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Winch/snatch block question

R

rrman61

Well-known Member
About to buy a 12,000 pound winch.a snatch block will double the capacity of the winch this I understand.what I need to know is do I need a 24,000 plus capacity snatch block?and just in case I ever need to what capacity double snatch blocks to triple the capacity?am I right is an electric winch rated for a rolling load not a 12000 pound static load?
 
Yes the snatch block should match or be heavier then the load. Or in other words if you can pull 24,000lbs it should be rated for that or more not less
 
The rating of the fixtures you use must comply with the loads applied. Thus the last connection to the load needs to comply with the force it applies to the load. 2X the tension on the cable in the case of one snatch block. 3X if the cable is passing through 2wo blocks and returned to the first, Etc. Careful analysis of the product description is always needed. Jim
 

Is you had a pull scale between winch and stationary object, the winch should not stall out until after the scale shows 12,000lbs.

On the first layer of cable on the drum only.
Pull strength goes down for each layer of cable.
 
Double07 is correct - the pulling force goes down as more layers are spooled onto the drum. Winches are rated on the first layer of cable, directly against the drum. Each layer added to this effectively "gears up" the system so the pulling force goes down and the line speed goes up. It's just like putting taller tires on a vehicle.
 
Yep goes down due to the fact the drum gets larger in diameter as the cable winds around it so the pull power is then lower. But I think the guy who say of goes up is talking about when you use a snatch block the pull is almost double
 
Think of it like this. You have one rope end dead ended, then through the block and back to the winch. Both cables have a load of 12000 lbs on them. The load on the block and it's rigging is 24,000 lbs because it has two rope at 12k each pulling on it.
 
And if you don't have double the strength you may have a death machine when it breaks and comes flying after you.
George
 
If you attach the winch to your truck or connected trailer to load something onto the trailer you are pulling against the parking paul in the transmission and could damage the transmission, have someone sit in the truck with their foot hard on the brakes.
 
To figure the pull on a snatch block you count the lines going to it and use this number as a multiplying factor.
A snatch block does not always double the capacity of a winch.
Since many will disagree with that I will say it again.
A snatch block does not always double the capacity of a winch.
Sometimes a snatch block only changes the direction of pull.
The angle between the 2 lines also needs to be figured in the calculation.

Here is a simple calculator.
This shows what is needed to move 12,000 lbs of weight.
Notice in the left picture you need a 12,000 winch and a 24,000 snatch block just to move 12,000 lbs.
But in the second picture from the left you need a 6000 lb winch and 12,000 lb snatch block to move this same 12,000 lbs.



cvphoto80331.png



So there are many calculations that go into winches; snatch blocks; and line pull force.
But for the lay person if you have a 12,000 winch you need a 24,000 lb WLL single sheve snatch block.

Also be very careful when buying a snatch block.
Lots of cheap snatch blocks are sold as "Capacity".
12 ton capacity.
Capacity equals breaking strength not WLL working load limit.
You need a snatch block with a 24,000 lb or 12 ton WLL not a 12 ton capacity.
 
Thanks guys Ill err on the side of caution and Ill put a saddle blanket or heavy coat on the cable just in case the load Im moving is only 6100 lbs but pulling it up onto a 3ft high trailer with ramps of course.
 
(quoted from post at 20:07:45 03/03/21) To figure the pull on a snatch block you count the lines going to it and use this number as a multiplying factor.
A snatch block does not always double the capacity of a winch.
Since many will disagree with that I will say it again.
A snatch block does not always double the capacity of a winch.
Sometimes a snatch block only changes the direction of pull.
The angle between the 2 lines also needs to be figured in the calculation.

Here is a simple calculator.
This shows what is needed to move 12,000 lbs of weight.
Notice in the left picture you need a 12,000 winch and a 24,000 snatch block just to move 12,000 lbs.
But in the second picture from the left you need a 6000 lb winch and 12,000 lb snatch block to move this same 12,000 lbs.



<img src="https://www.yesterdaystractors.com/cvphotos/cvphoto80331.png">


So there are many calculations that go into winches; snatch blocks; and line pull force.
But for the lay person if you have a 12,000 winch you need a 24,000 lb WLL single sheve snatch block.

Also be very careful when buying a snatch block.
Lots of cheap snatch blocks are sold as "Capacity".
12 ton capacity.
Capacity equals breaking strength not WLL working load limit.
You need a snatch block with a 24,000 lb or 12 ton WLL not a 12 ton capacity.
Click to expand...

Good chart John, I was looking for something like that. A couple of the explanations here give the impression that the winch line needs to be heavier too, but the tension on the line is reduced in a multi-sheaved set up. In the end, it still comes down to weight and friction and angle and erring to the side of caution is always best.
 
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