Receiver hitch winch capacity

[Britboaters]

I'm building a camper based on a GMC Topkick 4WD truck. Max weight should be in the order of 16,000 lbs. So conventional wisdom say I need a 25,000 lb winch !
So I bought a Sherpa 25k winch, with Dyneema rope. The winch is surprisingly light, at about 65 lbs.
This got me thinking I could mount it in a receiver hitch, both back and front - to either get me out of trouble, or further in !!

The 2.5", class V receiver hitches I've seen have generally been rated for 15,000 lbs towing capacity. This is designed for all the dynamic loading associated with trailer towing.
The hitch on the back of my truck is welded to a piece of 8" x 4" box, bolted directly to the frame with 8 - 1/2" grade 8 bolts; so I feel pretty confident in its strength. I can fab something similar for the front.

My rational is that the the crossmember will be about the same strength whether I mount the winch directly to it, or whether I weld in a receiver hitch. The actual winch mount that goes in the receiver can also be very stout. My concern is the 5/8" pin that holds the mount in the hitch. I've never seen any specs on capacity, or the steel used for these pins.
I can of course open up the holes and use a larger pin, maybe 3/4, or 1" based on the load calculation, steel specs and safety factor.

So what are your thoughts / experience on the real capacity of this setup please ?
Thanks
Bob

 

[DaveInDenver]

I'm not sure a winch cradle subframe that spans the frame members is the same as concentrating the load to a single point. You might be fine straight on but going off axis, I dunno. I've always felt those portable winches were OK for Jeep rock crawler class weight but not really ideal beyond that.

I've understood hitch pins to be grade 5 for the purposes of calculating capacity. I personally use a grade 8 bolt to hold the shackle adapter into my receiver because I just don't know if or what is true about them. At least a bolt from a reputable source I can know and trust.

You won't have 50k on the winch even in a doubled line. The winch will only have 25k ever. The bumper and truck will have to deal with two 25k loads and the connection for the block will see 50k, though.

 

[Britboaters]

Thanks Dave for your thoughts. Yes, always 25k on the winch.
3/4" grade 8 bolt in "single shear" has a capacity of about 40,000 lbs. So "double shear" would be 80,000 lbs giving a safety factor of 3:1 for my winch load.
It's interesting if we assume that the normal 5/8" hitch pins are grade 5, then in "double shear" the capacity is about 44,000 lbs. This is about 3:1 safety factor on a 15,000 lb rated hitch, in simple terms....
Bob

 

[DaveInDenver]

I calculate a 3/4"-16 grade 8 bolt to have cross sectional area of 0.373 sq-in, so it would be 55,950 lbf tensile (150 ksi) and 44,760 lbf proof (120 ksi). Therefore if you use the 70% of proof you get a single shear of 31,332 lbf.

I'm not a mechanical engineer, so these are just what I've picked up over the years, definitely no justification I can use at hand.

 

[Mundo4x4Casa]

As has been stated, all the shear force on a receiver hitch comes down to the central pin point. This might work with a direct line straight out pull, but add a side pull in the mix and you are asking the improbable of the set up. The other obvious question is, "can you lift the winch into position by yourself?" My 15K pound Warn winch weighs about 175 pounds with 90 feet of 7/16th inch wire rope, and even more with the carrier, so it's well and permanently connected to the front of my truck. I"ve had 6 or 7 winches of all kinds, including a factory Toyota PTO winch, on 4WD's over the last 50 years and they all had plusses and minuses. The biggest minus was having a 10K pound winch on a front portable receiver on one of my jeeps thinking I could move it to the rear which had a receiver if I had to winch back the way I came. The first time I used it was a side pull, granted not the best of measures, but that's what I was facing. It was a cheap, China Freight winch which self destructed on the first pull. The aluminum side bearing framing had too much load, warped; bound up the spool and broke the side bearing holder on one side right off. I did save the brand new 125 feet of cable and put a loop on one end with cable clamps and a large hook (with safety clip) on the other end for pulling down dead, 100 foot trees on the property using a snatch block on a right angle to stay out of the way of the fall. Another emergency side pull with my 15K Warn broke the roller fairlead, but still got us out of a bad jam with our 10,400 pound truck camper in 3 feet of icy, old snow on a side hill edging ever closer to the cliff. Like Dave, I'm no engineer either, but have hundreds of winch pulls, some in intricate, 2-winch extractions with many snatch blocks, cat chokers, straps, chains, and cables used in fun ways to get up and over an impossible looking object. But winching has always been a sport with me.
So my recommendation is to hoist that winch into a permanent perch. Have one custom made by a competent welder/fabricator to mate both disparate parts. Be sure to have the feet facing the pull.
My only observation on having a winch of that magnitude and truck of that much weight is you will only depend on your own devices or a truck of same or heavier for your extraction. No amount of smaller rigs will help you.
Here's a nice custom carrier job on a friend's 17,500 pound winch on his Ford truck camper. It has (almost) boxed frame horn extensions to support the winch. It's not going to fall off or contort.


Good luck to you.
jefe

 

[DaveInDenver]

winch which self destructed on the first pull. The aluminum side bearing framing had too much load, warped; bound up the spool and broke the side bearing holder on one side right off. I

I think this statement is important to highlight. If you look at the way winches are made the mount itself is critical to the integrity. There's only a couple of bars that connect across the drum otherwise, so the plate you're bolting to and its rigidity are vital.

 

[Britboaters]

Thanks for your inputs, Dave & Jefe.
My Sherpa winch, with Dyneema, only weighs 65 lbs - this is what got me thinking in this direction. The stout hitch mount would probably add 15 to 20 lbs, so still reasonable to move.
Clearly the winch mounting plate would need to be strong enough to fully support the winch, regardless if it is mounted directly to the vehicle, or to a receiver hitch. Also the effect of "off-center" loads on the winch itself would be the same whether the winch was mounted directly to the vehicle, or to a receiver mounting plate.
I'm starting to think a straight line pull would be fine, but an angle pull would put a significant "twisting" load on the hitch, depending on the angle. This could distort the hitch, at best, as there would be significant leverage based on how far the winch "sticks out" from the receiver hitch.

I got the shear load figures from the following reference:
https://www.nucor-fastener.com/Files/PDFs/TechDataSheets/TDS_013_Shear_Strength.pdf

Thanks for the input,
Bob

 

[ITTOG]

Please keep us updated if you do this. I have thought about doing this as well. But it was a recent thought so you are farther along than me.

Sent from my Pixel XL using Tapatalk

 

[TernOverland]

One suggestion might be to create a cradle with two stubs and two receivers. The cradle will have to be substantial. This would be a custom build, but I would not consider mounting a 25,000lb winch on a singe hitch stub.

I know it seems feasible to move this winch yourself. The first backpack I ever carried weighed 75 pounds. I walked around the yard with it a few times and thought "piece of cake". That thought faded quickly when I had to cross creeks, climb talus slopes, and slog through a muddy section of trail. The point is, you won't need a winch on a sunny day with a flat road. You will have to swap ends carrying that thing through mud half way to your knee or snow twice that deep. It might be on ice so slick you can barely stand carrying nothing. It's going to be bad, and on top of that, you risk a serious injury. All inclusive (68lbs + sturdy cradle), that unit will weigh close to 100 lbs. Maybe you are a big enough guy, that it won't matter. If it were me, I would build two sturdy carry hoops on it, and count on having a helper.

 

[Britboaters]

Thanks for the input.
I'm starting to think the forces involved are going to be too much, especially with angled pulls. Anything is possible, but there will be a lot of stress to deal with.
Thanks to all for the input.
Bob

 

[Mundo4x4Casa]

Brit,
I don't know how 'aggressive' you are concerning going out on a limb with traction. If you are not looking for trouble, you usually won't find it and visa versa. I'm in the 2nd camp and enjoy the smell of the traction free ozone and the way out of trouble. So, if you are trying to just get along, take your 65 pound rig along for a small semblance of insurance and peace of mind. You probably won't use it. I've found that most of the time, just reducing the pressure in the tires down, way down can usually get you out of traction trouble without using a winch. Only experience will help you here. jefe

 

[HenryJ]

The CST (Civil Support Team) vehicles here in Oregon use a twin receiver winch mount.

Can't find my personal pictures yet....