RC Radios, Transmitters, Receivers, Servos, gyros Discussion all about rc radios, transmitters, receivers, servos, etc.

Servo Selection

Reply

Old 07-22-2006, 05:54 PM
  #1  
frabru
Junior Member
Thread Starter
 
Join Date: Jul 2006
Location: Altadena, CA
Posts: 22
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default Servo Selection

I just took delivery of one of the new Great Planes Giant Super Sporster ARF's. They recommend the Futaba 9001 servos that have 54.1oz. of torque at .4.8 volts I prefer the Hitech servos to be used with my JR transmitter. The plane will weigh between 13 and 14 pounds.

I'd like to keep the price between $25.00 and $30.00.

Does anyone have experience with a sport plane of this size 82" wing span, and weight/

Thanks
frabru is offline  
Reply With Quote
Old 07-23-2006, 07:46 AM
  #2  
dirtybird
My Feedback: (5)
 
Join Date: Jan 2002
Location: San Tan Valley, AZ
Posts: 5,768
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Servo Selection

I would recommend Hitec 6xx series. Say the 645. They won't center as well as the 9001 but they are stronger so you can gear them down more and compensate.
dirtybird is offline  
Reply With Quote
Old 07-23-2006, 08:47 AM
  #3  
rlmcnii
Senior Member
My Feedback: (3)
 
Join Date: Jul 2005
Location: Pocomoke City, MD
Posts: 525
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Servo Selection

This should become a very interesting post. It brings up a lot of questions about servo specifications and analog vs. digital servos.

The 9001 is an analog servo with a coreless motor; it neither particularly powerful nor particularly fast. Futaba does not publish (at least on the web) its deadband. Is not deadband a measure of a servo's ability to center (that is, return to the SAME center each time) itself?

Is there some method to determine a servo's ability to center itself without knowing deadband?

The Hitec 635 is both faster and more powerful than the 9001. hitec publishes its deadband as 4usec...pretty small deadband. The 645 is much more powerful and a little slower, wider deadband of 8uSec.

Can a non-professional R/Cer tell the difference between 4uSec and 8uSec?? Does it make a difference on a sport, or for that matter a replica Edge, Extra, or Yak, if the person behind the sticks is not someone about whom you read in the magazines?

If a digital servo has the same deadband, power, and speed as its analog cousin, is it a better servo? See the specifications on Hitec 475HBs and 5475HBs. I was planning to use one of these on the ailerons and elevators of a Kange Waco. One of them may be a good substitute for the 9001. I know you can program a digital servo, I've done it a few times and the ability to reverse the servo is very helpful. However, if you tighten up the deadband too much the servo will just sit there and sing. It seems never to be able to find its center.

I realize that most of the very powerful servos are digital and that if you have a need for a very powerful servo you must go digital. What about a case such as is posed by the original question in this post? One can find very nice, i.e. powerful, fast, servos with pretty tight deadbands (4uSec) that fall well within the $25 to $30 range. Are digitals always better? Why?

I have re-entered R/C within the past couple years and am relatively inexperienced. This is a request for information. Comments???

rlmcnii is offline  
Reply With Quote
Old 07-23-2006, 12:59 PM
  #4  
frabru
Junior Member
Thread Starter
 
Join Date: Jul 2006
Location: Altadena, CA
Posts: 22
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Servo Selection

Hey guys, thanks for the input. I've read the specs on the Hitec HS 636, and along with the price of about $30.00, this may be the servo I'll use for all of the comtrols. both the elevators and ailirons use dual servos, and the rutter uses one. What is a good one for the throttle? Thanks

Frank
frabru is offline  
Reply With Quote
Old 07-23-2006, 01:01 PM
  #5  
frabru
Junior Member
Thread Starter
 
Join Date: Jul 2006
Location: Altadena, CA
Posts: 22
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Servo Selection

Opps, I ment tosay Hitec HS 635 HB.

Frank
frabru is offline  
Reply With Quote
Old 07-23-2006, 05:08 PM
  #6  
rlmcnii
Senior Member
My Feedback: (3)
 
Join Date: Jul 2005
Location: Pocomoke City, MD
Posts: 525
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Servo Selection

frabru,

I don't think the Super Sportster will be a killer 3-D machine, or are you planning on using it as one? If GP recommends the 9001 all around then any servo equal to, or better than, the 9001 should be fine. I think the very powerful servos are necessary for large, powerful (read: big gasser) 3-D machines with huge 3-D control surface movements.

There is a little factor of which you should be aware: Hitec recommends, when using karbonite-geared servos, to have one servo per surface per 12 pounds of airplane. You are real good on the elevators and perhaps marginal on the ailerons and rudder. However, the 635HB is so much more powerful than the 9001 you will not be loading it heavily at all. There is a Hitec Sub-Forum in this Forum. Perhaps you could ask the Hitec guy.

The Super Sportster is a nice looking airplane. Hope it works out well for you.
rlmcnii is offline  
Reply With Quote
Old 07-23-2006, 05:50 PM
  #7  
frabru
Junior Member
Thread Starter
 
Join Date: Jul 2006
Location: Altadena, CA
Posts: 22
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Servo Selection

Thanks for the information. No there is no 3D flying in my future. Just some easy Sunday sport flying. Very basic aerobatics. That's about it. So the Hitec 635 looks like a good overall choice.
frabru is offline  
Reply With Quote
Old 07-23-2006, 08:26 PM
  #8  
rlmcnii
Senior Member
My Feedback: (3)
 
Join Date: Jul 2005
Location: Pocomoke City, MD
Posts: 525
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Servo Selection

frabru,

Sounds as if you like to fly like I like to fly!! I can not imagine that the Super Sportster would load the 635HB to the point of failure. It will barely be working.
rlmcnii is offline  
Reply With Quote
Old 07-23-2006, 10:01 PM
  #9  
frabru
Junior Member
Thread Starter
 
Join Date: Jul 2006
Location: Altadena, CA
Posts: 22
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default RE: Servo Selection

Thanks for the vote of confidence. I ordered the Hitech HS 635HB's tonight.

Now if I could just decide on an engine.
frabru is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service