One wheel. If you have a single wheel and a rope, a pulley helps you reverse the direction of your lifting force. So, as in the picture below, you pull the rope down to lift the weight up. If you want to lift something that weighs 100kg, you have to pull down with a force equivalent to 100kg, which is 1000N (newtons).

In order to calculate the mechanical advantage of a wheel and axel, you can divide the radius of the wheel by the radius of the axle. If a wheel’s radius is 60cm and its axle is 30cm, what is the mechanical advantage of the wheel and axle? The output force of the wheel and axle is 2 times greater than the input force.

The mechanical advantage of the wheel and axle is essentially the ratio of the radius of the wheel over the radius of the axle. Remember that the radius of a circle is half its diameter. The ratio of the radii of the wheel and axle gives you the mechanical advantage.

Attach the rope first to the bottom of the upper fixed pulley, then loop the rope down through the wheel on the moveable lower pulley. Now, loop the rope back up through the top fixed pulley. Make sure the rope is fully seated into the grooves on the pulley wheels.

There are four pulleys on the door, one on each side at the top corner where the vertical and horizontal track join and one on the end of each spring. These pulleys have ball bearings which allow them to roll smoothly and quietly as the door moves up and down.

10,000 cycles

Garage door pulley’s are relatively cheap averaging around $12 – $68 dollars per pulley. However, you will have to make a service call for the repair expert to visit the home. A garage door service call is usually around $50 – $90 depending on the company you hire. Average garage door pulley repair cost is $102.

3-5 years

Chain Drive Openers The chains used on residential garage door openers typically have higher tensile strength and greater lifting capacity than belts. They also may last longer in certain applications.