Stainless welding and hitch questions

The E350 van I just bought is rated to tow 10k. I'm planning on towing 10k with it soon. The receiver hitch on it is rated for 7500

So I plan on removing the old, dented step bumper and adding a steel (or stainless) square tubing bumper and welding the center of the bumper to the top of the receiver tube to add strength.

I have access to some nearly free 4x4" stainless, or I can buy some mild steel. I've welded mild steel to stainless before in non-structural applications like exhausts, but never where it counts. Should I not use stainless for the bumper tubing?

Wait a minute... are you talking about using stainless for the receiver tubing, or just the "decorative" step bumper?

I've welded stainless to mild steel with no issues. I used stainless rod, but 6011 or 6013 will probably work just as well. The application was tool boxes to the underside of a truck box and lasted for years with no issues

SVreX wrote: Wait a minute... are you talking about using stainless for the receiver tubing, or just the "decorative" step bumper?

Stainless for a tubing bumper. The hitch receiver is already there in mild steel. I would just be adding a square tubing bumper and welding it to the existing hitch to add some support.

Don49 wrote: I've welded stainless to mild steel with no issues. I used stainless rod, but 6011 or 6013 will probably work just as well. The application was tool boxes to the underside of a truck box and lasted for years with no issues

Yeah... I would love to TIG this, but I'm wire-feed only :)

Any tips on what wire to use?

I would buy a good used hitch receiver rated for 10k, if something ever went wrong you could end up in a legal mess over the modified/underrated receiver.

ansonivan wrote: I would buy a good used hitch receiver rated for 10k, if something ever went wrong you could end up in a legal mess over the modified/underrated receiver.

True, but that's not much fun

Grassroots, man... grassroots

Using the receiver hitch to reinforce the bumper is fine.

Using the bumper to reinforce the receiver hitch is a bad idea I'd rather not know anything about.

Even if the tubing was sufficient, it would be transferring the load to the bumper mount bolts. Bad.

The receiver hitch transfers the load to the frame, and closer to the rear axle.

Plus, the stainless and the mild steel have different coefficients of expansion and flex.

Your "fix" is a bandaid without engineering which relies on the strength of welds made by a confessed non-pro.

Buy a 10,000 hitch.

Check to see if the hitch has a higher rating for weight distributing hitches. See here for an example: http://www.reese-hitches.com/ and look up your vehicle. Some hitches can carry more weight when used with weight distributing setup. Your hitch may be able to handle 10,000 lbs with the wd hitch. You can check with the manufacturer of the hitch to see or it is usually listed on the hitch label.

Thanks for that guys, but I know where to buy hitches. I build my own hitches all the time so I'm very familiar with how they get their strength. I just don't have access to the steel right now (or the time or garage space) to engineer a whole hitch. The current hitch receiver is rated at 5000/7500 with WD.

Assume for the sake of this thread that I know what I'm doing... except when it comes to welding stainless

Ok, so I'll skip the free stainless and buy some mild steel

SVreX wrote: Even if the tubing was sufficient, it would be transferring the load to the bumper mount bolts. Bad.

How is that any different from the current setup where it transfers weight to the four hitch bolts? I'm basically adding a complete hitch on top of the existing one - thick walled steel tubing with 6 grade eight bolts.

The receiver hitch transfers the load to the frame,

So does the bumper

Plus, the stainless and the mild steel have different coefficients of expansion and flex.

Good to know. I wasn't sure of that.

Your "fix" is a bandaid without engineering which relies on the strength of welds made by a confessed non-pro.

Non-pro at welding stainless to mild steel, yes. Non-pro at welding steel, not so true.

Thoughts:

309 wire is used to weld stainless to carbon.

You don't seem to be "engineering" anything as much as beefing it up.

The hitch rating wasn't "engineered" as much as it was "lawyered"

I'm sure reasonableness as regards tow vehicle and tongue weight are more important than the rating.

Trailer brakes, please.

The whole works is attached by a 5/8" pin, so don't overthink it.

-James

SVreX wrote: Using the receiver hitch to reinforce the bumper is fine. Using the bumper to reinforce the receiver hitch is a bad idea I'd rather not know anything about. Even if the tubing was sufficient, it would be transferring the load to the bumper mount bolts. Bad. The receiver hitch transfers the load to the frame, and closer to the rear axle. Plus, the stainless and the mild steel have different coefficients of expansion and flex. Your "fix" is a bandaid without engineering which relies on the strength of welds made by a confessed non-pro. Buy a 10,000 hitch.

This. Grassroots doesn't mean being unsafe.

SVreX wrote: Using the receiver hitch to reinforce the bumper is fine. Using the bumper to reinforce the receiver hitch is a bad idea I'd rather not know anything about. Even if the tubing was sufficient, it would be transferring the load to the bumper mount bolts. Bad. The receiver hitch transfers the load to the frame, and closer to the rear axle. Plus, the stainless and the mild steel have different coefficients of expansion and flex. Your "fix" is a bandaid without engineering which relies on the strength of welds made by a confessed non-pro. Buy a 10,000 hitch.

i've installed a few receiver hitches and looked at a lot of them that were already installed, and the only difference between the bumper mounting and the hitch mounting is how the bolts hold it together. they are in about the same place on the frame- within about a foot of the back of the frame.

the bumper bolts go in from the side and thus are in sheer all the time, and the receivers go up thru the bottom of the frame and as such are in tension with the tongue weight pushing down on them, but also in somewhat of a sheer when going or stopping.

we've got an older ag bumper with a built in hitch sitting up against a tree.. it's rated at 10,000 pounds and uses the stock bumper mounting points and hardware.

i've been thinking of getting an actual receiver for my 79 Chevy frame/87 GMC bodied pickup, but after looking at how beefed up my stock rear bumper is (3/8" plate between the 3/8" steel mounting brackets that are held to the frame with 3 1/2" bolts on each side) and the pair of 1" grade 9 bolts that hold the receiver bolted to the bottom of it- and also taking into consideration that no one ever used anything besides a bumper hitch until about 20 years ago- i decided that it's beefy enough as it sits. also, there is that single 5/8" pin that was already mentioned that takes ALL of the fore/aft loads of the trailer..

jamscal wrote: Thoughts: 309 wire is used to weld stainless to carbon. You don't seem to be "engineering" anything as much as beefing it up. The hitch rating wasn't "engineered" as much as it was "lawyered" I'm sure reasonableness as regards tow vehicle and tongue weight are more important than the rating. Trailer brakes, please. The whole works is attached by a 5/8" pin, so don't overthink it. -James

12" Trailer brakes are on both axles totalling four, Brake controller is my favorite Tekonsha Prodigy Digital unit.

I'm not overly worried about the hitch engineering itself. I've seen accidents where the trailer turned the tow vehicle into an accordion, and neither the 5/8" pin nor the direct shear forces on the bolts were able to break anything. In fact, the hitch probably saw upwards of 50,000 lbs shock load and it was the only part of the rig that wasn't broken.

novaderrik wrote: the bumper bolts go in from the side and thus are in sheer all the time, and the receivers go up thru the bottom of the frame and as such are in tension with the tongue weight pushing down on them, but also in somewhat of a sheer when going or stopping.

Not always. the new Reese 6000 lb hitch on my Sonoma uses the bumper mount bolts. You remove the bumper, slide the hitch in, and replace the bumper. All the bolts are horizontal.... but your point is valid.

Many people think that the greatest loads are up and down on a hitch, but actually the fore/aft loads are mostly equal.

curtis73 wrote: Many people think that the greatest loads are up and down on a hitch, but actually the fore/aft loads are mostly equal.

I have a hard time believing that.

I can hook up a trailer and FORGET to install the shear pin and successfully drive several miles down the road before it falls out.

As a minimum there is a tongue load of several hundred pounds before you ever start to move.

Picture a 5/8" steel round bar sticking out the rear of the vehicle about the same distance as the receiver hitch. Put the tongue weight of the trailer on it. It will fold in half before you move.

The same bar used as a pin for the receiver hitch will resist the shear completely.

They may be equal weights or ratings, but they are completely different forces. 5/8" in shear is quite different than 3" tubing subjected to bending stress.

SVreX wrote: I have a hard time believing that. can hook up a trailer and FORGET to install the shear pin and successfully drive several miles down the road before it falls out.I As a minimum there is a tongue load of several hundred pounds before you ever start to move. Picture a 5/8" steel round bar sticking out the rear of the vehicle about the same distance as the receiver hitch. Put the tongue weight of the trailer on it. It will fold in half before you move. The same bar used as a pin for the receiver hitch will resist the shear completely.

I feel like there's a story here

curtis73 wrote:

novaderrik wrote: the bumper bolts go in from the side and thus are in sheer all the time, and the receivers go up thru the bottom of the frame and as such are in tension with the tongue weight pushing down on them, but also in somewhat of a sheer when going or stopping.

Not always. the new Reese 6000 lb hitch on my Sonoma uses the bumper mount bolts. You remove the bumper, slide the hitch in, and replace the bumper. All the bolts are horizontal.... but your point is valid. Many people think that the greatest loads are up and down on a hitch, but actually the fore/aft loads are mostly equal.

i've never really looked at the hitch mounting arrangement on an S series truck- all my junk is full sized..

but you got me to thinking about the class 3 hitch that was on my 94 Caprice. i only ever used it as a convenient jacking point and with a car dollie to haul an 89 Grand Prix about 25 miles, but it was there if i ever wanted to pull a trailer. it used the 2 lower bumper shock mounting bolts (they were whatever the metric bolt that's slightly bigger than 3/8" is, so 10mm?) on each side and an existing hole in the side of each frame rail about a foot forward (also used for the bumper shock mounting, i think). so it was a 5,000 pound rated hitch that relied on a total of 6 10mm bolts in sheer to control all the loads..

SVreX wrote:

curtis73 wrote: Many people think that the greatest loads are up and down on a hitch, but actually the fore/aft loads are mostly equal.

I have a hard time believing that. I can hook up a trailer and FORGET to install the shear pin and successfully drive several miles down the road before it falls out. As a minimum there is a tongue load of several hundred pounds before you ever start to move.

Don't confuse friction with stress. Sure there is 1000 lbs of tongue weight which can easily reach 3000 lbs of temporary bounce weight, but think of the stress caused by slamming on the brakes and 10,000 lbs of shear weight hits those bolts and the shear pin. The tongue weight is nothing compared to the potential forces fore and aft on all those pieces of hardware.

Keep in mind that 30 lbs moving at 35 mph carries nearly 700 lbs of kinetic force with it. So a 10k trailer at 70 mph is nearly 500,000 lbs of potential fore/aft force. Comparing that to the up/down bounce forces seen at the hitch is pretty insignificant.

but you got me to thinking about the class 3 hitch that was on my 94 Caprice. i only ever used it as a convenient jacking point and with a car dollie to haul an 89 Grand Prix about 25 miles, but it was there if i ever wanted to pull a trailer. it used the 2 lower bumper shock mounting bolts (they were whatever the metric bolt that's slightly bigger than 3/8" is, so 10mm?) on each side and an existing hole in the side of each frame rail about a foot forward (also used for the bumper shock mounting, i think). so it was a 5,000 pound rated hitch that relied on a total of 6 10mm bolts in sheer to control all the loads..

Another misconception is that the bolts handle all of the loads. They don't. Their main purpose (regardless of horizontal or vertical) is to create a clamp load between the hitch and the frame. The resulting friction between the pieces means that the bolts actually never see shear loads (at least not generally... depending on design and installation).

You could take the hitch off of a truck that has just dead-headed into a cement wall while towing 15k and the threads of the bolt would be pristine. The purpose of the bolt is not to provide shear load support (otherwise they wouldn't use grade 8 bolts), they are there to provide tensile support to "lock" the hitch to the frame. In many ways it doesn't matter if the bolts are horizontal or vertical. If installed properly, the hitch can't move... in which case, it doesn't matter which way the bolts go.

Your argument concerning your 94 Caprice is a perfect example. You have the same setup as my 96 Impala. The hitches for our cars include two bolts vertically through the frame and two bolts horizontally through the bumper support. It appears as though all the weight is carried way back at those horizontal bolts, but the weight is carried by the fact that the clamping load between the hitch and the frame steel overcomes the tongue weight capacity. Its not the bolt that carries the weight, its the clamping that carries the weight.

novaderrik wrote: i've installed a few receiver hitches and looked at a lot of them that were already installed, and the only difference between the bumper mounting and the hitch mounting is how the bolts hold it together. they are in about the same place on the frame- within about a foot of the back of the frame.

Ever look at how your parents towed their 8000 lb travel trailers? I'm not so young that I don't remember Uhaul hitches that were chains wrapped around the bumper of a 78 Plymouth.

Sounds like you've got it all worked out.

My advice (and others) is to buy the 10,000 lb hitch.

You obviously have other ideas.

SVreX wrote: Sounds like you've got it all worked out. My advice (and others) is to buy the 10,000 lb hitch. You obviously have other ideas.

When it comes to physics and hitch engineering, I'm kind of a big deal. Just kidding.

I do respect your opinion and understand why you recommend the bigger hitch, but after building so many of them that's like telling a chef to just buy a Big Mac. I'm trying to avoid the big-dollar commercial option and stay grassroots. I'm also (not kidding) an environmentalist at heart, so using re-purposed steel and my own welding is better than using new virgin steel and lord knows how much fossil fuels shipping it to me.