fifth wheel to gooseneck adapters

[GWHaley]

I just did a search on this subject and all the threads are fairly old. I'm considering going this route, but am slightly put off by what I have read, so far. I found a new adapter from PopUp industries. Here is their site: www.popuphitch.com . If some of you could check out this site and give me some feedback, I would greatly appreciate it

 

[Mschevey]

Long responce

I still don't like the idea of this , but this looks like a well built unit and under normal use I think it would work.



Some explanation;



This is simplified as much as I could and will still be confusing.



The reason I don't like this idea in general is that normally the king pin exerts a lower bending moment (force) on the frame at the front of the trailer, than a gooseneck hitch will.



If you think of the pulling force from the truck acting at the king pin you are on average ~8 inches from the point where the hitch assembly attaches to the the trailer frame. This attachment (welds, bolts, etc. ) is subjected to a force trying to bend it that is equal to the pulling force (what ever is required to move the trailer) times the vertical distance (from above ~8 inches). Like wise there is a bending force applied to the truck. This bending force is applied to the connection points from the truck frame to the hitch. The force is again equal to the pulling force times the distance from the connection (king pin) to the attachment points (the pins holding the hitch to the rails if you have this style or the frame bolts for permanently mounted units. ) Most hitches have a height of about 16 inches.



Now if you look at a gooseneck ball the height to the connection is about 4 inches. The rest of the distance to the original connection hight, 12 inches, is is made up of the adapter. The new distance from the hitch mounting height on the trailer to the coupling point is 8+12=20inches. This is 250% of the original distance. Therefor the bending force to the trailer frame goes up by that same percentage!! Also the bending force for the truck goes down in relation.



For example if your trailer takes 1000 pounds of pulling force to move it the original moment is 1000 lbs. X 8inches = 8000 in. -lbs. or 667 ft. -lbs and the moment on the truck is 1000 lbs X 16 in. = 16,000 in. -lbs or 1,333 ft. -lbs. With the adapter the same force is required to pull the trailer but the load changes to: trailer; 1000 lbs X 20 inches = 20,000 in. -lbs. or 1667 ft. -lbs and for the truck 1000 lbs X 4 inches = 4,000 in. -lbs or 333 ft. -lbs.



Yes there is a considerable amount of overkill (safety factor in engineering terms) in the design of the hitch connection to the trailer. But that is there by design to account for the time you are pulling the trailer out of a rut (much higher pulling force) or when the truck hits a pothole and there is shock loading. Will this style hitch work YES, but you are not just changing how the connection is made, you are adjusting how the stresses of pulling the trailer are distributed.



Sorry for the very long answer to the short question, but I have been involved in this discussion on a number of different levels.



Mike Schevey

 

[GWHaley]

simplified explanation

Mschevey, thanks for the explanation, I understand that there will be loads exerted on the hitch area of the trailer that it wasn't meant to handle. Do you think the problems will show themselves by cracking of the welds, bending of the hitch itself, bending of the channel frame of the trailer or????

I am a certified welder (but obviously not an engineer) and can repair/strengthen any areas that might have a problem.

 

[Whitmore]

I have the adapter from camping world, it was the higest rated adapter I could find and it is plenty stought to say the least, bolted right up no problem at all. The first pull on my 27' trailer proved out exactly as Mschevy has explained and it was obvious to me that I needed to beefup the frame of my trailer. I got some 5" channel and put a couple angle braces from the outside framing back where the trailer makes the transion from verticle to horizontial and ran it on an angle all the way to behind the cross framing behind the hitch to stiffen the frame up, all this framing is flush to the existing framing and looks great... ... ... ... Results are now fantastic, no flex or jumping at all. If you are determined to have the goose over the 5th wheel than I highly recommend the frame of the 5er be modified to handel the extra mechanical leverage of the extended adapter.



cheers, Kevin

 

[GWHaley]

Thanks, Kevin. That's the type of info that I'm looking for. I'll be taking a look at those mods as soon as I get the adapter-by the way, did you look at the PopUp unit?

 

[Whitmore]

GW, I just did look at the hitch in question and it looks like a good design but the one from camping world is rated for 30K it is a 205B model. It doesnt have all the height adjustments that yours does but if your trailer kingpin setup is like mine than it has 3 levels of adjustment in it so that will be no big deal.



I am guessing here but try this site www.campingworld.com



cheers, Kevin



EDIT, I found the hitch I am talking about



http://www.campingworld.com/browse/skus/index.cfm?deptID=5&subOf=136,37&skunum=21064

 

[Mschevey]

GWHaley; In answering your questions, yes you can make modifications to the framework of most trailers to strengthen them, as Whitmore explained. But remember this is seat of the pants engineering.



There is no way to know what loads the front of the trailer were designed for. So to say weather you will have problems or not is hard. But I can say it is MUCH more probable that you will with the adapter (and no other modifications), than if you stay with the original hitch type.



Whitmore: thanks for giving a first hand perspective of what you ran into, and what you had to do to correct it.



Mike

 

[TPCDrafting]

I think if I were in a situation where I had to pull both 5th and goose I'd get the B&W turn over ball hitch which for extra you can get a 5'er hitch that fits into the GN ball hitch receiver. That way your not modifying the trailer. And once done pulling the 5'er you can simply pull out the 5'er hitch and your back in business with the goose and yer bed is empty and flat. JMO



On the other hand, a neighbor has a gn hitch on his 5'er and he has pulled it some (just got it set up last year) and hasn't had any problems. I alerted him to keep an eye on the framework and welds on his trailer. He's a frod guy and looked at me like I was an idiot. I almost hope he has a problem (not an accident) so I can rub it in his face. heheh

 

[merryman]

It only took less the 3K miles for the adaptor system to tear the King pin box out of my fiver.

The bad part was I had been warned and did not belive.

Vaughn

 

[kcv67]

I have been using the cushion hitch goose neck adapter. I have a 23. 5 light weight trailer and I put 6,000 miles on it last year. I towed it up in the mountains and down the freeway. I check the frame and hitch for cracks and haven't seen any thing yet. My trailer is pretty light, if I had a heavier trailer I would not use the adapter.