JR821 servos  
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JR821 servos - 6/2/2008 3:01:20 AM   
andy38


 

Posts: 25
Joined: 11/7/2004
From: edmond, OK, USA
Status: offline 		I have a knight 50 glow heli, am new to helis, currently am using 3 jrds821 servos on the swash plate, had one servo brake at the spline shaft at the top of the servo,plastic
too britle, and have had another stop working, what are your experiences with these servos.
       Post #: 1

RE: JR821 servos - 6/2/2008 2:24:06 PM   
BarracudaHockey



Posts: 10584
Joined: 7/13/2003
From: Orange Park, FL, USA
Status: offline 		They specifically tell you not to use those servos for a 50 size nitro heli, apparently they shear shafts due to vibration.

Common problem when used beyond their specs.

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RE: JR821 servos - 6/3/2008 12:43:56 AM   
andy38


 

Posts: 25
Joined: 11/7/2004
From: edmond, OK, USA
Status: offline 		But what servos would be best to use?

(in reply to BarracudaHockey)
       Post #: 3

RE: JR821 servos - 6/3/2008 10:17:40 PM   
BarracudaHockey



Posts: 10584
Joined: 7/13/2003
From: Orange Park, FL, USA
Status: offline 		Depends on how much you want to spend.

9252s are good. 9452s are better, BLS 451s and 8717s are best.

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RE: JR821 servos - 6/4/2008 12:17:05 AM   
bayward


 

Posts: 176
Joined: 11/19/2006
From: Arcadia, FL, USA
Status: offline
quote:

ORIGINAL: BarracudaHockey

They specifically tell you not to use those servos for a 50 size nitro heli, apparently they shear shafts due to vibration.

Common problem when used beyond their specs.



Interesting. The JR Servo Guide lists the 821 as a recommended servo for a 30 to 50 size heli. Where does JR say not to use them ?

Bob

(in reply to BarracudaHockey)
       Post #: 5

RE: JR821 servos - 6/4/2008 12:28:41 AM   
BarracudaHockey



Posts: 10584
Joined: 7/13/2003
From: Orange Park, FL, USA
Status: offline 		It used to be easy to find on JRRadios.com in the hobby wire section but I can't find it. Its on Specktrum RC's site though
quote:

New Guidelines for DS821 Servo Use
Tuesday, February 20, 2007

The DS821 servo is a powerful, accurate sport digital servo recommended for RC airplane applications up to 1.20-size. For helicopters, the DS821 operates best with 30-size glow models, and up to 50-size electric. Loads and vibration in larger models may cause premature failure of the servo resulting in damage or injury to property and persons.

Important: Do not use liquid thread lock with the DS821 servo!

Do not use any form of liquid thread lock to secure the servo arm screw to the output shaft of the DS821 servo. Chemicals in these liquids react with the polycarbonate gear set causing the plastic to become brittle, fracturing the final output gear.




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       Post #: 6

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