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Aileron trim servo

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Lew Gallagher

Joined: 04 Jan 2008
Posts: 402
Location: Greenville , SC

Posted: Thu Jan 28, 2010 6:22 pm Post subject: Aileron trim servo

Hey Guys,



I'm following up on Linn's advice to teach myself about the Parallax micro controllers and servos for aileron/rudder trim ... not for this project, but for the next one down the road.



It looks like there are MANY small hobby servos out there (Futaba) but with many different torque capacities.  Can somebody who's been this path before give me a model number that works?  These are durable and powerful enough?  Probably not a good idea to put them under the cowl to control air flow to oil cooler, etc.?



I haven't gotten into it yet, but I'm also wondering how you get the power supply down to 9v for the Stamp board? 



I know it's easier to just order Van's, etc.  but I really like the challenge and learning opportunity.



Later, - Lew

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_________________
non-pilot
crazy about building
NOW OFICIALLY BUILDER #40549
Fly off completed !

pitts_pilot(at)bellsouth.
Guest

Posted: Thu Jan 28, 2010 7:48 pm Post subject: Aileron trim servo

Lew Gallagher wrote:

 	  Quote: 	
		   

 <lewgall(at)charter.net>

 

 Hey Guys,

 

 I'm following up on Linn's advice to teach myself about the Parallax

 micro controllers and servos for aileron/rudder trim ... not for this

 project, but for the next one down the road.

 

 It looks like there are MANY small hobby servos out there (Futaba)

 but with many different torque capacities.  Can somebody who's been

 this path before give me a model number that works?

I used the one from Parallax (it's a futaba) .... just because I was 
	


ordering other stuff and already had one.  I needed two for aileron and 

rudder trim.

 	  Quote: 	
		    These are durable and powerful enough?

Well, it depends on the application, of course.  I think any of them 
	


would move a small trim tab.  They make really powerful ones that may 

even be able to be used as a door latch!

 	  Quote: 	
		   Probably not a good idea to put them

 under the cowl to control air flow to oil cooler, etc.?

They're pretty rugged.  Don't know for sure until someone tries it.
	


 	  Quote: 	
		   

 I haven't gotten into it yet, but I'm also wondering how you get the

 power supply down to 9v for the Stamp board?

LM7809 available from Radio Shack.  Cheaper elsewhere, but not with 
	


shipping!!!  I had used the BS2e on 12 V, but the voltage difference 

between that and the serial line (5V) will fry the serial port.  Worked 

great until I tried to program it again!!!

 	  Quote: 	
		   

 I know it's easier to just order Van's, etc.  but I really like the

 challenge and learning opportunity.

I wanted to have my trim equipment inside the surface being moved, and 
	


the small airplane servo fit the bill.

Linn



 	  Quote: 	
		   

 Later, - Lew

 

 -------- non-pilot crazy about building NOW OFICIALLY BUILDER #40549 

 Painting done! On with wiring and avionics.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p 83871#283871

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ricksked(at)cox.net
Guest

Posted: Thu Jan 28, 2010 8:27 pm Post subject: Aileron trim servo

Having quite a bit of R/C servo experience and Ray Allen being one of the first servo manufac. of servos for heavy duty use I can't see adapting some of the high speed/torq coreless bb servos for full scale use.



 In the large scale and ducted fan/turbine R/C aircraft the precise high torq BB servos really do fit the bill. For trim tabs you might as well buy a sail winch servo.. R/C servos as far as I know always draw current to hold position. For a long flight your asking that servo to maintain position and work constantly leading to early failure and not designed for that kind of extended use  like the Ray Allen trim servo which is geared to hold position all the time regardless if it has power...just something to think about...



Rick Sked

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pitts_pilot(at)bellsouth.
Guest

Posted: Thu Jan 28, 2010 8:48 pm Post subject: Aileron trim servo

ricksked(at)cox.net wrote:

 	  Quote: 	
		   

 

 Having quite a bit of R/C servo experience and Ray Allen being one of

 the first servo manufac. of servos for heavy duty use I can't see

 adapting some of the high speed/torq coreless bb servos for full

 scale use.

The Ray Allen servo's are just a motor with gear train, needing to run 
	


the motor forward and backwards.  It has no 'positioning' capability 

other than when you let your finger off the switch.  The model airplane 

servos are pulse width modulated (PWM) and seek a position based on the 

pulse width.

 	  Quote: 	
		   

 In the large scale and ducted fan/turbine R/C aircraft the precise

 high torq BB servos really do fit the bill. For trim tabs you might

 as well buy a sail winch servo..

?  didn't understand that one.  All I'm moving is a short length of hinge.
	


 	  Quote: 	
		   R/C servos as far as I know always

 draw current to hold position. For a long flight your asking that

 servo to maintain position and work constantly leading to early

 failure and not designed for that kind of extended use  like the Ray

 Allen trim servo which is geared to hold position all the time

 regardless if it has power...just something to think about...

The MA servos seem to last a whole lot longer than the MAs do! <GR>
	


Once the MA servo gets to it's commanded position .... nothing moves 

until the pulse width changes.  True, it consumes a little power, but 

it's miniscule.



I'm using the Ray Allen servo for the elevator trim only because it was 

part of the kit when I bought it.  I'd much rather have a smart servo 

that moves in small increments independent of how quick I am on the 

switch handle.



The only downside to using the MA servo is having to create the pulse width.

Linn



[quote] 

 Rick Sked ---

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ricksked(at)cox.net
Guest

Posted: Thu Jan 28, 2010 9:22 pm Post subject: Aileron trim servo

True dat Linn but you are reinventing the wheel, and in my ignorance I thought the servos were pulse code modulation??  Same thing?? and you hit the nail on the head...Why do you need a proportional servo for trim? Motor, gear box done....the R/C servo adds an additional fail point in the form of a potentiometer right? You've succeeded in reinventing the trim system and since were friends I totally know why you're doing it...cause you can and you're retired and it's what ya do!!!



Rick

Do not archive

Sent via BlackBerry by AT&T



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pitts_pilot(at)bellsouth.
Guest

Posted: Fri Jan 29, 2010 7:42 am Post subject: Aileron trim servo

ricksked(at)cox.net wrote:

 	  Quote: 	
		   

 

 True dat Linn but you are reinventing the wheel, and in my ignorance

 I thought the servos were pulse code modulation??  Same thing??

Well, no.  'Code' implies information sent in a string of bits .... like 
	


serial data.  The Trio 'gold standard' servos use a serial link to send 

positioning data.

 	  Quote: 	
		   and you hit the nail on the head...Why do you need a proportional servo

 for trim?

Because you can control it's exact position by sending pulses of a known 
	


width .... as in centering the trim, and you can control the speed 

(rate)the servo moves by changing the pulse width just a little and 

changing the time between pulses.

 	  Quote: 	
		   Motor, gear box done....the R/C servo adds an additional

 fail point in the form of a potentiometer right?

Oh, it gets worse than that!  What Lew and I are talking about is a 
	


little computer-on-a-chip.  It has 16 I/O pins and uses a little basic 

program that most anyone can write with a little practice.  I've used 

them in other applications.

 	  Quote: 	
		   You've succeeded in

 reinventing the trim system and since were friends I totally know why

 you're doing it...cause you can and you're retired and it's what ya

 do!!!

Well, that's pretty much it .... I think it boils down to trim by 
	


sledgehammer or mind-meld.  My friends liken it to polishing a horse 

turd .... what you get is a shiny turd.  Prettier, but still the same. 

Boils down to finess.  Like the door SB.  Sorry, couldn't resist!

Linn

[quote] 

 Rick Do not archive Sent via BlackBerry by AT&T

 

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