Westminster Electric Motor Kit

 

This model electric motor is called a Westminster Motor Kit. The key to getting it to work is making sure the contacts (shown circled in green in the diagram) are correct. The horizontal wire is taped to the rotor axle with red tape. A vertical wire pokes up through the base. The are not joined but just touching. They must rub against each other as the rotor spins. There is one on each side. I have always favoured holding them between finger and  thumb as shown below so that correct pressure is applied. You usually have to feel which way it is trying to spin and then give a push. The extra momentum given is enough to get it round to the far side and remake contact.

The picture above shows current entering the coil top left and slowing downwards on side A. It goes round the end and flows upwards on side B, leaving the coil top right. Even when the coil has flipped over 180 degrees on the axle, it must still be going down at A and up at B. Hence the sliding contacts. The sliding contacts are called a COMMUTATOR. The magnetic field is shown in green. By Fleming's Left Hand Rule, side A comes up and side B goes down. The connection to the battery is shown below.