OK to use chains?

Like Greg said, the key thing is the number of attachments to the object being pulled, which is like the number of "pulling points."
If you carry a three-handled jerry can by the middle handle, you're holding up all the weight. But if you and someone else each hold one of the handles, the load is split between you. Or if you use two hands to hold two handles, each hand holds half the weight.
Chuck
 
I stand corrected. I didnt read the article carefully enough apparently. I somehow missed the single pulley and looked at the double pulley, which decreases tension by 50%. That's where I got that from. my fault! and no i wouldnt use chains :Rockon:
 
Deuce 40s said:
I stand corrected. I didnt read the article carefully enough apparently. I somehow missed the single pulley and looked at the double pulley, which decreases tension by 50%. That's where I got that from. my fault! and no i wouldnt use chains :Rockon:
Click to expand...


no problem....

the Chapel Hill part explains it all...:lol: :lol:

Greg
 
Jeez I didn't mean to start something else, I just had a feeling some folks didn't know the difference, I have to take a recertification every year on confine space rescue, you would be stupid founded to what you can do with pullies. Ie. Ratio's an change of direction, you could vertually lift your jeep with one hand given enough pullies.
 
OK maybe I am being dense here but I hope there is someone smart enough and with enough time to explain this.

As I see it, simply running a winch cable to a snatch block and back to the vehicle is the single pulley argument in the linkd article.

In order to get the multiplicative value it would seem that you would need a pulley mounted to the stuck vehicle (the weight in the diagram) and a cable running through it to a tree or other anchor and then to another pulley attachment point then a separate pull source...

Am I missing something?

When using a winch in the past I have always used 2 "pulleys" when overloaded. 1 tree saver"ed" to a anchor, 1 through a custome shackle mount and then attach the winch to a 3rd point...

The article seems to clearly support my experince, but everyone's interpratation does not, so I will ask again, what am I missing?
 
ShyHiK5 said:
Am I missing something?

When using a winch in the past i have always used 2 "pulleys" when overloaded. 1 tree saver"ed" to a anchor, 1 through a custome rshackle mount and then attach th inch to a 3rd point...

The article seems to clearly support my experince, but everyone's interpratation does not, so I will ask again, what am I missing?
Click to expand...


your explanation is also how it was explained to me in person the other day from somebody that "studied" that type of stuff in college...

the single pulley makes no difference, regardless of where it's attached...

Greg
 
And before anyone posts that itis because it is hooked back to the vehicle all the "pulling" is still being done by the winch at the drum...

Unless someone can explain otherwise I will continue to spool out as much cable as possible and use 2 pulleys when necessary
 
When you hook the winch back to the vehicle, you are using the pulley pretty much as a second winch because you have two straight-line pulls, and the vehicle is moving closer to both pulling points. If it were simply attached to another tree, it would only be a single line pull since the vehicle is only going to move closer to one of the points i.e. the snatch block.

The only real way I know to explain it is to get you out in the garage, or sturdy tree branch, or even a swing set (for this case we'll use the garage) with your snatch block, a rope, and a rafter beam.
1) Tie the rope straight to the rafter, and pull yourself up the rope. Pretty tough, eh?

2) Now, attach the snatch block to the rafter, run the rope through it, and tie the rope to another rafter or something sturdy like your truck. Pull yourself up again. Just as hard, right?

3) With the rope still running through the snatch block, untie it from whatever you had it tied to and tie it directly to yourself. With the loose end, pull yourself up. It was a lot easier than before! This is because you are shortening the distance between two points using one line, and each pulling point (yourself AND the snatch block) is doing equal work even though only "one" of you is actually working.
 
what it all boils down to is the work that needs to be accomplished. work is equal to force times distance over which it is applied. the amount of linear force that can be applied by your winch is a limited amount. the amount of work that needs to be done (moving your vehicle from point A to point B requires an exact amount of work to be done to the vehicle) the force is also a set amount that lets just say cannot be changed. the variable we have left to work with is distance. by using the snatch block a.k.a pulley lets say we cut the distance your vehicle will move over a given period of time from 10 ft to 5 ft. this means the distance has been reduced by half and the amount of work that has been done has also been cut in half, but the force being applied has remained the same. so by reducing the distance and work components of the equation you have in effect increased the force component of the equation even though it's actual value has remained constant.
 
i also meant to mention that yes, using a single snatch block and hooking back to the vehicle will slow speed down. if the cable were attached to another stationary object it would make no difference at all because the cable would not be moving over the snatch block (the pulley wheel would not be moving). with the cable attached back to the vehicle the cable will be moving. for the vehicle to move forward 1ft, the cable will move one foot towards the pulley on one side and 1 ft towards the vehicle on the other side, so while the vehicle has moved 1 foot forward you have actually pulled
2 ft of cable. it maybe easier to look at it from the start and end points. if you pull straight cable and hook to a tree saver lets say you pull 50 ft of cable from where you're stuck and pull vehicle 50 ft till you run out of cable. the winch pullled 50 ft of cable and vehicle moved 50 ft. now lets say you use single snatch block and hook cable back to vehicle. now instead of 50 ft of cable you will have to pull 100ft of cable. this time you also pull till you run out of cable. vehicle still traveled 50 ft but winch pulled 100 ft of cable.
 
When you run the lead to a point an back to the pulling source you compound the pull, The wench is pulling the vehicle to the attached point compounded twice hence 1000lbs turns in to 500 pounds (2 to 1), if you then run from the vehicle back again to the anchor source you have 3 to 1, that same 1000lbs will be 333lbs. If you run back to the vehicle again 4 to 1 the weight now is 250lbs, thats how you see these cranes picking up 20 to 30 tons at shipping docks work, the next time you see one, look @ how many times the cable loops back to itself on pulley's.
 
As far as I am concerned, all have their place. A piece of chain to keep the axle from drooping to aid in jacking it works good. I would rather use a chain to tow someone back out of the woods than a strap, simply because the strap gets damaged when slack occurs. taking a tie wrap to keep the chain hooks from coming unattached works good too. A piece of chain around someone that has no tow points, and hooking a strap would cut it. is my way.
To yank someone, yes I prefer a strap, but have not done that too often, I use my winch.
now as for doubling a winch cable..... Make sure your cable, and hook are designed for it. Some hooks can be straightened out when doubling. Ask me how I know. Also, most cables have only one crimped sleeve where it makes a loop for the hook. All things to consider. IMO a clevis is better than using a hook any day.
 
Back
Top