Servo - July 2015

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Futaba comparison chart Use these to help you decide on which model fits your particular needs. My primary servo for light duty is the Hitec HS-425BB, and it’s the one I use in many of my talking and moving skull projects. For the price, it’s hard to beat and a good place to start. If it’s not up to the task, then I’ll start moving to a model with more torque.

If you’re not familiar with that term, it’s simply the amount of power a servo will impart with a one inch arm and is measured in ounce/inches. No need to be overly concerned with it at this point; just use it in your comparisons. When you are comparing servos, take note of the speed which is given in seconds. The lower the number, the faster the servo operates.

Motors

You have a wide range of choices when selecting the proper motor. AC motors require no special electrical knowledge to use. Just plug them in. Even though I occasionally reach for one, I primarily use DC motors; most often 12V models. There’s a multitude of kinds available with different speeds and strengths. The many different motors used in cars can be especially useful. Take, for example, wiper motors. They can be workhorses for many of the larger props. They have high torque; a low and high speed, depending on how you wire them; and most will allow you to reduce the voltage to get even slower speeds.

When I purchase a wiper motor, I always pick up one of the wiring harnesses as well. It comes with the appropriately sized connectors, and makes for a quick and clean connection to your power source. When shopping for the power supply, get one with sufficient amps. It’s suggested that you use one with at least five amps to avoid underpowering the motor.

I’ve also found many smaller motors from surplus houses that fit the need when working with smaller armatures. Please read the spec sheets carefully — especially when looking for a motor that will operate continuously and will do so without overheating. Many motors are not designed for continuous use and require downtime between activations.

Pneumatics

When it comes to building something that requires lots of power and/or fast activations, it’s time to reach for the air. The flexibility of using air will solve many of the problems that can come up. You can purchase pneumatic cylinders in a wide range of lengths, as well as bore. If you need more power, you can increase the size of the bore of the cylinder or boost the air pressure.