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

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Topic: New Andersen WD hitch

Posted By: BenK on 01/22/12 11:46am

shakyjay wrote:

snip....

I for one am going to be very interested to watch and see how it performs over time in real world applicatiions. That is the only real test that matters. Hopefully they can get enough out there to accomplish this. Personally I can't afford to go out buy something like this just to see how it works. Now if they need a tester and are looking for someone to give one to and report back I could do that. [emoticon]

When designing stuff for small firms, yes this boils down to something
like the after the best minds of the company & consultants finished
reviewing and our limited in-house testing.

But for larger firms. There are things like computer simulations AFTER
the above reviews. Then there are test in-house and outside firms who
specialize in that kind of testing. Also blind testing with a control
set.

Heck, with the power of computer simulation and their extremely reasonable
costing...most any small firm can have some level of computer
simulation. Most CAD programs has some level of finite analysis capcity

CDR's (critical design review) should be numerous and act as gates to
release to production. Many times or that they should include their customer(s)

Today's bean counter managed firms short change the above and use
the public as test mules.

Even then, there are potential scenario's that are rare and not found
during simulations/testing but out here in the public realm. This is
where 'ratings' comes into play. Both to address these potentials
and to meet regulatory agency requirements

This design is elegant, but there are potential issues that we have
brought up...so far. Maturation of the design is whats going on here
and should have been with them...inside the OEM...or...this is an
indication of the depth of their talent/knowledge/etc

PS...I don't know much about 5th wheel hitches, but in viewing their
video...like that they think outside the box for their new version
of Fiver hitches.

-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)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...

Posted By: Ron Gratz on 01/22/12 02:06pm

Hi John,

I can respond to some of your points -- but not necessarily in the order in which you made them.

JBarca wrote:

Chains towing the camper When the TV is stopped or rolling forward at low speed, the chains are pulling the camper. The chain force is high enough that is it pulling the camper forward and seating the tow ball into the latch side of the ball coupler. Clearance exists between the ball sphere and the front part of the coupler that normally pulls the camper. The rolling resistance of the camper on the 28.3" OD tires on concrete or black top is less then the chain force under these conditions.

Let's assume each of the two chains is pre-tensioned to 2000# and each chain is parallel to the longitudinal axis of the TT. The chains would be pulling rearward against the spreader plate with a combined force of 4000#. With the TT at rest, the tension in the chains would cause the ball coupler to push forward against the ball with a force of 4000#.

When being towed on level ground at 70 mph, the combined aerodynamic drag and rolling resistance acting on a TT probably would be less than 1000#, but let's assume it is 1000# for arithmetic simplicity. This means, as your title suggests, the chains would be towing the TT.

The combined chain tension of 4000# now is divided into 1000# pulling forward on the TT and 3000# pushing forward on the ball. IMO, it is highly unlikely that there would be any "banging" of ball against coupler. It looks to me as though the ball always will be pre-loaded in the forward direction.

Quote:

Tow ball towing the camper There may be a point where the wind drag on the front of the camper or up hill (gravity) loads increase enough that the TT drag is higher then the WD tension in the chains. In this case the TT would shift backwards by the clearance in the coupler when the wind drag force overcomes the WD chain force. The tow ball leaves the coupler latch and now becomes seated into the front part of the ball coupler. The TT is now pulled by the ball coupler.

Now, let's assume you actually could tow a 10,000# TT up a 6% grade at 70 mph. This would result in an additional towing force requirement of 600#. The previously calculated forward force on the ball would be reduced from 3000# to 2400# -- still sufficient, IMO, to preclude any "banging" of ball against coupler.

Quote:

What we do not know yet, is on a 1,400# TT tongue weight, 9,200# GVW TT does the wind drag or up hill drag ever get high enough to let the ball coupler tow the camper? And any guesstimate on what speed that may be? I picked those weights only because they line up with my camper. The issue can occur under other TV and TT combos as well.

IMO, if each chain is pre-tensioned to 2000#, it is highly unlikely that the combination of wind drag, uphill drag, and rolling resistance will ever result in the ball pulling forward against the coupler.

Quote:

The high load on the coupler saftey latch is a large concern. If the TT seats and reseats back and forth constantly as you tow down the road, the fatigue on the coupler saftey latch is something to think through.

IMO, the TT will not seat and reseat back and forth. However, I do think that coupler manufacturers should be asked to comment on any possible consequences of operating with the coupler constantly pushing forward against the ball.

Quote:

We understand how it has the ability to distribute weight. How effective it is and sensitive it is is another question.

IMO, your previous post gave a excellent analysis of how much WD torque might be generated by the Andersen hitch. The new hitch is rated for 1400# tongue weight. I doubt that a combined chain tension of 4000# would provide sufficient WD torque for a 1400# TW. It would be good if Andersen could provide some before and after axle load data.

Ron

Posted By: JBarca on 01/22/12 08:34pm

Ron,

Thanks, your thoughts confirmed mine. Just I did not have the drag estimates at speed. I did the force to get the 9,200# TT rolling and it was so low that I thought I made a mistake.

The TT drag does not seem to be enough to allow the tow ball to come off of the safety latch. So as I suspected they are towing with the chains potentially all the time.

I'll have to investigate the ball coupler saftey latch further. I have never even seen a rating on the latch when used in this manor. The rating is normally always by the ball pulling the camper by the coupler nose and the amount of tongue weight.

I still do not like the fact that one could be potentially towing the camper with the urethane spring frame brackets where the chain attaches. And as the WD chain force goes up as we suspect it will, this issue of the pulling on the brackets gets worse.

Maybe Anderson will publish some more WD data to help alleviate these concerns.

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: Gallifrey on 01/23/12 07:14am

This hitch looks very attractive to me, even if it's just to speed up hooking up the hitch and avoid grease everywhere. But, as already pointed out, it does seem odd to be constantly pulling a trailer by the brackets holding the chains.

Anyway, if someone were to try this hitch out and it did damage the safety coupler, any ideas on how much it would cost to repair or replace the coupler?

Posted By: BenK on 01/23/12 10:57am

Think there is another metric and that is during acceleration.

Would that then pull the ball away from the coupler back side to transfer the
loading to the coupler front side?

How much is the force during acceleration and will that over come the tension
of the plastic springs ?

Would there also be enough force to repeat this during the drive? Guess dependent
on the frontal area of the trailer and other drag vs the TV pulling to a higher speed

With my setup and the controller leading the trailer braking, that would also
have the trailer pull the coupler off the back side.

Also assume the contact area of the plate steel hole and the ball tail end would
not work itself. That the contact area is sufficient to distribute that constant
load change from working the metal contact area.

Posted By: Ron Gratz on 01/23/12 01:08pm

BenK wrote:

I believe the new SAE J2807 Recommeded Practice for towing performance requires a SRW TV, operating at its GCWR, should be able to accelerate from 0 to 30 mph in 12 seconds. The corresponding acceleration, assuming it is constant, would be 3.7 ft/sec/sec or approximately 0.11 G. The force required to accelerate an 8000# TT at 0.1 G would be 880#.

Even if a TV could achieve twice this rate of acceleration, is seems unlikely that the combined acceleration force, aerodynamic drag, and rolling resistance would ever be great enough to exceed the forward thrust of the coupler against the ball.

Quote:

Would there also be enough force to repeat this during the drive? Guess dependent on the frontal area of the trailer and other drag vs the TV pulling to a higher speed

I believe SAE 2807 also specifies a TV should be able to accelerate its GCWR from 40-60 mph in 18 sec. The corresponding acceleration would be about 0.03 G. Again, not at all likely that the coupler would be pulling rearward against the ball.

Quote:

With my setup and the controller leading the trailer braking, that would also have the trailer pull the coupler off the back side.

Not sure what controller you have. Let's assume the leading "boost" is set to 20% of maximum TT braking force. That probably means the boost-related braking force would be about 10% of the TT's weight.

If we assume the TV weighs 7000# and the TT weighs 8000#, the boost braking would decelerate the combination at about 800/15000 = 0.05 G. In addition to decelerating itself, the TT would be pulling rearward against the TV with a force of about 350#. Again -- not nearly enough to overcome the forward thrust of coupler against ball.

Quote:

Also assume the contact area of the plate steel hole and the ball tail end would not work itself. That the contact area is sufficient to distribute that constant load change from working the metal contact area.

I don't know what you mean by this, so I cannot comment.

Ron

Posted By: BenK on 01/23/12 01:41pm

Thanks for the analysis and my last comment...what if the ball does bang back
and forth inside the coupler...then does the chain plate at the bottom of the ball
shank then get bangs around?

Does it then deform the hole and/or the shank?

Since your analysis says the likelyhood of the ball banging around the coupler
is slight in relation to the acceleration numbers...this is a moot point

Have a P3 and my brake pedal light switch makes about 1/64"-1/32" before the
MC rod is moved. Set my P3 to skid the trailer tires at approx 25 MPH on dry
pavement.

Your comments settles or at least alleviates my concerns on the possible movement
of the ball within the coupler, but am still not comfortable with the WD forces
on the coupler latch/pawl.

Posted By: SoCalDesertRider on 01/23/12 04:31pm

Gallifrey wrote:

Anyway, if someone were to try this hitch out and it did damage the safety coupler, any ideas on how much it would cost to repair or replace the coupler?

Most likely, it wouldn't damage the coupler body itself, but may very well destroy the latch. A latch kit for a common, rebuildable coupler isn't much money and is easy to replace. Not all couplers are rebuildable. To replace the whole coupler, I charge $150-200 for labor, plus the coupler, $30-60, to come out to wherever the trailer is and do the job. Mobile welding rates vary by geographic area. Shop welding rates also vary in comparison to mobile rates.

01 International 4800 4x4 CrewCab DT466E Allison MD3060
69Bronco 86Samurai 85ATC250R 89CR500
98Ranger 96Tacoma
20' BigTex flatbed
8' truck camper, 14' Aristocrat TT
73 Kona 17' ski boat & Mercury 1150TB
92F350 CrewCab 4x4 351/C6 285 BFG AT 4.56 & LockRite rear

Posted By: JBarca on 01/23/12 07:51pm

red31 wrote:

Would this system be less stressful on the trailer's a-frame members?

Hi Red,

A quick answer to your question is, it depends.

The hitch is advertized as one size fits all and does not list a bottom end but does a top end of 1,400# TW and 14,000# tow rating. If every trailer and TT A frame was built like the 1,400# TW, 14,000 GVW rated frame is, then this would be easier to answer.

Let's look at a few things and the differences of a traditional WD hitch and the new Anderson as they pertain to TT's.

For explanation purposes the conventional WD hitch has chains or L brackets to hold the ends of the WD bars. I'll use the chain example however both have the same effect on the WD bar for what I am going to state.

On a conventional WD hitch when TV and TT are towing down a level road straight ahead each chain is under equal loading. And so is the Anderson.
During a turn with a conventional WD hitch on level flat road the chain load is again close to equal in the big picture of things. There are some smaller changes but not drastic. On the Anderson in a turn the chains change force from the left to right side some. The inside chain become a little looser and the outside turn chain becomes a little tighter. As the turn continues the hitch shank slips in the shank socket both chains came back to be closer to equal. The chain forces change but not what I would consider major. As long as you always went camping on perfectly level ground there would be a lot less A frame issues on a conventional WD hitch.
Now lets enter the real world of camping. The TV going in and out of turns all the time where an angle exists between the TV ground and the TT ground. Here large changes will come in the conventional WD hitch. If the TV is tilted enough the WD head tilts with the truck and the inside turn WD bar and completely unload. The outside WD bar now is taking all the load so that out side bar can approach being twice as loaded in the chains. This action creates an unbalanced load in the A frame. That unbalanced load in some cases has broken the A Frame on TT frames that have had issues if the tongue weight and WD bars where large enough. The Anderson chains do not change as drastic in loading even on uneven ground. So in this perspective the Anderson is better IMO.

Here are some pics to show what I was referring too. Here is the turn.
[image]

The inside WD bar I could rattle around with my foot. In my case I had a 5" C Channel A frame. 5" C Channel is strong enough to resist the twisting that can come from a WD hitch for the 1,200# TW that camper had.

Now what WD forces can do if the A frame is not strong enough for these unbalanced loads?

One mode of failure is the A frame side rails twist. The header and battery shelf needs to resit that twist. If they cannot then the header can buckle and the battery shelf. Here is the start of the problem
[image]

Left gone unchecked the header buckles more and more and eventually separates from the A frame members.

Below you can see here how the chains pull on the top of the A frame creating the force that makes the twist. The key to not having this become a problem is to have the A frame rails stiff enough or reinforced to resist the twist or the header made to handle the twist. In my case my camper in this pic was made strong enough to resist the twist.
[image]

The Anderson does not have the same loading on the top of the A frame or large unbalanced chain loads so that mode of failure would not be the same as a conventional WD hitch on a light A frame.

The Anderson does have other concerns the conventional WD hitch does not.

The chain loads on the Anderson are a lot higher then the conventional WD hitch. We are still sorting out if it is 2, 3 or 4 times higher. While they pull forward they are at an angle to the A frame pulling inward. So you are pulling on the bottom of the A frame at an angle and with a higher chain load. If you have a light A frame the higher WD chain force and the angle of pulling is a new thing to work through if it is a problem or not.
The next area of concern is the urethane spring bracket. They provide a clamp feature that uses 5/8" bolts to squeeze the side of the A frame for grip. And they want those bolts torqued to 150 ft. lb. On a big A frame that is beefy, that is not a problem. In thin wall box tubing of light weight TT's it may deform the tube and then you are towing the camper by pulling on that deformed tube. See here for the clamp.

Since all A Frames are not created equal, making a generic marketing statement that one size fits all is a stretch. If you have a thin wall tube A frame, check with your TT manufacture if the A frame can handle this hitch.

Hope this helps

John

Posted By: BenK on 01/23/12 08:30pm

Most of the trailer frame deformation can be solved by a cross member and should/could
be part of the WD Hitch kit.

That would add cost, but a better solution to all. From busted self tappers to
deformation to sliding along.

Issue would be that the A frame angles may or most likely not be 'standard'. So
even more expense for the HD Hitch OEM to provide cross member kits
Then to solve that issue, a variable gusset at both ends of that cross
member...more cost but net less cost for this

But that is the best solution to all of this, IMO

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