Mechanical Sequencer

Some weeks ago, when I built the LEGO logical gate, I thought that it'd be really cool if the gate could be automatically powered, rather than hand operated. For that purpose, however, I need some automatic mechanism to push and pull from the rods at the appropriate time. Thus, I needed to create a "sequencer", i.e. a device in which I could program a sequence of moves to be performed mechanically.

One solution, of course, was to just use mindstorms, but I thought that defeats the purpose of a mechanical computational device (using an electronic computer as part of it). Thus, I discarded the idea.

Another simple solution is just to use "pistons", which can convert in a simple way rotational movement into a continuous push and pull movement following a sinusoidal function. However, what I needed is to be able to sequence more complex moves, like: 1) rotate axle 1 to the right for 2 seconds, 2) stop 3) rotate axle 2 to the left for 3 seconds, 4) stop. etc.

For that reason, I build this simple proof-of-concept machine:

The machine is composed of two main parts:

1) "the program": the slowly rotating axle has two grey arms that control when the output axle (the large gear in the back) rotates to the left, to the right, or stops. In the picture above, everything is set so that the output axle rotates 50% of the time to the left, and 50% to the right.

2) "the switch": Using a Technic Changeover Catch, the power is used to rotate the output axle left, right or to stop it.

The simplest way to understand how it works is with a video:

It's hard to appreciate because of the high rotation speed, but the output gear alternates between rotating left and right. Here's a second video where I changed the "program" to make it rotate left for 1/4 of a period, then right for 1/4 of a period, and then stay still for 2/4 of a period. The second video is awful, since I was moving the camera too much, but I think you get the idea :)

Now I need to make this smaller, and stack several of those in order to use them as the control mechanism for my LEGO logic gates :)