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About Electromechanical Technology

The Electromechanical FAQ

What are electromechanical machines?

They are machines which use electricity to move or control the movement of mechanical parts, and/or use moving parts to generate or control the flow of electricity. Very often the term is used to refer specifically to mechanisms operated by solenoids and motors.

How are they useful?

Some electromechanical devices are more or less complete machines or appliances in their own right. The electric bell, for example, is almost purely electromechanical and is an excellent example of how the technology can be put to work. An electromagnet strikes a hammer against the bell gong and opens a pair of contacts to switch itself off. A spring pulls the hammer back and switches the magnet on again, and the process repeats. The electricity provides both the motive power to drive the hammer and the automation to make it strike repeatedly. It also provides the means of communication from the push button to the bell, and all this is achieved with one coil of wire on a steel core, a steel arm, a spring and two contacts! Other electromechanical devices are used as components of larger systems. Consider a modern car; many of the operational functions are supervised by microcomputers such as the engine management system and body computers. These get their work done for them by electromechanical actuators in the same way that the human brain calls upon muscles in the body to carry out physical work. Examples include fuel injectors, ABS control valves, stepper motors for the climate control air handler, even the humble starter motor.

Until recently, the "brains" of many machines were electromechanical too. In the golden age of the record-playing jukebox for instance, machine decisions about 'which record to play next' and 'how many plays to credit for three nickels' were carried out by electromechanical devices such as stepping switches and relays. Electromagnets and motors would then do the physical work of fetching the record, playing it and putting it back again. The overall behaviour of the machine was determined not by a central 'brain' per se, but by the complex arrangements of interacting mechanical parts, electromagnetic devices and switching circuits, often with a few electronic components thrown in as well!

Why are electromechanical machines interesting?

There are moving parts in nearly every electromechanical machine, and in most of the older machines you can see them move. They were often designed by highly ingenious and imaginative engineers, who arranged them to work in elegant or crafty ways that can be fascinating to watch. One of the unique features of many early electromechanical control systems is that you can see them "thinking". You cannot see a person multiply two numbers in their head, but you can see them multiply on an abacus. Likewise you cannot see an electronic telephone exchange route a call, but you can see an electromechanical one almost "counting on its fingers" as it does so, and a technician can work out who is calling whom just by watching the mechanism in action. Many of the early machines are visually appealing, as they were often finely engineered products in an era of elegant and statuesque machines.

Is electromechanical technology outdated and obsolete?

No. As long as we want electronic machines to carry out tasks in our own physical world, we will probably need electromechanical devices. The most energy efficient cars, the most advanced assembly-line robots and the sleekest mobile phones all rely on them. Only electromechanical computers and controllers are truly obsolete, having been replaced by faster, smaller, cheaper electronic ones. Some electromechanical machines, such as power station generators, have no practical substitute yet. Everything we plug into the wall outlet is ultimately powered by electromechanical technology.

I thought that old electromechanical machines were terribly unreliable and clumsy. Are they?

Sometimes. Like other kinds of mechanism, many electromechanical devices need careful adjustment and periodic maintenance. Compared to their electronic counterparts which are usually maintenance free, electromechanical control systems were often labour-intensive and unforgiving. When properly maintained they could be surprisingly reliable, but a single dirty contact might bring an entire machine to a halt or make it erratic and inaccurate.

Why were they so fiendishly complicated?

Many simple-looking electronic devices are actually just as complex or more so, but we can't see all the individual microscopic components locked away inside the chips, nor can we "see" the software running in them. Every piece part in an electromechanical machine can usually be seen, counted, looked up in a price list, and cursed when it jams, so an electromagnetic lift controller with 500 parts can appear much more complicated than an electronic gadget with 2000 'parts' hidden away on one chip. On the other hand, most of the components in complex electronic circuits each work in simple and identical ways, whereas each part of an electromechanical system was often made to do many duties in unfathomable and peculiar configurations.

Are they dangerous?

Large old machines are quite likely to be dangerous, regardless of whether they are electromechanical or not. In the early days of electricity, there were few established standards and ground rules for safety, and risk of injury was an accepted part of working with machines. It was considered reasonable to build a machine that could electrocute a careless user, and to assume that users would look out for themselves and take care not to get electrocuted! Many appliances, however, were and still are perfectly safe given proper maintenance.

Surely it's impractical to keep these dinosaurs working, long after the supply of parts has run out?

Some machines are indeed rather tricky to maintain but others are no trouble at all. One of the great advantages of early electromechanical systems is the relative ease of replicating many of the parts using conventional workshop tools and techniques. By comparison, some electronic components are almost impossible to manufacture on a small scale and their unavailability might put out of action every machine which depends on them.


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