8411 and 8411SA torque specs.

[Earl Haury]

The fail point of the 8411 output shaft / spline (gear held in chuck) for one sample each is:

Plastic shaft / arm - shaft spline failure @ 480 oz in
Plastic shaft / Al arm - shaft spline failure @ 560 oz in
Metal shaft / Al arm - shaft failure @ 1600 oz in

The plastic spline failures still retained enough "friction" to have control - albeit out of trim.
The metal shaft broke immediately below the splines. (I've seen this occur on big gassers also.)

None of this addresses gear strength, (I did this experiment because some heli guys said that the metal arms stripped the splines on both the plastic and metal output shafts.)  but as Richard points out, the metal will take more abuse.

Earl
  ----- Original Message ----- 
  From: Richard Strickland 
  To: discussion at nsrca.org 
  Sent: Thursday, July 29, 2004 8:59 AM
  Subject: Re: 8411 and 8411SA torque specs.


  From a strictly mechanical point of view and as a practical matter--and all gear sizes being equal, the metal gears will take more ABUSE.  The rating would be driven by the torque of the driver, in this case--the motor.  Less likely to strip them out on hard landings or whacking surfaces on the tailgate.  It would be interesting to do a study on air loads in a typical pattern ship on what the ideal ratings would be--probably much lower than many of us think!

  Richard
    ----- Original Message ----- 
    From: Bill Krueger 
    To: NSRCA 
    Sent: Wednesday, July 28, 2004 9:55 PM
    Subject: 8411 and 8411SA torque specs.


    I found that the torque rating from JR on the 8411 and 8411 SA are the same! 

    I would think that this means that the SA  plastic gear version is capable of handling the same torque as the metal gear, at least I would hope it means their "toughness" is the same.  

    I would expect that if the SA versions gears could not handle the torque without failing that they would rate the two servos differently.....What I am getting at is if the ratings are the same why would a person ever use the metal gear version?  If the ratings are the same than the plastic SA's gear train must be just as tough as the metal gear 8411.

    In other words can I use the 8411SA on a 35% plane with as much confidence as using a 8411 metal gear?

    flierbk
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