Cable pulleys are the original steroid. They make us stronger with little to no exercise required.
Science is strong, and pulleys are some of the earliest examples of this in action. With cable pulleys, ancient buildings were built, elevators rise like they’re levitating, and our world turns.
Let’s take a closer look at some cable pulley facts.
Pulleys Are Levers
Think about a bike or a seesaw.
As you shift into lower gears or move up and down a seesaw, it becomes easier to pedal, and the seesaw moves more.
In these situations, you’re creating more leverage that you can use to lift heavier weights. We know, clear as mud!
In the same way, it’s impossible to lift a hay bale into a barn by strapping a rope to it and pulling upward with your strength alone. However, if you use a small pulley assembly, a hay bale is easy to lift.
This is because the pulley magnifies the force you exert on the rope wrapped around it.
A pulley can do this because it effectively spreads the energy you exert over a distance that’s larger than the original distance without changing the length of the rope. This decreases the force you need by the same factor.
So, what do cable pulleys do? They help us lift heavy things more easily.
How Pulley Count Effects Cable Pulleys
With pulleys, more is merrier. If one pulley makes lifting more manageable, then a second pulley will make the first pulley’s job more manageable, and so on.
Here is what you can expect to experience as you add more cable pulleys to your assembly.
One Pulley
A single cable pulley won’t do much to increase the leverage you have, but it does help by reversing the direction of the force you need to use.
So, if you want to lift a single pound, you’ll have to apply a pound of force to the other side of the road. The benefit of a single pulley is all in the logistics. You can now add weights to the side you pull on to use gravity to lighten your load.
Two Pulleys
Two wheels are where things start to get cool. If one wheel is walking, using two wheels is like riding a motorcycle.
If you’re lifting the weight from the one-wheel-example, you will only need half a pound of force to lift the weight and equal distance. Why is this?
Well, now you’re effectively using two ropes, each exerting a pound of pressure to raise only one one-pound object. A little mind-bending, but true. This phenomenon is called “mechanical advantage.”
Mechanical advantage measures how much a machine multiplies the force you exert. The more mechanical advantages you have, the better off you are.
The only catch is that an increase in mechanical advantage will also increase the distance you have to carry the object you’re lifting. To figure out the mechanical advantage, use this equation.
The distance pulled / The distance moved = Mechanical advantage
Think back to the bike example. As you go into lower gears, you can move up hills with less effort, but you move at a slower overall pace.
Four Pulleys
We’re hopping into a jeep now, ready to tackle the stickiest mud and steepest mountainsides.
If you’ve been paying attention to the running theme in this breakdown, then you know how four wheels will affect the force you need to lift a pound of stuff. If you have four cable pulleys lined up, then they will allow you to quarter the energy you need to use.
You can now use 1/4 pound to lift a pound of material, but you’ll be moving a 1/4 the pace.
Using four pulleys is where the question “how much mechanical advantage is too much?” comes into play. It’s excellent that lifting has gotten so much easier, but will an additional cable pulley slow you down too much to be feasible?
Adding pulleys is always a balancing act between mechanical advantage and efficiency. If you need to lift something extraordinarily heavy, then add as many pulleys as possible. To make your life easier, maybe stop at two or four pulleys.
Is There a Downside to Pulleys?
Pulleys are some of the best inventions ever. With the discovery of cable pulley information, civilization was able to industrialize, construct mighty monuments, and make life more comfortable in general.
Unfortunately, pulleys have limitations. Everything still must obey the laws of physics. We know, it’s a sad day.
A pulley doesn’t create energy; it spreads out the load that power applies to at any given time. So, you will always have to do the same amount of work.
It’s not like you can hook up a 100 pulley system that will pull a five-hundred-pound weight up if you apply five pounds of force. Instead, you’ll be applying five pounds of pressure for one hundred times as long. A
dditionally, pulleys have friction. So, some of the energy you use to lift a weight is lost to the nether, never to be used by you again.
All of this means that pulleys call for balance and moderation. Like we stated before, experiment with your pulley setups until you find the perfect balance of mechanical advantage and convenience.
Pulley Yourselves up by the Bootstraps and Start Experimenting!
You could do a lot of fiddly calculations to figure out exactly how much adding a pulley will help you. However, pulleys are a rare form of tech that you can experiment with easily.
(Unless you’re a working engineer. Your job probably depends on those fiddly calculations, definitely don’t skip them.)
So, grab some different pulley assemblies and set aside a day to test them out. Put up a double pulley and try that, then swap out for a four pulley system and try that out. Finish off by adding more pulleys if you need them or choosing the cable pulleys with the best compromise between mechanical advantage and convenience.
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