How do I Make a Homemade Pulley System With a Mechanical Advantage of 10?

With three lines of rope suspending its load, this pulley has a mechanical advantage of three.

Pulleys are ingenious tools. Using simple physics principles, they let people lift and maneuver objects much heavier than they otherwise would be able to lift. The key lies in mechanical advantage. By increasing the number of rope lines suspending a weight, you decrease the amount of force needed to lift it. The cost is that you increase the distance you must pull the rope to lift the object up. A mechanical advantage of 10 means that you lift a tenth of the object's weight, but must pull the rope 10 times farther.

Things You'll Need

• 10 pulley wheels
• 2 strong axles, wide enough for 5 pulley wheels each
• Suspended beam, or other support for pulley system
• Weight
• 5 lengths of rope, four about 10 feet long, one about 100 feet long

Instructions

1. Slide five of the pulley wheels onto each axle. They should be able to freely rotate independently of each other.

2. Tie one of the axles to the suspended beam or other support using two of the ten foot lengths of rope. Tie one length of rope around each end of the axle and around part of the beam. You may use other ways of fastening the axle to the beam, but the important thing is that the pulley wheels can still turn, and the whole unit is secure and won't fall down under weight.

3. Tie the other axles to the weight using the remaining two ten foot lengths of rope. Again, methods may vary depending on the shape of the weight, but the important thing is that the pulley wheels can turn and the weight is securely fastened to the axle.

4. Tie one end of the 100 foot length of rope to the suspended beam or other support. Tie it next to the axle, so that it is adjacent to one of the pulley wheels.

5. Orient the weight underneath the support beam so that the two axles are parallel to one another.

6. String the rope through the first of the pulley wheels attached to the weight (the one closest to the rope), then up through the first of the pulley wheels attached to the support (the one adjacent to where the rope is tied).

7. Continue to string the rope through the pulley wheels, going from weight to support alternately, successively down the line from the two wheels you began with in step five. At the end, the loose end of the rope should come from the last of the five wheels on the support.

8. Pull the loose end of the rope to lift the weight with a mechanical advantage of ten.

Tips & Warnings

• You can use other methods of attaching the pulley wheels to the weight and to the support at the top. The method provided here is just one possibility.

• If you are lifting a heavy weight, it is vital that the attachment of the axles to the weight and to the support are secure and not in danger of coming loose, breaking under tension, or lolling to one side. Failure to attach them securely could result in a dangerous situation.

References

• SWE: Pulleys
• Wisc-Online: Mechanical Advantage

Resources

• Read this Article in Spanish