Goal this week was to make something dynamic, kinetic. Some form of art or a mechanically interesting product. I must admit, I oscillated between two ideas for 2 days and then jumped straight to a compleatly different one. It came to me, because I once saw a similar mechanism as a kid but was never able to find it again.

     Its based on a mechanically easy way of making moving stairs. The are actuall stairs for people on a very similar somewhere in Scandinavia. This system uses a Scotch yoke mechanism to lift up and bring down to separate and interlocking parts of stairs. The movement is phase shifted by half of a period. Odd stairs and even ones are moved separately, lifting a steel ball up the stairs step by step. Originaly my goal was to power the contraption using a solar panel, but since its foggy these days (March), it would be working well. I used a USB-Mini B port, so the contraption can be powered by powerbank, solar or from a socket.

     The machanism is driven by a DC motor with included gearbox. Torque can be controled by a transisor trimmer. With the USB-Mini B port its all simply soldered together and hidden in a side compartment. For connecting the motor and driving wheel of the yoke, thin steel rod is used. (schematics and photo coming soon).

     Now to the making process. With little time, I focused on a proper model a double checked all tolerances in CAD. With no test print it turned out pretty well. Ofcourse it wasn't perfect on the first print. One very flat corner of the stair segment peeled of the print sheet a little bit and caused extra friction. A worse problem was however with the top of the stairs. See, the stair segments supposed to up and down 13 mm each time and thats with tolerance. But, the yoke below was was not lifting them exactly those 13 mm but rather something like 12,8 mm. This prevent the ball from jumping up the stairs and makes it stuck on one.