24 November 2007: I'm starting off with a smallish, but powerful electric motor that was harvested from a broken Epson inkjet printer. I'll also be using a 42V mains PSU that came out of the printer.

The first task is to build a suitable mount for the motor - I did this by cutting a hole through a piece of hardwood (maple, possbily) I reclaimed from an old pallet - unfortunately, my smallest holesaw is just a tiny bit bigger than the diameter of my motor, so I cut a couple of slots alongside the hole, then back into it, like this:

Then I inserted the motor in the hole and drove a screw into each of the slots - forcing the free tongue of wood inwards a little, gripping the motor very tightly.

26 November 2007: Well, things progressed quite fast with the build and unfortunately, my camera battery was flat, so I couldn't document it completely. I epoxy glued a ply disc to the motor spindle and mounted the whole assembly onto a square of plywood, like this:

Then I built it into a ply case and fitted the motor board as a false bottom. The space below the false bottom allowed me to fit the PSU and wiring.

It's a different PSU to the one I originally intended to use - that one kept cutting out - I think it probably couldn't handle the initial load of the motor, at least not with the ply disc attached - I expect it draws a bit of current when it's getting up to speed. This one is only 18V, but the motor is designed to run on anything between 12 and 42 Volts, so that's fine.

The device is wired according to this diagram:

There's a reason for doing it this way - when it's switched on (as shown above), the motor power circuit is complete and the motor runs. When it's switched the other way, the motor terminals are connected together - not only does this disconnect the motor from the power source, but it also brakes it - the motor continues to spin fast because of the ply disc acting like a flywheel - this generates electricity (the motor becomes a dynamo), but the current generated flows in a direction so as to try to turn the motor in the opposite direction - thus slowing it down.

This effect is described by something called Lenz's Law - and it's the same reason a bicycle dynamo becomes harder work to run when you turn on the light and draw power from it.

Anyway, Physics lesson over... The inside of the spin art machine looks like this:

Aha. You noticed the telltale splodges and splatters of paint there, didn't you?

Paint went everywhere - most of it stayed inside the box, but there was a fine aerosolised mist that wafted out and coated everything.

The paint I used was non-drip emulsion from my stage scenery painting box - a bit thick for this purpose, so I used a number of techniques:

• Initially, dabbing splodges of paint onto the card, then running the machine; this resulted in a bold radial pattern
• Dripping water onto the spinning card helped to spread things around a bit, but also made the most mess, as the water was blitzed almost to vapour by the spinning disc
• Dragging a brush across the spinning card resulted in a nice swirly tight spiral

The results? Not bad at all; Judge for yourself:

I still need to make the machine presentable though, so I gave the outside a lick of paint:

30 November 2007: When the paint dried, I went over all the edges with some black duct tape - and here it is - the finished (well, more or less) machine:

I'm probably not going to try to make it any more presentable than this - after a fairly short period of used, I think it's going to acquire a rich patina of paint blobs and mess anyway.

I might add a speed control at some point, as it spins very fast and this tends to favour the radial patterns and suppress the circular ones forming (unless a brush is used when the thing is in motion)