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

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Topic: New Andersen WD hitch

Posted By: Lady Fitzgerald on 01/29/12 11:42am

BenK wrote:

...Then how does the one decouple the trailer from the TV?

The ball has to move rearward (away from the TV) and out of the coupler
glob (front section that has the coupler glob go below the ball
hemisphere.

Once away from the front of the coupler glob, there is NOTHING below
the ball hemisphere other than the latch pawl, which is moved out of
the way when the latch is lifted

That is what am trying to get folks to understand and why personally
think that force on the latch would not be good for it

You are making too much of this. When at rest, the top of the coupler will be centered on the top of the ball so there will be nothing in the way of the ball when you raise the jack.

Frankly, we can postulate until the cows come home but, because of all the variables that exist (both one we can see and ones we can't), nothing will be established until someone other than Anderson does independent tests under actual working conditions to see what actually does happen. This can be as simple as installing a couple of video cameras on the tow vehicle, one showing a top view and one showing a side view, adding witness marks to the coupler and the hitch to make detecting any movement easier, then towing the TT at different speeds to see what happens.

Jeannie

Posted By: JBarca on 01/29/12 12:46pm

Hi All,

I would like to ask you all to please be kind and not get my thread locked by the moderator.

State your opinion and it can disagree as needed, just leave the negative words out of it that will get the thread locked.

I would like to still be able to reply on any findings I can get from my ball coupler manufacture on their thoughts of towing a TT with a WD hitch that applies large amounts of pressure to the latch under forward towing.

I will also attempt to explain in more detail where we believe these higher forces are originating from with the Anderson unit and how they are larger then the TW pressing down on the ball coupler. These higher WD forces in the chains can cause the TT ball coupler to rise up and stop rising only by when all the vertical clearance inside the coupler is reached.

Anyone else is also welcome to help show this too. (Ron, hint hint [emoticon]

)

This all originates with what some feel are large forces in the WD chains created by the Urethane springs during WD. If the chain forces are high enough they will overcome the down force of the TW and the coupler will cam itself up. These forces where attempted to be explained on this page and on this page.

If folks believe there are not high forces in the WD chains, please help us understand your point and why as we may have missed something.

Thanks

John

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: BenK on 01/29/12 01:27pm

Maybe an oblique direction into a necessary rat hole...how does a
coupler work and the metrics there of

As for visualization in the mind vs seeing a video, not everyone can
decipher whatever from eyeballing it either

By visualization, I mean to be able to 'see' in ones mind what computer
simulation does. Of course not the depths that a computer can, nor
have the DB that a computer has...but...some folks DB is deeper than
a computer's DB in some areas. Nor is the programer of that simulation
all that well versed in that design 'enough'...garbage in...garbage out

Actually, in order to fully 'see' a ball inside a coupler, the coupler
either has to be transparent and/or instrumented to simulate a visualization
of it in a dynamic situation

This is where computer simulation and/or a persons ability to mentally
do a similar simulation.

Like the wiper arm analogy. Yes it is a good one and has differences
on how those moments are imparted on the end components. Main difference
is that it is an over center mechanism. Whereas the Anderson is not,
that is the elegance of their design, but, they are now placing
the forces on a component that 'I' think a weak link in their design

The Anderson design imparts the moment on the TV using the same moment
on the hitch ball/shank. Whereas a traditional WD system does not
place any WD forces on the ball nor the coupler...other than moves
some of the tongue weight back onto the tongue. Also, the force
vector is 90* from a traditional WD Hitch Spring Bars vector

Couplers were/are not designed for that and why my first sentence
Reference to getting at that weak link of the Anderson food chain

In order to get past that weak link (some don't think so), one must
understand how it works both in a static condition and in 'ALL' dynamic
conditions

The margins of that component/system must be known and understood
in reference to the specification (it's application...the bigge
question is whether they spec'd it out for the kind of loads the
Anderson Hitch system imparts on it)

Then come to a resolution whether those forces are detrimental or not

Posted By: Ron Gratz on 01/29/12 03:02pm

JBarca wrote:

I will also attempt to explain in more detail where we believe these higher forces are originating from with the Anderson unit and how they are larger then the TW pressing down on the ball coupler. These higher WD forces in the chains can cause the TT ball coupler to rise up and stop rising only by when all the vertical clearance inside the coupler is reached.

Anyone else is also welcome to help show this too. (Ron, hint hint [emoticon]

John, thanks for the invitation to join in, but, if I correctly understand what you are saying, I must respectfully disagree. In particular, I would disagree with the last sentence above.

I will re-use the image from my last post to try to explain my thoughts. The coupler illustrated below is typical of many I've looked at. Forces may be transmitted between trailer and ball in two ways.
1&3) Force between trailer and ball can be transmitted indirectly via the latching clamp ("underjaw", in the schematic below).
2) IF there is a contact surface between the inside of the coupler and the upper rear of the ball, a longitudinal force can be transmitted via this surface. I say "IF", because the shape of the ball socket on some couplers does not appear to provide any surface which can contact the upper rear curved face of the ball.

Any force transmitted to the upper rear surface of the ball will have an upward component of reaction tending to push the coupler upward relative to the ball. (I believe this is the point you are making.) Any force transmitted to the lower rear surface of the ball will have a downward component of reaction tending to push the coupler downward relative to the ball.

After looking at different coupler designs, it is my current opinion that, for the majority of couplers, the net reaction of ball against coupler will tend to push the coupler downward relative to the ball. I think it is unlikely that the chain forces in the Andersen hitch would cause the coupler to rise upward relative to the ball. And if there were a coupler configuration which did result in a net upward lift, I doubt the magnitude of the lifting force ever would exceed the downward force due to tongue weight.

OTOH, if I mis-understood your point -- then I don't have to be disagreeable. [emoticon]

Posted By: rexlion on 01/29/12 07:14pm

In my old Equal-i-zer hitch, the square bars in the L-brackets create an upward force at the ball and downward force at the socket. I agree with Ron and disagree with BenK on that point.

Mike G.
Liberty is meaningless where the right to utter one's thoughts and opinions has ceased to exist. That, of all rights, is the dread of tyrants. --Frederick Douglass
photo: Yosemite Valley view from Taft Point

Posted By: JBarca on 01/29/12 07:18pm

Ron Gratz wrote:

JBarca wrote:

John, thanks for the invitation to join in, but, if I correctly understand what you are saying, I must respectfully disagree. In particular, I would disagree with the last sentence above.

snip...

Forces may be transmitted between trailer and ball in two ways.
1&3) Force between trailer and ball can be transmitted indirectly via the latching clamp ("underjaw", in the schematic below).

2) IF there is a contact surface between the inside of the coupler and the upper rear of the ball, a longitudinal force can be transmitted via this surface. I say "IF", because the shape of the ball socket on some couplers does not appear to provide any surface which can contact the upper rear curved face of the ball.

Any force transmitted to the upper rear surface of the ball will have an upward component of reaction tending to push the coupler upward relative to the ball. (I believe this is the point you are making.) Any force transmitted to the lower rear surface of the ball will have a downward component of reaction tending to push the coupler downward relative to the ball.

After looking at different coupler designs, it is my current opinion that, for the majority of couplers, the net reaction of ball against coupler will tend to push the coupler downward relative to the ball. I think it is unlikely that the chain forces in the Andersen hitch would cause the coupler to rise upward relative to the ball. And if there were a coupler configuration which did result in a net upward lift, I doubt the magnitude of the lifting force ever would exceed the downward force due to tongue weight.

OTOH, if I mis-understood your point -- then I don't have to be disagreeable. [emoticon]

Hi Ron,

I believe we are lost in the words "or" I missed something. Reading your sentence in blue above I agree with. LOL...

You are stating reaction from the ball and I was talking force on the A frame towards the ball. We may be saying the same thing. Or I missed something....

Let me show and explain and you tell me where I go wrong or we have agreement.

EDIT 1-30-12 A point to clarify, we need to declare if the tongue jack is up or down supporting the TW when tightening the urethane springs. Odds are higher that the jack is down supporting the tongue.

If the tongue jack is down, odds are higher the ball will drop down when it locks into the lower rear part of the coupler.

If the tongue jack is up, then it depends on the stiffness of the rear springs of the truck in relation to the TW if the tongue will rise or the ball will drop.

My analogy of the coupler rising was based "no" jack being down and heavy truck suspension in relation to TT TW. That may not be a real condition in most cases as even I have the jack down... but it was how my brain was thinking about it at the time. And may be where the mix up of which part is moving up or down...LOL [emoticon]

This is why diagrams are better then words most time... Put the tongue jack in the equation [emoticon]

I had the luxury the other night to go out to the camper and on my Shelby Class 4 coupler and fiddle with it using a Putnam 24,000# 2 5/16" goose neck tow ball. Here is what I found.

With the coupler latch closed, (locked) I have 1/8" front to back clearance and 1/8" up and down clearance between the tow ball and the coupler. That actually surprised me it was that much, I was thinking more like 1/16". If my hands where not freezing so bad I would of measured it in 3 place decimal...

I also noted on "my" coupler there is a good match angle on the back top side of the tow ball in relation to the top rear part of the ball sphere inside the coupler. The match angle can make a nice cam ramp. The flat line is the region I am talking about. Ignore the arrows for right now.

See this pic
[image]

I concluded;

When the raw TW (no WD) is pressing down on top of the ball all 1/8" clearance is on the bottom of the tow ball. When this is occurring I have about 3/16" of metal contact in this back region. And the tow ball is up agasint the "front" of the ball coupler and I have about 1/8" clearance on the back side of the tow ball and the latch.

When the 1/8" clearance changes from the bottom of tow ball to top area of tow ball, with the ball top flat I end up with only about 1/16" of metal contact in that same back region. This also creates the tow ball to be fully seated into the latch. And I now have the 1/8" clearance horizontally in the front between the ball and the coupler. Again clearance in 2 directions.

With that amount of clearance and the cam angle being as steep as it is, I came to the conclusion (maybe right or not) that when the TT is pulled forward by the tightening the urethane springs, the WD chain force being so high for my truck, that the "coupler will ride up" the cam angle and stop only when I run out of the 1/8" clearance.

The coupler latch is now firmly seated into the back side of the tow ball and the TT tongue has lift "up" 1/8". This now creates 1/8" clearance on the front dome of the tow ball and some clearance on the top front of the tow ball up by the flat.

Edit: 1-30-12. On my heavy suspension truck the belief is the tongue will raise in relation to the ball first. On lighter TV's, the ball may drop as the rear of the truck sagged first. The end result is the same, the ball moved into the lower rear part of the latch and stopped when all bottom clearance is gone. The coupler clearance is now on top.

This may be part of the miss-understanding issue on which part is moving first. In theory if there was a rigid post to the ground that could not compress under the hitch shank, then the TT tongue would have to raise up as the ball cannot drop if the WD chain force of the Anderson is high enough in relation to the TW. Different truck suspensions will react different yet the end result of the clearance around the ball is the same if the WD chain force is a lot higher then the TW.

This is how I see the tow ball being seated into the back side of the ball and the TT tongue lifted "up". See image below.

Sorry my hand was a little jiggly tracing this. The hands are not as steady as they use to be....LOL The years on the broad are now long ago...
[image]

If we are in agreement here, (Yes/No?) then this comes down to the WD chain force.

The question is: Is the WD chain force high enough to lift the tongue 1/8" up, to allow it to fully seat into the back side of the tow ball? The way I saw it, to be fully seated in the latch the tongue has to move up the 1/8".

The invite hint, hint was to help confirm that on my TT and TV to use as an example, that the force needed to be generated in the Anderson WD chains total would be approx. 7,800# to create what I declare is proper WD on this truck.

I have a 1,400# loaded TW, I run the WD so the front of the truck is approx 100 to 150# light on purpose. Partly due to 2 stage rear suspension that this truck is more stable when the helper springs just kiss the truck bracket and for the new SAE recommendation to help ward off oversteer.

I did not do the moments yet to confirm the reactions however if I was in the right league of 7,800# force pulling on an estimated 8" Anderson tow ball creating the 5,225 ft. lb of torque needed into the receiver for proper WD on the TV, then the 1,400# raw TW was not enough to hold down the TT tongue from not lifting "up" that 1/8".

Did I mess up seeing this?

Thanks John

PS the invite is still there on the WD chain force....LOL

* This post was last edited 01/30/12 08:07am by JBarca *

Posted By: JBarca on 01/30/12 07:55am

Ron,

I added a clarifying statement in blue above. Since the truck is being supported by springs (suspension) each TV may react different pending the rigidness of the rear suspension compared to the TT TW.

And a point to clarify, there was "no" TT tongue jack to the ground when I was describing this. Both of us never stated if the jack was up or down when we where tensioning the urethane springs. If the jack was down, odds are higher the ball will drop down first as the truck will compress easier in most cases. If the jack was up then it depends on the stiffness of the suspension on if the tongue will rise or the ball will drop.

The net end result would be the same the ball is seated in the lower rear part of the latch with no clearance left under the bottom rear part of the tow ball.

A better way to state this is the ball moved "towards" the lower latch sphere and stopped when no clearance was left. Which part is moving up or down "when" depends on a few other variables being in the equation.

Thanks

John

* This post was edited 01/30/12 08:17am by JBarca *

Posted By: BenK on 01/30/12 11:57am

John,

Think you should review your sketch of the 'under jaw' (green)

As I believe it does NOT go above the ball's equator, as it has to drop down in
order to release the ball from the coupler. The second image shows
it just tangent to the equator...could one take their naming of an
'under jaw' as saying it does NOT go above the equator?
[image]

If so, it will then have a greater down force and that is held in check by the
latch bolt. What size is that bolt and what grade? What is the static
force and what are the dynamic forces. Lucky that this design does
NOT have the ball rotate very much inside the coupler. Otherwise the
pawl would need to have side contact and at a much tighter tolerance
than they are now
[image]

I also think this image below is incorrect. The ball does NOT engage
the coupler or anything at the rearward end of it's travel inside the
coupler. The only engagement is when the latch has moved the pawl
(#3 in the above image) upwards...but the above, second, image shows
that the top rear portion of the ball does contact the coupler
glob...we need to get a hold of some to scale diagrams... [emoticon]

My reasoning is that if it did contact at the rear portion of the ball,
then how does one ever get the ball out of the coupler? Even if the
latch is released...does the pawl completelt get out of the way to allow
the ball to drop straight down...but then the front of the coupler
glob has a formed area that goes BELOW the equator of the ball....therefore
the ball has to move backwards in order to clear that...but...then if
the ball is in contact with the rear portion of the top glob...how
does it move backwards to clear the front section???

This other image shows that the rear, top portion of the coupler glob
does NOT engage the ball. Which is correct? Plus, this goes back to
the discussion on what the heck that flat is for? {edit}...My original supposition
was that the flat spot is to allow the ball to move backwards to get
out of the coupler globe

[image]

Back on the to scale diagrams...must also have exploded diagrams that
are also to scale, as a 2D diagram will have interfaces/interferences
missed or out of context

Anyone have an old coupler they are willing and capable of slicing in
half to show us a decent cross section? or can someone find a diagram
that they can post for us?

Then the question of whether 'that' one is representative of 'all'
couplers and latch systems?

* This post was edited 01/30/12 12:31pm by BenK *

Posted By: BenK on 01/30/12 12:40pm

PS...must reiterate that I think the Andersen design is elegant, but as with
all things...it is only as good/strong as the weakest link

"The devil is in the details of any design"

In this case, IMHO, it is the latch assembly...which was never designed for this
kind of service. It's duties mainly reside in keeping the ball inside the globe
with 'some' dynamic forces from the trailer pushing/banging into it or while
going backwards

In going backwards for the original design criteria...how fast do you
suppose the specifications were for in MPH? How many service miles?
Service miles as being warranty and that then goes to the MTBF in that
condition(s)

100 miles at the full forces? 1,000 miles? Surely not tens of thousands, right?

Of course to hold during an accident and Ron provided those numbers
and links they are held to by the regulatory agency(s)

Posted By: BenK on 01/30/12 12:52pm

rexlion wrote:

In my old Equal-i-zer hitch, the square bars in the L-brackets create an upward force at the ball and downward force at the socket. I agree with Ron and disagree with BenK on that point.

Never disagreed on how a traditional WD Hitch system works

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