People think pulleys increase pulling power.

[MOguy]

MOguy, you are correct in that you say you do not understand pulleys. The pulley attached to the tree is giving a 2:1 mechanical advantage with the line coming from the winch and back to the vehicle. It would be a change of direction pulley if the cable ran from the winch through the pulley and to an anchor. The key is the cable runs from the vehicle through the pulley and back to the vehicle. Just because the pulley is attached to an anchor does not make it a change of direction only pulley, it can also provide mechanical advantage.

I have operated these system at work during training. Go get a pulley on an anchor, a rope and do a pull. Pull one foot and see how far your load moves. Now ad an additional pulley to the load (or within the rigging) and do the same thing. In the first example you will see you move 1 foot and you load moves one foot. In the second you will see you move 2 foot and the load moves one.

I have a store bought game hoist. It is 3:1. I have done the same experiment with that. Try it and see how things work out.

 

[Joe917]

I have operated these system at work during training. Go get a pulley on an anchor, a rope and do a pull. Pull one foot and see how far your load moves. Now ad an additional pulley to the load (or within the rigging) and do the same thing. In the first example you will see you move 1 foot and you load moves one foot. In the second you will see you move 2 foot and the load moves one.

I have a store bought game hoist. It is 3:1. I have done the same experiment with that. Try it and see how things work out.

You are missing the difference. You are comparing two different things. Instead of walking back from the pulley to pull a load towards it you should be sitting on the load pulling yourself and the load towards the pulley. The vehicle is the load and doing the pulling.
Think about pulling yourself up a rope. Each one foot pull lifts you a foot. Now put a pulley at the ceiling and run the rope from you up and back down. Now when you pull down 1 foot of rope you will go up 6 inches. 2:1

 

[ducktapeguy]

I think there’s a lot of confusion here. Load and anchor can be used interchangeably depending on what’s being pulled. If your dragging a log or winching attached to a tree, it’s the same thing because the two are moving relative to each other. In one case the Jeep is the load, in the other its the anchor.

BTW, the picture is correct in all cases

 

[MOguy]

You are missing the difference. You are comparing two different things. Instead of walking back from the pulley to pull a load towards it you should be sitting on the load pulling yourself and the load towards the pulley. The vehicle is the load and doing the pulling.
Think about pulling yourself up a rope. Each one foot pull lifts you a foot. Now put a pulley at the ceiling and run the rope from you up and back down. Now when you pull down 1 foot of rope you will go up 6 inches. 2:1

Like this video, but even then doesn't there have to an anchor. In the illustration is the tree not the anchor? Wouldn't the winch need to be at the tree?

Everything I have seen is with moving force outside. This pic is with the moving force inside. So I think I am wrong here. I have no issue being wrong, esp if I learn something. I am going to try to do this later today.

 

[Joe917]

The winch at the tree going to a pulley on the Jeep and running back to an anchor on the tree is exactly the same as a winch on the Jeep to a pulley on the tree run back to the Jeep.
Rigged correctly a single pulley can give mechanical advantage. Hope that helped.

 

[MOguy]

Seeing is believing Below are pics. My Jeep moved one foot, I used 1 foot of cable. 1:1, no mechanical advantage. That is not my vehicle or picture in my avatar.
https://m.facebook.com/story.php?story_fbid=2029614787053536&id=100000151022825

https://m.facebook.com/story.php?story_fbid=2029615047053510&id=100000151022825

https://m.facebook.com/story.php?story_fbid=2029614360386912&id=100000151022825
https://m.facebook.com/story.php?story_fbid=2029615607053454&id=100000151022825

https://m.facebook.com/story.php?story_fbid=2029620643719617&id=100000151022825

 

[DaveInDenver]

 

[MOguy]

View attachment 440219

I was beginning to believe until I did my experiment

 

[DaveInDenver]

That is just a screen grab from the Army Field Manual FM 20-22, Vehicle Recovery Operations. It's perhaps not authoritative as such but does serve to offer standard terms and explain fall line, return line and dead line and where the force is and isn't in sheave rigging.

https://www.steelsoldiers.com/upload/misc/FM20-22.pdf

 

[Joe917]

My last post on this.
Look at Dave in Denver's attachment, Second from top, 2:1.
The tree would be where the Load is on the right.
The Jeep would be on the left with the hook attached to the Jeep and the winch pulling the line.
Your pictures of your experiment don't work.

 

[MOguy]

I did it in the real world and provided pictures. Do your own experiments and post your results

 

[Kyle Kelso]

You guys are missing the point here. MOguy has done his experiment and proved he is right, thereby disproving fundamental physics. We should be honored to be discussing the upcoming physics curriculum changes here.

Sent from my LG-H873 using Tapatalk

 

[Kmrtnsn]

I can't wait for someone to show him that the rope between pulleys is no different that different size gears meshing and how transmissions work.............

 

[camp4x4]

Force upon the load will increase at the expense of increased time. Power remains the same.
For example, A winchrope doubled back to your Jeep doubles its overal pulling force. But also doubles length of winding back in, thus doubling time.
Power remains the same.

That makes sense. Thx!

 

[MOguy]

I really don't care if I am wrong or right, I just want to know. After watching the video I thought I was wrong. After setting it up and doing it I saw something else.

I am encouraging anybody here to set it up for themselves and post the results. I will take you less than 10 minutes.

I do believe you can increase mechanical advantage by have the pulling force in the system but not with using two lines. Show me I am wrong.