Dual Cam Setup

Just an update. The trailer is still at the welding shop. They haven't had a chance to go over it carefully to generate a quote for fixing it.


The dealer says there's a chance it will be covered under warranty. I'm not optimistic and if the repair cost from the welding shop is lower than what I'm expecting I may just have it fixed before I get to the dealer.


Reese is sending some new parts. I asked if I could get the bent brackets from the cam to the chain. They no longer make them. The bent brackets were supposed to move the up force away from the side of the cam to prevent twisting, but too many people were installing them backwards. I think they could have fixed that problem with a 1 cent sticker vs sticking with the straight bracket.


1) Is there some way to calculate the forces applied to the frame. For example, when in a turn all the WD "lift" is applied to one snap up. How much is that weight and how might it be distributed to the 4 places it touches the A-Frame.


I'm wondering if the currently shipping Dual Cam is even appropriate for heavier GVWR trailers with thin tube frames. Every time I think about the best way to fix it, I end up with a non-trivial change to the frame or the WD/Sway system. Then I wonder, how did American engineering and manufacturing get to a point where the end user must redesign a product, bought to enhance safety, in order to make it safe at all?

BarneyS wrote:
Good discussion guys! Now you know why I prefer the old style Dual Cam that mounted with the large U bolts. Used one for many years before I went with the Hensley. Never had a single problem. :) Too bad they discontinued it.

Enjoy your campout John!
Barney

Hi Barney,

Yes, the older DC had the saddle clevis and that was a better concept. I have seen it show up again for sale. I can't image these sellers has that much old stock still left. I have not heard anything official from Reese that it is back in production though. See here:

http://www.pplmotorhomes.com/parts/rv-hitches/dual-cam-sway-control.htm

http://www.ebay.com/sch/sis.html?_nkw=Reese+Dual+Cam+Sway+Control

http://www.rvplus.com/reese-products-dual-cam-sw.cont.w-8u-bolts-zz-26001.html

What mrekim has run into I have not see this bad, this fast...with a setup that was optimized. The learning never stops...

The campout was good. Hope next time the others can make it too:) Hint hint..

Thanks

John

JBarca wrote:
From what I can see from here, I do not see an issue with your approach. I'm assuming something will be done on the inside as well.

Yes inside and outside.

JBarca wrote:

The curved ends on your template, do not know if this was intentional or not. If you meant it to be that way, I do not see it hurting anything however do not know if will help any either.

In my case I was going to bolt it on, I was even looking at 1/4" rivets...

The curve was there in case it ever got welded. I read that you never want to do a horizontal weld on a frame because that area may be prone to stress cracks. I also read that that square edges welded to the face of a frame are another area where "stress risers" (I think that was the term) could form. The curve was an effort to address both in one shot.

JBarca wrote:

Have not heard the term "rosetta" used like this before. However if they are referring to punching/drill or cutting a few select holes in the reinforcement plate to then plug weld or weld around the ID of the hole to join it to the tube to help spread the load, yes this is done often when laminating thinner plates to make a heavier one.

Yes, that's what he was suggesting.

JBarca wrote:

As to the 1/8" tube A frame, I know what your welder is referring too. They keep light-weighting the campers constantly and you end up with what you have. If they are use to dealing with equipment trailers and they see an RV... their head will shake from the time it comes in until the time it leaves...

That sounds about right.

From what I can see from here, I do not see an issue with your approach. I'm assuming something will be done on the inside as well. The curved ends on your template, do not know if this was intentional or not. If you meant it to be that way, I do not see it hurting anything however do not know if will help any either.

Have not heard the term "rosetta" used like this before. However if they are referring to punching/drill or cutting a few select holes in the reinforcement plate to then plug weld or weld around the ID of the hole to join it to the tube to help spread the load, yes this is done often when laminating thinner plates to make a heavier one.

As to the 1/8" tube A frame, I know what your welder is referring too. They keep light-weighting the campers constantly and you end up with what you have. If they are use to dealing with equipment trailers and they see an RV... their head will shake from the time it comes in until the time it leaves...

Good luck and let us know how it goes.

John

I dropped the trailer a a local welding/fabrication shop. They're going to get me a formal quote during the week.

His first pass gut feeling was to plate the entire length of the A-Frame on both sides (probably 3/16th) with some rosetta ( I think that was the term) welds in the middle.

He was not happy to see the 1/8 tube frame in combination with the cam setup. Too much stress on one side of the A-Frame.

He's going to work up a complete quote during the week.

Here's my initial plan in a photo:

Good discussion guys! Now you know why I prefer the old style Dual Cam that mounted with the large U bolts. Used one for many years before I went with the Hensley. Never had a single problem. :) Too bad they discontinued it.

Enjoy your campout John!
Barney

mrekim wrote:
I'm positive we got to 50 degrees on a right hand turn many times. That's just a normal turn.

Is it possible that the bent style brackets that connect to the DC arm are "better". Does it seem like they would move the load inward - maybe reducing the amount of force pulling down on the DC frame mount as well as moving the chain inward so it's less likely to go "over center" on the snap up?

Yeh, with a compound angle turn it does not take much difference in truck surface to TT axles surface angle to create all the load on one WD bar, and the turn of any degree escalates it. If the truck is going up hill in relation to the TT and turning on uneven ground, the WD load goes even higher until the back of the truck lifts up to semi equalize the load. We have sort of nick named this up hill effect, "backflex" in the hitch. The kind you get coming up and over one of those real nasty high up Railroad crossings.

Until one starts really studying how a hitch head manipulates itself around and what is going on in the WD bars with changing head angles just towing down the road, one never realizes how much the forces move around constantly in most any kind of turn up and down hill action.

The bent chain keeper plate verses the straight and does it change the loads on the snap up any? For reasons not yet understood, Reese has gone in and out of bending that chain plate. During the 2010 year time frame they did some design tweaks to the HP Dual Cam. And they also changed where it was made or at least some of them. I have the 2nd generation DC that was created back in the year 2000 ish time frame and it has the straight plate. Colors re gold. Then they starting around late maybe 2009 into 2010 the bent chain plate started showing up on new hitches, still gold, but they did not yet have the new redesign DC arms of the 2010 3rd generation which are silver and black and the Yoke is really different.

Why the bent plate? I “believe” do not know for a fact, they where trying to get the chain force more vertical. The original style DC had a clevis clamp that pulled on center of the cam arm. That vintage DC arm allowed that. However the frame brackets used long U bolts over the frame. This center action created chain pull more like a non DC WD hitch with the chain attached to the WD bar.

I do not know all of them, but following RV net on hitches since 2003 most of the reported snap up issues come when the DC is involved and they “seemed” to start showing up when the new 2nd generation DC arms that bolt direct to the frame started to be sold. Again this same year 2000 time frame is when digital cameras and the gaining popularity of camping forums of people reporting issues was on the rise to even hear about the problems. It is a fact the chain plate is pulling the cam arm on a slight angle verses the older clevis style. And it appears as long as the snap up bracket stays held dead tight to the frame the issue does not rear it’s ugly head so much. Thus the belief the bent chain plate was an attempt to get the chain forces more vertical to help this issue.

I now have seen the straight flat chain plate come back on the scene in a hybrid vintage just like yours. You do not have the DC adjusting arms/yoke of the 2010 design tweaks that had the bent chain plate yet your yokes are different than mine. Look at them closely. You also have a non machined cam arm where mine is machined in the cam area. So why didn’t; Reese just put the bent angle chain plate on yours? That is a real good question.

It may have been that people did not realize there is a right way and a wrong to hook them up. The angled plate for sure can create an issue put on wrong and it really aggravates the problem. The straight plate can still be flipped wrong, but the effect with U bolt thread in or out is not so pronounced.

I can see the bend slightly reducing the chain angle from vertical as opposed to having a straight plate. However since the DC arm is still only held on one side, there is still a cantilevered effect and a side pulling load in the chain regardless of a straight or angle plate. It could be less on the angled plate than the straight. That said, I do not feel the angled plate is going to totally solve the issue even if it helps it some percentage. I do not see that the angle hurting the situation so the angle should be a good thing, just make real sure it is installed correct.

To help spot the design changes, look at the colors of the parts as this seems to come along with the changes for the most part. The yoke and cam arm gold colors (zinc chromium oxide coating I believe) are the year 1999 to 2000 2nd generation. The silver cam arm and the black yoke are the 2010 vintage 3rd generation design tweak and yours, well it is silver and black but yet looks similar to the older gold one and has straight chain keeper plates. I can tell they are made from a different casting mold.

So that is the history. If you have a really large vise, it is not that hard to create angled chain plates.


PS I'm going camping for 3 days so may not be back for a bit.

I'm positive we got to 50 degrees on a right hand turn many times. That's just a normal turn.


Is it possible that the bent style brackets that connect to the DC arm are "better". Does it seem like they would move the load inward - maybe reducing the amount of force pulling down on the DC frame mount as well as moving the chain inward so it's less likely to go "over center" on the snap up?

mrekim wrote:


I guess it's possible that a turn got all this kicked off, but it would have had to have been a right hand turn to load the driver side right? I don't think we've had any tight right hand turns at all.

Having the snap up not flat on the top of the frame due to it being more than 90 degrees is not likely a contributing factor?

Is 1/8" typical for these frames?

A right turn was needed to do this damage on the left side. If the compound angle between truck and trailer was great enough, the same all one side loading will still occur without that much angle.

Here see 50 degrees can cause the outside WD bar to take all the load and the inside nothing. Here see this





If the snap-up is not 90 degrees to the top of the frame with no bolts, I can see it can aggravate the problem

1/8" tube, that sounds like the average RV frame. You will not find a 1/4" one other than a really old camper.