Weld the trailer hitch receiver together?

Teikas Dad · Aug 9, 2014

I recently bought a used pickup to tow the trailer that I'm going to buy for my tractor. I want an 18' flatbed trailer and the only ones I can find are rated for 7000lb GVW. With the weight of my T/L/B and the trailer combined I'm right at about 4900lbs. I figured that was too close to the limit on a 5k lb rated trailer, that's the reason for going bigger.

My question has to do with the hitch receiver on the truck. The truck is a 2000 and going by the date on the Reese hitch that is on the truck, the hitch is a 2006 model. It's the universal fit type receiver hitch where there are two brackets that bolt to the frame of the truck then the center of the receiver, which is a large round tube with the receiver welded on, mounts inside the frame brackets. The hitch is rated for 5k W/C and 7k L/D. There are two flat plates on the end of the center tube that get bolted to the frame bracket with 4 bolts on each side. Here's what the center tube looks like:

This is what it looks like with the frame brackets bolted on:

I took the receiver/hitch off the truck as I want to clean it up, repaint it and I'm going to replace all the bolts with grade 8 bolts as the existing bolts were a bit rusty. After I took it apart I started thinking about welding the center tube plates to the frame brackets in an effort to strengthen the receiver. I'm not looking to increase the GVW of it, I just want to make sure that the bolts don't shear and leave my tractor and trailer in a ditch someplace. I contacted Reese and they only use grade 5 bolts so just going to grade 8 will make it stronger but I tend to overthink and over do everything.

Am I better off to leave well enough alone and just go with the grade 8 bolts or would bolting it together then welding the crosspiece plates to the frame brackets be a better way to go?

I'm going to post this on the trailer thread too for all the towing experts to comment on.

Thanks

Sodo · Aug 9, 2014

Additional structural members from the center of the hitch out to the truck frame would make a difference in strength. But keep in mind Reese puts a big safety factor ontop of those 5,000 & 7,000 ratings, probably 3X or even 4X, so you are nowhere near the "true" limit. Well anyway it sounds like you want a project and want it to be bomber, I can understand that.

IMHO there's little you can do out at the adaptor ends (welding or g8 vs g5) that will increase the strength. Grade 8 and grade 5 make no difference in that configuration because the bolts are short, there's no stretch that you are gaining, it won't make any difference. Also they are out at the perimeter of the adapter plates, it's already a very strong configuration. A grade 8 is no advantage when a grade 5 will never break. You can torque a grade 8 to a higher torque though, which might make you feel better!

That said I like grade 8s, you can just pound them in like nails and then brush the threads out with your glove and the nut still spins on, and they can resist corrosion better.

A hitch you buy from Reese is designed to "bolt on", and probably accommodates access to the spare tire? If you add a support member that perhaps made spare tire access a little more difficult (but still reasonable) strength would increase a lot. Here's a bolt-on suggestion, obviously you can weld-on too. Or maybe there are other bolt holes in the truck frame that you can get to. If you do something like what is shown here, double the strength is reasonable, and safety factor would double as well, (to 6x or 8X).

Shield Arc · Aug 9, 2014

Why not weld them? While you're at it, skip weld a piece of 3/8 or 1/2-inch flatbar across the top on the tube. And weld it to the frame brackets. Then you are good to go.:thumbsup:
When skip welding something like this, before painting I like to use caulking between the welds to stop water from getting in between the metal.

Sodo · Aug 9, 2014

Shield my "general caution" would be to avoid welding out in the middle of a torsion member that experiences cyclic loading. I personally would shy away from welding out in the middle of that torsion member, UNLESS what I welded on, was increasing the torsional rigidity, which a flatbar does not. A flatbar rib/gusset increases the bending strength though.

Welding on 3/4 of a square tube on the backside would increase the torsional section. Or welding an angle onto the round might be sufficient and fairly easy to do. Lots of ways to do it but you need a "closed section" to add to the torsional rigidity, which I think might be preferable to just increasing the bending strength. These are good options that avoid compromising spare tire access.

Shield Arc · Aug 9, 2014

Sodo said:
Shield my "general caution" would be to avoid welding out in the middle of a torsion member that experiences cyclic loading. You could increase the bending strength but reduce the fatigue strength.

Sodo are you an engineer? If so are you a PE?

Sodo · Aug 9, 2014

Engineer, not a PE

Shield Arc · Aug 9, 2014

Guess you're not going to answer me?

I built this hitch for a friend years ago. See the skip welds in the center? What kind of leverage load do you think this hitch sees?

Shield Arc · Aug 9, 2014

Sodo said:
Engineer, not a PE

I've had lots of engineers work for me. Until you get that stamp, I don't put much stock in what they have to say.

I was a project superintendent for this company most of my life. And I only have a high school education. How many engineers do you think they have on the payroll?
General Construction Company

Arc weld · Aug 9, 2014

Don't know how good the OP's welding is but I'm sure Reese has to have all their ducks in a row to avoid lawsuits from their hitches breaking. Putting a flat bar stiffener on the tube would make it stronger. That's what they do on a lot of I beam spreader bars used for lifting. You'd want it along the back side opposite the receiver tube to be the most effective.

Teikas Dad · Aug 9, 2014

Thanks for the input all. Shield Arc, I've never seen that graph with all the different bolt strengths. The bolts I got to hold the brackets to the frame are 9/16 gr 8 and the bolts that hold the cross piece to the frame brackets are 3/8 gr 8. Reese originally supplied the same sizes in gr 5, at least that's what I took off the truck.

Looking at the graph above, the 9/16 gr 8 bolt is good for over 28k lbs of tension and over 22k lbs of shear. The 3/8 gr 8 bolts are rated for over 12k lbs tension and 10k lbs of shear. I don't think my 5000lbs of tractor and trailer will break those..I hope! As Arc Weld and Sodo point out, Reese probably over engineers the hitches by a significant factor. Maybe I'll just stop being so OCD and bolt the thing together! I gotta stop overthinking the little stuff. I do really appreciate all your input though. That's the great thing about this forum, no matter what you're trying to find out there's someone (usually many more than one) who's been there, done it and got the T-shirt so the rest of us can avoid the same pain.