20000 lb trailer hitch for 1998 Marathon 45' XL

[Jon Wehrenberg]

That last illustration David attached shows how a flexing of the cradle (the arms springing up and down) shows up on the rear cap as stress fractures. The attachement to the upper structure of the coach by the arms contributes some strength to the cantilevered arms, but you should note that the arms are substantially inboard of the outer vertical members, so as the engine cradle arms are flexing up and down, there will also be some flexing up and down in the horizontal members which extend outward from the cradle to the rear vertical members. But the bottom line is that adding a ton of weight on the hitch exerts a lot of force on the entire rear structure of the engine cradle arms and upper structure of the coach. I strongly suspect a 40 foot coach can tolerate a whole lot more tongue weight than a 45 foot coach.

[jack14r]

I cannot find any spec that states a 2000 LBS tongue weight only 1500 LBS for tongue weight.

[travelite]

There's one other component, the diagonal labeled (34) in the attached drawing. This diagonal further supports the engine beam. One end is attached to the engine beam the other end attaches to house framework. Initially I thought it tied into the 3"x9" rear sub frame rails but it doesn't. Lots of areas to check for cracks.

That's it for pictures folks!

[Jon Wehrenberg]

What that item 34 does is support the cradle arms, but since it does not attach to the subframe around the rear axles it is ultimately pulling on the rear structure as the cradle flexes up and down.

Jack, Prevost may have new limits. If my brain is functioning properly I recall the cradle reinforcement at one time was rated for a 2000 pound hitch weight. I don't know if Prevost revised their limitation or if there is different limitation for 40 and 45 foot coaches.

The illustrations David posted sure make the situation very clearly understood and as he states in his last post there are a lot of areas to inspect for stress or fatigue cracking. If cracking is found I wonder if the repair is to weld the crack or to plate the crack and weld it. Plating is likely to just tend to relocate the cracks that occur in the future to the next weakest point.

[travelite]

I'd probably weld the crack and place a couple of nicely arced gussets spanning the crack interface on both faces of each orthogonal member and reduce the load:

[lbriant]

I will keep you posted,
My lift will be here next week, my bus already had one on it but they took the lift with them I just have the three recivers on the back, bolted and welded on,
I will be pulling our Jeep wrangler unlimited behind the Bike lift,
Thanks for all the imput and nice pictures!!
the good lord willing we wont have any issues,