Question about CMP winch?

[Phil Waterman]

Well that's two conflicting answers that only deepens the mystery. First thanks to everybody for trying to find a definitive answer.

Keith you found the rating that I remembered, kind of interesting that it gives it in tons. Which leaves us with long tons 2240 lbs or short ton 2000 lbs both are used in manuals CMPs sometimes with no indication of which. So that would give us a capacity of 14.5 tons which could be 32,480 lbs or 29,000 lbs a significant variance. I suspect that this breaking strength of cable and I suspect the figure on the data plate Keith found of 7500 lbs is the working load lifting load.

The wide variance in these figures is why I asked the question in the first place, because as has been pointed out the winch system is only as strong as the weakest part. Which if and when it breaks release all the energy stored in unspooled cable which can be considerable.

Bob as to the suggestion of a electric winch, where would be the challenge in that besides as you will note in the picture I've mounted a hydraulic lifting arm on the truck already 500-1000 lbs capacity with a 1750 lbs Warn electric winch. This is very useful for loading engines, steel beams etc into the truck. (much better than my back)

Half the fun (justification) for having three trucks is using them, being a little older and wisher I hope using with out breaking or wearing a bit of winch gear.

For now I think I will go with the approach of improving all my load attachment gear, ie chains, load straps, scotch cables up to atleast 12,000 lbs to match the snatch block I have. The point raised by Grant and hrpearce about load chaining the truck down. I think I'll go with letting the holding power of the scotches and engine at high idle be the load limiters.

I'll keep you posted on what I find.

But it would really be interesting to find a real answers to the design capacity of CMP winches. Or is this another case of they designed as heavy as they could and hoped it would be strong enough to do the job in the field.

On last point the long chassis with winch doesn't use the flex joint found on the 101 wheelbase units. It has all normal drive shafts though they are a little lighter design than the regular drive shafts.

Pictures of winch work to follow.

[Barry Churcher]

Phil, I don't have the correct answer to your query but I do know that if the winches are heavily loaded the frame will twist before anything breaks. When I was working on my artillery tractor I went through three badly twisted chassis before I found a good one. The best chassis came from a truck that had spent it's life as a tow truck.
Cheers,
Barry

[Grant Bowker]

Vol 4 of the AEDB Design Record lists the capacity for the chassis winch as "The maximum pull developed by this winch is 11,000 pounds with a ratio of 6.2 to 1 in the winch drive unit."
From the same source: "125 feet of 5/8" diameter cable was normally fitted on this drum."
Yet another, different answer.......

[Lynn Eades]

Back then ,I would say your winch is rated in long tons. Short tons were used for shipping purposes.
Now Tony's going to say something profound

[Tony Smith]

Or we can try to calculate it?

The Ford Engine makes 178 ft lbs of torque. Multiply by 6.4:1 1st gear gives 1139.2 ft lbs. Multiply by the winch ratio of 6.66:1 gives 7587 ft lbs. What is the diameter of the winch drum? If we hypothetically say the layer of cable is 8 inches from the centreline if the drum (divide by .66), that gives us 11495 lbs of pull.

The Chev engine will have different torque (170 ft lbs @ 1200) and gear (7.058 to 1) figures, and the actual diameter of the drum needs to be measured, but are we in the ballpark?

[Phil Waterman]

Originally Posted by Barry Churcher

Phil, I don't have the correct answer to your query but I do know that if the winches are heavily loaded the frame will twist before anything breaks. When I was working on my artillery tractor I went through three badly twisted chassis before I found a good one. The best chassis came from a truck that had spent it's life as a tow truck.
Cheers,
Barry

Barry - You hit the nail on the head about hard use, this particular 1941 C60L had been hard used and abused. It spent part of its life building Mount Ascutney Ski Area in Vermont, from the cable reel frame on the back it was used to drag cable up the mountain. It had been rolled at one point bending the cab frame and brake peddle, the clutch housing had so many cracks in that when you tapped it with a hammer it went thud.

The winch guides all showed evidence of hard use and have actually been worn by the cable pulling across them. Given all that one of the first things I did was check all the diagonal measurements across the frame and the silly thing was straight and flat.

In parts of the world where there are multiple CMPs to choose from I'm sure that this one would have been considered a parts truck.

[Phil Waterman]

Originally Posted by Barry Churcher

Phil, I don't have the correct answer to your query but I do know that if the winches are heavily loaded the frame will twist before anything breaks. When I was working on my artillery tractor I went through three badly twisted chassis before I found a good one. The best chassis came from a truck that had spent it's life as a tow truck.
Cheers,
Barry

Barry - You hit the nail on the head about hard use, this particular 1941 C60L had been hard used and abused. It spent part of its life building Mount Ascutney Ski Area in Vermont, from the cable reel frame on the back it was used to drag cable up the mountain. It had been rolled at one point bending the cab frame and brake peddle, the clutch housing had so many cracks in that when you tapped it with a hammer it went thud.

The winch guides all showed evidence of hard use and have actually been worn by the cable pulling across them. Given all that one of the first things I did was check all the diagonal measurements across the frame and the silly thing was straight and flat.

In parts of the world where there are multiple CMPs to choose from I'm sure that this one would have been considered a parts truck.