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Old 06-08-2012, 09:27 AM   #113
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Interesting thread with detailed explanations. However, I have been to two of Andy Thompson's seminars and read all his writings printed in Airstream Live magazine. He certainly appears to be quite knowledgeable about on the static and dynamic forces of various types of towing equipment. He has built, tested and sold many safe and successful configurations.

Iím not in the market for a new hitching system, but if I were, I would like to read what Andy has to say after he has had an opportunity to test and evaluate the Anderson WD Hitch on different size Airstreams and in various towing conditions.
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Old 06-08-2012, 10:21 AM   #114
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It should be clear which way the forces are directed by which way the chain is running. With the Andersen, the chain is pulling the bottom of the hitch head back, which cause the ball to be pulled back into the coupler, creating a hitch head rotation (lifting the ball and rear of tow vehicle).

Those that keep commenting that there is already a lot of force on the rear of the coupler when you are stopping (with little or no trailer braking) or going down hill, are correct, the Andersen would be ADDITIONAL force being applied to the coupler.

I'm most concerned with what happens when you approach a steep incline (say a gas station) and the tow vehicle noses up, applying a huge amount of force on the chains. The heavy duty coupler pawl will probably be fine, but what about the much thinner latch mechanism that locks it into position? Raising the front of the vehicle 12 inches is a huge amount of force being applied to the coupler vs ball. This is where you see broke chains and WD bars (or bent A frame on the trailer), which happens and is documented in the forums. Will it be the coupler now?

The other important thing I agree with the others on, friction has never been as effective as geometry in preventing sway. Meaning if any of you are selling your ProPride send me a PM! Seriously though, I'm very interested and hopeful this is a effective hitch.
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Old 06-08-2012, 10:33 AM   #115
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I'm most concerned with what happens when you approach a steep incline (say a gas station) and the tow vehicle noses up, applying a huge amount of force on the chains. The heavy duty coupler pawl will probably be fine, but what about the much thinner latch mechanism that locks it into position? Raising the front of the vehicle 12 inches is a huge amount of force being applied to the coupler vs ball. This is where you see broke chains and WD bars (or bent A frame on the trailer), which happens and is documented in the forums. Will it be the coupler now?

I think thats why they have those big rubber washer thing a mjigs (what are they called) behind the chain. It takes out the stress put on the chains. Or some of it.
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Old 06-08-2012, 10:35 AM   #116
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It should be clear which way the forces are directed by which way the chain is running. With the Andersen, the chain is pulling the bottom of the hitch head back, which cause the ball to be pulled back into the coupler, creating a hitch head rotation (lifting the ball and rear of tow vehicle).
A regular WD also does this. Isn't thats how a WD works.
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Old 06-08-2012, 10:48 AM   #117
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I think thats why they have those big rubber washer thing a mjigs (what are they called) behind the chain. It takes out the stress put on the chains. Or some of it.
Purman,

Yes, those "thing a mjigs" are the actual springs. They are urethane, just like the urethane bushings used in after market suspension systems for bushings. They will compress, and so the serve the function that the spring action does in bars on regular bar type WD hitches.

There is a huge difference, however, because they release their stored spring energy very slowly, compared to a steel spring, and that is how Andersen claims no bounce, or porposing that we get when we hit bumps on the highway.

There is another difference with the Andersen "springs", and that is they are very stiff (compared to steel leaf type springs), and may present the same type problems as an Equal-I-zer hitch with 1200 lb bars and a 500 lb tongue weight.
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Old 06-08-2012, 10:54 AM   #118
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A regular WD also does this. Isn't thats how a WD works.
Purman,

The resulting force seen by the tow vehicle is the same, however the forces in play at the hitch are very different. This is what I keep trying to explain to you.

With the Andersen, the chains pull forward on the "A" frame, causing the coupler to be pushed forward against the ball.

With a bar type WD hitch, the ends of the bars are pulled up against the "A" frame, causing the coupler to be pushed down against the ball.

It is so clear, I really don't see why folks don't understand it.
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Old 06-08-2012, 11:09 AM   #119
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Originally Posted by purman View Post
A regular WD also does this. Isn't thats how a WD works.
With a regular WD hitch, the chains are pulling UP on bars, which cause the hitch head rotation. No additional force is created at the back of the coupler vs the ball.
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Old 06-08-2012, 11:17 AM   #120
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Purman,

The resulting force seen by the tow vehicle is the same, however the forces in play at the hitch are very different. This is what I keep trying to explain to you.

With the Andersen, the chains pull forward on the "A" frame, causing the coupler to be pushed forward against the ball.

With a bar type WD hitch, the ends of the bars are pulled up against the "A" frame, causing the coupler to be pushed down against the ball.

It is so clear, I really don't see why folks don't understand it.
Because that isn't what is happening... if there is any weigh distribution happening, the front axel of the tow vehicle is being pushed/twisted down, and the resulting force at the trailer is the rear is being pushed/twisted down. The forces have to be the same.

In either case, you are adding load to the ball and coupler, which is an uncompressible metal blob that is going to end up with the same net amount of force applied to it. The idea of 'down' being a better force than 'forward' ignores the fact this joint is under constant changes of force and extreme loads from being the one point where 5-6000lbs of TV couples 5-6000lbs of trailer. A few hundred pounds of pressure from a chain is a fraction of the force... as is a few hundred pounds of spring-bar pressure.

With the Andersen, at least you are eliminating the grinding of the ball when turning... That might make the whole thing actually last longer.... who knows...
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Old 06-08-2012, 11:50 AM   #121
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You missed a critical point. There is NO MOTION at the coupling thus NO WARE.

Since the ball and the coupling are locked together as a single unit there will be no ware at that point.


I asked this on another forum but everyone became defensive so I bowed out.

How does the ball lock into the coupler and not pivot?

I understand the sway damping material is on the ball shaft. However, if the ball can still rotate in the coupler it really will not matter if the rotational force is greater than the force the material can apply.

Also, if the ball is locked into the coupler so it does not rotate, how do you turn a corner? Does turning the corner work against the sway damping material on the shaft of the hitch ball?

Since it was said earlier this was a HAHA killer my ears perked up... you know I'm all about HAHA killing. (I kid, I kid... wait, maybe I don't)
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Old 06-08-2012, 12:00 PM   #122
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if there is any weigh distribution happening, the front axel of the tow vehicle is being pushed/twisted down, and the resulting force at the trailer is the rear is being pushed/twisted down. The forces have to be the same.
Actually the forces are not the same. First we have to accept that in order to restore weight to the front of the vehicle, the hitch head must have a rotational force applied to it. A rotation that lifts the hitch, forcing weight towards the front of the tow vehicle and back to the trailer axles. The difference is how you do that and where the force is applied.

With a regular WD hitch, the force is applied by lifting bars UP. The stress point is the top of the ball and the frame of the trailer (where the chains run vertical). Whats important here is, it's the top of the ball. The fulcrum leverage distance is usually around 30 inches (the length of the bars).

With the Andersen, the force is applied by pulling the hitch head BACK and the stress being applied to the back of the ball vs the coupler (where the pawl is held down with a thin latch). I'm guess the actual leverage length (from the top of ball to bottom of hitch) to be less than 10 inches (height of hitch head).

I have no dog in this fight, only trying to clarify were the stress points are and how they are very different than any hitch we've seen yet. For better or worse, only time will tell.

Just for fun, google up a fulcrum lever distance calculator and see just how much less energy is required to move an object when it's 3 times longer.

P.S. Sean you're just gonna have to get one and find out.
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Old 06-08-2012, 12:03 PM   #123
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P.S. Sean you're just gonna have to get one and find out.

Good point. I should order one.

Or, I could trade one for all the used Arrows I have laying around the shop.
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Old 06-08-2012, 12:10 PM   #124
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With a standard WD system the ball has little to do with the WD force.
The end of the spring bar in the hitch head is the fulcrum the bottom of the bar pulls back on the hitch head and the top of the bar pushes forward on the hitch head.
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Old 06-08-2012, 12:14 PM   #125
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Old 06-08-2012, 12:19 PM   #126
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Sean, don't do that yet.
I have to say I don't see a true pivot point here. More like a flex point.
This set-up for some reason reminds me of post tensioning in a concrete building. (don't make me explain that). I see more of a flex and an arch than a pivot point.

Remember arched structures also distribute forces to the ends or buttresses of the vertical piles.

Way off base here, but thats what you get. Think about the relationship of the receiver to the bars.

Dan
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