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Old 11-14-2015, 02:35 PM   #15
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Ron

What you have presented is an Equation. Equations have variables and thus do not lend themselves to all encompassing Statements.

My comment about Statements refers to the all too often misleading comments presented to RVers like a WD hitch transfer weight Equally to the TV and trailer or the Fixed Number of links one should drop once hitched.

We can sit here all day and discuss the mathematics and vectorial analysis of a hitch, but I am trying to give some basic understanding of what they are meant to do.
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Old 11-14-2015, 03:58 PM   #16
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Huh?

Quote:
Originally Posted by Ron Gratz View Post
Actually, the ratio of the transfer is a function of a) the TV's wheelbase, and b) the distance from the TV's rear axle to the midpoint between the TT's axles.



Yes, a single statement can be made:

The ratio of load added to the TV's front axle divided by load added to TT's axles is approximately equal to b/a, and
the ratio of load removed from the TV's rear axle divided by load added to TT's axles is approximately equal to (a+b)/a.

For example, if TV wheelbase = a = 140", and TV rear axle to TT axles = b = 280", and 200# is transferred to TT's axles:
TV front axle load increase = 200*280/140 = 400#, and
TV rear axle load decrease = 200*(140+280)/140 = 600#.

The load transferred to the TT's axles is a function of:
1) combined downward force exerted on A-frame by WDH lift chains,
2) longitudinal distance from ball to lift chain brackets, and
3) distance from ball to midpoint between TT axles.

Specifically, load transferred to TT axles is approximately equal to combined lift chain force times ball to bracket distance divided by ball to TT axles distance.

Ron
Ron,
Wow, That is really impressive, but I have no idea what you are talking about. It reads like it is something important. Could you translate that into layman's terms and explain how it might benefit us?
Thanks!
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Old 11-14-2015, 04:41 PM   #17
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Quote:
Originally Posted by Msmoto View Post
As one tilts the head towards the trailer does this not add tension to the bars, pushing them up more at the trailer end? And, as the bars are pushed up, would this not force more weight onto the TV?

I had my ball tilted toward the trailer, was getting a couple hundred pounds more on the front TV wheels, so straightened the ball head up (tilted forward) and this lessened the front bias on the TV and now I am about equal on all four TV wheels.

You are correct, tilting the ball toward the trailer, DOES give more WD to the front axle of the TV. The OP of this just needs to get a longer shank to get the AS level, and the TV sitting the way it needs to be..

For whatever it's worth.
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Old 11-14-2015, 06:25 PM   #18
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Quote:
Originally Posted by dickschaak View Post
---Could you translate that into layman's terms and explain how it might benefit us?
Thanks!
Dick,

As HowieE pointed out:
"---As the angle is changed it transfer weight proportionally to that angle to or from the TV/trailer not to either or the TV and the trailer for a given set of bars. As the angle is tilted rearward additional weight will be placed on the front axle of the TV and on the trailer axles.---"

If you add the fact that the sum of the loads added to the TV's front axle and TT axles is equal to the load removed from the TV's rear axle, you have the basic explanation of what a weight distributing hitch is meant to do.

Some people (e.g. those who are close to overloading their TV's rear axle capacity) find it helpful to know approximately how much load the WDH might cause to be removed from the rear.

For example, if your TT's tongue weight causes 400# to be removed from the TV's front axle (and 1200# to be added to the rear axle) and you adjust the WDH to restore 400# back onto the front axle, you can estimate that the WDH will cause approximately 600# to be removed from the rear axle -- leaving a net load addition of 1200-600 = 600# on the rear. If you restore only 200# to the front, the WDH will cause only about 300# to be removed from the rear -- leaving a net load addition of about 900# on the rear.

Some people adjust their WDH based on front-end height rather than going to the trouble of measuring axle loads. If the front axle is returned to its unhitched height, you can estimate that the net load change on the front is approximately zero. However, knowing the rear-end height change will not tell you about the rear-end load change.

Having a way to relate rear axle load removal to front axle load restoration might come in handy.

Ron
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Old 11-14-2015, 07:29 PM   #19
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What difference does changing the tilt (angle) of the ball/coupler connection have to do with weight distribution? Isn't weight distribution a function of lift applied to the w.d. bars?

Or are you saying changing the tilt of the ball/coupler connection is also lowering the w.d. bars, and if the same length of chain is used to connect the bars to the A-frame, more lift is applied to the w.d. bars? (Realizing that unless the w.d. bars aren't tilted down somewhat, little or no lift is available.)

I think Andrew Thomson's article above describing how tilting the ball and bars downward keeps the tow vehicle and truck more stable in turns, and helps keep the trailer in-line with the tow vehicle as well as helping it return to center after turns is a more in important function of tilting the ball and w.d. bars downward?
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Old 11-15-2015, 08:55 AM   #20
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Quote:
Originally Posted by dkottum View Post
What difference does changing the tilt (angle) of the ball/coupler connection have to do with weight distribution? Isn't weight distribution a function of lift applied to the w.d. bars?

Or are you saying changing the tilt of the ball/coupler connection is also lowering the w.d. bars, and if the same length of chain is used to connect the bars to the A-frame, more lift is applied to the w.d. bars? (Realizing that unless the w.d. bars aren't tilted down somewhat, little or no lift is available.)

I think Andrew Thomson's article above describing how tilting the ball and bars downward keeps the tow vehicle and truck more stable in turns, and helps keep the trailer in-line with the tow vehicle as well as helping it return to center after turns is a more in important function of tilting the ball and w.d. bars downward?

That is the way that I understood the article also. Thanks for posting it. Just noticed that you are from Minnesota. We live in Woodbury.
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Old 11-15-2015, 03:50 PM   #21
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Quote:
Originally Posted by dkottum View Post
What difference does changing the tilt (angle) of the ball/coupler connection have to do with weight distribution? Isn't weight distribution a function of lift applied to the w.d. bars?
Yes, weight distribution is a function of lift applied to the WD bars -- along with distance from ball to lift brackets and distance from ball to midpoint between TT axles.
However, the amount of "lift" is a function of WD bar stiffness and the amount of "bend" which can be created by pulling up on the bar ends.

Increasing the rearward tilt of the ball mount causes the rear end of an unloaded WD bar to move farther below the lift brackets.
This means the bar end can be lifted a greater distance -- creating more bar curvature and more lift force (i.e. more downward force on the A-frame).

Quote:
Or are you saying changing the tilt of the ball/coupler connection is also lowering the w.d. bars, and if the same length of chain is used to connect the bars to the A-frame, more lift is applied to the w.d. bars? (Realizing that unless the w.d. bars aren't tilted down somewhat, little or no lift is available.)
Yes, although not unanimous, that does seem to be the majority opinion of those posting in this thread.

Quote:
I think Andrew Thomson's article above describing how tilting the ball and bars downward keeps the tow vehicle and truck more stable in turns, and helps keep the trailer in-line with the tow vehicle as well as helping it return to center after turns is a more in important function of tilting the ball and w.d. bars downward?
Some setups require little or no rearward tilt in order to generate sufficient load distribution. Some require much or maximum tilt.

IMO, the primary function of a WDH is to add load back onto the TV’s front axle and to remove some of the load which was added to the rear. I believe any increase in yaw stability resulting from rearward tilt is a secondary benefit. Andrew appears to agree with this based on his statement: “Though the primary job of the equalizing hitch is to transfer weight to the front axle of the tow vehicle, how the weight is transferred impacts handling.”

Andrew goes on to state: “However, the main reason for the rearward angle is to change the direction of weight transfer so we have additional traction in sharp turns and additional stability at high speeds.” But, if by “additional traction” Andrew means more load on the TV axles, his ensuing narrative and his table of test results at the top of page 52 seem to show that extreme rearward angle causes the load transfer to remain essentially the same as TV/TT articulation increases. If there is no change in load, where does the additional traction and stability come from?

Furthermore, if you convert the front and rear heights from the table on Page 52 to estimated load changes using an assumed spring rate (I used 100 lb/inch/wheel, but any value can be used), the results indicate the angled mount at 22° gave virtually no load change on the TV while the vertical mount at 22° gave a load increase of about 100 # (using my value of 100 lb/inch/tire).

Of course, simply changing the TV/TT articulation from 0° to 22°should not change the load on the TV (as was the case for the angled mount) so I’m guessing there is an error in the data for the vertical mount. I’m also guessing that Row 2 of the table (“Tow vehicle with trailer in straight line”) applies only to Row 3 and does not apply to Row 5. If so, subtracting Row 5 from Row 2 would give erroneous results for Row 6.

IMO, the test results do not support the hypothesis that increasing the rearward angle gives additional traction in sharp turns and additional stability at high speeds. And, even if there is benefit at articulation of 22°, there is no evidence of any benefit at articulation around +/- 5° which is the range of interest for sway control. Perhaps this is why Andrew recommends using a friction sway control when the WDH does not have integrated SC.

In short, I am not convinced that extreme rearward tilt of the ball mount is a substitute for other means of sway control -- the bicycle forks argument notwithstanding.

Ron

BTW -- If we want to make this a Minnesota thread, we lived in Ely prior to becoming full-time RVers.
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Old 11-15-2015, 04:37 PM   #22
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Ron, I surely never intended to indicate downward tilt (if needed) for weight distribution was less important than to assist in sway control and handling in turns but rereading I guess that's how it sounds. Weight distribution is the priority.

Thanks for pointing that out. I do believe Andrew T. uses a number of seemingly insignificant strategies in setting up hitches, including downward tilt of the w.d. bars, shortening of hitch stingers to decrease ball distance to tow vehicle rear axle, changing to lower profile tow vehicle tires for less sidewall movement, selecting tow vehicles based on stability rather than size, to get excellent results from tow vehicles that leave many of us just shaking our heads.

While we may believe tilting the w.d. bars at an extreme downward angle is of little benefit, lots of little benefits become a great improvement.
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Old 11-16-2015, 10:32 AM   #23
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WD Hitch adjustment...how many miles to get correct?

The important message see is that a heck of a lot of trial and error is often required. My goal was to get the trailer level, weight on the front and rear axles of my TV about equal, and have the entire rig drive comfortably.

One variable is of course, what we carry in our TV, in the bed or rear storage area, and how this affects the weight on the TV axles before the AS is connected. In my case, 60 gallons of diesel, generator, air compressor, heavy ground blocks, all of which alter the GVW of my TV.

Across the scales: TV Front 4430 lb, rear 4390, AS 7200.

My suggestion to anyone is to attempt to set up as per the guides from Reese, here is a starter video
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Old 11-16-2015, 01:00 PM   #24
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My suggestion to anyone is to attempt to set up as per the guides from Reese, here is a starter video
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Old 11-16-2015, 02:21 PM   #25
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The above video in general is a good illustration of the principles of a WD hitch. It was not a setup for a Reese SWAY CONTROL system.

However I like to go a bit further, especially when working with an Airstream and bring in those consideration when setting up a WD Sway control system.

First of the axles used on and Airstream require that the final position of the trailer be parallel to the ground. To accomplish this it will take a bit longer in the final adjustments.

Second I like to tow the combination to the point of installation having traveled at least 200 ft. in a straight line. This ensures that things are as straight as they will be while on the road.

Once on place disconnect the trailer and go through the set up as described above. It will be necessary to separate the TV and trailer a few inches while working but do so without moving the TV steering wheel. Before moving the TV, and without the trailer load on it, place a piece of masking tape on the front and rear fenders of the TV and mark a measurement on each. This is just a reference number so the number means nothing at this point. As you go through the set up keep 2 things in mind. You are attempting to get the front axle measurement of the TV as close as possible to the reference mark you just made. Not exact but close and limited by the type of suspension your TV has, A frame suspensions are more critical than I beam as they tend to effect tire ware as they go out of alignment with height changes. You do not want a Lower measurement as that indicate you are overloading the front axle.

The placement of the yokes over the trailer frame are not as critical as noted in the video as the chain angle has No Effect on anything. Yes if off by an in. or more you may want different yokes more for looks than mechanics.

What is important for the sway control systems is that the bars have to ride fully seated on the saddles, be it a Duel Cam system or Straight Line system. If setting up a sway control system leave the bolts holding the Duel Cam trailing arms loose to the frame until the last thing. Likewise leave the yoke adjusting nuts loose on the Straight Line system. Make all adjusts to the system to get the ride configuration you want an then while the bars are loaded on the saddle hit the point of contact between the bars and saddles with a 2 pound hammer. This shock will seat the bars on the saddle and you can now tighten the mounting nut on the Duel Can trailing arm to the trailer frame or set the adjustment nuts on the Straight Line yokes.

Since the sway control aspects of this type of hitch is ALL IMPORTANT these steps ensure things are in fact straight. I find it necessary to mark the bars left and right as they are not always the same length as supplied from the factory. If the bars are slightly different in length the system can be additive to sway rather than damping to sway.
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Old 11-16-2015, 02:53 PM   #26
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Forgot to mention.

When all is done measure the frame height front and rear of the trailer while on concrete or a very flat roadway. Try for less than a 1/2 in. difference. Keep in mind if the trailer is riding high in the front that increases the tongue weight. If high in the rear that decrease it. Both will effect steering so get it close.
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Old 11-16-2015, 03:38 PM   #27
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Wow, had I know there was this much to setting up a hitch, I never would have been able to do it. I just remember someone saying, make sure the ball is about 19 3/4 inches high, the end of the WD bar in the resting position should be about 6-8 inches off the ground (adjust head pitch to make this happen) this should allow you to hook up to about the number 8 link in the chain.

This should get you real close.

Enjoy,
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Old 11-16-2015, 03:40 PM   #28
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[QUOTE=HowieE;1711237]Forgot to mention.

When all is done measure the frame height front and rear of the trailer while on concrete or a very flat roadway. Try for less than a 1/2 in. difference. Keep in mind if the trailer is riding high in the front that increases the tongue weight. If high in the rear that decrease it. Both will effect steering so get it close.[/QU. Per ride height, do you have it backwards?
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