How to make a simple pulley system

The simplest way to harness the energy generated by an electric motor or source of motion are pulleys, as these devices can transfer motion and angular velocity that can be harnessed to move any device using mechanical energy. In this article, we will see how to make a simple pulley system, which allows us to move a blade, a cam and a connecting rod simultaneously, in a simple assembly. An interesting physics experiment that we can take advantage of with a lot of imagination.

Pulley system


- A 3-volt motor.

- Two cardboard tubes.

- Thick cardboard and cardboard.

- A piece of plywood.

- Glue.

- Two AA batteries.

- Three medium rubber bands.

- Various studs

- 80 g thick paper.

Creation of the pulleys

To create the pulleys, we take the cardboard tubes and cut them in half (or in quarters if the tube is very long) to obtain smaller tubes. Then, we cut 6 cardboard circles of about 5.5 cm in diameter and glue them to the cardboard tubes, making sure that they are well centred, until we get a kind of spools. These spools will be our pulleys.

Once the pulleys are dry, we make three paper rods of about 12cm each, which we will use as pulley shafts. To insert the paper rods into the pulleys, widen the centre of the shaft of the pulleys. pulley Use a pencil until the rods fit snugly and pull them out on the other side, taking care to leave 2 cm for the pulley to be recessed in the final assembly.

How to make a simple pulley system 1

Pulley system housing

The base of the box is made from a 25×10 cm piece of cardboard. With the base assembled, we place the electric motor at one end, leaving enough space to place the batteries. Now, we make a couple of cuts on the sides of the motor. Through these slits we introduce some strips of paper to hold the motor. After attaching the motor, we finish adding glue to fix it more to the cardboard and we make a rectangle-shaped (cardboard) support, which we glue with a paper rod to the motor shaft to prevent it from moving.

How to make a simple pulley system 2

Next, we finish the box with two 25×6 cm pieces of cardboard to which we make three holes 4 cm high and evenly spaced along the length of the cardboard pieces. Then, we fix the pulleys in these holes (as you can see in the figure), and then join the motor shaft with pulley one, then the shaft of this pulley with pulley two and repeat the same operation with the third pulley. We glue all this assembly on the base, make the covers of the box with two pieces of cardboard of 10×6 cm and fix them to the box.

How to make a simple pulley system 3

Assembly of the pulley system

We make a cross with a cardboard circle of about 2.5 cm in diameter, to which we make 4 cuts to insert four 3×1 cm strips of cardboard. These strips will be fixed to the circle with glue. When the cross is dry, we will place it on the first one. pulleyThe engine is located closest to the engine.

To make the cam, we draw two small circles on a piece of wood, one smaller than the other and 5cm apart from the centre. Then, we join the ends with an arc and cut out the piece of wood (see figure). This will be our camThe box will be lifted up by the box each time the pulleys. This cam is attached to the second pulley.

How to make a simple pulley system 4

Next, we create the connecting rod with a wooden circle of about 3cm in diameter. We cut a 6×1.5 cm piece of wood, attached it to the circle at one end (with a tack) and put another tack at the other end. Then, we create a support for the crank arm with cardboard and attach it to the box.

Now, all that remains is to supply power by closing the battery circuit. We will observe how the energy from the batteries can move three mechanical devices at the same time, using the principles of classical physics, specifically dynamics.

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