Servo torque .90 size? - RCCanada - Canada Radio Controlled Hobby Forum
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Old 11-04-2009, 11:12 AM   #1
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Servo torque .90 size?

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I have a .90 size seagull etra 260 in need of servos. I also have a bunch of like new HS-425bb servos looking for a new home. I am concerned about the amount of torque required on a .90 size planes ailerons and elevator. The elevator system uses two servos to run seperate flight surfaces approx 3" in chord and 10" in length. The ailerons are approx 2.5" in chord and run around 25" in length. I would like to use the 425bb servos on a 6 volt system. At 6 volts they are rated to provide 57 oz-in of torque. Is this enough or am I just asking for trouble?

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Last edited by Norm; 11-04-2009 at 12:16 PM.
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Old 11-04-2009, 11:22 AM   #2
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Re: Servo torque .90 size?

This link to a servo torque calculator may be interesting to you.

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Old 11-04-2009, 02:16 PM   #3
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Re: Servo torque .90 size?

I wouldn't use anything lower than 100oz per surface. The Hitec 5625 is a good start in all surfaces.
57oz of torque is ok for a trainer but if you are going to fly hard on that, you should go a little higher in torque.
This includes your rudder as well.

You could use the 57oz of torque for your throttle though.

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Old 11-04-2009, 04:40 PM   #4
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Re: Servo torque .90 size?

Lack of torque is one issue because the servo is more prone to failure if it's being constantly pushed to its limits but the other bigger issue is the strength of the gear train inside the servo. Big surfaces combined with weak gears = potential flutter = destroyed airframe. These bigger planes, unfortunately, require some higher end gear if you want them to perform reliably. Might as well bite the bullet and drop some cash on some good servos. They will pay for themselves.

Last edited by Ramz; 11-04-2009 at 04:53 PM.
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Old 11-04-2009, 07:22 PM   #5
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Re: Servo torque .90 size?

Originally Posted by DPO1 View Post
This link to a servo torque calculator may be interesting to you.

Thanks for posting this link!
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