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Old 03-25-2006, 09:37 AM   #43
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Quote:
Originally Posted by chuck
no...the spring bars are supporting the a-frame at that point.
This makes sense to me, I think? First of all, I would never think of opening the coupler with the bars on. If the WD bars are pulling down 800 lbs and your tongue weight is 600 lbs then your ball has a negative 200 lbs (more or less) on it. That is why the rear of the TV comes up and the front goes down with the WD bars attached. I have no clue what the correct numbers are, maybe someone from MIT could explain this better...
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Old 03-25-2006, 12:54 PM   #44
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Originally Posted by azflycaster
This makes sense to me, I think
It doesn't to me. I was not going to pursue this further, but as it has been raised again, I will put forward my understanding of the situation in an intuitive non-mathematical way:-

Imagine that the trailer is attached to the stationary tow vehicle via the ball, on a level road. The load distribution bars are not yet fitted. Let's suppose the tongue weight on the ball is 700 pounds. The front trailer jack is raised, as are the 4 stabilizing jacks.
Now insert one bar into the TV hitch, stand beside it, and strongly lift the end where the chain attaches. You will feel the bar pulling down against your hand. When you now attach the chain to the A-frame, this force pulls down on the A-frame and hence the hitch cup, instead of on your hand. The front end of the load bars are pulling the hitch ball up. The load bars thus "clamp" the ball and hitch harder together. The force holding the cup onto the ball is now GREATER than the 700 pound original tongue weight, and the hitch is safer from uncoupling than it was before the bars were fitted. If this analysis is correct, releasing the hitch lock should never release the hitch, unless the front jack is down. If the front jack is down, all bets are off, and the unlocked hitch will uncouple if the jack is raised sufficiently.
That's my humble understanding of the situation.
Nick.
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Old 03-25-2006, 01:43 PM   #45
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Nick's assessment is correct. That's also why you need to use the tongue jack to take enough pressure off the load bars to be able to lock or unlock them into place with a 1' lever bar.

Roger
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Old 03-25-2006, 01:55 PM   #46
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hi nick.....

i can't understand the uncoupling either....i need pictures of this issue....

also i agree with your thinking....on loads increasing at the ball....

w/d systems don't lighten the tongue weight....
but distribute it away from the ball....we all agree on this right?

well, inorder to redistribute the tongue/ball load and decrease the 'increased load' effect on the t.v. rear axle.....the spring bars actually INCREASE downward forces at the ball and add rotational tension as well....

i've read that net ball loads increase 300-500 lbs....while the torque is 1500-2000lbs.....

that is why the t.v. frame can be levered to load front axle and lighten the rear axle...

the dynamics of w/d systems aren't really like a wheel barrel.....

thanks for touching on this point nick...

cheers
2air'
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Old 03-25-2006, 04:50 PM   #47
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Originally Posted by 2airishuman
hi nick.....w/d systems don't lighten the tongue weight....
but distribute it away from the ball....we all agree on this right?
Absolutely!
Nick.
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Old 03-26-2006, 03:18 PM   #48
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Weight distribution provides a vertical torque on the hitch receiver. That is why the spring bars attach to the receiver by fitting into a slot so they can get force over distance for torque. Pulling up on the end of the spring bar tries to twist the hitch receiver so the back end goes up and the front end goes down.

Since the end of the spring bar that is lifted is back on the A frame. it pulls down on the trailer. Figure the spring bar chains are 2 feet behind the ball and from the ball to the trailer axle is ten feet. This means the tension pulling down on the A frame from the spring bars is split 1:5 with four fifths of it pushing down on the ball and one fifth pushing down on the axles.

You can also figure the torque on the receiver. The spring bar slot is maybe 4 inches or a third of a foot long. The tension on the spring bars is maybe 200 lb (the tension on the chains you lift to set the spring bars) at two feet when resting. So 2x200 -> 400 ft-lb and that means the stress on the part of the bar inserted into the hitch receiver is 1200 lb to get that torque in only a few inches.

The basic idea is that load leveling stiffens the hitch point from bending vertically. It does so by using spring bars to put a torque on the hitch receiver.

Sway control usually dampens horizontal rotation with a braking mechanism.
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Old 03-27-2006, 05:22 PM   #49
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One more time....

First of all, I also agree that wd does not reduce the tongue weight. However I still believe in my answer about the coupler popping up if it is released. The reason we raise the hitch (and truck rear) to install and remove the wd bars is to put the weight back onto the ball and off of the arms. That being said I wrote to Reese's tech support about this issue. The response is as follows...

Quote:
If you could "unhook/unlatch" the couple from the hitch ball, it is very possible for the tongue of the trailer to lift off the ball when the weight distribution system is still attached. Remember, the spring bars are lifting the trailer tongue and the back of the tow vehicle up and forcing the front end of the vehicle down (we are looking for the point where the back end comes up and the front end down and the vehicle is level).
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Old 03-27-2006, 05:55 PM   #50
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The reason we raise the hitch (and truck rear) to install and remove the wd bars is to put the weight back onto the ball and off of the arms.
oh, my. this just won't do.

As for Reese quote, yes, a bounce can happen to lift an unsecured ball. That is why there is a latch.

But the reason that lifting the hitch releases tension on the spring bars is because you are releasing the load on the spring in the bars that occurs when the angle between the ball mount assembly and the bar position is relieved.

This is all behind the basic adjustment of the hitch. Dallas (WBCCI/VAC #8481) puts it this way:
Adjust the hitch ball height to 'level' the trailer
Adjust the weight distributing bars to 'level' the tow vehicle
Adjust the hitch head angle to 'level' the bars.

You can achieve the same effect as raising the tongue by changing the hitch head angle. What you do is to change the torque applied to the small 'el' end of the spring bar when its other end is chained to the A frame. When there is no torque by the spring bars on the receiver there is no load leveling force. Either changing the hitch angle towards the trailer or using fewer links in the spring bar chains 'winds up' the spring in the spring bars that creates the load leveling torque on the receiver.

The fact that spring bars are chained to the A frame and that chains can only provide tension should really clarify the myth about a load leveling system lifting the ball.
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Old 03-27-2006, 06:31 PM   #51
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Quote:
Originally Posted by Leipper
Adjust the hitch ball height to 'level' the trailer
Adjust the weight distributing bars to 'level' the tow vehicle
Adjust the hitch head angle to 'level' the bars.
These three lines have put it all into perspective for me.....Thank you

Getting my new tires tomorrow and we are all hooked up and ready to roll!
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Old 03-27-2006, 06:45 PM   #52
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Originally Posted by Leipper
The fact that spring bars are chained to the A frame and that chains can only provide tension should really clarify the myth about a load leveling system lifting the ball.
Absolutely! Bryan, you are my hero!

I know that a couple of equations wouldn't help clarify the situation for many of the non-specialist mathematicians on the forum, so here is another totally practical way of deciding on the issue:

Step one: connect the trailer to the tow vehicle while stationary. Raise all the jacks. Release the hitch lock. Could the hitch jump up off the ball? Well, obviously not, there is a tongue weight of, say, 700 pounds, pressing down on the ball.

Step two, with the hitch lock still off, install the load distribution bars into the hitch, and have one person on each side lift the end of the bar upwards. The back of the tow vehicle is lifted as is the trailer hitch on the A-frame, beacause it is sitting on the ball. The tongue weight on the ball cannot decrease by doing this. A decrease could only take place if the hitch was tending to be lifted off the ball when the bars are lifted. As the coupling sits on the ball, and the ball is being lifted, the coupling is subject to the same forces as the ball. Could the hitch jump off the ball? No.

Step 3. Leave the hitch unlocked. Connect the chains to the A-frame, and tension the chains, so that the chains take the place of the people. The huge tension in the chains is pulling DOWN on the A-frame and hitch, so the
downwards force on the ball is even higher. Could the hitch jump off the ball now? Certainly not.

Provided the vehicles are stationary, and all the jacks are raised, that's my second humble practical attempt to show how the hitch cannot jump off the ball.
Nick.
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Old 03-28-2006, 03:10 AM   #53
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Nick,
Thanks for the imput. My original post was only to explain why the tongue raised when the coupler was unlocked by chuck. I also believe that the Reese tech reply has merit also. I agree that a test would prove this one way or another. I will visit my trailer later this week (RV storage yard) and duplicate your step3. Here is how I will do it.
1. Have no levelers down on the trailer
2. Raise the tongue and lower it on the ball (do not latch the ball)
3. Install the wd arms (weaker settings at first)
4. Watch the coupler for any lift
Does this sound like a pratical test to you?
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Old 03-28-2006, 04:56 AM   #54
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Originally Posted by azflycaster
Does this sound like a pratical test to you?
AZ, yes indeed, but with the proviso that after 2., the front jack must be fully raised so that it does not touch the ground thereafter. Good luck with the experiment. You have my admiration for being open to experiment, rather than taking a dogmatic position.
Nick.
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Old 03-28-2006, 05:24 AM   #55
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Abnormal driving conditions

Under normal driving conditions towing a trailer;
The towing vehicle is rated for the trailer being towed, the electric trailer brakes (if so equipped from the factory) are in good operating condition, the trailer tires are of the correct type & in good condition, the safety chains are rated for the trailer load & connected properly both at the trailer & the tow vehicle, the breakaway switch (if so equipped) is functioning correctly.

Every state has slightly different travel trailer requirements concerning the necessity of axle brakes, tow chains, breakaway switches, clearance & stop lights, etc....

Perhaps I am mistaken, but no state mandates the use of an equalizer hitch or a sway control device. These devices enhance the towing experience. They provide a safer ride by allowing less sway and better weight distribution.

No one knows for sure what happened to cause the damage noted in the description and pictures at the beginning of this Thread, except the driver & passengers (if there were any) in the vehicle that towed the trailer.

If the driver of the tow vehicle did fall asleep while towing, from personal experience, I believe the most important thing that saved his bacon was his driving skills (which were enhanced by an equalizer hitch/sway control device). Nothing is a substitute for experience.

My point is, towing enhancements were not engineered to substitute for driver care while towing. If you fall asleep at the wheel or drift off the road surface because of inattentive driving, be prepared to wake up in a hospital or not to wake up at all.
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Old 03-28-2006, 06:36 AM   #56
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Originally Posted by Trulyvintage
Every state has slightly different travel trailer requirements concerning the necessity of axle brakes, tow chains, breakaway switches, clearance & stop lights, etc....

Perhaps I am mistaken, but no state mandates the use of an equalizer hitch or a sway control device. These devices enhance the towing experience. They provide a safer ride by allowing less sway and better weight distribution.
Jim,

Searching the Code of Iowa I find that section 321.430 requires brakes, a WDH and sway control on travel trailers over 3,000 lbs GVWR.

Quote:
321.430 Brake,hitch and control requirements:

3. Every trailer or semitrailer of a gross weight of three thousand pounds or more, and every trailer coach or travel trailer of a gross weight of three thousand pounds or more intended for use for human habitation, when operated on the highways of this state, shall be equipped with brakes adequate to control the movement of and to stop and hold such vehicle, and so designed as to be applied by the driver of the towing motor vehicle from its cab, or with self-actuating brakes, and weight equalizing hitch with a sway control. Every semitrailer, travel trailer, or trailer coach of a gross weight of three thousand pounds or more shall be equipped with a separate, auxiliary means of applying the brakes on the semitrailer, travel trailer, or trailer coach from the cab of the towing vehicle. Trailers or semitrailers with a truck or truck tractor need only comply with the brake requirements.

Roger
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