Dual Cam Setup

TUCQUALA wrote:
OK, John, I have a stupid question!!! I have the early gold yokes ('04 purchase) and when adjusting, easy to tighten up inner nut before cinching down the outer nut. But how in **** do you adjust the length of the cam if you can't rotate the inner nut as you stated!!??? The keyway would prevent the cam from being turned, and I'm sure you aren't supposed just let the inner nut float on the threads!

Maybe if one was right in front of me, I could understand what you are saying, but I still can't see how the cam can be adjusted if the inner nut can't be "spun".

H'mm not a stupid question. Your right. I'll dig some and report back.

They may have relived the inside of the yoke so the corners of the nut allow it to spin and I miss-spoke. (it happens...) The pic was not clear enough to see that detail.

mrekim may be able to clear this up quick, can you spin the upper nut when it is agasint the yoke?

TUCQUALA wrote:


What do the experts think of the use of washers to get the cam bracker properly positioned in Mrekim's case?? Could that have increased the forces at the bolts since there would be less frame contact with the bracket?? Could the bracket have resisted the twist forces with full contact?? My brackets are flat against the frame both on the side and bottom of the frame and have exhibited no loosening or bending in the frame. Agin, just a thought!!!

I'm not and expert, just commenting on the flat washers. There should not be any binding of the DC frame plate internal radius fitting over the A frame outer bend radius. If there is, the frame plate will rock around and soon be pulling self taping screws out of the frame. Using washers is a way to shim that difference. Those of us having square corner C Channel A frame have to space away the frame plate. Reese even states in the directions on my vintage to do this.

With that said, with a very flexible A Frame, concentrating large loads in small places generally aggravates bending of the thin tube.

On your frame, do you by chance have a caliper and can measure the thickness?

I have other camper friends with Jayco's and tube frames running 1,200 to 1,400# TW with the DC and 1,500# WD bars with no issues. Some of them use reinforcing plates.

The tube frame itself is not an issue, going too thin can be.

fingered it out myself, brain-dead tonight!!!

Picking up from this response

JBarca wrote:


So how does any of this relate to mrekim's bent in right side A frame? This side did not bend the snapup yet we have evidence the cam arm rotated enough to cause the frame to bend.

There are a few factors in this equation. Some are these 3. Their may well be more however these 3 come to the top of the list. Anyone with more, please add.

1. A new 2013 1" offset on the cam arm frame plate.
2. An 6" A Frame made from 11 gage tube steel on an 1,100# loaded TW which is very inline for the size of camper.

3. Another factor not yet discussed is hitching up. Mrekim when you hitch up do you flip the snap up's real easy either by your hand or gently pressure on the pipe OR do you pull full weight of the spring bar with the pipe to snap up? What do you do tongue jack during snapping up?

Before I go down the road of no. 1 and 2, need to know how number 3 is performed. Please give us the details on how you snap up?

Mrekim has confirmed no. 3 is not an issue and he uses little effort when snaping up during the hitching process. This now leaves no, 1 and no 2 as possible factors.

This is a "hypothesis" not backed up by the usual evidence however it is at least a possibility. (yet to be proven) Both 1 and 2 contribute together to aggravate the problem.

The combination of the larger 1" offset on the new 2013 upgrade of the DC frame plate creates a slightly large lever effect (increase moment of force) when the WD chain is pulled up hard over the 1/2" or 3/4" of the prior vintages. It in itself is not a large change however we have the thin tube A frame in the middle of the mix. I'll say the somewhat obvious, if the frame cannot resist the bending moment of the side loaded DC, the frame is going to bend. In this case using the original vintage with 1/2" offset may or may not have made a difference. The only point I'm making is, the 1" offset is a larger lever moment. Since we still do not know what all of the chain loads are in all towing conditions, it is hard to tell if this increased lever is a factor or not.

When WD is engaged there is a large downward force on the top of the A frame by snapup. There is also an equal and opposite reaction of force pulling up on the cam arm as tension is applied to the WD bar.

When towing if you bounce over a bump or pot hole, an dynamic impact load goes into the hitch. If you are turning even a small amount the load on one side of the A frame can be higher then the other. The heavier loaded side is pulling up on the cam arm even more.

In this case, if the frame cannot resit this normal action associated with this style DC, something is going to bend. In this case the A frame.

This comes back to high point side loads into thin wall rectangular tubing. Hind site is always 20/20. Adding thicker spreader plates to even out the side loads is for sure a positive step to help prevent this from reoccurring.

Some research on this year/model or others in the same weight class by Coachman may turn up others with a common problem.

Hope this helps

John

mrekim wrote:

JBarca wrote:

3. Another factor not yet discussed is hitching up. Mrekim when you hitch up do you flip the snap up's real easy either by your hand or gently pressure on the pipe OR do you pull full weight of the spring bar with the pipe to snap up? What do you do tongue jack during snapping up?

I raise the tongue and use the pipe. It's not much effort to use the pipe.

mrekim wrote:

JBarca wrote:

Was the bent chain plate on the left side of the TT where all the big damage or on the right side where only the bottom of the frame bend in?

Just the driver side - side with most damage.

OK got it. This helps eliminate no. 3 from the mix. I throw a 6" wood block under the tongue jack to gain more jack height and jack both TT an TV up real high once coupled. You can some times flip the snapup's by one hand. Or gently on the pipe.

Keep doing the gentle snap up process. First it is dangerous pulling the full weight with the pipe, and 2nd the chain plate will bend doing this enough. Not every one realizes this and they actual pull full load with the pipe.

"If" full load was pulled during snap up then that is a high off center load twisting the cam arm. However this does not seem to be the case in your situation. So now back to no. 1 and no. 2 possible reason.

The discoveries continue,

Well somewhere along the way since the 2010 design upgrade they also change the yoke.

See this pic of the 1st vintage from my 2003 HP DC. You where able to spin the nut when adjusting the DC very easy. There was room to do this.


Now look at the 2010 yoke with the molded in steel black bar above the nut. Now in 2013 that molded in steel black bar is gone. Spinning the nut "must" still be possible however it may not be as easy as the 2001 HP DC vintage. On the 2010 vintage you could not slide the cam arm back and forth on the yoke without spinning the nut as it was locked by the molded in steel bar.


The 2003 vintage adjusted very good/easy, just the heavy thick yoke could hit the WD bar if the installer did not setup the chain links under load correctly. The 2010 vintage I'm sure was a hand full, the 2013 vintage does appear to be better than the 2010. Never saw that before until mrekim posted. This is not part of any of the failures seen in this post, just a side line learning.

(Edited 11-28-13 to correct that the upper adjusting nut can spin in the yoke)

Does this view help at all?

OK I found a top view



It is hard to tell if the centerline of the threaded shaft to the end of the cam lobe is different. While they may have several molds to make these, you can tell by the outer radius on the cam lobe boss is radius's different, can't tell for sure if the center line distance is different. If it was, this would also move the chain closer to the frame and possibly bind on the WD bar. I'm "assuming" they did not change this center distance.

JBarca wrote:
Do you have a top view looking straight down?

JBarca wrote:

3. Another factor not yet discussed is hitching up. Mrekim when you hitch up do you flip the snap up's real easy either by your hand or gently pressure on the pipe OR do you pull full weight of the spring bar with the pipe to snap up? What do you do tongue jack during snapping up?

I raise the tongue and use the pipe. It's not much effort to use the pipe.

JBarca wrote:

Was the bent chain plate on the left side of the TT where all the big damage or on the right side where only the bottom of the frame bend in?

Just the driver side - side with most damage.

mrekim wrote:

JBarca wrote:

This is "different". What you mean "teardrop" replacement?

I bent one teardrop bracket(Connects chain to cam arm). My replacement for that one bent teardrop bracket was an entire DC kit.

OK, now I get it. When you say "teardrop" you mean chain plate. Yes it does look like a tear drop shape and I recall it bending.



Was the bent chain plate on the left side of the TT where all the big damage or on the right side where only the bottom of the frame bend in?

Or both sides?

I have seen these bent before by the way the user does their snap up action. It may or may not be in your case. The answer to no. 3 above will help answer this.