Weld the trailer hitch receiver together?

[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.