Coast Resorts Open Roads Forum: Towing: New Andersen WD hitch

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Topic: New Andersen WD hitch

Posted By: dougsee3 on 01/24/12 08:23am

I can not post a pic. from my phone.
If you look at the TT hitch were the ball fits into the top of the ball socket.
The trailer TT hitch would have to rise up away from the ball to put excessive force (or all of the force) against the coupler latch.
What the latch is really doing normally is preventing the hitch from lifting off the ball rather than taking all pressure from braking and in this case the chains forcing the latch against the ball.

2008 Pace Arrow 33V
8.1 Workhorse
Acme Eze-Tow Dolly
_________________________
Last RV
2005 2500 Avalanche 8.1/3.73
2004 30' Terry Quantum 290FLS

Calgary Alberta

Posted By: red31 on 01/24/12 08:58am

Thanks John, that does help.

I guess my question was too simple. I was wondering if a-frame members were more resistant to let's say a 4x load applied the way Anderson does versus the vertical load of 1x by spring bars. Some particular spec (compression, modulus, inertia, ect, over my head!) of a tube to 'better' resist a force, ie the bending spec is X versus Y pulling on bottom which is Z times greater. I see there is a lot more going on, great explanation.

Posted By: JBarca on 01/24/12 11:09am

dougsee3 wrote:

Dougsee3,

Good point. I do not know what your coupler looks like. I just happen to have these pics on my photo server from long ago. This TT coupler was in an accident where the TT flipped on it's side so if someone finds damage in these pics that is why.

This Shelby coupler is the same type as mine. I will try to get pics of mine tonight if the weather cooperates.

On this brand/model coupler "it appears,” the entire rear portion of the latch withdraws from the ball. The top of the coupler "appears" to have a small formed dome in the top of the coupler.

The question now is does that formed dome create enough of a ledge to keep all the force of the WD from the Anderson unit to not apply it to the latch?

OR

Does the strong WD force pulling back does still apply force on the latch even with the domed top?

This could be a race of forces as to who wins. If the WD chain force is high enough it “may” overcome the tongue weight pushing down.
Then do the chains still pull the ball out of the dome partially and down into the latch and you still end up with latch issues? H'mm good question. I need to think on this one some more. Not enough time duirng lunch.

Does yours look like this?

[image]

All ball couplers may are not made the same.

Thanks

John

PS If you need help posting pics, PM me an email address, I can help.

John & Cindy

2005 Ford F350 Super Duty, 4x4; 6.8L V10 with 4.10
CC, SB, Lariat & FX4 package
21,000 GCWR, 11,000 GVWR
Ford Tow Command
1,700# Reese HP hitch & HP Dual Cam
2 1/2" Towbeast Receiver

2004 Sunline Solaris T310SR
(I wish we were camping!)

Posted By: JBarca on 01/24/12 08:01pm

See if this helps any.

I went out and looked at my ball coupler. This is the one I have. http://www.shelbyindustries.com/custdocs/class%20iv%20a-frame%20coupler.pdf

I also took a number of dimensions to make a drawing of the coupler cross section. This was in an effort to help sort out if this top dome plays a role in removing some force off the latch by the Anderson WD system. After seeing what is in these pics I came to a conclusion without the drawing.

The top dome is 1/4" above the top of the latch area. You can see this in this side view.
[image]

Here are some other shots of the coupler.

Latch open
[image]

Latch closed
[image]

Front view
[image]

Side view with tow ball in place and latched. I also measured the clearance up and down and front to back when latched. Both where 1/8" total movement.
[image]

Now the views that where convincing to me of what would occur when hitched up and WD engaged.

A side shot with the tow ball next to the coupler. Notice the flat spot on top of the tow ball. Every tow ball I have in 2 5/16" has this flat spot. I do not know if every 2 5/16" ball has this, mine do. That flat spot will play a key role in the next pics.
[image]

Two side shots mocking up how much engagement at the top of the tow ball will have with the Anderson WD hitch pushing the coupler forward and pulling to tow ball to the back of the latch area.
[image]

And 1 more
[image]

From those last 2 pics I have come to this conclusion:

The flat top tow ball eliminates approx 3/16" of the top of the ball sphere from touching inside the ball coupler.
1/8" of vertical clearance exists up and down with the coupler latch.
If the ball drops 1/8" down from clearance plus the 3/16" flat top ball, there would be no dome engagement if the ball is pushed down and back into the latch.
The back of the ball sphere and the back inside of the coupler dome are curved and create a very good sliding cam angle of the 2 parts in relation to each other.

From the above bullet points I conclude:

A 1,400# tongue weight creates a 1,400# downward force to seat the coupler on the ball.

For a tongue weight of 1,400# the Anderson WD hitch could produce between 6,000 to 7,800# of force pulling on the bottom of the chains. Even if it was 4,000# as Anderson stated in their video it would not change the conclusion.

The higher WD chain force will overcome the tongue weight pushing down. The TT will cam up on the back side of the tow ball and create the 1/8" clearance up top. The TT tongue will lift up the 1/8"and combined with the 3/16" flat to ball, there is no dome engagement left. Almost all 6,000 to 7,800# of WD force pulling on the tow ball will be transferred into the safety latch.

This is my conclusion from what I saw tonight. Anyone see something I missed in this theory to change the outcome?

Thanks

John

Posted By: SoCalDesertRider on 01/24/12 08:18pm

John, I agree with your conclusion. All of the weight distribution force is on the latch and all of the truck/trailer pulling force is on the chains and the chain latches. I would not run that hitch system with a conventional coupler.

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Posted By: BenK on 01/24/12 08:46pm

BenK wrote:

John !?!... you've got me !!!!

Cleaning out the garage and coming in to check this site, so apologize for the
quickie comments...

Well, lots of assumptions on my part.

Assumed the ball is held in there by a traditional nut, but will have to see
how they capture it

Thought a traditional coupler with a pawl, but in looking at the image...there
is no latch.

So how in the world did they get the ball past the interference fit?...but that
is another assumption...that the coupler has an interference fit for the ball
like these images:

[image]

so if traditional, then that pawl will take the forces...but...since not traditional
how do they keep the ball from coming off?

By interference, meaning that the coupler has a lower hemisphere smaller
in dia than the ball dia. The pawl moves out of the way to allow the
ball to move backwards and then drop out.

That is also how I saw it.

I've not seen all of the types of couplers, but *ALL* of the one's
have seen look like the cross section diagram above

Architecturally these latches reduce the dia of the opening below the
ball equator so that it will not come out. Not to have that kind of
force on it statically and worse dynamically

Any asked them about this and if so, what was their position ?

Since the original image did not have a latch, did they remove the
latch and is now riding on what?

Posted By: Michael in MN on 01/25/12 06:43am

First I'd like to express my appreciation for the analysis that John, Doug, Ben, Ron and the others have put into this. It is clear to me that this changes how the load is transmitted though the hitch, but it's not clear to me that the change is sufficient to reject the design. The latch appears to only be required to carry the load back to a pin or ramp that transfers the load out to the body of the coupler. As long as the latch mechanism is in compression and the pin that carries the load out to the coupler are reasonably strong, the design should work.

From my (limited) point of view, in conventional designs the latch mechanism already has to carry the force of the trailer when backing up (static load), and it already has to carry any impact that occurs when the truck decelerates faster than the trailer (hitting large pothole with the truck), and because existing latch designs seem to be doing this without catastrophic failure, the existing latch designs must be reasonably sound.

One application I can see for this is for the minivan + 3500# trailer combination. On the light weight end of the towing spectrum, traditional WD hitches add significantly to the tongue weight, and this design is probably 100# lighter than other designs, so perhaps this WD design is appropriate even though there may be limitations that make it unsuitable for heavy trailers?

--Mike

-----------------------------
LivinLite Camplite 16BHB
2015 Silverado 1500

Posted By: Campin LI on 01/25/12 09:13am

It looks like the ball that comes with the hitch is round at the top. Back to the first post with the link to their web site. Looks like you have to use that ball because it is part of the system. On their web site scroll down to the picture that shows it and click on the picture to enlarge it.

Posted By: jerem0621 on 01/25/12 09:35am

I have been watching this thread with great interest. Here are some of my thoughts on this topic .

As to sway control I believe something that has not been discussed much is the "locking in" of the ball and coupler. The coupler does not pivot on the ball itself. Rather the ball "shank" handles he pivoting when executing turns.

However, locking the coupler to the ball and removing the pivot action does not eliminate all movement on the ball. The coupler can still wobble on the ball much like a standard WD hitch can torshionally left to right In my mind I am comparing this to a pull rite or a Hensley Arrow which locks the coupler 100% and emliminates the sway compleatly by locking the coupler rigidly in place and reducing trailer tongue movement to only what the hitch will allow.

Mounting and weight distribution

Since the A-arm mounts on the Andersen hitch carry the WD load horizontally along the A frame there is very little room for error IMHO. The chains pull the brackets and likewise the trailer towards the hitch. If these brackets slip ANY then WD will be lost potentially resulting in a chain being forced to take the entire load of the trailer while the other goes slack. The chain of events in my minds eye work like this.

1) chain A's mount slips forward resulting in a failure to carry much if any load
2) chain B takes the load from the failed chain A
3) Chain B's A arm mount breaks or slides forward under the pressure or the mourning plate under the ball mount sheers off under the pressure.
4) loss of WD happens along with the potential for loss of control

In my mind. The technology is not proven so I will not be buying it. To many negatives pointed out IMHO.

Thanks!

Jeremiah

TV-2022 Silverado 2WD
TT - Zinger 270BH
WD Hitch- HaulMaster 1,000 lb Round Bar
Dual Friction bar sway control

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Posted By: BenK on 01/25/12 10:32am

Think an elegant and out of the box architecture, but the devil is always in the details...

The coupler latch/pawl is there for the worst case when Mr Murphy crosses your path

To keep the ball from coming out. Never was it designed for this kind of loading
except for braking where the TV has more than the trailer provides

A can do for now, but longevity is the main issue for me.

How long will that latch assembly last over time? What kinds of forces will it
see in 'normal' situation and in emergency and/or shock loading situations?

Another mentioned but not discussed yet. Is the chain/plate pin. Double shear
and assume the ball shank hardened along with the tube welded to the chain/plate
That is what rotates the whole thing against the friction material.

Again, how long will it last? Is the contact PSI distributed to lower that PSI
enough to not deform or work the metal over time?

A new thought that Ron might have a better understanding and explanation: When
the trailer tries to sway and the friction material resists...there is going to
be a push on the TV's rear end. What will that do to the suspension/tires/etc
Or does the whole TV see it and dependent on the tolerances in the food chain
from the ball to shank to receiver to frame...then down to the suspension

Where would the pivot then be? The CG of the TV?

-Ben Picture of my rig
1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
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