What is a Pulley?

A pulley is a simple machine that is the basis of much modern machinery. This machine changes the direction of an applied force, allowing a heavy load to be moved. A person can pull on the cable part of the device, and it will pull a weight. There are six simple machines: an inclined plane, a lever, a screw, a wedge, a wheel and axle, and a pulley.

At its most simple, a pulley is a wheel with a groove. A rope, belt, or cable runs inside the groove. That mechanism can be used alone or connected with others in a pulley system. The greater the number of pulleys in the system, the less force it will take to lift an object.

A block and tackle system, which is a basic system, can illustrate how this machine provides this kind of lifting advantage. A 10-pound weight has a rope attached to it. To lift the weight, a person will need to exert 10 pounds of force  straight up. If the weight is attached to one pulley, the person still needs to exert 10 pounds of force  but the direction it needs to be exerted in is down, instead of up, making use of the individual's body weight more efficiently. If the weight is attached to two pulleys, the person will need to exert only 5 pounds of force. Four pulleys will require 2.5 pounds  of force, and so on.

There are three basic types of pulley systems: (1) fixed, with a fixed axle, (2) movable, with a free axle, and (3) compound, with a combination of fixed and movable axles. Movable and compound axles, by multiplying the force, are more efficient than fixed systems.

Another type of system is the belt and pulley system, which can often be seen under the hood of a car. These systems are closed systems in which several pulleys are connected by one belt. They allow for the transmission and amplification of energy from one pulley to another.

The History of Pulleys?

Objects similar to pulleys, which contained vines or ropes, are believed to have been used by the Mesopotamians as early as 1500 B.C. to lift water buckets. Archimedes of Syracuse invented the first compound pulleys 287 BC - 212 BC. Plutarch reported that Archimedes moved an entire warship, laden with men, using compound pulleys and his own strength. During the 12th century, people used pulleys to build cathedrals, according to the University of Nebraska-Lincoln.

What are the most common educational plastic pulleys available?

Product            Product Code
Single Pulley with a 50 mm (diameter) sheave. Pulley5
Double Parallel Pulley with a 50 mm (diameter) sheave. PP55
Triple Parallel Pulley with a 50 mm (diameter) sheave.     Pulley555
Quadruple Parallel Pulley with a 50 mm (diameter) sheavePulley5555 
Double Tandem Pulleys have sheaves with 50 and 40 mm diameters.Pulley54 
Triple Tandem Pulleys have sheaves with 50, 40 and 30 mm diameters.Pulley543 
Replacement sheaves, pack of 5.5Sheaves 

Where can I buy pulleys?

Depending on your experiment or project, you can find the above mentioned pulleys by visiting our online store. ScienceKitStore.com offers single piece pulleys or you can go with the complete pulley demonstration set.   

What are some different type of pulleys?


Table Top Pulley with Rod and Clamp

Product: SF40-276

Great for experiments calling for a pulley at different heights, this pulley rotates 360°. Adjusting up to 10 cm, it locks in place with a thumbscrew and can attach to surfaces to 5 cm thick. Two-piece apparatus includes glass filled nylon molded clamp and pulley; sheave 2" (50 mm) diameter; stainless steel rod.



Table Clamp Pulley (Bench Pulley)

Product: P64101

This vertical bench pulley consists of a 4 cm plastic pulley mounted on a table clamp with low friction brass cone bearings. It can be used on lab tables or inclined boards for experiments involving the resolution of forces, friction, motion, etc. It can clamp onto surfaces up to 3 cm thick. a crosspiece on the screw offers more gripping force and the felt padding inside the clamp protects table surfaces.



Table Clamp for Rod

Product: AS3467X

Designed for clamping to table edges up to 45 mm thick with a thumbscrew and for supporting a rod with 10 mm in diameter. Usually used for holding pulley with rod; however, it may be used with any other rod with 10 mm in diameter.


Small Pulley for DC Motors

Product: MPUL10

Small pulley (Motor Pulley) with 2 mm bore for DC micro motors. 


Pulley with Three-Way Attachment

Product: AS3468

For clamping to vertical or horizontal rods and to laboratory tables, boards etc.. Comprised of a specially designed cast bracket which can be clamped on flat surfaces 38 mm thick and hold a supporting rod 13 mm diameter. At the rear of the bracket, a light alloy pulley about 70 mm diameter is mounted on brass bearings. Includes two clamping screws for fitting to bench and vertical rod support. Hammer-tone stove enamel finish.


Pulley Demonstration Set

Product: 3472A

For demonstrating and performing quantitative experiments on fixed and movable pulleys, trains of fixed and movable pulleys, the wheel and axle and the capstan etc.. Helps to understand the concepts of the mechanical advantage, the efficiency of fixed and movable pulleys, etc.. Comprised of a rectangular laminated wooden base about (l x d), 20 x 82 cm, which supports two threaded rods measuring approximately 12.5 mm x 81 cm in metal flanges and is fitted with a capstan and a screw eye. Eight clamps (hook collars) are provided for suspending pulleys and cords on an adjustable cross rod approximately 12.5 mm x 81 cm, held by right-angle clamps. Supplied with: 8 single pulleys 2 triple tandem pulleys 2 quadruple pulleys 1 wheel and axle 7 weight hangers (5 of 50g and 1 each of 10g and 20g) 15 slotted weights (2 each of 10g, 20g, and 50g, 4 each of 100g and 200g and 1 of 500g) 3 right-angle clamps 1 spool of cord 1 tommy bar to tighten the vertical rods and instruction manual Rods, pulley and clamps are made of either plated metal or polished aluminium. Slotted weights and weight hangers are made of brass. 


Rope, Line for Pulley
Product: NYLON30M

30 meters (100 feet) Nylon multifilament (8 strand) braid rope string for pulleys. Available in 2mm and 5mm diameter. The 2mm diameter string is used for educational plastic pulleys, while the 5mm ropes are used for metal pulleys.

Typical Strength (2mm): 50 Lbs 

Typical Strength (5mm): 500 Lbs


Pulley with Rod

Product: AS3466

For applications where a pulley is to be supported at various heights and angles. Specially suited for inclined plane experiment. A metal pulley, diameter 50mm is mounted on a metal frame attached to a plated rod about 10mm in diameter and 15cm long.


Pulley with Table Clamp

Product: AS3467

Useful for experiments in which a pulley needs to be supported at various heights and angles. The pulley can be removed and used separately. Designed for clamping to table edges up to 45mm thick with a thumbscrew and for supporting a 50mm diameter pulley and rod. Pulley adjusts to 10 cm height (minimum) and rotates a full 360º. All parts are metal. This is a set including the pulley and the clamp.

Bench Mount Pulley

Product: LC531

Horizontal bench pulley LC531 is a horizontal pulley with table clamp. It is made of sturdy cast iron frame, and 35 mm diameter metal pulley. Holds pulley in a horizontal position when mounted on the edge of a table.


Fixed Pulley, For Mounting on a Plane Surface

Product: AS3464

Suitable for experiments involving inclined plane where mounting on plane surfaces is required. Consists of a pulley, diameter 37mm mounted in bracket having two fixing holes for screwing on to a surface. Both parts are made of aluminum.

Sheave/wheel diameter: 25mm
Sheave's grove: 3mm
Mounting Base: 12mm x 46mm
Load limit: Not tested.

Available Late August 2015


Metal Pulley, 25mm, Single

Product: MP1

Metal pulley, single wheel 1 inch (25mm diameter, casted from zinc alloy and plated by nickel. Used for science experiments in physics and mechanics.

Metal Pulley, Double Parallel

Product: MP11

Metal pulley, double parallel wheels with 1 inch (25mm diameter each, casted from zinc alloy and plated with nickel. Used for science experiments in physics and mechanics, as well as industrial applications. Accepts ropes of 2mm up to 6mm in diameter.