Adding kingpin extender

[wcrews]

need thoughts on adding kingpin extender to my Jayco Super Lite fifth wheel. 31 ft. 9000 lbs. Would like to pull with 1/2 ton, 5 1/2 foot bed . Bought camper for kids and grandkid, do not make long pulls and only go out 4 ord 5 times a year.

[ParTheCourse]

Adding length to the kingpin is often frowned upon by RV and hitch manufactures, might be worthwhile to check with them. A few minutes looking over your truck manual regarding towing weight capacities may be time well spent also.

[IC2]

Most manufacturers do not warranty the frames of their 5ers with the adapters simply because of the added lever arm and the strain that it puts on that frame. The mfr of mine stated that it could cause possible frame failure

As far as pulling the 9000# 5er with an F150/1500 class truck, specially with the really short bed probably will be extremely difficult if not impossible. Firstly - the weight and secondly that short bed plus the fact that any Jayco that I have seen does not have a 'nose' that's recessed to the point where you can even make a reasonably tight turn. I have a 6.5 foot bed, F350 pulling a 10-11,000# Titanium with a very aero nose and recessed for shortbeds and with the hitch set 2-4" behind the axle centerline can j-u-u-s-t make 90* as long as there isn't a significant dip associated with the turn. Then of course, there's that lack of horsepower/torque, truck tires that are not rated for the 2-3000# of bed weight, a differntial ratio that might be way too low numerically, suspension that wont handle that weight, brakes that are too small, a cooling system that wont handle the extra load, a transmission that is too light duty.

I apologize for being a naysayer, but you will need at least a 3/4 ton pick up to safely haul that camper - and a 1 ton is better -even for a few times a year.

(I can already hear the folks disagreeing with me getting ready to down play this)

[wingnut60]

ParTheCourse,

"Adding length to the kingpin is often frowned upon by RV and hitch manufactures, might be worthwhile to check with them"

It has been my experience that any mfg is ok with an extended pin box, it is the gooseneck adapters they don't want. Is that what you are referring to?

Joe

[RustyJC]

Quote:

Originally Posted by wingnut60 ParTheCourse, "Adding length to the kingpin is often frowned upon by RV and hitch manufactures, might be worthwhile to check with them" It has been my experience that any mfg is ok with an extended pin box, it is the gooseneck adapters they don't want.

With all respect, that's not the case. To cite one example, Jayco did not approve an extended pin box on the Designer 3610RLTS 5th wheel.

A longer lever arm is a longer lever arm - both amplify moments (torques) applied to the pin box/frame area for a given force. The difference is that a kingpin extension amplifies the torques generated by the pin weight of the 5th wheel and the vertical "shocks" from expansion joints, potholes, etc. while a gooseneck adapter amplifies torques generated by acceleration and deceleration forces.

Rusty

[wingnut60]

Best that I had not said ANY--I based my statement on visits to many rv lots which have fivers with extended pin boxes, obviously installed at the factory. My BIL has a 36 Jayco Designer that came with the extended box???
Rusty, what about DRV and our trailers--don't they install extended boxes at the factory? Or am I just confused as to what the term means?
Joe

[TXiceman]

A 5er designed with an extended pin is one thing...adding a longer extension is not wise. It will put additional stresses on the welds in the pin box/frame attachment area. It would be better to get a slider hitch and use it.

ken

[wingnut60]

Guess I am hung up on what the OP meant then...seems like Mor-Ryde and several others make extenders and there are so many out there being used, I would think there would be problems with all the frames they are used on--after the factory build.
Confused, I am.
Joe

[TXiceman]

There are lots of products out there that are not good ideas or work...look at Slick 50. As a mechanical engineer, I tend to look at things from that view point and I see lots of ideas that are not a good idea from and engineering perspective. They may work OK, but I would expect to see a larger than normal numbers of failures.

I would not want to experiment on my RV.

Ken

[RustyJC]

Quote:

Originally Posted by wingnut60 Best that I had not said ANY--I based my statement on visits to many rv lots which have fivers with extended pin boxes, obviously installed at the factory. My BIL has a 36 Jayco Designer that came with the extended box??? Rusty, what about DRV and our trailers--don't they install extended boxes at the factory? Or am I just confused as to what the term means? Joe

Several of us (myself included) have firsthand experience with the Jayco Designer 3610RLTS 5th wheel. It was delivered with a vertical pin box, and Jayco would not approve the use of any extended pin boxes with this 5th wheel.

If a 5th wheel was designed to utilize an extended pin box, that's one thing - that's the situation with the standard equipment extended pin boxes on the Doubletree Mobile Suites and other 5th wheels that provide them as standard equipment. To add a pin box extension to a 5th wheel that did not originally utilize one, or to use a longer extension than originally supplied is a totally different matter - those applications need to be run by the trailer manufacturer for a design check to ensure that the pin box/frame area will not be overloaded.

Rusty

[dayle1]

Quote:

Originally Posted by wingnut60 Guess I am hung up on what the OP meant then...seems like Mor-Ryde and several others make extenders and there are so many out there being used, I would think there would be problems with all the frames they are used on--after the factory build. Confused, I am. Joe

Most manufacturers have several specific extension lengths that they approve for use with their frame. But there are also even longer extensions that they DO NOT approve. Replacing a stock extension with an air, rubber or other isolation extension that is the same length should not be a problem. But, when in doubt, call the manufacturer.

[wingnut60]

Well, I am beginning to understand this. Anyone want to start a list of Mfgs that DON'T want you to add an extender? I am not an engineer, but I do realize the stress increases with the distance from the attachment point. Made an assumption that since so many were in use on so many brands of trailers, there would be some trend established in failure/problem if adding an extender was a problem. I vaguely remember some threads in different forums about the frame cracking in some older units, but not one about a newer--say, post 2000?
Learn something every day.
Joe

[Ray,IN]

It begins with frame design, which is done by the RV manufacturer for their specs. Few actually build their own frames. Lippert Components, Inc. - Informational Publication and other suppliers of trailer frames build to those specs, and will not warranty any deviation or a additions to that design. Anyone may request a custom frame design change to accommodate extended pin boxes, gooseneck hitches/adapters. Then the frame is designed and built to withstand the additional stress' and torsion of these different adapters.

[Quick Trip]

I have a 2004 Komfort 23' FS fiver which came from the factory with a 10" extended pin box. In five years of use I have never hit the truck or the rails. I use a Reese 16K Hitch. (non-slider)
Good Luck & Drive Safe!