Why bother to build useless devices?
Why build them? That's a good question, considering that they never work as you may have hoped. I submit that you can still learn a lot from hands-on experience with devices of faulty design. You learn some of the reasons why the design was misguided. Also you learn one of the dirty secrets hidden during the many centuries of futile efforts toward over-unity machines: They perform miserably! Since the 11th century (actually earlier) folios and books of mechanisms have included one or more of these misguided designs (often with mild and cryptic disclaimers attached). Yet no one forthrightly declared how poorly they perform, based on his own experience with an actual machine.Leonardo Da Vinci probably built and tested a few overbalanced wheels, but only tersly dismissed them without giving details of how far they fell short, even in comparison with the notoriously inefficient (though useful) machines of his day. We strongly suspect that those who thought perpetual motion was possible had never bothered to actually build even one such machine.
The finished model makes a nice conversation piece to display on your desk at home or work. If anyone asks, you can say it is symbolic of the uselessness and futility of many of the activities of the workplace.
Materials.
Most of the classic perpetual motion designs may be easily built from parts already on hand, or readily available at your hardware or home-improvement store. If you are handy with wood, use that. If you like metalworking and have the equipment, that's great. If you are niether, consider steel construction set parts such as Meccano, Erector, Mech-Tech, Mech-Struct, Steel-Tech, Exacto, Temsi, Merkur, Eitech, etc. Some of these are no longer available as new sets, but a web search will reveal sources of supply of parts and even used sets. A trip to a yard sale or local antiques store will often yield old sets at reasonable prices. In this document I will show examples of how these can be used.
Taccola's wheel.The idea of a mechanically "overbalanced" wheel actually originated in the Orient, and is probably the inspiration for Villard's wheel (see below). It is one of the simplest to build. This model, from the Deutsches Museum, is made of wood with brass hinges. Hans-Peter Gramatke is assisting, preventing the wheel from moving so that it could be photographed in the museum's low light without blurring.
The wheel of Villard de Honnecort.
Villard's diagram shows strange perspective (common in his time) and does not show any constraints on the hammers. In later centuries diagrams of this device were more explicit in showing methods for positioning the hammers at extended position on one side of the wheel. Our model uses smooth pins as hinges, and also as position constraints.
Performance. All of these wheels have positions of static equilibrium, and these photos show them in one of those rest positions. The inventor assumes that if the wheel is given a clockwise push, it will continue to rotate. But to get the wheel moving, you must manually turn it till a hammer is at the top and pointed straight up, then that hammer falls. At the same time, the hammer must rotate, which gives the wheel a counterclockwise force (backward) on the main wheel. So as the hammer falls, the wheel gets an impulse in the wrong direction. Then, when the hammer hits a pin, this gives the wheel an impulse in the "correct direction". The hammer gains some energy from falling in the gravitational field, but no more than the energy you had to input to get the wheel started. There's no net energy gain, actually an energy loss, due to inelastic compression of materials. The wheel comes to rest and assumes another equilibrium position before making even one complete revolution.For comparison, you can then observe the wheel's performance with the hammers locked in one position, either extended, or not. Now the wheel performs much better, and a small push will cause it to turn many revolutions before it stops due to friction. The bottom line is that when you disable the hammers (which the inventor supposed were giving it excess energy) the system performs much better. This illustrates a simple and effective way to test a mechanical perpetual motion design.
Note. Frank Hornby, who invented and patented the Meccano construction set system in 1901, is said to have wanted to build a perpetual motion machine when he was a child. As children do, he grew out of that notion. We don't know whether he ever used Meccano to build a classic perpetual motion device, but he could have done so easily, as we have shown. Read More
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