Pulleys: Part Three
Combination Pulleys
Let’s review:
In our last lesson you built a
Fixed Pulley
(the pulley wheel is attached to the structure)
And then you built a
Movable Pulley
(the pulley wheel is attached to the LOAD, not the structure)
Today we will build another
Movable Pulley
So let’s get out your supplies…
...and prepare your LOAD
Fixed point
Fixed Pulley
Movable Pulley
Set up your pulley system just like the last lesson…..
Pull the string to lift the LOAD.
Feel how much effort it takes. You are strong, so it probably feels easy.
(Remember that the string going over the fixed pulley just makes it easier to pull on the string)
New System Set-up
Step 1- take down the pulley system from prior page
Step 2- remove the string
Step 3- attach the string to one of the clips as shown in these pictures
(the last photo shows it is wrapped around the clip an extra time for strength)
Step 4-
Loop the string up over (or through) the cabinet handle.
The handle is a Fixed Pulley
The clip with the string attached is called a
Fixed Point
Fixed Pulley
Fixed Point
Step 5- Feed the string through the second clip, from back to front
Step 6-
Loop the string up over (or through) a second cabinet handle.
Pull down on the end of the string.
How much effort does it take to raise the LOAD now?
Is it easier?
Does the Load feel lighter?
This is called a
Combination
Pulley
It uses a combination of both
Fixed and Movable
Pulleys
(Another name is a
Block and Tackle pulley)
Fixed Pulleys
Movable Pulley
Fixed Point
This Combination Pulley
is like having two friends helping you lift a load.
Each of the numbered sections of string represents a “helping hand”.
Each section of string shares the weight of the LOAD, and reduces the EFFORT needed to lift it.
1
2
3
Time to watch the rest of this video on Pulleys.
You may start from the beginning, or start from minute
2:50