Marvelous Magnetic Machines: Building Model Electric Motors from Scrap

Hardcover, 160 pages, 177 photos and illustrations.
Marvelous Magnetic Machines: Building Model Electric Motors from Scrap
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You’re standing in front of an old card table in a driveway at a garage sale. On that table is a one-quart aluminum saucepan, a votive candle holder, pieces of some office machinery, and a wooden awards plaque. What do you see there? If you did not answer “a six-cylinder radial electromagnetic attraction motor,” then you need this book!

H.P. Friedrichs (author of The Voice of the Crystal and Instruments of Amplification) returns this time to explore the principles behind the operation and construction of  five simple, yet impressive, model electric motors.

Aspiring mechanical model makers are often discouraged by their lack of access to machine tools, like mills, lathes, or drill presses. Friedrichs demonstrates that with some basic knowledge, an open eye, and a sharp mind, one can use commonly available (and often discarded) parts and materials to engineer one’s way around any lack of expensive machine tooling. In fact, every motor in this book was built from scrap, and can be assembled with hand tools.

You’ll learn where to hunt for and find materials, and where to salvage suitable bearings. You’ll know where useful solenoids can be extracted from scrap, and how to fabricate bobbins to wind your own. You’ll learn how to time your motors, fashion a connecting rod, make a commutator from scratch, use a hall effect sensor to detect magnet position, use a transistor as a switch, and much more.

Hardcover, 160 pages,177 photos and illustrations.
H.P. Friedrichs is a degreed electrical engineer (BSEE), inventor, and author with more than three decades of experience working in domains ranging from audio, medical, and radio, to software, automotive, and aerospace. At present, he is a Principal Engineer with Honeywell, involved in the design and support of specialized equipment used for testing and validating aircraft power generation products.

He has five U.S. patents to his credit and holds three radio licenses including Extra-Class Amateur (AC7ZL), Commercial Radio Operator with Radar Endorsement and GMDSS
Operator/Maintainer with Radar Endorsement. He is also a certified VE.

Friedrichs is the author of numerous technical articles appearing in a variety of magazines, newsletters, and web sites but is best known for his books The Voice of the Crystal and Instruments of Amplification. Now cult classics among "from-scratch" electronics experimenters, these books have enjoyed favorable reviews from the editors of such prestigious periodicals as QST, CQ Magazine, Practical Wireless, and Make Magazine.

H.P. Friedrichs lives in Tucson, Arizona, with his wife and his German Shepherd/laboratory assistant — who is prone to "borrow" books and tools but not return them.
Complete Reviews from the Specialized Press

“The weather is cold or wet or it’s late and all you want to do is tinker with a small project on your workbench. You turn on some tunes low in the background, spread out a few tools, maybe a cold adult beverage off to the side and you have some parts of various types sitting on the bench in front of you. You slide your stool over and sit yourself down, and with the light focused on the parts, you feel better already, you’re exactly where you should be, and an hour or two later (was it that long?) you’ve put something together, solved a few problems and your world is a better place. If that scenario strikes a chord, I have a book for you, Marvelous Magnetic Machines.

Not junk, … parts

H.P. Friedrichs saves the parts from old machines and electrical devices, constantly on the lookout for anything that might be useful because he’s always assembling his finds in his mind into something else. If you have a box your wife thinks is full of junk, but you keep explaining, “That’s not junk, those are parts,” then you know what I’m talking about and you’re the target for the projects in this book. You can’t build these projects, not because you lack the skill, but because each one shown depended on the parts Friedrichs had available and you might have a different parts pile and what you build will depend on what you have.

We’ve highlighted sculptures built from scrap before on The Kneeslider and some of them are extremely cool, but no matter how they look, they don’t move, they just sit there, while these projects begin as inanimate objects and turn into little motors, machines that rotate, click and clatter.

Low cost and fits on a workbench, what’s not to like?

One feature of his projects is their cost, or lack of cost, since many, if not most, of the parts are free or purchased for next to nothing at garage sales or swap meets or sometimes just found. An electrical engineer by trade, but a committed tinkerer by avocation, he leads you through a process and after a while, you get the feeling you could do the same.

Personally, when I saw the cover image of the book, I was hooked. After reading some preview text and looking at the images, I ordered it and then I saw he wrote two earlier books, "The Voice of the Crystal" and "Instruments of Amplification" and yes, I ordered those, too. The Voice of the Crystal isn’t some new age novel, it’s about building crystal radios and a whole lot more from scratch, every component and it’s fascinating. He shows you how to make condensers, headphones, coils, tuners, all sorts of things and everything is absolutely from scratch. Instruments of Amplification goes further, you can make a vacuum tube, a transistor, transformers, it’s an amazing list of things I never imagined possible.

No, I haven’t built any of these yet, my little project at the moment involves programming and writing a lot of code, but when that’s finished, or at least at a point where I can stop for a short while, I may try one of these to unwind. If a little workbench project sounds like it might be fun, check out these books. I think the kinds of people who read The Kneeslider, people like us, are exactly the kind of people who do things like this.” - Paul Crowe, The Kneeslider


"Motors combine the almost magical property of magnetism with electricity to move the world around us. Many of us like to make things, and use motors in our designs. Mr. H. P. Friedrichs has written a delightful book on how to make five motors that are works of art, and how to do so with scrap materials. They are not necessarily motors that you would use to power something (although they could do this), but are machines of artistic, intricate and interesting construction that are designed to be a delight to watch.

To make these clever creations, we need to understand how motors work. With clear explanation of how electricity and magnetism work together to create the forces that move things, Mr. Friedrichs shows us what is behind the function of these motors that are clearly not from your mother’s sewing machine. He tells us “Build a homemade motor that works, and you’ve demonstrated a certain mastery of a force that, because of its utility, is largely responsible for our present quality of life.”

In the construction of these motors, a number of parts are needed. Instead of giving us a parts list and a recipe to put them together, we are given the knowledge of how to make the parts that are needed, or how to adapt parts that we can obtain from discarded everyday mechanical and electrical devices. I find this information valuable, and helpful to the creation of my own things. A motor made using this book will probably not look just like the pictures, but will reflect the things you learn and the available parts that you adapt from other things. The designs remind me of Thomas Edison’s inventions displayed in his reconstructed laboratory in Greenfield Village in Dearborn, Michigan. The parts have a purpose, but are neatly constructed and arranged to make the mechanism pleasing to look at as well as functional.

We start by learning about the Peewee Motor, a clever little thing that uses a solenoid to drive a flywheel with a mechanical crankshaft linkage. A solenoid is taken from an old copier. A bearing, capstan and flywheel come from an old tape recorder. Places to get these and other parts tell us how many great parts are available if we just know where to look. An old trivet or plaque makes for a handsome display base. On the way during the construction of this motor, we must make provisions for timing of the solenoid’s activation. Plentiful photographs and 3D drawings make it easy to visualize the construction.

Later Mr. Friedrichs expands on that with the Christmas Motor, with six solenoids and more advanced needs in timing and mechanical operation. Where do the parts come from? Mr. Friedrichs describes 17 different sources where ball bearings can be obtained! Take a threaded bushing from an old potentiometer, a support from an old candle holder, an aluminum saucepan for a crankcase, and other parts from the many places that are described and you can get most of the parts you need.

Among my favorites is the “Little Twister” motor: a brushless motor that is based on the principles of the motors in our computer’s cooling fans. So that’s how they work! Parts from an old VCR, an old lamp for the base, and an old candle holder for the flywheel give the project some beautiful parts. Thorough instructions on how to accomplish “jeweling” or “engine turning” of the mounting plate faces gives a nice look to the metal. I know I will use this technique, as it is quite pretty.

This motor has more complexity in the timing, so we learn about Hall Effect sensors and transistors to drive the coils. Although these parts are inexpensive to buy, we learn about sources where they can be salvaged. There is more electronics involved with this motor, and Mr. Friedrichs gives us the knowledge needed to understand what is needed. Then we also have the ability to apply these features to other creations that we might come up with after being inspired by this book.

Because much of this book contains the use of electricity and electronics, Mr. Friedrichs finishes with some good information on the use of electronics. He includes information on power supplies, multimeters and other test instruments. He also has a section on motor balancing. These educational parts round out the book to be an education in electronics and mechanics that the hobbyist who is designing and building things at home will find to be a valuable resource to help him in his endeavors." - Victor Chaney, Nuts and Volts Magazine


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Year Published:
Hardcover, 160 pages,177 photos and illustrations.
H.P. Friedrichs
Technical Editor:
Leonardo Barsantini