Winch Shear Pins

[gringeltaube]

..................................
Also thinking of including some steel in the next test series, for the sake of completeness...........! Guess I then need to build a heavy duty "pin cracker" with a hardened shaft...!
G.

Well, finally.... did some more testing, including all kind of materials combining different hole and pin diameters...... and found at least some that could be considered good alternatives to the original genuine GI spec aluminum shear pins!

A VERY BIG THANK YOU to Kenny (Recovry4x4) for sending me these to have for comparison!!!!!!

(For anyone interested there still are some more left for further experiments.)

In general the torque figures were relatively consistent and predictable comparing similar material and sizes. Pin diameter matters much more then hole diameter or shape. Obviously it makes a big difference if a bolt sticks with its full diameter inside the shaft or is threaded partially or full length.

The chart (and pics) below show what was done. Hope it is easy enough to understand.

Enjoy!

G.

 

[m16ty]

Looks like the thing to do is go with 5/16" brass if I read your chart correctly.

 

[gringeltaube]

Looks like the thing to do is go with 5/16" brass if I read your chart correctly.

Yes, but only if the shaft hole was already enlarged. Average shear strength was about 10% over stock AL pins for 5/16" brass pins. Turning them down to 7.4 - 7.5mm diam. would bring it very close to what the military had.

G.

 

[Floridianson]

It is allways a good idea with a new to you winch to check the band brake. Make shure it is clean not rusty and crusty and backed off. Don't back off so far that the bolt comes off the nut on the band.

 

[Jake0147]

It would look to me like "cheating" with the 9/32 inch brass would get about 83 or 84 percent of the original strength of a winch that is built for three times more than 90 percent of any of us would ever use it for... Nice... I'll bet they've got piles of that down at the hardware store, right in the bin next to the original shear pins... Still probably easier to get though.


So, I'm winging this here... This is calculations of thngs that are beyond me... Since the worm gear (I believe) a 23 to 1 ratio, which is a poor place to be from an efficiency standpoint, meaning between that and the band brake about 50 percent of what goes into the winch will be lost as friction (depending on the load of course, but breakage happens at high load when efficiency is worst)... Driving the winch backwards is much less efficient, more like 15 percent. I'm thinking that using that 9/32 brass rod, backing off a correctly set band brake, you'd probably end up with a fifteen percent gain in the input torque? So probably if you weren't actually holding loads with the winch, you could end up with a winch output that is just about right... Maybe?

 

[m16ty]

With that chart and knowing accual torque values you can figure accual line pull. I don't have time at the moment but I'll set down this afternoon and figure it and post up.

 

[gringeltaube]

....for the AL pins it would be about 25,000lbs, first layer on the drum, single line.......!

 

[kipman]

I am using grade two steel bolts.

 

[Keith_J]

I am using grade two steel bolts.

Don't use your winch with anything but aluminum or possibly brass. Steel, even mild steel, has over DOUBLE the shear modulus than aluminum.

 

[m16ty]

but I wonder if there are any mild steel (non graded) pins similar to the ones I used to use in my bailer that would work. I hadn't considered brass. Any comments?

I'm familiar with shear pins used in a New Holland baler. They would be too hard.

Anybody considering using anything but the stock pins needs to take a look at the chart gringeltaube took the time to research. All of the steel pins he tested were above the safe limit.

PLEASE READ THR CHART. He has taken hours of his time and money to do testing with nothing to gain other than helping us not destroy our winches.

 

[bottleworks]

Yes, but only if the shaft hole was already enlarged. Average shear strength was about 10% over stock AL pins for 5/16" brass pins.

What [SIZE=-1]Alloy of Brass were you testing with?
[/SIZE]

 

[Irv]

Shear pins: Steel is a huge mistake.

My friend also thought steel was simple. He put a roll pin in there. The hook on the 5T winch got caught on the bumper and the next thing he heard was the PTO being ripped off of the side of the transmission. Time for a new PTO and new transmission. It literally tore a large chunk away from the tranny.

What we need to find is the particular alloy of aluminum that is specified. They would not cost much to make. I can have a boatload made in a shop. All I need is one to work from and the alloy. Irv

 

[smoothnu]

I have used a cotter key that just fits in with great success. I have no way to test the tinsel strength though. It maybe to strong. If it is I have been very fortunate. Has anyone tested a cotter key? That would be a cheap fix if it is safe.

 

[hank]

I wonder how well a pto farm tractor pin from tractor supply would do ?

 

[m16ty]

What we need to find is the particular alloy of aluminum that is specified. They would not cost much to make. I can have a boatload made in a shop. All I need is one to work from and the alloy. Irv

2024 AL

I wonder how well a pto farm tractor pin from tractor supply would do ?

Too hard.


Both of these questions have been answered earlier in the thread.

 

[gringeltaube]

What [SIZE=-1]Alloy of Brass were you testing with?
[/SIZE]

Good Q., wish I knew the exact specs...!
Store doesn't know..., hopefully their supplier does.... will try to find out anyways and let you all know!

G.

 

[Billy Bobbed]

My brotherinlaw got his old dump truck with 10 tons of dirt stuck in his yard yesterday,so he called me to pull him out.I thought this would be a good time to try the winch out for the first time.I chained my truck to a tree and I sheared 3 aluminum pins real easy.I even double lined it.I thought this winch was stronger than that.I know its a lot of weight to pull but it didnt do much pulling before it stopped pulling.I was going to put a bolt in it but couldnt do it I didnt want to break the winch.After pulling hime forward and backwards a few times I got him out.One day im going to really need that winch to pull me out,is it going to do the job.

 

[rosco]

Over the years, I have done extensive winching with both the Garwood & Braden winches. I use soft steel sheer pins. I have never torn up anything!. That said, keep in mind that sheer pins will just naturally get tired and fail, even within the recommended load limits. The Garwood should be capable of dragging a Deuce with its brakes locked, at an idle. If you have to rev the engine, to do the pull, you need a snatch block in the line, maybe even two, depending on conditions. Winching is serious business. Nothing is "Fool Proof"! The winch, drum, line - everything, needs constant attention/constant vigilance. It is inherently dangerous!!!! Winching takes substantial skill, care, and thought! It also takes substantial grunt work. There are no short cuts!

Lee in Alaska

 

[stumps]

The quickest killer of shear pins is allowing the winch or load to jerk. Slow and steady are the rule with winches. No quickly winding up the cable and letting it snap tight, or dumping the clutch... Slow and steady.

Also, if a truck is buried in the wheel trenches it dug, a straight pull is going to take a tremendous amount of force to free her. Dig a ramp out of the hole, arrange your winch cable so that it pulls up and forward.

Think about the last time you creeped your truck over a high square curb head-on. That is easy compared to pulling a truck that is buried up to its axles.

Also, if the holes that the winch shear pin fits through are wallowed out in size, you are never again going to get good service out of a shear pin. You must either replace the parts, or take them to a machine shop and have them renewed back to nominal size.

-Chuck

 

[LanceRobson]

My brotherinlaw got his old dump truck with 10 tons of dirt stuck in his yard yesterday,so he called me to pull him out.I thought this would be a good time to try the winch out for the first time.I chained my truck to a tree and I sheared 3 aluminum pins real easy.I even double lined it.I thought this winch was stronger than that.I know its a lot of weight to pull but it didnt do much pulling before it stopped pulling.I was going to put a bolt in it but couldnt do it I didnt want to break the winch.After pulling hime forward and backwards a few times I got him out.One day im going to really need that winch to pull me out,is it going to do the job.

This is a great example of why the military selects and train "operators", not "drivers". I'd suggest you leave the winch alone until you learn how to use it. You're going to damage it or get someone hurt.

The vehicle operator's manual clearly states that the winch will only provide it's rated pull with a nearly empty drum. Every layer of cable means that more cable is pulled in for each drum revolution and the winch is operating at lower efficiency.

Think about the load you were trying to pull. Let's say the truck weighs 20,000 pounds. It has 20,000 pounds of gravel in it for 40,000 pounds total. If it is mired to the axles (or close to them) it will take up to it's own weight of line pull to free it. If he can spin his tires (slowly) to help that will reduce some but not much.

You were asking the winch to do something way beyond it's ability. The shear pins did exactly what they should have-they sheared before you broke the winch or the cable. A 10K winch with most of the cable off the drum and a snatch block is still only going to have 20K of potential from which you subtract friction loss in the block. Even with a snatch block the winch was overloaded.

You need to have nearly all of the cable off the drum and have a straight pull to a load that is being pulled straight at you to get the full rated capacity from the winch. If you can't do that, use snatch blocks to get the fleet angles right or to help get the cable off the drum. You may have to move your truck and re-rig every 25 feet or so the keep the drum nearly empty.

Download FM 21-20, Recovery Operations, from the resources section or buy a copy. After reading it, put it in your glove box or pamphlet bag with your heavy leather gloves, a punch (to remove broken pins) and a hammer.

Lance