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1- Acquiring the motor

For this you are either going to buy a motor, or scavenge and reuse one. Favouring the latter and more environmentally-friendly option, these writings assumes you will scavenge one. The picture shows an old washing machine motor salvaged from a machine my parents were throwing out. These tend to be a good and surprisingly plentiful (keep your eyes out) source of one horsepower series wound commutator motors. It should provide plenty enough power to drive a small wood lathe like the one I am planning.

If you do get a washing machine motor try and grab the whole machine – then in the comfort of your own home you can take your time to work out how the wiring went. If like me you were on a time budget to get it away from your parents sub-Arctic outside shed just cut it out and get as much of the electronics as possible.

To extract the motor, turn the machine upside-down and you should be able to see the motor. It is now simply a case of unbolting it from its mountings.

These motors can be run off both DC and AC making them quite versatile little beasties.

In the picture I am testing the motor with a DC bench supply, made from an old computer PSU (power supply unit – check out Sitnalta’s instructable). DO NOT CONNECT THE MOTOR TO MAINS VOLTAGE without any load attached. Series wound motors have no theoretical limit to their speed and the centrifugal forces can fling the motor armature apart! Even with a modest load a direct connection to 240V mains is a bad idea, as the speeds are likely to strain the bearings, brushes and frame – all of which are not designed for unlimited power without a hefty mechanical load.

Another way to test a motor of this sort without a bench-top supply is to attach a 1000W electric heater wire between the brushes. The current passing through the resistance wire should be enough to limit the speed of the motor.

The series wound washing machine motor will look something like this

If you can, salvage other bits that look important. You can make do without but if you can get em…

Make sure to fasten the motor to something solid so it doesn’t fly across the room when you first switch on.  Here I use the home made bench (reclaimed wood) with vice to hold the motor firmly.  This was one of my first projects – If you don’t have a bench, get building – making a lathe without one would be very tricky.

Even on with my 12V bench top supply I thought it wise to start with some load on the motor shaft. This wire brush clamped in place did the trick and helped clean some of the rust off too ; )

Unless your a wiz with electric motors already, this may require some research and learning. That’s half the fun!

Motor brushes – worth unscrewing to examine – check for pitting or excessive wear. They can usually be replaced relativity cheaply if necessary.

While the brushes are out check the surface of the commutator. Unless the motor is brand new it will be blackened where the carbon brushes have rubbed – that’s ok, just check for any uneven segments or pitting.. If there is any it’s probably worth looking for a new motor, especially if there is sparking between the brushes and commutator when run at low 12V bench supply speeds.

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Responses to 1 – Acquiring the motor

  1. Selim

    Luckily I found the exact motor you’ve displayed on the website, but couldn’t work it out where to connect 12V power ? There are many red and black cables and one yellow-green .

  2. Bongo

    Hi Selim,
    Oh great, good find. Unfortunately there is no ‘standard’ for the wires connecting the motor, even similar motors in different models of washing machine can be different. So probably the best thing to do is forget about the wire colours and concentrate on where they connect to on the motor.

    Basically you can test the motor is several different ways, the 12V power wants to go to one brush, then connect the opposite brush to one of the field coil connections, and finally the other end of the field coil to the negative of the 12V power. This is what is known as ‘in series connection’, and why these ‘universal style’ motors are often referred to as series wound motors.

    For testing it is also useful to first use a multimeter to check the field coils are unbroken by measuring the resistance between contacts. This will also help you figure out which contacts are what. It is worth remembering that there will be three field coil contacts – only ever apply power between two of them – the pair you choose will determine the direction of rotation. To help you out with finding the right connection points I will try and label the motor pictures on this and the next step (hover the mouse over to see the captions).

    As an aside, I wouldn’t use a 12V car battery for the tests – that packs a bit of a punch…
    Hope this helps, let me know if you are still having problems.

  3. bruce

    I once salvaged a washing machine motor, but wasn’t aware it was mandatory to salvage the control electronics as well. Ooops. I always assumed these were ‘universal’ 240V
    types, not 12V. I’ll have to check if it has a number and data is online.
    If we assume that I have a motor not unlike yours ( it sure looks like it ) then I have a series wound 12V motor. Now, a field-coil type is better. You can control the speed with a simple regulator on the field winding ( like the old car dynamos ). I wonder how difficult it would be to convert one. If I ever get a second motor, I’ll try it. It might be interesting to ramp up the voltage to 18V or even 24V. Possibly PWM? You could get a nice slow but very powerful turning lathe – useful if you’re using those huge logs of yours.

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