Servo Types

[Ed Miller]

All the analysis aside, Futaba 9202 coreless and 9001 coreless are a direct drop in replacement for the Futaba 148's already installed. The 9202's have 2 BB whereas the 9001's have 1 BB on top of shaft and a bronze bushing in bottom of shaft. The 9001's are cheaper and for all practical purposes will be fine. I've used both and can't tell the difference in the air. I suspect you will wear out the plane before you wear out either servo. If $$ is no object then the Futaba 9252 and 9151 digitals will drop in place with no mods. I have found generally I need more expo with the digitals over coreless. I went from Futaba 9204's coreless to Futaba 9252's and 9151 digitals on my Hanson Dalotel and found the digitals stronger/quicker around center thus requiring the increase in expo. I use 5 cell packs.
Ed M.
  ----- Original Message ----- 
  From: Ryan Wiesehan 
  To: discussion at nsrca.org 
  Sent: Saturday, March 20, 2004 5:37 PM
  Subject: Servo Types


  Hello,

  I tried to research this on my own without rehashing servo talk on the list, but I couldn't find an answer that satisfied my curiosity.  I will outline my research first so that you may better help me out.  I want to put new servos in my Used Summit III, it has 148's in it now and I think it flies great, no problem with torque, and there isn't a centering problem between days and flights.  But, I am always hearing that better servos will make you fly better.  And I want to be a better flier.  So, I have spent the last three weeks researching servos.  This research must be one of those instances when you are confused because you are paying attention.  I want is spend less than $180, $25 - $40 per servo and 40oz ok ailerons, 60oz rudder and elevator.  Here is how it breaks down in my mind from the research.  

   

  1.         The four basic qualifying specs for servos:  speed, torque, weight and price.

  2.         Then you have motor type and non-digital vs. digital.

  3.         Lastly, you have brand, and I've tried JR, Futaba, Hitec, TowerHobbies and Expert.  

   

  I am most interested in hearing your opinions about #'s 1 and 2; I don't really care to debate brand in this thread

   

   

  3-pole non-digitals; can have problems centering due to the splits in the armature.

   

  5-pole non-digitals; don't know there isn't really much information.  Would someone help?) I assume they have better centering and maybe more power than a 3-pole, I am thinking these might work for me so please try and sell me on the coreless. 

   

  Coreless non-digital; has a different armature system without poles that allows for better centering and a lighter core.  Most of the low end coreless seem like they are slower than a 3-pole.  I am starting to thing that the standard specs for speed are misleading. If the coreless motor is lighter and accelerates more quickly than a 3-pole why does a $30 coreless post the same specs as $9 el cheapo?

   

  Now, here is where I really get confused, change all of the above to digitals.  If the circuit board is always sending centering and position location at 3 times the rate previously to a 3-pole motor, why wouldn't I want to buy it?  It should center fine because with a digital servo centering is powered. 

   

  Wow, sorry, that was a long email.  I guess all that I am asking is for someone to explain why money spent on servos is valid.  Because, I just took out my plane last weekend after all this research and I couldn't figure out how it could be better. 

   

  Thanks,

   

  Ryan Wiesehan

   

  FreightQuote.com

  New Business Sales 

   

   

   
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