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Blazing_Zippers's avatar
Blazing_Zippers
Explorer II
Sep 12, 2017

Cougar pin box flex

I'm asking for advice that might help me make a decision.
We have a 2016 Cougar 279RKS fifth wheel with an Anderson ultimate hitch. The trailer was "used" for about three months before we bought it from a dealer.
Here is the situation; There is 1 inch flex where the pin box goes up into the trailer-meaning the actual front of the box moves up and down into the front of the trailer.
I took the trailer to a reputable (I think) dealer and they tore the plastic off to expose the frame. Surprisingly, I was more then impressed with the frame construction and how clean the underside was. Nothing at all seemed to be cracked, twisted, bent, or damaged.
Now- the Anderson operates on a single point of attachment, which, in our case, is at the very front end of the trailer pin box. A traditional fifth wheel hitch has a plate for the trailer pin box to sit on.
My question is; would a traditional plate type of fifth wheel hitch alleviate the flex issue somewhat by spreading the pin box weight over entire plate?
Mind you, I'm NOT saying anything what so ever against the Anderson, but possibly in our case, it isn't the best choice.

9 Replies

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  • jerem0621's avatar
    jerem0621
    Explorer II
    Sep 12, 2017
    Something is wrong. There should not be anywhere near that much movement.

    Thanks!

    Jeremiah
  • Dayle1's avatar
    Dayle1
    Explorer II
    Sep 12, 2017
    N-Trouble wrote:
    Me Again wrote:
    NO! The distance of the fulcrum point is only about 4 or 5" different. Chris


    That 4-5" is like a 20% increase in the length. Still dont think it will make a difference?


    It is not 20%, and the pin box itself does not flex. The upper frame flexes and that distance is from the king pin back to where the frame rails attach to vertical supports right at the front legs, a distance easily in excess of 5 ft.

    My last fiver had 1-1/2 inches of flex. It was repaired under warranty and part of the fix was my design. The manufacturer and Lippert applied those changes to new units as well.

    Just tightening bolts or screws that secure the sidewalls to the frame is not a permanent fix. Even the slightest flex from repeated hook ups will loosen those connections. More steel is really needed.

    There are two areas of flex. 1) the box steel frame rails that span about 5 ft forward of the front legs can bow and 2) the crossmembers across the front and back of the pin box mount will bow so the pin box rotates slightly, the front crossmember bows up while the rear crossmember bows down.
  • joebedford's avatar
    joebedford
    Nomad II
    Sep 12, 2017
    When I thought we had a broken frame in Nashville I pulled off all the skirting and didn't find a problem with the frame. However, the lag bolt that connects the frame to the right RV sidewall was loose - just lying there.
  • laknox's avatar
    laknox
    Nomad
    Sep 12, 2017
    Blazing Zippers wrote:
    Well, DARN! I was just focused on the frame, but then 'OL Biscuit comes along and brings up another place where the issue might be. Hadn't thought of that.
    I was hoping the plate might "fix" the flex, but you guys brought up interesting points.
    Thanks...


    IMO, the =dealer's= guys should have thought of it...

    Lyle
  • Blazing_Zippers's avatar
    Blazing_Zippers
    Explorer II
    Sep 12, 2017
    Well, DARN! I was just focused on the frame, but then 'OL Biscuit comes along and brings up another place where the issue might be. Hadn't thought of that.
    I was hoping the plate might "fix" the flex, but you guys brought up interesting points.
    Thanks...
  • N-Trouble's avatar
    N-Trouble
    Explorer
    Sep 12, 2017
    Me Again wrote:
    NO! The distance of the fulcrum point is only about 4 or 5" different. Chris


    That 4-5" is like a 20% increase in the length. Still dont think it will make a difference?
  • N-Trouble's avatar
    N-Trouble
    Explorer
    Sep 12, 2017
    The trailer frame has no concept of the shape/size of the attachment point, it only sees the overall load. You can put the load on the head of a needle but it all looks the same to the trailer frame.

    The Andersen however will exert some additional force as it simulates an extended pinbox. The load has moved from the factory kingpin location out an additional 4" due to the coupler.

    Take the coupler spin it 180* like some with longbeds run it, reattach your trailer and you'll see the pinbox flex has reduced. You've just decreased the length of the lever arm (pinbox) by 8".
  • Me_Again's avatar
    Me_Again
    Explorer III
    Sep 12, 2017
    NO! The distance of the fulcrum point is only about 4 or 5" different. Chris
  • Old-Biscuit's avatar
    Old-Biscuit
    Explorer III
    Sep 12, 2017
    NO......
    Flex/movement in pin box can occur with traditional 5th wheel hitch

    When they had the overhang cover off did they hook and unhook 5th wheel to see WHERE the movement was coming from??????


    A little 'flex' is normal (1/4") but 1" is NOT normal.....something is moving

    Might not be pin box structure/support/cross frames.
    But could easily be sidewall(s)

    Have seen where sidewall bolts/mounting plates were broken and sidewall lifted when pin box was 'loaded' BEFORE the horizontal frame member actually moved.
    Lag bolts had to be installed in a 'W' pattern to re-attach sidewall to horizontal frame.

    1" movement...something is broke.


    Find someone with a 5th wheel hitch and hookup for a test.
    You will have same movement.

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