Maximum rated pin weight, fifth wheel?

[BadDogPSD]

I just watched JD's (Big Truck Big RV) interview with the folks at Lippert about frame flex. It makes sense that a certain amount of flex is designed into the frames and also (to me) makes sense that certain situations can lead to excess flex and even 'failure'. At one point in the interview, the engineer states that each 5th wheel frame they produce has a maximum recommended pin weight. I will call Lippert and Grand Design to see if this information is available.
For 5th wheels, it seems that we focus on trying to not overload the rear axle on our tow vehicles. I'd have a hard time overloading the axle on our F450, but
I can see how it would be pretty easy to make the front of the trailer heavier than the frame & pin box were designed for, especially when you start putting dynamic loading on them. Starts, stops (especially hard 'panic' stops), rough roads at highway speeds, heck the darn joints in concrete freeways can cause some pretty serious porpoising at times. That can be a lot of repetitive stress on the RV's frame.

[bhspaulding]

I was watching a you tube video interviewing engineers at Lippert at frame flexing and bending and he said there is a maximum pin weight, so it is out there.

[C&D Meyerhoff]

I was watching a you tube video interviewing engineers at Lippert at frame flexing and bending and he said there is a maximum pin weight, so it is out there.

Agree with you....I heard the same thing and would believe Lippert could quote that number for a given frame design.

[BadDogPSD]

The best I could get out of Grand design was that the pin weight needed to be between 15 % - 25% of the loaded trailer weight. So for my 16.8k momentum that's 2520 - 4200 lbs.

[ajg617]

I've now asked Lippert what the max pin weight is for the 1621 chassis - they said their engineering department would get back to me - nobody has.

[Steven@147]

I've now asked Lippert what the max pin weight is for the 1621 chassis - they said their engineering department would get back to me - nobody has.

That would very interesting to me as well. What is the maximum pin weight for a given frame / floorplan? On our 16.8 GVWR our pin is 3600 so we are around 21%. We don't have a W/D or genset.

As in another thread you were saying aft of the axles there isn't any storage space, it's all up front, bedroom, closet, under bed storage, main storage compartment. There is a little bit of storage under our tri-fold couch but not enough to amount to much.

The only modification we have done was to install a MORryde pinbox. As others just said bebopping down the highway there is a huge amount of pulling/pushing/jarring/chucking/yanking/ (insert favorite here) going on as we drive the highways of America. It's not like the pin area is built like a semi truck/trailer connection.

[ajg617]

That would very interesting to me as well. What is the maximum pin weight for a given frame / floorplan? On our 16.8 GVWR our pin is 3600 so we are around 21%. We don't have a W/D or genset.

As in another thread you were saying aft of the axles there isn't any storage space, it's all up front, bedroom, closet, under bed storage, main storage compartment. There is a little bit of storage under our tri-fold couch but not enough to amount to much.

The only modification we have done was to install a MORryde pinbox. As others just said bebopping down the highway there is a huge amount of pulling/pushing/jarring/chucking/yanking/ (insert favorite here) going on as we drive the highways of America. It's not like the pin area is built like a semi truck/trailer connection.

I really would like to know what the max pin weight is considering GD will either placard the 310GK at 15K or 18K GVWR depending upon the 7K or 8K suspension. Has to be the same frame. We're at 21% if we use the 15K figure but only 17% if we use the 18K number. Also, the Goosebox adds some weight (60-70lbs I'd guess) directly onto the frame cross member over the factory pinbox.