Teaching my boys practical electromagnetism

[tech-artist]

I need help designing some build-from-scratch DC motors. I'm looking to build really robust motors that I can be be sure will demonstrate clearly the principles involved, but that can be modified by my boys and that they can really *play* with and use to run simple toys. I've already shown them the Beakman's motor design that permeates the web. Frankly, it didn't hold their attention long. Sure, they thought it was nifty, but they rightly believed it to be absolutely useless beyond "Gosh, it spins!" It's too delicate, has erratic commutation, and is not self-starting since it has just a two-pole rotor.

A little background: my boys are nine and eleven, and I want to teach them the basics of EM without using much beyond grammar school arithmetic and geometry and *heaps* of demonstrations. I figured I'd start with "simple" things like electromagnets, motors, telegraphs, telephones, etc. Old school stuff.

Both boys are quite bright (the younger one scarily so; I don't know if he's genius range IQ for sure, yet, but I do know he's smarter than either my wife or myself ... let's just say he gets into *interesting* trouble).

At one time I homeschooled both boys, but they just flat wore me out, so now they are in a regular school. I'm a recovering engineer (bachelor in robotics engineering in 1987), and now I'm a sculptor (long story), so I'm comfortable teaching them tech and maths as well as practical how-to-build-it stuff. The problem I'm facing is building good demo equipment.

Since then I've sought out the books from my boyhood in the '60s and '70s, books like "A Boy and a Motor" by Raymond F. Yates and "Electrical Things Boys Like to Make" by Sherman Cook. Yates wasn't as good as I remembered, but Cook was very good. Still, Cook had no self-starters and no PM designs.

Then I dove into the various books available from Lindsay Publishing, such as Morgan's "The Boy Electrician", Hasluck's "Dynamos & Electric Motors", and I've also managed to find two books from the Percival Marshall "Model Engineer" series, "Small Electric Motor Construction" and "Small Dynamos & Motors."

These books come closer, being from an era where it wasn't an unusual idea to build your own motor to do useful work. That strength is also their weakness, however. Lots of materials and processes described in them were common a hundred years ago are not so common now, things like bakelite rods, silk- and cotton-covered wire, and neighbourhood electrical supply shops willing to sell small quantities of multi-pole rotor laminations suitable for making small motors.

My question, then, is where should I start with producing homebrew designs suitable for *this* century? Where can I even get silicon steel to make our rotor laminations? Or would cannabalizing Mabuchi motors be my only realistic bet?

 

[kuruman]

My recommendation is to use the wonderful old homebrew designs and bring them up to date with whatever "modern" versions of the materials exist today. Teach your boys by making them active participants in the updated design. For example, "The old design called for cotton-covered wire which we we can no longer get. What is the function of this item, what is a reasonable substitute and why do you think so?" Make them feel that they own the project. And yes, if you have to cannibalize something, by all means do so. It will teach your boys resourcefulness.