the road... creating a dangerous driving condition. Wait until winter, go find an icy road, hook up a heavy trailer and go for a ride... you'll figure it out in a very short time. A WDH is just meant to put the front tires back on the ground.

And the old dated system does it very well. Simple, uncomplicated and very rarely "breaks".

And a WDH really isn't meant to correct sway, like when you get passed by a big rig... don't start confusing the two. Sway control may or may not be a by-product of a WDH, but it's not it's purpose.

You can buy a WDH, a WDH with sway control (common name is 4point hitch) or add sway control to your setup. But you aren't buying a WDH that corrects for sway. The friction WDH provide sway control, but it does so by not providing as much weight distribution... tighten those bar up too much, and you won't be able to corner.

The anderson you guys are talking does the same thing... only the turning will never be an issue. But you also loose some of the weight distribution.

In this instance you are not going to be able to get your cake and eat it to.

I suspect the anderson is a very good choice for the trailers such as the Scamp, Casita and so on because of their overall weight, I can't see it being a good choice for trailers with some approaching a 1000# + tounge weights.

Neither of my HiLo's sway when towing. I don't have any sway control on either. The reason? They are only about 6' high when being towed, so the lateral wind forces have a lot less to work with.

Don't over think this too much... next thing you know, you'll be ordering a $3,000 Hensley for your 13' Scamp.

[Jared J]

It makes perfect sense to me, how it works. I completely disagree with how it works with the coupler, though. IMHO, it would be a requirement to run a bullydog coupler with that setup.

[David78073]

Originally Posted by Jared J

It makes perfect sense to me, how it works. I completely disagree with how it works with the coupler, though. IMHO, it would be a requirement to run a bullydog coupler with that setup.

Why is that?

[Jared J]

Originally Posted by David78073

I'm not sure why everyone is so worried about what force is applied to the ball and hitch on the rv... the weight is already there when you hook up the trailer, grease the hitch on the rv and move on. It's a round ball going into a round coupler... and I can't recall hearing from anyone they had to replace their hitch or coupler because it wore out. But then most people I know actually perform maintenance on their vehicles... let's see, grease the coupler and lube the release...

Grease has nothing to do with it. That little latch behind the ball on most couplers was never meant to take that kind of force. Under the right (wrong) conditions, you're putting the trailer weight and a large part if the vehicle weight on that little latch with the Andersen setup.

A fifth wheel has nothing to do with this discussion. The jaws on my fifth wheel have 1-1/8" thick hardened steel to wrap around the 2" kingpin on my scamp. That doesn't come close to the little 1/8 or 3/16" steel latch behind the ball on most couplers.

Oh, and I've replaced several couplers because they were so thin, they were starting to bulge on top. To be fair, I would be amazed if it got that way behind most of these light campers.

[Jared J]

Originally Posted by David78073

Why is that?

Because it is using the coupler latch to hold up the trailer and vehicle under some circumstances. That was never designed to take that force.

[Jim Bennett]

Originally Posted by Byron Kinnaman

I think you need to look at where the forces are and the direction. As I see it as the chains are tightened the bottom of the ball (under the hitch, attached to plate) is pulled back forcing the coupler to apply forward force the to ball. You would have equal forces pushing on the top of the ball and pulling on the bottom of the ball. All the forces would be contained between the tongue, the coupler and ball. I don't see anyway those forces can be transferred to any other part of the tow vehicle. The only left is friction.

This tension in the bottom, combined with the compression in the top make for one heck of a torque on the ball hitch, twisting it forward, and because it is affixed solidly to the tow vehicle, the this torque forces the front of the tow vehicle down.

See my explanation to Jack with imagining this setup hooked to your backside. If your reckoning was true, you would not fall forward.

I'm surprised you don't understand vertical and horizontal planes. I'll explain. Side motion of the trailer around the ball would be on the horizontal plane. Up and down motion of trailer around the ball would be on the vertical plane.

My education money was fairly well spent, I did learn how to discern between horizontal and vertical. I just don't see what horizontal movement has to do with weight distribution. Potential for sway, yes.

Originally Posted by Jared J

It makes perfect sense to me, how it works. I completely disagree with how it works with the coupler, though. IMHO, it would be a requirement to run a bullydog coupler with that setup.

Originally Posted by Jared J

Because it is using the coupler latch to hold up the trailer and vehicle under some circumstances. That was never designed to take that force.

I have wondered along the same lines, as there is a fair bit of pressure on the hitch retaining system of any type of hitch. and no doubt the bullydog hitch would suit better. However, I have not had any issues, and have not heard of any either.

[rabbit]

It may be that the chain produces a force tending to pull the shank of the hitch head CCW toward the ground, and tending to produce a semi-rigid arch in the tongue/tv connection which can be read as weight added to or removed from the several axles My SWAG is that the force produced, given the vector along which it's produced, is inferior to the levering force applied by a spring arm. This is only a hunch, fellers. I don't have a sheepskin to hang it on.

I notice that the AS boys are complaining that the anchor yokes for the chain are easily displaced from their initial position on tongue members. Whatever force is available is negated by that glitch. I would like to see the before and after numbers on wheel well hgt. in Byron's table. A link would presumably provide a legible version the interpretation of which would be more than wishful thinking.

jack

[cpaharley2008]

Jack,
You are on the right track. Like it was stated earlier, it is perfect for t/w less than 500#, more than that and it's efficiency drops, as noted on the AS forums which all have heavy tw. The ability to grasp the frame is via bolt and a set screw, both of which will move if too much force is applied. The Lance 1575 which was used in the table has a very light t/w and I was surprised someone used a w/d hitch as the lightweight frames on the Lance is made by (Norco I think) were riveted and they did not recommend using a w/d setup.

[Byron Kinnaman]

Originally Posted by Jim Bennett

This tension in the bottom, combined with the compression in the top make for one heck of a torque on the ball hitch, twisting it forward, and because it is affixed solidly to the tow vehicle, the this torque forces the front of the tow vehicle down.

I think you're seeing some magic. The torque on the ball is created by equal forces on the top and bottom therefore how can any force be transferred to the tow vehicle.

[Brian B-P]

Originally Posted by rabbit

The elastomers and chains of the Anderson most certainly DO resist rotation of the coupler about the ball but in which plane? Vertical, horizontal. Both? If horizontal rotation is what's being restricted, I'd say the darn thing is a sway control and nothing more.

The friction between the cone and the head applies torque about the vertical axis, or if you prefer, controls motion in the horizontal plane... which is what is needed for sway control. As far as sway control is concerned, the chains and elastomeric springs are just to force the triangular plate, and thus the cone, to rotate with the trailer; as long as they don't go slack, the tension in them is irrelevant.

If the chains were in the same horizontal plane as the ball, then it would be nothing but a sway control (and that variation might be an interesting related product for Andersen); however, the chains pull several inches below the ball, so the rearward force on the plate, and corresponding forward force on the ball, combine to apply torque about the lateral horizontal axis to transfer load between axles - that's weight distribution. There is no movement required, but if there is movement about the axis you could call it movement in the longitudinal vertical plane. This has already been well described multiple times above - this is just my version, with the horizontal/vertical issue addressed.

[Byron Kinnaman]

Originally Posted by Brian B-P

The friction between the cone and the head applies torque about the vertical axis, or if you prefer, controls motion in the horizontal plane... which is what is needed for sway control. As far as sway control is concerned, the chains and elastomeric springs are just to force the triangular plate, and thus the cone, to rotate with the trailer; as long as they don't go slack, the tension in them is irrelevant.

If the chains were in the same horizontal plane as the ball, then it would be nothing but a sway control (and that variation might be an interesting related product for Andersen); however, the chains pull several inches below the ball, so the rearward force on the plate, and corresponding forward force on the ball, combine to apply torque about the lateral horizontal axis to transfer load between axles - that's weight distribution. There is no movement required, but if there is movement about the axis you could call it movement in the longitudinal vertical plane. This has already been well described multiple times above - this is just my version, with the horizontal/vertical issue addressed.

If you look closely at the way the system is designed you'll see that the forces applied to the ball are equal and opposite. The top of the ball has the same forces applied as the bottom via the plate, chains, etc. Therefore the ball has a lot of torque with the top forces in the forward direction and bottom forces in the rear direction. Since these are equal and opposite forces there cannot be any transfer of force to the tow vehicle.
If they are not equal and opposite please explain how they are not.

[Brian B-P]

Originally Posted by Byron Kinnaman

I think you're seeing some magic. The torque on the ball is created by equal forces on the top and bottom therefore how can any force be transferred to the tow vehicle.

The forces producing "weight distribution" (that is, forcing a shift from the middle axle - tug's rear - to the end axles) are not both on the ball; they're forward against the ball and rearward against the plate at the bottom of the post/cone on which the ball sits. These are horizontal forces, vertically separated and thus forming a couple. That's a couple, no net force - the hitch isn't trying to push the rig anywhere.

This is just like the more conventional WD design, in which vertical forces at the bar ends and the ball, horizontally separated, form the same force couple (with lower forces but longer lever arms).

No magic, just basic physics applied to solve a problem... which is engineering.

[Brian B-P]

Sorry, I posted by response above before I realized that Byron had responded to my previous post. So... step by step:

Originally Posted by Byron Kinnaman

If you look closely at the way the system is designed you'll see that the forces applied to the ball are equal and opposite.

I agree. In fact I think I've posted that a few times.

Originally Posted by Byron Kinnaman

The top of the ball has the same forces applied as the bottom via the plate, chains, etc.

I agree. Again, I've posted that a few times.

Originally Posted by Byron Kinnaman

Therefore the ball has a lot of torque with the top forces in the forward direction and bottom forces in the rear direction.

Okay, you're calling the spherical bit plus the long cylindrical post it sits on - or maybe the whole system head - as the "ball". Given that, we are saying exactly the same thing: the forces by the coupler and chains on the ball/head together apply a (potentially huge) torque.

Originally Posted by Byron Kinnaman

Since these are equal and opposite forces there cannot be any transfer of force to the tow vehicle.

Correct. The hitch is not trying to push the tug forward, or pull it rearward; there is no net horizontal force. It is also not fundamentally trying to lift it up, or squash it down... although tug is lifted somewhat by the trailer due to the reactions to this torque. In this respect, the Andersen design is just like every other WD system.

The tug must react to this torque on the hitch head. The reaction comes from increased force downward against the ground at the front tires, and reduced force downward against the ground at the rear tires and at the hitch. Just as with the hitch components, this is parallel forces separated by distance - in this case vertical forces of one or two hundred pounds separated horizontally by several feet for a typical FiberglassRV hitch user - forming a force couple.

The trailer is on the other side of the WD mechanism, so it must react too, in the opposite direction. The forces are reduced net force downward on the hitch and increased downward force at the trailer tires. Typically for travel trailer and tug, these forces are still smaller than ones on the tug, because they are more widely separated.


Although everything about WD systems - including this one - is relatively basic physics, most people who don't take an active interest in mechanical design have difficulty understanding them.

[Brian B-P]

Originally Posted by David78073

A conventional system can practically transfer all of the weight

There's the problem - all what weight? The amount of load to transfer to properly use a WD does depend on the hitch load (if the intent is to return the front axle to non-trailering load), but it also depends on the tug's wheelbase and rear-axle-to-hitch distance.

It doesn't matter if a system can be modified and abused to lift the tug's rear axle - enough capacity for operation is what matters, and there is no common definition of that. Since the Andersen No-Sway is intended by the manufacturer for use with typically configured rigs having up to 1400 pounds of hitch weight, it presumably has enough capacity for any of our trailers if properly installed.

Originally Posted by David78073

... my 22' HiLo has a 750# system, my 29' HiLo has a 1400# system...

***the 1400# system will make the vans rear tires just barely touch the ground as the tounge weight of the 29' is only 700#...

That's a colourful description, but I'm sure if you grab one of those rear tires you will be unable to budge it. This is a common problem with discussion of WD systems, although usually regarding the front axle: people say that after the trailer is hooked up and without WD the front tires are "barely touching", when if fact they are carrying only a few percent less load than without the trailer. If the (overly stiff or not) WD system is applied to return the front axle to its non-trailer load, then the rear axle is still carrying even more than it would without the trailer - a ton or so depending on the size of the van.