Question about CMP winch?

[Phil Waterman]

What pull are they rated at?

I’ve looked through my various manuals and though I think I remember seeing it once I can’t seem to find it. My reason for asking is that I finally mounted the 125 feet of 5/8 in cable on my 1941 C60L and well if you’ve got a winch why not use it. But looking at the breaking strength of the cable 20.6 Tons I realized that this is not something you want to use with 3/8 chain from the hardware store.

One of the first things I discovered/read in the drivers handbook is that the cable must be wound on to the drum under tension. In doing this I soon discovered that the winch was perfectly happy to drag the truck with the brakes locked on. After a couple of tries I learned the proper amount of brake to wind cable on smoothly. Then I started playing a little with the winch, thanks to Bob I have a pair of the winch scotches my first experiment was to place the scotches as shown in the book using some 6000 lb tow cable and chain lengths for proper adjustment. With the truck sitting on the hard packed gravel drive and the cable run out 50 feet and chained to a very large pine tree, transfer case in winch position, slowly released the clutch and the cable brake and throttle just above idle, the truck started to move slowly back as the scotches sank into the ground and the truck just kept moving. The scotches just cutting two trenches, then I applied the brakes both drum and parking to check what was happening under tension.

What was very clear is that there is a great deal of pulling power available, two that the light chains and cable I’d used on the scotches were exceeding their useable strength (near breaking), third that if I’m going to actually use the winch I should use only scotch cables and attachment chains that are rated to the capacity of the winch. Hence my question what is the rated capacity of the winch?

One last point unlike most US Military winches that have a shear pin which is defeated when it breaks the first time and is replaced with a harden bolt, I don’t remember seeing any designed shear pin in the CMP winch, is there one?

[Grant Bowker]

There is no provision for a shear pin as such on the setup used in the 101" wheelbase. The front of the flexible coupling is keyed to the output shaft of the transfer case and the rear of the coupling has 4 bolts similar to a universal joint (probably the same bolt pattern on the input of all versions of the winch but this hasn't been checked in the parts manuals). From memory, I think the cross section of the bolts exceeds the key but the areas are close enough that it would depend on the materials of the two parts which failed first. Neither one counts as a user freindly, field replacement item like a real shear pin should be.

[hrpearce]

Hi Phil,
I don't know the rated pull of the winch but when I got my blitz it was set up for log snigging. It's got a heavy 4" box section welded across the back of the chassis to back it up to a tree to ancre it. My Father in law said that if you used scotches and a log snaged the U bolts holding the axle on snaped.
The winch on mine was mounted above the chassis and geared down 2 to 1and even having double the engine power going to the winch the engine stalled before you reached the capasity of bolts or keys.

[Bob Carriere]

Hi Phil

Can't put my finger on it but I have references to 14000 pounds for the winch.

Now if the set up on my truck is correct the gear selection affects the speed an power of the winch..... in other words 4 speed forward when retrieving and one reverse when powering the rope off the drum.

I suspect that with the engine in high 4th gear at idle.... you would stall the 82 HP engine before shearing anything.

My expereince with winches is limited tot he Dodge M37 which conveniently blew a shear pin everytime the sucker was buried in deep mud..... installing a new pin meant digging a hole.... that filled with water/mud....... an laying on your back to replace the pin. Being ingenious and stupid we replaced our soft pins made of cheap 4 inch nails with concrete nails..... voila!!!!

When skidding heavy large dead elms the weigth of the tree trunk would pull the Dodge forward even with all four wheels locked.... so I would let it roll until I could rest the front bumper on a suitable stump..... push the gas..... and the screw drive held by 4 bolts on the face of the winch where the drive shaft would go in...... actually sheared and pulled itself out of the winch bending the small drive haft...... a visit to the junk yard for the parts set me back $350 for part of the truck I had purchased for $700...... was more carefull after that.

I am sure that nay heavy winching would have included tying the front of the truck's D rings onto something of substance. You are correct in making sure the end chain, hook, ect. is on par to the full potential of the winch.

When working with the Dodge we very seldomed used any engine speed above idle and still managed to pull other civilian 4x4 Blazers, etc. without any hesitation.

I would suggest getting/using a surplus deuce winch chains set for the CMP as they are probably readily available in the states.

How much cable could you safely wind up on the winch drum...?

Bob

[Keith Orpin]

Guys,
I've just been though my reference books and various manuals, and the plot thickens !
If you reference the early manuals, (and to be honest there is very little mentioned) they suggest 125ft of 5/8" cable should be used. However, if you refer to the MBC2 manual, it states that 125ft of 11/16" cable should be used, giving a figure of 14500 lbs as the winch capacity, little wonder Phil that your C60 was being dragged backwards !
Like Bob, I thought I had seen reference to 14000 lbs somewhere else, but so far this is the only evidence I have found.
As for a shear pin, I can find no mention of one, in any of the parts books or manuals, nor do I remember finding one when I rebuilt my Chevy.
Keep looking guys
Regards
Keith

[Phil Waterman]

Hi Keith and Everybody

You are correct in that the manual calls for 11/16th cable but as that is not readily available, I went with 5/8ths whats a 1/16th among friends.

Where did you find the figure of 14,500 lbs this is what I have not been able to find.

My reasons for asking these questions is that I know how much energy can be stored in a steel cable. Does anybody have a strength figure for 1941 11/16th cable as compared to modern cable?

Not with the winch but in the past I have seen what happens when you start loading steel cables near to breaking. I've shared the picture below the result of trying to pull a 4,000lb truck out of a snow bank with a 11,000 lb CMP the with a tow cable rated at 6000 lbs math just doesn't work, but the cable didn't break.

I'm really trying to figure out how to load limit the winch and attachments to something less than breaking strength.

The Ice Storm of 2009 has left me with a lot of broken and dieing trees that I want to snake out with out cutting truck sized holes around the house. Also I don't want to end up wearing a chunk of cable, or chain.

From the load in the truck you can see what I'm up to.