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Jan 21, 2003, 09:18 PM
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dottney's Avatar

retract servo

OK guys put your thinking caps on. Can you use a regular servo (i.e.: HS81MG for example) as a retract servo? I have a retract servo and am not quite sure what makes it special except that its bigger than what I'd like to use. Do retract servos have some sort of "limiting movement" on it to control the throw or are they just real strong servos?
thanks in advance
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Jan 21, 2003, 10:26 PM
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Gerald's Avatar
Servos designed specificaly for retract duty are usually slower as a consequence of lower gearing, which also gives them more torque. Additionally they usually rotate 180deg. All the units I've seen are in the "standard" size class though.

For small retracts you may be able to get away with using a smaller servo like your HS81MG. Just be absolutely sure that the mechanism is free moving and doesn't bind or jam anywhere. If it jams the servo will consume a lot of current and may fail or cause your BEC to fail.

I used a single HS85MG as the retract servo for my 1/12 scale FW190A
Last edited by Gerald; Jan 21, 2003 at 10:31 PM.
Jan 22, 2003, 11:14 AM
Registered User
I have used a HS 80 as a retract servo and it is still working well. I had very light wheels, balsa / ply hub with closed cell foam for the tyre. This made the retracts work without a lot of load on the servo.
Jan 22, 2003, 04:45 PM
Superhero, Third Class
astroboy's Avatar
I tried an HS81 in my Herr Mustang, but had a lot of trouble getting the linkages adjusted right. I could see the servo shaft flexing. I replaced it with an HS85BB, and the problems all but vanished. The ball bearing-supported shaft made all the difference. I later stripped one of the gears, and replaced them with the metal set; so I'd recommend the HS85BB with metal gears.

Jan 22, 2003, 07:50 PM
Registered User
dottney's Avatar
Thanks guys,

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