Weld the trailer hitch receiver together?

[Teikas Dad]

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]

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]

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]

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]

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]

Engineer, not a PE

 

[Shield Arc]

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]

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]

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]

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.

 

[Sodo]

Well I knew some PEs that I would put little stock in what they had to say too, PE or not. It depends a lot on their specialization, natural ability, and their attitude too. Some inspector types who hold a stamp start to act out with their ego, where the task at hand becomes secondary. Like the parkinglot security guard who wishes he was a sheriff! :laughing: Can be a real PITA.

Anyway, in your hitch pic, that round tube is huge, short, straight, and STOUT! I don't see it as a torsional member prior, but may have become a torsional member after you added the leverage of the extended hitch (!) . The heavy sq tube below does add strength in this case, but the torque is all still going thru the same bolts on the frame flange up above. This is a case where I would use grade 8 bolts at the frame.

If you are even interested in an engineer's p.o.v., I would have advised adding structural members that extend forward to the frame, very similar to my recommendation in this thread. Engineers like triangulation, with direct paths, it's efficient.

Skip welds can increase the number of stress risers, but add the benefit that if a weld starts to crack, it ends at the weld end, thus can't propagate along the whole weld thus are often used in design. They are efficient, look good when consistent and reduce weld time, warpage and more. But I would not use them along a torsion member, unless the element added was increasing the torsional strength significantly.

The skip welds that you show here are in towards the center of the torsional member and well-gusseted around them. If they were at the outside it might be a concern. I would not have any concerns with the skip welds here. Basically with the addition of all those gussets and the lower sq. tube that is one strong chunk of steel. But in any case understood it's out the door.

 

[Shield Arc]

I've seen flatbar / plate skip welded to pipe spreader bars, more so than beam spreader bars. A lot of times there will be a series of hole drilled in the plate so the lifting bridle can be positioned for making angled picks. Also seen flatbar inserted in the inside of pipe spreader bars too.

 

[Shield Arc]

Sodo let me guess, you worked for Waste Management?
https://www.wm.com/index.jsp

 

[Sodo]

Be careful confusing static loading with dynamic loading. A lifting bridle is "static" loading (not moving, or very slow). Aside from "errors", or consistent overload, it will probably never "fatigue". Static loading is when you attach the trailer to the truck, and it sits there.

A trailer on the freeway is dynamic loading, thumping over concrete freeway slabs, for hours and hours, counting up thousands of "stress cycles". This exceeds the static strength requirements by far. At one per second thats 3600 cycles every hour. Every time steel hits it's strength limit, a counter ticks off, and when that steel element accrues it's maximum number of cycles (at the max loading it can resist) a crack starts. After the start of a crack (or many small cracks), the strength is reduced. If the loading still continues with this reduced strength (due to cracks), the cracks grow faster and sometimes in other directions too.

Anyway one way to avoid all kinds of engineering is to simply make it 4 or 5 times stronger than the basic engineering need, and it lasts forever (overbuild).

Back to the issue though, the methods you are proposing are good for static but do not address dynamic strength (= on the road).

But anyway back to the OP,,,, First of all I doubt there's a need to do anything to the Reese hitch, it's engineered to a safety factor of 4 or 5 times the 5,000 or 7,000 lb rating. If you weld it as you said, with the bolts in it does gets stronger. You could add some gussets out to the farther bolt holes if you want to do something simple. If you really want to increase the strength, send some ideas I'll give my impression and opinion.

I would want a truck rated at 10,000 lbs to pull 7,000, I'm with you on that. My truck was rated at 6500 lbs and towing 5200 seemed sketchy. I bought a bigger truck! But with hitch strength I think you can go with Reese's ratings (that's just my opinion).

 

[Sodo]

Sodo let me guess, you worked for Waste Management?
https://www.wm.com/index.jsp

oh geez he's at it again :confused3: sorry not interested - members are sick and tired of bickering, OK?

 

[Shield Arc]

oh geez he's at it again :confused3:

At least I didn't call you a lier, like you did me.

 

[mikehaugen]

Unless you are a pretty decent welder, I would stick with the bolts. I have seen many times where people have welded things like that and actually made it weaker due to undercut. You may also end up stiffening an area that shouldn't be and start applying more stress somewhere else on the hitch. Shearing grade 8 bolts would be the least of my worries in that situation.

 

[Sodo]

Unless you are a pretty decent welder, I would stick with the bolts. I have seen many times where people have welded things like that and actually made it weaker due to undercut. You may also end up stiffening an area that shouldn't be and start applying more stress somewhere else on the hitch. Shearing grade 8 bolts would be the least of my worries in that situation.

A very good point! And there is no chance of shearing grade5 (or8) bolts anyway

Stiffening areas that need to flex to survive can created stress risers elsewhere. This is why I was thinking to brace (reduce movement) only at the main hub of that hitch & don't weld on the torsion members.

 

[Arc weld]

"Anyway one way to avoid all kinds of engineering is to simply make it 4 or 5 times stronger than the basic engineering need, and it lasts forever (overbuild)."

"Stiffening areas that need to flex to survive can created stress risers elsewhere."

These two statements seem to contradict each other.

Many weldments need to have some deflection built into the design in order to avoid failure from being too stiff. I'm sure Shield Arc could shed a couple billion lumens on this as bridges are a classic example of when over welding can lead to failure. I wouldn't say a lifting beam is a static load. It could be under a lot of stress if it was picking up something that weighed several tons. One of the better examples I've heard comparing static and dynamic loading is a simple table. A table designed for a 1000 lb static load would hold 1000 lbs. sitting on it. A table designed for a 1000 dynamic load would hold 1000 lbs. dropped on it. Big difference. Basically a dynamic load means under stress and a static load means just sitting there. Since this is a welding forum, the first question you need to ask when welding anything, is if it is a static or dynamic load. Then you can base your design and the type of filler metal to suit the type of load.

 

[Shield Arc]

It's obvious Sodo has never been on a derrick working on a ferry dock when a 300-car ferry comes in. Especially when the captain hits the brakes. When everything starts bouncing around, it gets pretty interesting:shocked:. When we set this passenger ramp at Pier 52 down town Seattle. Had it in the air when a ferry came in to dock. The derrick has a 250-ton land crane boom in it. I just knew the waves were going to buckle the boom.
When pining this ramp up. We had to soak the pins in dry ice and alcohol to shrink them enough to go in the holes.