People think pulleys increase pulling power.

#61
Yes, the pulley attached to the vehicle is moving along with the vehicle if that is what you are asking. That doesn't change the fact that you have a 3:1 mechanical advantage in the previous picture.

I'll try another video for you but honestly, at this point I don't know how to explain this to you. if this doesn't work then please go to your local high school, tech school or college and ask to speak to one of the physics instructors.
So you then understand that in order to gain mechanical advantage there has to be a pulley moving in the direction of the load within the system.

The video posted has two pulleys and it shows a 2 to 1 mechanical advantage he even explains that the fixed pulley is only for change of Direction the pulley that give this mechanical advantage is the pulley on the load not the one that's fixed.
 

robert

Expedition Leader
#62
Actually the amount of cable on the drum will affect the pull but in a different manner
The amount of cable on the spool increases/decreases working load depending on amount of line on the spool. Your winch is rated on the first wrap of the spool but obviously you can't safely pull on that wrap, you need a safety factor. Each successive wrap decreases your pulling power but that doesn't change your mechanical advantage, it only explains why you may need to increase your mechanical advantage i.e. add more pulleys into the system to make up for lost power- which will obviously require more line. This is why most recommendations are to go at least 1.5x your vehicle weight.
 

robert

Expedition Leader
#64
Watch and listen to Robert's video in post number 60.
OK, I should have looked at his setup more closely- what he is doing is redirecting the force (his hand) as if using a second vehicle to extract the stuck vehicle (the weight he is moving). Just ignore it and watch the other videos.
 
#65
OK, I should have looked at his setup more closely- what he is doing is redirecting the force (his hand) as if using a second vehicle to extract the stuck vehicle (the weight he is moving). Just ignore it and watch the other videos.

We can't ignore this, its correct. This is where we starts. The key to Mechanical advantages of having a pulley moving within the system in the direction of the load. Once people understand this we can move further.
 
#68
the pulley doesnt need to move, the load is moving towards the pulley, so relativly speaking, the pulley is thus moving towards the load.


the distance between the load and anchor are decreasing. this happens with any straight line pull.
however when you had a pulley and hook the winch back to the anchor, its the same as having two pullies move towards each other. as you need twice the winch line, so when its looped back the vehicle, if you spool in 6 inches of line, its technically 3 inches of line from each side the pulley, therefore 2:1,

when its a straight pull, 6 inches wound in, is 6 inches straight.
 
#69
1 foot mark for tire
View attachment 440331





2 foot mark for cable
View attachment 440332

cable from winch back to Jeep
View attachment 440333


cable moved on foot
View attachment 440334
Tire moved one foot
View attachment 440335



cable moved 1 foot, tire moved one foot 1:1 mechanical advantage.
I think you’re measuring the wrong side of the pulley. Hard to tell the overall setup from the pictures, but if you’re measuring from the mark on the cable to the pulley, you need to be measuring from the winch side of the cable. The pulley moved one foot, the actual cable moved two.
 
#71
I think you’re measuring the wrong side of the pulley. Hard to tell the overall setup from the pictures, but if you’re measuring from the mark on the cable to the pulley, you need to be measuring from the winch side of the cable. The pulley moved one foot, the actual cable moved two.
The length of the cable does not change regardless of where you measure the cable. if you started a 30-foot cable you'll end with a 30-foot cable. If It Moves one foot over a pulley on one side it'll move one foot over the pulley on the other side the relationship or the where you gain mechanical advantage is how those two pulleys close together or separate way from each other that's the variable that's where things change.
 
#73
the pulley doesnt need to move, the load is moving towards the pulley, so relativly speaking, the pulley is thus moving towards the load.


the distance between the load and anchor are decreasing. this happens with any straight line pull.
however when you had a pulley and hook the winch back to the anchor, its the same as having two pullies move towards each other. as you need twice the winch line, so when its looped back the vehicle, if you spool in 6 inches of line, its technically 3 inches of line from each side the pulley, therefore 2:1,

when its a straight pull, 6 inches wound in, is 6 inches straight.
Test it
 

DaveInDenver

Expedition Leader
#74
Beautiful graphic showing fall line, return line and dead line. You gain advantage in this scenario because the left side is moving twice the amount of rope, both sides will get shorter and in effect the sheave is a second winch that's a reflection of the source.
I feel like this thread doesn't have enough graphics of trucks and pulleys and trees and lines... He's my contribution (though not my image)... this was the point I was trying to clarify way back on page 1:

View attachment 440428
 
#75
If I were 10 feet from a tree and I ran a cable to a tree with a pulley and back to the jeep I would have 10 feet of cable to the tree and 10 feet back to the jeep. If i pulled my Jeep 5 feet forward I would have five feet of cable to the tree and five foot of cable from the tree to the jeep. The cable moved the same on each side of the pulley. I pulled 10 feet or cable and moved so 5 feet so 2:1. If the cable is run back to the load wincing yourself you gain advantage. Wincing others you need the third pulley. Pic is right.

I did measure wrong but not on the wrong side, I needed to measure both sides.

A. True
B. False.

Thanks heading down this bumpy road with me but I was not trolling. everything changes when you're pulling force is within the system.
 
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