gringeltaube

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cranetruck

Knowing the gear ratio and the number of layers on the drum, one should be able to calculate the pulling capacity with a shear pin of a given shear strength.....
Gerhard probably has the formulas handy (=I won't bother digging for them).

One or more snatch blocks is the best solution for most questionable pulls IMHO.

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gringeltaube

Not that handy....
Had to do some measuring & testing first, with real size parts and “sacrificing” half a dozen of my pins to determine their actual strenght...



Found following:

1)Most of the (rebuilt) winches I checked have the hole in the input shaft already re-drilled to the next common size 5/16”!, same for the corresponding drive shaft yoke; probably during depot rebuilt?
2)The shear pins I used for this are home made, out of brass which already had proven to have a shear strength very similar to some old AL pins I once found hidden in a tool bag. (I’m positive these were OEM)
3)Two 7.1mm (nominal 9/32”) diam. pins sheared each at about 250ft-lb, inserted in its stock size 7.2mm diam. hole.
4)Surprisingly it took more or less the same torque (245ft-lb) to break the same diameter pin but in a hole enlarged to 8mm (5/16”+)! Tested for a second time to confirm this! Wish I had AL pins to compare in this case!
5)A 7.94mm (5/16”) diam. pin in a 8mm hole shears at 350ft-lb! I repeated this test too, to be totally sure. So certainly size makes a big difference here!

Having this data its simple math to at least estimate the real capacity of our 10K-Garwoods:
Not taking into account friction losses and the minimal force to overcome the internal band brake, we have a minimum of 250ft-lb multiplied by 23 (23:1 reduction ratio), makes for 5750ft-lb on the drum. The drum itself has a diameter of 5” so if we started with the wire rope all out, the center of the ½” rope would be winding in at a distance of approx. 3” from the drum’s axis, for the first layer. Since 3 inches = ¼ of a foot, and to maintain the same torque figure our force needs to be multiplied by 4 and that means that we actually could pull over 20,000 pounds, single line!!! (pretty tough job for a ½” rope… imagine with the larger pin or even a steel bolt!)

Now lets say we only pulled out the first 10 meters (last layer) for a light duty winching job only: then it would be pulling in at about 5” from the drum's center, so we have 5750 times 12, div. 5 = 13,800 lbs.!

Conclusions:
Are our winches under-rated? YES!
Do we need much stronger shear pins? NO! (IMHO)


G.

Recovry4x4

Gerhard, do you need some OE pins to do some testing on? If so PM me your address and I'll send you some for the cause!

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m16ty

Gerhard, Thanks for your testing on this subject. Get some AL pins from Kenny (I'd send you some myself but I don't have any) and test them if you don't mind .

tm america

when i put my winch on it had a bolt i put the correct shear pin in there . it broke just winding the cable up on a tree with light load on the breaks.put another one in was testing the winch lock broke another one .that was the last time i used a shear pin .now i use a grade three bolt .havent broke the bolt broke the cable once but it had a bad spot in it i make sure to use snatch blocks if needed just dont like loading the cable like that if i can help it

m16ty

I've got a winch but haven't installed it yet so I don't have any first hand knowledge of deuce winches or shear pins. Seems like the more we talk about shear pins and answer questions the more questions it brings up.

Why are there reports of the pin breaking under no or very little load? Is there a bunch of bad pins floating around?

swbradley1

If I were you I would be more worried about snapping bumpers off your truck than shearing a little pin.

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gringeltaube

Really appreciate your offer Kenny! If those are good ol' OEM pins I would hate to crack even one in pieces, just for testing purposes, even if it was "for the cause"... Let them live and die in real "battle"...
Can't we get known and proven "aftermarket" ones from one of our vendors? (Not for free of course!) I mean start with what can be readily supplied/replaced any time?
I would be glad to provide comparative data for anyone here and especially test those pins claimed to be the best!
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.

gringeltaube

Good Q.! .... But how "bad" must they be .....!?

Lets asume they give up at one half, no - one quarter! of the desired strenght (or what a "safe and sound" shear pin could do): that bad guy still would be able to produce way over 1ton of tension in the rope in its upper layer, more than enough to lift a complete MF engine W/tranny or at least .... have it tight and neatly wound on the drum!

G.