It's not a Schwintek failure

[d2reid]

Another Schwintek failure. It’s not the slide system this time. It’s rough campsites. ??? Coming out of really sloped campsites my rv rotated to an angle that dragged on my trucks bed rails. It caught on my Gator X tonneau cover. This in turn caught my front cap, which in turn tore loose, which in turn jammed the corner of my slide, which in turn pulled the left rear bottom Schwintek shoe loose and crushed it. Estimated around $5000, looks like an insurance claim in my future.

This is really a kind of Mementum 376 issue. The distance from the front cap to the slide wall is inches. There is not a lot of meat there to hold things together. So, just my opinion, when looking at 5th wheels you need at least a foot of wall between the front cap seal and the forward slide. This is not something that will cause probelms within 3 years and 25,000 miles, but 7 years and 200,000+ miles it gets a little weak.

[howson]

d2reid -- Good grief, Dallas!

[Scott'n'Wendy]

Wow...
Hope it gets fixed relatively painlessly.

[Cate&Rob]

Yikes! Dallas . . . you do have a way of always “pushing the envelope”.

Rob

[TucsonJim]

Dang Dallas. Best wishes for a rapid and well done repair.

Jim

[Lonestar]

Wow. What a bummer. I agree about the Momentum construction issue.

How much space do you have between truck bed rails and trailer? I've got about 8" and at times it looked like I might touch.

[d2reid]

Yikes! Dallas . . . you do have a way of always “pushing the envelope”.

Rob

Do not... I just have fun.

[d2reid]

How much space do you have between truck bed rails and trailer?

5", which apparently is not enough. One of the things that will happen during the repair is raising my hitch. But that gets to be an adventure in itself. If you raise it too much then you unbalance the 5th wheel and end up with rear axle issues.

[JBill9694]

"Unbalance the 5th wheel" is not a term I've seen before, d2reid and not sure I understand how this may cause rear axle issues om the truck, I presume. The hitch is basically a pinned connection with vertical and horizontal loads that changing the height of the hitch 3" won't significantly impact, although I guess one could say it is applying a moment to the base of the hitch when actually towing the trailer, which would result in uplift on the front anchor bolts of the hitch base, and downward force on the back bolts. Still, if the majority of the load on the hitch is the vertical weight on the hitch, I'm not envisioning much impact from increasing the hitch height by 3". Now, if raising the hitch requires modifying the frame of the hitch, that would be a completely different issue.

[TedS]

Changing the hitch height 3" only changes the trailer angle less than 1 degree. Not much effect.

[Jlawles2]

Theoretically (remember that word) here unless you are running independent suspension, the "equalizer" (remember this one also) should by means of pivoting keep the loads between the axles the same under normal circumstances.

HOWEVER, from my observation of how the equalizer holes are placed, this theory is not accurate. From what I can tell the holes in the equalizer (even the after market ones) are not in line thus the equalizer becomes a variable proportion device.


As the left lower circle raises, it pushes the front of the equalizer up which increases the horizontal distance between the swing shackle and the pivot point, while the rear swing shackle on the equalizer moves down and forward decreasing the horizontal distance to the pivot point on the equalizer.

From there a bunch of odd complicated but simple math happens and we see that as axle load on the front decreases the rear increases.

This is why as you brake the front axle looses load and starts to skid first.

[Cate&Rob]

Jlawles2. Hi Joseph,

This geometry actually gets really complicated. Many years ago, Gyrogearloose and I were trying to model this . . . and never quite got there. In addition to what you have modelled, the compressed leaf spring gets longer and the relaxed leaf spring gets shorter. In the braking reference, the reaction around a fixed hanger vs the reaction around the pivoting equalizer has a limit to do with why the front axle lifts.

Rob

[Jlawles2]

Thanks Rob. There is a lot of stuff going on but that was a "simplified" explanation.

In addition to all of the stuff going on there is axle wrap (spring localized rotation) that leads to changing end conditions, etc. As long as the frame is relatively level the loading condition is somewhat even.

I wonder if anyone has ever played with shimming the axle to spring to set the equalizer parallel with the ground when the frame is not parallel to the ground.

[Scott'n'Wendy]

Theoretically (remember that word)

This guy KNOWS the difference between books and actual experience.....


As do you Rob...

Prior to this forum.....I NEVER would have thought the front axle lifts under heavy braking.....and now I think about it each time I have a reason to panic stop.....

[Cate&Rob]

For anyone who has not seen the LCI Correct Track video (it's 10 years old !) there is a lot to "observe" in this video that LCI created to feature their trailer alignment system that was part of early build Grand Design products. https://www.youtube.com/watch?app=desktop&v=Bp5iRVPwYZg

At the start of the video, watch for the continual side-to-side flex of the hanger. Albeit . . .this is a much taller hanger than used on newer GD products.

At about 2:50, watch for the heavy braking. (Trailer moving left to right). You can see the right (leading) tire stop rotating as the suspension lifts it from the ground. This is the geometry discussed earlier and will happen on any twin axle center equalizer suspension (not just Correct Track)

Rob