North Country
Gold Member
Your linked page doesn't have a drawing that represents the stuck tractor. The above described scenario will get you 2:1 on your pull force.
Stuck tractor - ways to lift?
- Thread starter MNBobcat
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Your linked page doesn't have a drawing that represents the stuck tractor. The above described scenario will get you 2:1 on your pull force.
Mechanical advantage using pulleys with various rigging. The diagram is for lifting, with the hook being the moving load.
"Gun tackle" does not require the top pulley as part of the mechanical advantage. It only reverses the direction of the pull to make it more convenient for lifting.
"Gun tackle" does not require the top pulley as part of the mechanical advantage. It only reverses the direction of the pull to make it more convenient for lifting.
The easiest way to understand the pulley thing is: Disregarding friction, the force in the cable to the tree equals the force in the cable to the tow vehicle, since it is all the same cable. If you look at the single pulley, which has the cable running though it to the tree and tow vehicle on one side, and a single chain to the stuck vehicle on the other, you will see that the force on the chain to the stuck vehicle must be double that to the tow vehicle. A big advantage of this method over a come-a-long or winch is you can use the momentum of your tow vehicle (which should be on dry ground) to really nudge the stuck vehicle along. Just remember that the force is much higher (2x) in the single connection between the stuck vehicle and the pulley. I have broken a few mighty strong looking chains compared to the 1/2" cable that I usually use. Another advantage here is that the tow vehicle can be kept safely out of the line of recoil when and if that chain to the stuck vehicle snaps. The operator of the stuck vehicle is at risk however and I prefer to leave that vehicle unocupied with the transmission in neutral.
tree
pulley ---- stuck vehicle
tow vehicle
tree
pulley ---- stuck vehicle
tow vehicle
This diagram...
...is not really accurate. The principle is there, but the angles of the lines of force decrease the sum of effective force on the load.
The easiest way to understand the pulley thing is: Disregarding friction, the force in the cable to the tree equals the force in the cable to the tow vehicle, since it is all the same cable. If you look at the single pulley, which has the cable running though it to the tree and tow vehicle on one side, and a single chain to the stuck vehicle on the other, you will see that the force on the chain to the stuck vehicle must be double that on the cable to the tow vehicle. A big advantage of this method over a come-a-long or winch is you can use the momentum of your tow vehicle (which should be on dry ground) to really nudge the stuck vehicle along. Just remember that the force is much higher (2x) in the single connection between the stuck vehicle and the pulley. I have broken a few mighty strong looking chains compared to the 1/2" cable that I usually use. Another advantage here is that the tow vehicle can be kept safely out of the line of recoil when and if that chain to the stuck vehicle snaps. The operator of the stuck vehicle is at risk however and I prefer to leave that vehicle unoccupied with the transmission in neutral.
Stargazer
Gold Member
Hi Why not use the skidsteer to dig behind or if only forward the rear wheels then planks brush what not to get out agree use the skid to move mower out of way. again depends on weight of mower/ will skidsteer get stuck. Glad bucket lifted rear enough to get planks in.
pat32rf
Veteran Member
I assume we are talking about a skidsteer on tracks? I've never used one on wheels that had enough clearance or traction to do much....
I've found that it can be a lot easier to chain one timber to the outside of each wheel, like a big paddle, than one accross them both.
When lifting from the rear, never try to lift from the 3pth ARMS. The linkage tends to buckle and that gets REAL expensive....(seen it happen) Dig down to the draw bar if you must lift this way, but even so, most drawbars are not designed to withstand an UPWARDS force....
I prefer a winch and enough pulleys to do the job....
I've found that it can be a lot easier to chain one timber to the outside of each wheel, like a big paddle, than one accross them both.
When lifting from the rear, never try to lift from the 3pth ARMS. The linkage tends to buckle and that gets REAL expensive....(seen it happen) Dig down to the draw bar if you must lift this way, but even so, most drawbars are not designed to withstand an UPWARDS force....
I prefer a winch and enough pulleys to do the job....
TripleR
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Had it been a John Deere tho it would have bent or broken the axles.
larry
I "think" the height of the big Case helped as it was pulling in an upward angle. that or we were just lucky. Of course Vincent has been doing this sort of thing for 60-70 years too.
Gator6x4
Super Star Member
I think the time has come to call a WRECKER. A wrecker can hook to the draw bar and the tractor can be pulled from the field. No damage to the tractor, less damage to the field. The area where the tractor is stuck will harden and be like cement when it does dry out. Mother Earth does not like to be churned, driven on, plowed or stirred when wet.
RoyJackson
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If you read post #17 (of this thread), you'll know the OP got his tractor out...so all this discussion of pulleys, leverage and mechanical advantage...or a wrecker...is moot for this thread.
RickB
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- Just a Scag
Roy, you must have forgotten that you are on TBN; the cyber-capital of moot.
sldva00
Silver Member
Sorry Roy, moot or not, I think this might clear things up a little.
Using a single pulley all depends on where the pulley is placed.
1. If pulley is placed on tree, then yes, it will take the same amount of force to move the tractor. The tree will experience twice the amount of force, but the tractor and towing vehicle will experience the same amount of force. If tractor weighs 2000 lb, then the tree would exert 4,000 lb of force while the tractor and towing vehicle would exert 2000 lb.
2. If pulley is placed on tractor, then it will take half the amount of force to move it. The tractor will exert its 2000lb force, but the tree and towing vehicle would only need to exert 1000 lb of force.
The force at the pulley is divided into the lines coming out of it.
Using a single pulley all depends on where the pulley is placed.
1. If pulley is placed on tree, then yes, it will take the same amount of force to move the tractor. The tree will experience twice the amount of force, but the tractor and towing vehicle will experience the same amount of force. If tractor weighs 2000 lb, then the tree would exert 4,000 lb of force while the tractor and towing vehicle would exert 2000 lb.
2. If pulley is placed on tractor, then it will take half the amount of force to move it. The tractor will exert its 2000lb force, but the tree and towing vehicle would only need to exert 1000 lb of force.
The force at the pulley is divided into the lines coming out of it.
Attachments
RoyJackson
Rest in Peace
- Joined
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- Messages
- 24,646
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- Bethel, Vermont
- Tractor
- John Deere 4052R Cab,, Deere 855D UTV, Z920A Zero Turn Mower and assorted implements
Nothing to be sorry about...info is good if anyone gets stuck and has access to the equipment and fixed objects close enough to use.
kday64
Gold Member
The Mechanical Advantage (MA) for simple pulleys equals the number of times the rope changes direction.
Simple pulleys are those where internal friction is assumed small enough to be ignored and the cable is assumed to be non-elastic. Additionally there can only be one mounting point for each side of the pulley system.
Case #1: 1 pulley -> MA = 1 -> direction of force reversed. -> force pulled equals force applied at both mounting points -> tension in line equals force pulled on rope.
Case #2: 2 pulleys -> MA = 2 -> force exerted on pulley mounting points equals twice the tension in the line.
Remember MA has it's disadvantages. If the MA of a simple pulley system is 10 and you need to pull an object 20 feet, you will need 200 feet of rope. However the force exerted on the mounting equals 10 times the tension of the line.
Multiple mounting points can only lesson a systems MA.
~Kevin
Simple pulleys are those where internal friction is assumed small enough to be ignored and the cable is assumed to be non-elastic. Additionally there can only be one mounting point for each side of the pulley system.
Case #1: 1 pulley -> MA = 1 -> direction of force reversed. -> force pulled equals force applied at both mounting points -> tension in line equals force pulled on rope.
Case #2: 2 pulleys -> MA = 2 -> force exerted on pulley mounting points equals twice the tension in the line.
Remember MA has it's disadvantages. If the MA of a simple pulley system is 10 and you need to pull an object 20 feet, you will need 200 feet of rope. However the force exerted on the mounting equals 10 times the tension of the line.
Multiple mounting points can only lesson a systems MA.
~Kevin
chopped
Veteran Member
There should be a lighthouse on Moot Point so it can be avoided.
Bruce
GOOD ONE>>:thumbsup::thumbsup:
pat32rf
Veteran Member
The MA fun starts when you add ANOTHER piece of cable and pulley to the equation. Then you get 4000lb of force from one 1000lb winch and two pulleys..
