By Craig Weeks
What happened to the good ol’ days? In my generation, if we weren’t outside riding bikes or playing war, we had to break out a deck of cards or a board game to keep ourselves entertained. No DVD, Xbox, or PlayStation—in fact, the first computers were military-only and so large they needed and entire room to house them. And, the first electronic games were only seen in the wealthiest of households and would only keep a player’s attention for about two seconds today. The first cell phones were called “car phones” and were only found in Rolls Royces and the like. Eventually they became small enough to fit in a suitcase-size package when they became cellular phones but were still only within reach of the rich and famous. Now, nearly every United States household has a computer of some sort that is more powerful than the first computers that ran the entire country. We can even monitor and control our home security systems from anywhere in the world with our smart phone, provided we can receive a cellular signal.
Well, things are not much different in the world of fire apparatus. Diesel engines from the 1960s, 1970s, and early 1980s only needed fuel to a properly set up and timed injection system. As long as you could initially spin the engine, it would continue to run without any electrical power, and the only way to shut it down was to either cut off the fuel or air supply. Bumping up the horsepower or improving off-the-line performance was as simple as tweaking the fuel pressure regulator, fooling the boost aneroid or forgetting to reinstall the throttle delay valve. Yes, you old-school diesel techs know exactly what I am talking about. And as long as the electrical system could maintain 12.5 volts, it was good enough to operate any incandescent light bulb or rotating emergency light motor. Alternating flashers were the size of today’s compact car starter motor and were operated by an electric motor spinning a contact rotor switching power from one pole to the next, each operating a light. But, today’s modern fire apparatus, although quite impressive and able to do some amazing things, require a lot of electric power to function properly and can be extremely temperamental because of the available technology.
Modern Apparatus Technology
So let’s see, what technology goes into the modern fire apparatus allowing it to function? Well, every major operating component has a computer, better known in the vehicle world as a power control module (PCM), which usually deals with chassis functions, or an electronic control module (ECM), usually working with powertrain components. The engine, transmission, and braking systems each have one, and each one communicates with the other to ensure optimal drivability. It makes you wonder how this is done with such tiny wires considering wires were so much larger and vehicles were so much less powerful in the past. Those who understand electrical systems, get this—if you can convert battery voltage from 12 to 10,000 volts, what you needed 50 amps to do before you can now do with milliamps, and wire size is determined by amps. Besides sending and receiving thousands of bits of information per second, this is the job of the ECM, and this is just to make the vehicle move from point A to point B.
But, what about what’s on the surface? Obviously that depends on the apparatus. We could use a pumper for example, but let’s complicate it a bit with a quint. Five major functions, right? Pump, tank, hose, aerial device, and ground ladders. The chassis ECMs, through input signals, know if the fire pump, aerial ladder, and perhaps a hydrostatic driven generator are engaged and will only allow certain functions if any one, or combination thereof, are in use. And, interlocks send signals to these computers, preventing unsafe operation such as the parking brakes not being set or the outriggers not being deployed.
Fire and hydraulic pumps still require some type of rotary motion to operate, and I don’t foresee any changes in the near future. But, moving fluid, be it water or oil, to its destination is often controlled through modern technology. Electronic pressure governors and discharge gate controls use pushbutton and even touchscreen technology to control a constant pressure and flow rate—regardless of lines opened or closed and/or changes in supply—and a computer interface makes corrections, either adjusting engine rpm or discharge gate positions. This can also be accomplished through wireless control consoles carried by the operator.
Similarly, hydraulic controls send signals to control valves through potentiometers and servos to control the fluid flow rate to a given hydraulic cylinder, and variable displacement hydraulic pumps sense the demands of the system to provide a constant rate of pressure and flow regardless of engine speed or operator activity.
More technology, including LED lighting systems, sirens, and apparatus monitoring systems in Apparatus Technology: Part 2.
CRAIG WEEKS is division chief/fleet manager for the Los Angeles County (CA) Fire Department and president of Specialty Fleet Consulting.