New Andersen WD hitch

Now I am wondering if the hitch ball for the Anderson WD hitch says 14,000. Lol

Ron...gotta learn how you find these links !!!

No time right now to read and digest it all, but scanning see that the design
margin is mandated (most will use it as their max, but it should
be their min), a good thing

Am still undecided and uncomfortable with the latch being the contact point for
the whole shebang...for now.

Based on my gut and that most all of the couplers I've ever seen/touched/etc all
had the latch worn more than the rest of the coupler. Of course the latch is the
only moving part... :B Even had to rebuild several because they were rusted
and banged up to the point of either stuck or none working

Finally, those specifications are for a different application where the latch
is NOT the contact point that carries the brunt of the trailer's
weight and forces 100% of the time. The coupler latch that these
specifications only get banged occasionally and during that worst
time, when Mr Murphy crosses your path, during an accident or
avoidance maneuver...

PS...this is personally the way I review any design and what teach all
of the designers under my management. CDR, critical design review, where
all invited are to comment. Toss rocks at whatever looks/feels/etc like
a weak point or issue. Resolve to whatever metrics on the table and
continue till the rocks bounce off or are acceptable 'enough' to the
specification(s)

I had a bit of a revelation last night on my way home from work... For those having a hard time envisioning how the system redistributes the forces, look at a standard spring-loaded wiper arm. The spring on the wiper arm applies force on the trailer the same way the chains/bushings on the Andersen system apply force to the trailer tongue.

Just thought I'd share it in case anyone had problems understanding what's pulling who where. :)

-Joe

A couple of thoughts on the latch issue.

1. Has anyone factored in the weight of the tongue pressing down on the ball, countering the force trying to pull the latch into the ball?

2. Since the ball does not rotate in the coupler (or very minimally at worst, not enough to create a wear issue), wear on the latch won't be an issue. Assuming pressure from the tongue weight does not pull the ball away from the latch (I'm thinking it will), the only time the full pressure from the hitch will be against the latch would be when it is static. As the trailer moves forward, any pressure on the latch (assuming there is any) should be reduced or removed from the latch.

3. (OK, I lied about only a couple of thoughts.) In any kind of hitch, the latch would have to take the entire force from the tow vehicle when backing unless the tongue weight is countering some or all of that force by forcing the dome of the coupler onto the upper curvature of the ball (as, again, I feel it does). Since hitches don't normally break when backing, I feel the concerns for the hitch latch when using the Anderson WDH are exaggerated.

I don't have a trailer handy to do this right now but has anyone tried to back a trailer without the latch being engaged? That would give an idea of how much effect tongue weight would have on countering the sideways force being exerted.

gijoecam wrote:
I had a bit of a revelation last night on my way home from work... For those having a hard time envisioning how the system redistributes the forces, look at a standard spring-loaded wiper arm. The spring on the wiper arm applies force on the trailer the same way the chains/bushings on the Andersen system apply force to the trailer tongue.

Just thought I'd share it in case anyone had problems understanding what's pulling who where. :)

-Joe

Hi Joe,

OK I am not following your wording. The traditional WD hitch applies forces in different directions on the TT A Frame then the Andseron does.

However you used the words "standard spring-loaded wiper arm".

What are you referring to as a standard spring loaded wiper arm?

Do you mean a windshield wiper arm acting on a windshield of your auto? If so need a little help with the analogy.

Thanks

John

comments embedded below in blue

Lady Fitzgerald wrote:
A couple of thoughts on the latch issue.

1. Has anyone factored in the weight of the tongue pressing down on the ball, countering the force trying to pull the latch into the ball?

the weight of the tongue only pushes 'down' on the ball and into
the tapered friction material

2. Since the ball does not rotate in the coupler (or very minimally at worst, not enough to create a wear issue), wear on the latch won't be an issue. Assuming pressure from the tongue weight does not pull the ball away from the latch (I'm thinking it will), the only time the full pressure from the hitch will be against the latch would be when it is static. As the trailer moves forward, any pressure on the latch (assuming there is any) should be reduced or removed from the latch.

go back to the first or second page to see the rudimentary
force vector sketch made up.

I'll repost it below

3. (OK, I lied about only a couple of thoughts.) In any kind of hitch, the latch would have to take the entire force from the tow vehicle when backing unless the tongue weight is countering some or all of that force by forcing the dome of the coupler onto the upper curvature of the ball (as, again, I feel it does). Since hitches don't normally break when backing, I feel the concerns for the hitch latch when using the Anderson WDH are exaggerated.

How many miles does most hitch latches see during it's life time
vs the tens to thousands of miles going forward?

Then consider how much wear most latches display with maybe ~20 miles
of backing up in their whole life time

Also consider the whopdeedo's (up and down cresting a bump/hill and
bottoming in a gully, etc. That will have the ball go 'up' and 'down'
against the latch. Plus there will be a bit of left and right turning
of the ball and is in how much tolerance there is in the pin holding
the plate to the bottom of the ball shank

I don't have a trailer handy to do this right now but has anyone tried to back a trailer without the latch being engaged? That would give an idea of how much effect tongue weight would have on countering the sideways force being exerted.

This is how many unhook...unlatch and back up to move the
ball out of the coupler glob's front area, where the ball is captured
securely

This is John's picture of a coupler latch that has seen many miles
and assume just backing up of, say 5 miles or so. That latch pawl
looks worn from just a few miles and think how it would look with
tens to thousands of miles

Just went ahead and modified John's coupler latch pawl image to show where this
hitch's forces will be



Here is the cross section of some coupler latches to show where that
pawl is in reference to the rest of the coupler

HI Lady Fitzgerald

I'll try and comment on some of your questions.

Lady Fitzgerald wrote:

1. Has anyone factored in the weight of the tongue pressing down on the ball, countering the force trying to pull the latch into the ball?

Yes we have however we may have not explained it well enough. We do not yet have a confirmed set of forces in the chains on the Anderson unit for a known TW on a known TV wheel base and the TT ball to axles distance. Anderson had mentioned on the Forest River forum they where going to post weights this week. As of this note they have not yet. Here on page 2 I posted possible chain tensions for my camper with a 1,000# TW and my actual 1,400# TW.

They where estimated as 5,700# for the 1,000# TW and 7,800# for the 1,400# TW on what I considered acceptable WD on the TV. Anderson stated in their video at the SEMA show that they like to compress the springs 1/4" which gives about 2,000# of force on each chain. They never stated what TW that lines up with, what TT ball to axle distance or what TV wheel base or ball overhang. Or what they declare proper WD as.

All we know is they are creating 4,000# of force in both chains pulling the TT forward into the back side of the ball coupler. Even using their numbers for what ever TT & TV they line up with the chain force will over come any average TT tongue weight pushing down. With the Anderson WD hitch the only down force into the tow ball is the raw TW.

How do you see that the TT tongue weight will overpower the WD chain force?

Since the ball does not rotate in the coupler (or very minimally at worst, not enough to create a wear issue), wear on the latch won't be an issue. Assuming pressure from the tongue weight does not pull the ball away from the latch (I'm thinking it will), the only time the full pressure from the hitch will be against the latch would be when it is static. As the trailer moves forward, any pressure on the latch (assuming there is any) should be reduced or removed from the latch.

You are correct that rotational grinding wear on the latch will be low to none.

As to the latch being under pressure, this again comes back to the high forces in the Anderson WD chains. The chain force is high enough that the TV pulling the camper will not overcome the WD chain force. Ron G. showed this here

The tow ball will stay lodged into the ball coupler saftey latch under the conditions we could think of.

Did you see some other way that the TV or TT could over come the forces in the WD chains?

3. (OK, I lied about only a couple of thoughts.) In any kind of hitch, the latch would have to take the entire force from the tow vehicle when backing unless the tongue weight is countering some or all of that force by forcing the dome of the coupler onto the upper curvature of the ball (as, again, I feel it does). Since hitches don't normally break when backing, I feel the concerns for the hitch latch when using the Anderson WDH are exaggerated.

If you are backing up with a conventional WD hitch installed and WD engaged, the forces down on the coupler are much higher then the TW itself. The WD adds more force pushing down on the tow ball. Since a TT on large OD tires on hard surface road does not take much to push forward or backwards it may be possible for the slight top of the tow ball to still stay engaged in the coupler dome. The latch may never be touched or seldom touched.

If you where backing up a trailer with no WD hitch engaged it would be easier to slip the ball back into the latch. Again the trailer rolls so the force is not a lot to push the trailer.

It is not a stretch on a light weight trailer with no WD to jerk the truck back and the coupler latch takes a hit.

In the case of the Anderson the WD chain force is so high that if the trailer is still able to roll I do not see it ever taking pressure off the latch going forward or reverse.

Ron G has found where when a coupler is rated in accordance with VESC V-5 and SAE J684 that SAE J 684 states the latch area can handle the same forces on a lab bench in forward or reverse and not seperate from the ball.

Up until the new Anderson hitch, most WD hitches allow the trailer to be pulled by the ball coupler front portion. The Anderson has changed that concept. The trailer is now be towed by WD chains with high forces against the coupler latch. While we have decades of trailers be pulled by the front portion of a ball coupler, we do not have so many being towed with high constant pressure up against the latch mechanism. That is part of what all this conversion is about.

If we understand the SAE J684 correct, on a bench test the latch can take the force and not separate from the ball. We do not know if there is latch damage preventing the latch from working properly and freely like we know it does when pulling a camper forward by the ball.

I'll reserve making a complete assessment of the hitch until I can connect with Shelby Industries on if they agree that towing my camper with these high loads pushing on the latch all the time is something they have field tested and are OK with doing so.

I don't have a trailer handy to do this right now but has anyone tried to back a trailer without the latch being engaged? That would give an idea of how much effect tongue weight would have on countering the sideways force being exerted.

I am usually up for a hitch experiment however backing up my TT with the latch not seated is one I will pass on. If I jam the latch and bend it, (my luck it would do that) I have to cut the coupler off as I cannot change latch parts on my brand coupler. However I have experimented with a tow ball being held up inside the coupler and pushed forward and back on it to give me an idea what is going on when the Anderson pulls on the bottom of the ball shank.

It does not take much force to slide the tow ball into the coupler latch when the tow ball is pushed by hand or when the Anderson WD chains are pulling on the ball.

See this pic mocking it up


The red line on the top left shows the angle of contact. With the coupler latched the Anderson WD chains pull the TT coupler latch into the back side of the ball as the TT rolls forward. The angle helps cam it in there. The coupler will slide up and lift until all clearance is gone in the vertical direction. On my coupler that clearance is 1/8". When the WD chain force exceeds the TW the coupler will lift up. That is the key understanding. The chain forces are a lot higher then the TW force pushing down.

There is then almost no engagement left on the top of the tow ball sphere with the coupler dome. The ball will just stay wedged in the bottom rear side of the latch until the WD chain forces get low enough for the tongue to drop back down. If the WD forces in the chains ever approached closer to the TW or the TV pull forces ever overcome the WD chains then the ball coupler front portion will start towing the camper again.

Hope this helps

John

Everytime your trailer bucks over bumps that pawl gets loaded. Also when decelerating without trailer brakes applied it takes a load.
I think ALL designs have some problem. I really never have understood the whole weight distribution thing. If you have to much tongue weight for your truck, its time to get the right truck.
A little is okay but transfering 1000's of pounds is a mistake from the get go in my opinion.

JBarca wrote:

gijoecam wrote:
I had a bit of a revelation last night on my way home from work... For those having a hard time envisioning how the system redistributes the forces, look at a standard spring-loaded wiper arm. The spring on the wiper arm applies force on the trailer the same way the chains/bushings on the Andersen system apply force to the trailer tongue.

Just thought I'd share it in case anyone had problems understanding what's pulling who where. :)

-Joe

Hi Joe,

OK I am not following your wording. The traditional WD hitch applies forces in different directions on the TT A Frame then the Andseron does.

However you used the words "standard spring-loaded wiper arm".

What are you referring to as a standard spring loaded wiper arm?

Do you mean a windshield wiper arm acting on a windshield of your auto? If so need a little help with the analogy.

John, I hope Joe doesn't mind if I try to answer on his behalf.

The schematic diagram in this patent document represents what I would consider to be a standard spring-loaded wiper arm.

Now, think in terms of Part 2 being the ball mount, Part 3 being the ball (pivot point), Part 1 being one side of the A-frame and chassis rail, and Part 4 being the WD tensioning spring as used in the Anderson hitch. Spring tension produces a torque about the pivot point. This torque causes the wiper blade to be pressed against the windshield.

The blade's force against the windshield is the analog for the added force of a trailer's tires against the pavement. Per Newton's third law, the pavement, in turn, pushes up against the tires. It is this added upward force against the TT's tires which causes load to be removed from the TV's rear axle, with some of it being transferred to the front axle.

I think the spring-loaded wiper arm provides an excellent analogy for how the Anderson hitch can function as a weight distribution hitch.

Ron