Tuppance Arcade Machine (2004)

I'm not really sure what these two pence shunting machines are called, but you can see what I mean in the picture. You drop the tuppences onto an arm which slides backwards and forwards, the coin lands either on the arm, and gets pushed off, or in front of the arm and gets pushed into the pile of coins. The aim is to try and make the coins fall off the front edge, from where you can collect them.

The frame is made from balsa wood, and the gear box is made from Knex. Very useful stuff Knex, it can do a lot more than be a kiddies toy. The motor is geared down twice, giving it plenty of torque and not much speed. The motion is then spread out between three arms which push the main arm backwards and forwards like in the animated gif. In the photo, they are easily visible as the big red cogs.

Having now made one of these machines, I can see how easy it is to tweak them to make it near impossible, or very easy to win. If the coin has enough space to fall flat, it will be pushed underneath the pile, which frequently pushes coins off the edge. If the coin cannot lie flat, it will be pushed up on top or into the middle of the pile, doing very little at all. I have set my machine in between, the coin can lie flat if timed correctly to be dropped onto the edge of the arm as it is coming towards you, when the arm moves back again it will be pushed off onto the base ready to be pushed underneath the pile. However if you just drop the coin in front of the arm it will almost certainly be pushed into or on top of the pile.