Gooseneck to 5th wheel adapter

[rowilson]

Does anyone know which manufacturers state that you can use a 5th wheel to gooseneck adapter on a their camper without tearing up the pin box? I'm looking at getting a camper but don't want a 5th wheel hitch. This isn't something that's an option as I'll buy a tag trailer instead. I know some manufacturers definately say not to use them but others say it's alright.

Thanks for the help.

 

[mberry]

B&W Turnover ball makes a 5th wheel kingpin adapter for their gooseneck hitch. No need to worry about what trailer brand you can buy that way since it doesn't change the trailer in any way. You may want to check into that.



Companion 5th Wheel Hitch - Model #3000

The B&W Companion RV 5th Wheel Hitch is available as an accessory to the B&W Turnover Ball Gooseneck Hitch continuing the B&W tradition of 'a hitch when you need it, a level bed when you don't. '



The Turnover Ball hitch is first installed and then the Companion latches into the 2½ inch square hole. Many RV hitches use mounting rails bolted into the truck bed and when you remove the hitch the mounting rails are still there. The Companion hitch was the first hitch on the market to have all the mounting rails below the truck bed floor.

 

[rweis]

In thread along this line, RustyJC had some pertinent comments about the moment arm forces generated due to the GN configuration. You might search for those comments.



Bob Weis

 

[SnoKing]

People using the extend adapters are just fooling themselves into thinking they are not going to have a problem. Do to the way a 5th wheel pin box is built, none can take the extra torque that the extension puts on it. SNOKING

 

[klenger]

Specifically, what is it about the 5th wheel hitch that you don't like?



There are several 5th wheel hitches on the market (Turnoverball, Reese, and Pullrite), that allow all the parts to be removed in a few minutes for a clean bed. See http://www.klenger.net/dodge/pullrite/index.html for my comments on the PullRite.

 

[rowilson]

I already have a Kurt brand flip over gooseneck ball in the bed and don't want any more holes in the floor. I know that the moment of leverage on the pin box increase with the lengthened pin and that's why I'm looking at which trailer beefs up the pin box so I won't have the problem of broken welds. This way I don't have to put another plate in.

 

[SnoKing]

The problem the way I see it, is the a gooseneck trailer brings all the steel together at the top of the gooseneck, and that area can be as tall as necessary to handle the loads. In a 5th wheel trailer, they are trying to keep the floor area as thin as they can for Bedroom headroom and truck bedrail clearences, and where the pin box is located out in the middle of the sea sorta speaking in relationship to the frame. They only build this area strong enought for the pin boxes they offer. SNOKING

 

[GAmes]

I can tell you from experience that a pin box on a 5er as light as 10k will not handle the load in a panic stop. When truck and trailer came to a stop without T-boning a fool who ran a red light the gooseneck was at about a 45 degree angle to the trailer. The plate that the pin was welded to had torn like paper. A local welder cut the plate completely off and replaced it with a steel plate about a half inch thick. About a year later I traded it in without any other problems. On that particular trailer (Fleetwood Terry) the weak link was the thin steel the pin was welded to.

 

[CUMMINZ]

adapter for 5er to flipover ball

I am using flipover ball and have not put many miles on it. There are several threads already running pertaining to this type of setup and it is obvious that there are 2 sides to this fence. Try looking at the threads pertaining to adding a hitch to the back of 5ers to haul either boats or vehicles. These same guys that talk about having NO problems adding 5 or 6k trailers behind their 5ers??? Give me a break,,, Adding a 5k anything to the back of a 5er will place 10 times the load on a 5er pin box than will a conversion to ball alone.

 

[RustyJC]

Give me a break,,, Adding a 5k anything to the back of a 5er will place 10 times the load on a 5er pin box than will a conversion to ball alone.

Would you care to share your engineering proof that such is the case? If you'd like, I'll share mine proving that it's not.



Rusty

 

[CUMMINZ]

Proof

I have no proof. I would like you to dazzle us with your figures.

 

[RustyJC]

If you're looking to be dazzled, I'm afraid you'll find applied mechanics and vectors disappointingly boring.



Rusty

 

[CUMMINZ]

Proof

Rusty

Please do what you said you would do. Prove to us that conversions are dangerous.

 

[RustyJC]

If you're actually interested in seeing comparative calculations, I'll work some up as I have time available. Watch this space.



Rusty

 

[RustyJC]

OK, for illustration purposes, let's assume the following:



Pin box is square in cross section, 12" on a side.



Pin box wall thickness is 1/4", welded on front and rear sides with 100% penetration.



Pin box load plate is 12" below junction of pin box to frame.



Centerline of kingpin jaw recess is 3" below pin box load plate.



Gooseneck adapter bolts onto and extends 18" below pin box load plate.



5th wheel trailer weighs 16000 lbs.



Truck makes 0. 5G stop - trailer brakes not engaged - producing an 8000 lb retarding vector at the hitch/trailer interface.



First, let's consider the 5th wheel hitch. The 8000 lb retarding vector is applied by the jaws of the hitch to the kingpin bore recess. The pin attempts to produce a torque of 8000 lbs x 3 inches (0. 25 ft) = 2000 ft-lb. However, to induce a torque to the pin box-to-frame joint, the pin box must be free to rotate. Unfortunately, the 3000 lb pin load means that the pin box load plate remains firmly against the 5th wheel hitch load plate. This results in a shear load being applied at the pin box to frame junction. Since the pin box is welded at the front and rear, the area taking the 8000 lb shear load has a cross-sectional area of 12" per side x 2 sides x 0. 25" wall thickness = 6 square inches. The resultant shear stress is 8000 lbs / 6 square inches = 1333 pounds per square inch.



If we add the 5000 lb towed load behind the 5th wheel, under a 0. 5G stop, the additional retarding force generated would be 2500 lbs. This produces a total retarding force of 8000 + 2500 = 10500 lbs. Substituting 10500 in the calculation above, the resultant shear stress is 10500 lbs / 6 square inches = 1750 pounds per square inch - a 31. 3% increase over the 5th wheel base stress of 1333 pounds per square inch.



Now, with the gooseneck adapter installed and using the base case above (i. e. , no towed load behind the 5th wheel), the distance from the pin box to frame junction to the gooseneck ball is 12" + 18" = 30". The retarding vector of 8000 pounds is applied at the gooseneck ball, and with no 5th wheel hitch load plate present to prevent rotation, a torque of 8000 lbs x 30" (2. 5 feet) = 20000 ft-lb is produced, and the torque is trying to rotate the front of the pin box vertically downward while the rear of the pin box is being compressed against the 5th wheel frame. If we assume the rear of the pin box is fixed against the frame, a lever arm from the rear to the front of the pin box of 1 foot is created through which this 20000 ft-lb torque is applied. This produces a tensile force of 20000 ft-lb / 1 ft, or 20000 lbs in the front weld of the pin box. Since the front weld has an area of 12 inches long x 1/4" (0. 25 inch) thick, the weld area under tensile stress is 3 square inches. The stress level is 20000 lbs / 3 square inches = 6667 pounds per square inch. This represents an increase of 400% over the base 5th wheel stress of 1333 pounds per square inch and an increase of 281% over the 5th wheel + 5000 lb towed load stress of 1750 pounds per square inch.



Rusty

 

[CUMMINZ]

5er conversions to ball (are you safe)

Several forums have had lots of conversation about safety issues with 5er to goosneck conversions. I have posted on the internet at: http://www.gorowan.com/2004ram/pin_box/ ,,,,,

Are you safe pulling a trailer behind your 5er or placing others at risk?

 

[RustyJC]

Please see response HERE.



Rusty