Need help choosing a servo or motor

Comments

• Mike G Posts: 2,702

  2010-12-29 05:42 edited 2010-12-29 05:42

  If I remember correctly, digital servos can do around 400oz-in. See the HSR-8498HB and similar.
  
  Servos have specifications one of those specs is torque; oz-in or cm-kg. Use the specifications to find a servo that fits your needs. Be aware that 25lbs is much different than 25 ft-lb. Where ft is the distance (radius) for the center of rotation. You need to lift 25lbs... but how long is the lever?
  
  The boebot has continuous rotation servos. I don't think that would be a good fit for a leg servo. Regardless, hobby servos use pulse width modulation (PWM) to control angular position and the STAMP or Prop can send PWM.
• erco Posts: 20,261

  2010-12-29 09:03 edited 2010-12-29 09:03

  25 lbs is a lot! Depending on how far you want it to rotate, you'll have trouble getting an affordable servo that will last. "Cheap, strong, or durable, pick any two". Have a peek at Hitec's pan mechanism to get ideas to gear a servo down for higher load: http://www.servocity.com/html/gdp985a-bm_pan_system.html
• sports_eclipse Posts: 2

  2010-12-29 15:49 edited 2010-12-29 15:49

  Thanks guys for your replies. well the legnt of the shaft is about 2ft long and the most movement would be from 0degress to about 90degrees if that makes any sence. basically form the standing osition to the sitting position. also any tips on where i can get gears for this project
• Mike G Posts: 2,702

  2010-12-29 16:31 edited 2010-12-29 16:31

  Wow 2 ft @ 25lbs.... That will be a challenge.
  
  Did you take a look at the link provided by erco? Lots of resources including gears.