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Old 09-07-2012, 06:28 PM   #449
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It's really pretty simple.

Load transfer requires torque to be applied to the hitch head.

For a bar-type WDH, the applied torque is equal to WD bar length multiplied by total lift chain force.

For an Andersen WDH, the applied torque is equal to vertical distance from chain to ball multiplied by total chain force.

To generate the same torque (hence, same load transfer), the ratio of Andersen chain tension to bar-type chain tension is equal to the ratio of WD bar length to Andersen chain-to-ball vertical distance.

For example if the former is 30" and the latter is 8", the Andersen chain tension must be 3.75 times the bar-type chain tension.

If we assume a 1000# tongue weight requires a bar-type chain to be tensioned to 1000# for adequate load transfer, the same tongue weight would require an Andersen chain to be tensioned to 3500#.

Ron.
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Old 09-07-2012, 06:32 PM   #450
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You are still making assumptions as you don't have the exact measurements or angles, you want the facts call Andersen.
I don't think I made any assumptions. I simply drew a schematic of the forces. If there is a 10 degree up angle on the chain, that improves the torque equation by a small amount. The sine of 10 degrees is .17, which is still an awful lot less than 1.

P.S. Double click my attachments to make them large and white background. They look very readable to me.
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Old 09-07-2012, 06:39 PM   #451
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I'll make the drawings a little bigger
You will still be making assumptions with out the right dimension and angles of the hitch. If you really want the true physics of this WD you will need to call Anderson. Not back of the napkin calculations based on how you think it works.

I'm not trying to be rude just trying to get you what you want. And if you want the true Physics of this thing you are going to have to talk with Andersen.. If you are ok with your calculations thats fine, but you are the one who was looking for the physics on the Andersen not us.

The the torque on a regular WD is slightly back also, not true horizontal.
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Old 09-07-2012, 06:47 PM   #452
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Quote:
Originally Posted by Ron Gratz View Post
It's really pretty simple.

Load transfer requires torque to be applied to the hitch head.

For a bar-type WDH, the applied torque is equal to WD bar length multiplied by total lift chain force.

For an Andersen WDH, the applied torque is equal to vertical distance from chain to ball multiplied by total chain force.

To generate the same torque (hence, same load transfer), the ratio of Andersen chain tension to bar-type chain tension is equal to the ratio of WD bar length to Andersen chain-to-ball vertical distance.

For example if the former is 30" and the latter is 8", the Andersen chain tension must be 3.75 times the bar-type chain tension.

If we assume a 1000# tongue weight requires a bar-type chain to be tensioned to 1000# for adequate load transfer, the same tongue weight would require an Andersen chain to be tensioned to 3500#.

Ron.
Is that per-side or total for both sides.

I don't believe the clevis pin thing that holds the chains to the plate is rated pass 3000# Plus the darn thing is made in China. The only peace I could find with China stamped on it. Thinking about replacing it..

Here is a picture of what I'm talking about. It's stamped ( wilit 3/8 China. ) They usually have a weight stamped on them. This one doesn't.
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Old 09-07-2012, 07:44 PM   #453
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I had looked at replacing the Chinese Dee Shackles when I first got my hitch. Those that I found a the local farm supply were rated at 1 ton and those supplied carry a notation "WLL 1 ton". But if you look closely at the ones supplied they had to grind off material to get them through the chain.

I am looking for someone that has a press with a pressure gauge and measure what force is required to compress my bushing equal to when I am hitched. That will tell us what the force applied to the chains is.



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Old 09-07-2012, 07:53 PM   #454
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I am looking for someone that has a press with a pressure gauge and measure what force is required to compress my bushing equal to when I am hitched. That will tell us what the force applied to the chains is.
HowieE,

Look for an automotive shop that does work on differentials. They have to use a press to get pinion bearings on and off, and should have one with a gage. I know my frined here that does that kind of work has one, but I'm a long way from you.
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Old 09-07-2012, 08:05 PM   #455
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Originally Posted by purman View Post
You will still be making assumptions with out the right dimension and angles of the hitch. If you really want the true physics of this WD you will need to call Anderson. Not back of the napkin calculations based on how you think it works.

I'm not trying to be rude just trying to get you what you want. And if you want the true Physics of this thing you are going to have to talk with Andersen.. If you are ok with your calculations thats fine, but you are the one who was looking for the physics on the Andersen not us.

The the torque on a regular WD is slightly back also, not true horizontal.
Purman,
My process is just to start with the schematic and make sure I have the fundamental mechanics right. I don't need any exact measurements of any kind to do that part. The force diagram would look the same no matter what the measurements are. If I get that part right, I can plug in all kinds of numbers and do the math. So, really - don't worry - I am not making assumptions! I've look carefully at the information on the Anderson site and that is how I made the schematic of the principles involved. I am not at the "data" point yet in my understanding.

The simplification to this is that the Anderson hitch has rotated the torque force 90 degrees clockwise (roughly), and they use a strain force in place of a bending force to get the torque. That's all there is to the principle of the thing compared to a bar-style WD hitch.

The question is why? Why is it superior to rotate this force and make it strain in place of the more typical bending force? Well, there are some convenience reasons. But are there mechanical reasons? Good question.

Just from the schematic only, my gut reaction is that the strain force can become quite high when going over bumps at speed. Since the force is proportional to the square of the speed, this can get big very fast. Maybe as high as 10X the static strain. Of course there is a compliant spring inserted in the chain. That seems to be an escape valve for all this increased strain. It's an interesting issue.
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Old 09-07-2012, 08:10 PM   #456
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Is that per-side or total for both sides.
3500# per chain -- 7000# total.

Ron
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Old 09-07-2012, 08:14 PM   #457
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Originally Posted by Ron Gratz View Post
It's really pretty simple.

Load transfer requires torque to be applied to the hitch head.

For a bar-type WDH, the applied torque is equal to WD bar length multiplied by total lift chain force.

For an Andersen WDH, the applied torque is equal to vertical distance from chain to ball multiplied by total chain force.

To generate the same torque (hence, same load transfer), the ratio of Andersen chain tension to bar-type chain tension is equal to the ratio of WD bar length to Andersen chain-to-ball vertical distance.

For example if the former is 30" and the latter is 8", the Andersen chain tension must be 3.75 times the bar-type chain tension.

If we assume a 1000# tongue weight requires a bar-type chain to be tensioned to 1000# for adequate load transfer, the same tongue weight would require an Andersen chain to be tensioned to 3500#.

Ron.
You missed 1/2 the force for the Andersen, the chains pull back and the tongue pushes forward.
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Old 09-07-2012, 08:24 PM   #458
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3500# per chain -- 7000# total.

Ron
Then I'm pretty sure the link holding the chains to the plate would fail at that point. something is amiss.
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Old 09-07-2012, 08:34 PM   #459
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You missed 1/2 the force for the Andersen, the chains pull back and the tongue pushes forward.
Nope -- didn't miss 1/2 the force.

Torque can be calculated about any point. I assumed the ball was the fulcrum.

You also can assume the bottom of the shaft (where the chains attach) is the fulcrum. Then you can use the tongue push against the ball multiplied by distance between ball and bottom of shaft.

Or, you can assume the vertical center of the shaft is the fulcrum and use the push force at the top multiplied by one-half the ball to bottom distance PLUS the pull force at the bottom multiplied by one-half the ball to bottom distance.

Whichever way you choose, the torque and forces are the same.

Ron
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Old 09-07-2012, 08:44 PM   #460
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Originally Posted by Ron Gratz View Post
Nope -- didn't miss 1/2 the force.

Torque can be calculated about any point. I assumed the ball was the fulcrum.

You also can assume the bottom of the shaft (where the chains attach) is the fulcrum. Then you can use the tongue push against the ball multiplied by distance between ball and bottom of shaft.

Or, you can assume the vertical center of the shaft is the fulcrum and use the push force at the top multiplied by one-half the ball to bottom distance PLUS the pull force at the bottom multiplied by one-half the ball to bottom distance.

Whichever way you choose, the torque and forces are the same.

Ron

Thats a lot of "assuming" and you know what happens when you assume
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Old 09-07-2012, 08:59 PM   #461
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Then I'm pretty sure the link holding the chains to the plate would fail at that point. something is amiss.
Chains and attaching hardware usually are identified by "Working Load Limit" which typically is 1/3 of "Breaking Strength".

Ron
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Old 09-07-2012, 10:27 PM   #462
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So, I've been staying up on this thread since the first day it was posted, and I'm curious. Why are there no pics of this hitch set up? I see pics of broken "conventional" hitches, but non of the usual "look what I bought and look how I put it on" posts. I value the back and forth engineer speak too, but I'd like to also see how this fits with the tanks and all the other stuff that was talked about at the start of this thread. I was hoping for some visual aids for us less intellectual young guys.
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