Pulley question
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This image is the pulley arrangement of a Precor C024ES machine. Image I think the arrangement produces a 2:1 mechanical advantage, but empirical testing is causing me to doubt the exact number.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
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This image is the pulley arrangement of a Precor C024ES machine. Image I think the arrangement produces a 2:1 mechanical advantage, but empirical testing is causing me to doubt the exact number.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
That arrangement gives no mechanical advantage. It just redirects the direction of the force. Pulleys with mechanical advantage are an assembly where one of the wheels is suspended from the other.
"The difference between genius and stupidity is that genius has its limits." - Albert Einstein
"If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010
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This image is the pulley arrangement of a Precor C024ES machine. Image I think the arrangement produces a 2:1 mechanical advantage, but empirical testing is causing me to doubt the exact number.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
The greatest advantage is gained by having someone else perform the work.
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That arrangement gives no mechanical advantage. It just redirects the direction of the force. Pulleys with mechanical advantage are an assembly where one of the wheels is suspended from the other.
"The difference between genius and stupidity is that genius has its limits." - Albert Einstein
"If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010
Since the top pulley moves, there is a definite advantage, I just don't know by how much.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
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Since the top pulley moves, there is a definite advantage, I just don't know by how much.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
Pulley - Wikipedia[^] My assumption from the diagram is that both wheels are held fixed. Although the normal advantage is usually done with a "block and tackle" configuration, as you can see in the wikipedia image, they may be separated. In the normal Block-and-Tackle configuration, the advantage comes from the lower pulley doing the lifting when it's ropes are shortened and the amount of shortening is proportion to the number of wraps around the pair (usually - 1 for the first wrap over the top wheel). You pull 1m and it shortens the configuration by 1/n m, lifting the weight with a mechanical advantage of n. If a wheels can move, aside from turning, not evident from the image, it can possibly be a 2:1.
"The difference between genius and stupidity is that genius has its limits." - Albert Einstein
"If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010
-
This image is the pulley arrangement of a Precor C024ES machine. Image I think the arrangement produces a 2:1 mechanical advantage, but empirical testing is causing me to doubt the exact number.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
A bit more than 2:1 as the anchoring point of the cable on the upper right also moves up relative to the lower pulley, but not as much as the upper pulley.
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Pulley - Wikipedia[^] My assumption from the diagram is that both wheels are held fixed. Although the normal advantage is usually done with a "block and tackle" configuration, as you can see in the wikipedia image, they may be separated. In the normal Block-and-Tackle configuration, the advantage comes from the lower pulley doing the lifting when it's ropes are shortened and the amount of shortening is proportion to the number of wraps around the pair (usually - 1 for the first wrap over the top wheel). You pull 1m and it shortens the configuration by 1/n m, lifting the weight with a mechanical advantage of n. If a wheels can move, aside from turning, not evident from the image, it can possibly be a 2:1.
"The difference between genius and stupidity is that genius has its limits." - Albert Einstein
"If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010
W∴ Balboos, GHB wrote:
My assumption from the diagram is that both wheels are held fixed.
Yes, but as I noted, the top pulley moves up & down with the lever.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
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W∴ Balboos, GHB wrote:
My assumption from the diagram is that both wheels are held fixed.
Yes, but as I noted, the top pulley moves up & down with the lever.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
David Crow wrote:
with the lever.
Then it is, in pulley terms, fixed. On the other hand, if the rope is held fast, the mechanical advantage of the lever comes into play.
"The difference between genius and stupidity is that genius has its limits." - Albert Einstein
"If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010
-
This image is the pulley arrangement of a Precor C024ES machine. Image I think the arrangement produces a 2:1 mechanical advantage, but empirical testing is causing me to doubt the exact number.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
Not 2:1. The upper wheel and the anchor point do not move upward at the same distance. The difference is because they are along the lever which means the lift will be a function of the distance from the fulcrum and the angle through which the lever moves. That is just the pulleys alone. You also have to take the total length of the lever into account to get the total mechanical advantage.
If you can't laugh at yourself - ask me and I will do it for you.
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W∴ Balboos, GHB wrote:
My assumption from the diagram is that both wheels are held fixed.
Yes, but as I noted, the top pulley moves up & down with the lever.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
As W∴ Balboos, GHB says, it isn't a pulley problem. It is a moment arm problem. As I attempt to show in this [crappy force diagram](https://www.codeproject.com/Uploads/Membership/Uploads/1921380/junk.jpg), if you are lifting a 100 lb weight, the wheel closest to the lifter will be pulling down on the top bar with a force of 200 lb at the wheel connection point, and the pin location will be pulling down on the top bar with a force of 100 lb. That is an incomplete force diagram, but may get you started thinking about the physics.
The Science of King David's Court | Object Oriented Programming with C++
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This image is the pulley arrangement of a Precor C024ES machine. Image I think the arrangement produces a 2:1 mechanical advantage, but empirical testing is causing me to doubt the exact number.
"One man's wage rise is another man's price increase." - Harold Wilson
"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons
"You can easily judge the character of a man by how he treats those who can do nothing for him." - James D. Miles
OK, I'll have a stab (retired aero engineer, if I get this horribly wrong my excuse is that I have been going down the pub for the last 10 years): assuming some approximate dimensions for simplicity
location: Lift pt pulley 2 pulley 1 cable att pivot
distance from pivot: 1 3/4 1/2 1/4 0
fixed/moves: m m f m fIf the lifting lever rises by 1 unit, then the weight rises by the sum of the cable extensions: * cable att: cable extends by 1/4 * p1 has no effect as it is fixed * p2 cable extends 3/4 * 2 = 1.5 (this is a pulley effect - cable must extend on both sides of pulley) So total cable lift is 1.75, ie force at lift point = 1.75 * weight.
