My truck had a fifth wheel hitch in it. So it has 4 brackets that are welded to the frame, and rest against the bottom of the bed for the rails to bolt to.

Now, I have obtained a 4'x3' piece of 3/8" plate. I plan on bolting this piece of plate to my bed, and cutting a hole in the middle for the ball. I had my uncle (a machinist) make me a "nut" of of some stock, so that I can weld it to the bottom side of the plate to make the ball removeable. The nut is long enough so it will cover all the threads when the ball is screwed in.

Has anyone used a setup like this before? I have seen quite a few done this way, and I have even seen some just bolted to the sheet metal . This setup doesnt bother me because of the brakets welded to the frame.

Just wanted some input.
Later.
Phillip

 

Without some bracing, isn't the plate going to flex up and down. And I would be worried about the machined nut. There is a lot of force on that ball. You might be better off with something engineered commercially. JMHO.

Casey

 

Ouch!! 4x3=12

12 square feet of 3/8ths plate and 4 bolts!


Question...... how long before you have the $$$ saved for a new bed????

Answer........ a long time!!


TOO much of an area for 3/8 plate which is I doubt is coldroll steel.

I estimate 1/4 to 1/2 inch of flexing up and down, providing you haul anything.

The bed won't last long.


IMHO

 

just my observation, its probably hotrolled plate, after he welds the "nut" on, it will be hot rolled in the heat affected zone of the plate.
I dont have my copy of Roarks handbook with me, but there are calculations on how much deflection from what kind of load. On the plus side, the load will be pulled parrallel to the plate, not vertically.

 

as a matter of interest , i am an apprentice machinist and i can make a nut that will be equal to anything you may buy for this application ( excluding of course very exotic material ) . so if a qualified machinist made the nut i would have all confidence that it would hold anything the threaded portion of the ball would hold.

i think maybe i would put a cross brace or two on top of the plate to prevent any anticipated deflection , this could be made from like 1/4 x 2 bar stock and welded every 2 inches for 1 inch on both sides.

 

oh i forgot ........... a nut with threads longer than the diameter of the threaded portion it screws onto is over kill and serves no usefull purpose other than to waste machinist time and money............ a 1/2 inch bolt needs only a thread depth in the nut of 1/2 inch

 

Actually, the threads should be about 1.5 times the thread diameter. this is to cover the difference in the material strength between the plate and the manufactured screw. Low carbon steel has a yeild strength of between 35K to 60K, Most screws are much higher.

 

Not a good idea I am afraid the plate will give way too much unless you are hauling fairly light loads. I warped a 7/8" plate with supports under it while pulling a grain trailer out of a field...but my gross weight was over 40k when I crossed the scales

 

I do not know what you guys are scared of! I HAVE exactly what he is talking about! and I have towed HEAVY!!! probably TOO heavy! but I trust this set up a heck of alot farther then any flipdown deal or somthing you put a little pin through! the only thing I would do diferently is possibly, weld another 3/8 plate about 2ftx1ft over top of the first plate with a hole big enough for the shank of the ball to slip into as its turning into the nut a little more "beef" never hurts!

 

i guess i will take a turn here,i would go with the cross bracing on the plate as noted before, and make sure the bolts are big enough that are holding it to your brackets or number of bolts,also look at the welds and how much weld there is holding your brackets on the frame,the added plate in the area of the ball would be good to....

 

On my 98, it is set up similar. I lifted the bed and mounted the plate underneath. I cut a 4 inch hole for the ball to fit through. Never had any flexing to worry about, but don't pull toooo heavy with it usually.

Only problem I have, is every time I load something in the bed, I have to use a pallet or something in the bed to clear the ball. It is also very good for tripping over.

Just make sure the welds are good since someone else did them.

Ed

 

Lemme see pics please. My truck has the same 4 bracket with the hitch missing. I'm looking for a gooseneck hitch, and this sounds interesting.

 

actually it serves 2 purposes.

1.) wastes machinest time.
2.) acts as a Thread Protector. This is why he did it.



Each bracket that is welded to the frame has 2 bolt holes. So there will be 8 grade-8 bolts holding the plate down. I also had some 1/4" plate, and I cut out a circle that is about 10" in diameter, and I cut a hole in it for the ball to slip through. This will help displace the weight of the tounge better (i.m.o.).

The machined "nut" that I had made acts only to hold the ball in, and protect the threads. The ball in my 2500 has no threads. It only has a 7/16" bolt to keep someone from pulling it out. The weight of the trailer holds the ball in. If for some reason the trailer raised enough to pull the ball up that high, then I wouldnt want to be connected to that trailer anyway....lol.

I dont tow super heavy anyway. The most weight my truck will see on a gooseneck hitch wont be over 15k lbs.

I will try and post some pics when I am done. I would have it in already, but it rained all day yesterday.

 

There is a company that makes a gooseneck hitch that mounts on 5th wheel rails. We first put this in my truck to use so we could take it out and use the bed as normal when not using the trailer. It is rated at 26k

Picked up a big Snowcat in Minnesota, and hauled it back to Phoenix. Coming thru one of the major cities in route, we hit some construction, good bumps and bent the rails on the mounts.

The load was only 12k.

The hitch dealer replaced the hitch under warranty, and we went to a standard goosneck hitch, where we can pull the ball out and turn it over, thereby allowing us to use the bed as normal.

The big difference is that this new mount has heavy metal underneath the bed to hold the weight, bounce and sway that the trailer gives the truck.

 

In my old Chevy 3/4 ton and in my current dodge I have had a piece of 1"x6" steel welded across the frame with a hole in the center. Never had any problems with it. A buddy of mine who hauls cattle for a living had his plate (same setup as mine) bend a good bit after 4 years of constant heavy loads. But I don't see why your setup won't hold up.

Tom