Monday, July 5, 2010

By The Numbers: Servos

  • Dimension: height, weight, length.
  • Weight: and how much it weighs.
  • Operating Voltage: electrical input range. for planes, this is almost always 4.5-6.0 volts.
  • Operating Speed: how fast the servo motor turns. this measured in "seconds to rotate 60 degrees." often, there are two measurements, one for 4.5 volts (lower) and one for 6.0 volts. Be careful when there's only one number given, to make sure which voltage is being reported.
  • Stall Torque: How hard the servoc can twist. At the given number, the servo will stall. The measurement is how much force is done from a particular arm radius. Like speed, there are often two numbers specified, for 4.5 and 6.0 volts.
Two other important bits:
  • MG usually indicates "metal gear"
  • Digital servos provide faster response, tighter accuracy, and higher "standing" torque at the cost of increased power consumption and a high-pitched squeal when operating.
  • For small park fliers and foamies, the standard 9g and 5g servos are fine, e.g. the HTX-500 and HTX-900.
Example: http://www.superflyrc.com/Power-HD-HD-2216MG_p_51.html
  • Dimension: 22.8x12x29.4mm
  • Weight: 15.8g
  • Operating Voltage: 4.5 - 6.0V
  • Operating Speed: 0.13sec/60°at 6.0V
  • Stall Torque: 54.12oz-in @ 6.0V (3.9kg-cm)

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