abh3

Here's what happens when you use a bolt: Winch Fragged

My A3 has the hydraulic setup but the pressure valve seems to be set pretty low so the winch doesn't have that much pull to it, at least in terms of trying to pull out stuck farm tractors, even using the G.I. block...

The solution for those of us trying to pull big things out of where the shouldn't have gone, as opposed to pulling ourselves out, is having several blocks on hand for the job, NOT back at the shop, hanging in the barn where they are safe!!! Blocks are where you find them, just missed a few by running errands instead of stopping RIGHT THEN at the roadside junk-sale, they were gone an hour later. Keep your eyes open!

gringeltaube

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.

Attached Images

	Shear Pin Test, Material vs. Shear Strength 02.jpg (106.0 KB, 220 views)
	Shear pin test 011 (Small).jpg (68.9 KB, 178 views)
	Shear pin testing 008 (Small).jpg (75.5 KB, 151 views)

m16ty

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

gringeltaube

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.

__________________
James

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

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