Linear Motor Experiments - Small Scale Trains

[@AlwaysCensored-xp1be]

Paper trackwork. Been looking at polybak/laser board for PBR carriages. Might be lighter than 3D printed.

[@louiej5]

How does this work? Is this like an asynchronous induction motor where coils induce eddy currents in a piece of metal without physical permanent magnets, or are there many individual electromagnets that pull another permanent magnet like a synchronous motor? I'm just wondering where that pulsing sound comes from.

[@modelrailmusings5981]

It is just a basic linear motor - the coils are electromagnets, while the trains have matching permanent magnets on the underside which jump to line up with them. The pulsing sound comes from how I achieve the low speeds. The chosen coil and magnet spacing means that each proper step forward is exactly 1mm, or around one step per second at that speed - silent, but much too coarse. So, microstepping is used to synthesize 0.25mm steps, or about 4 microsteps per second here. This involves dithering back and forth between two adjacent coil states with a changing duty cycle: 100/0, 75/25, 50/50, 25/75 and finally 0/100 to advance 1mm. This happens at audio frequencies, so you can the whole train rattling!

[@kirboysgaming6937]

Hi

[@Ben777Transport]

Where did you get the consist/carriages for this build and if so, do you have the files for them?

[@modelrailmusings5981]

These are my own 3D print designs. The locos are up on Thingiverse (search for "Puffing Billy"), but I never got around to uploading the carriages as there didn't seem to be enough interest.