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Electronic Rudder Trim

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CDE2fly(at)aol.com
Guest

Posted: Fri Nov 02, 2007 7:16 pm Post subject: Electronic Rudder Trim

I'm nearing the completion of a Model 7 and considering the installation of  an electric rudder trim tab.  I've got the intercoastals in the fin and it  looks like the RAC system servo would fit inside the fin if mounted as far  forward as possible.  From the servo, I would run a small pushrod to a  hinged trim tab attached to the back of the fin.

  

 The only concern I have is the possibility that I would increase the  possibility of fin flutter by adding some additional weight behind the  rudder/fin hinge line.  The servo itself weighs 4 oz. plus another  couple of ounces for the mounting hardware  (although it would be mounted  close to the hinge line) and I suspect the trim  tab would weigh a  couple of ounces.   

  

 My feeling is that this would not be enough weight to be concerned  with...any thoughts?

  

 Thanks,

  

 Chris



See what's new  [quote][b]

jcorner(at)shaw.ca
Guest

Posted: Sat Nov 03, 2007 5:32 pm Post subject: Electronic Rudder Trim

Chris



I have been using electronic rudder, elevator and aileron  trim on my  

Model 2 for several years and have not had any problems with flutter.



I have used heavy duty R/C servos with great success.  So much so  

that I am incorporating built-in servos on my Model 5, I have attached a

photo of the rudder servo installation.



JIm



Model 2, 582,  IVO med IFA, 1100 hrs



Model 5 under construction

Calgary AB



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Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Sat Nov 03, 2007 7:53 pm Post subject: Electronic Rudder Trim

At 06:31 PM 11/3/2007, you wrote:

 	  Quote: 	
		  I have used heavy duty R/C servos with great success.


	


Jim,

         How do you drive them? I mean, what electrical signal do you 

supply and how do you control it?



Thanks,

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

jcorner(at)shaw.ca
Guest

Posted: Sat Nov 03, 2007 9:19 pm Post subject: Electronic Rudder Trim

Guy



Jointly with the help of an R/C tech type, a Motorola M68HC908  

microcontroller has been programmed to generate the required pulse  

widths

to operate the servos.  Variable potentiometers are used to input a  

signal to the microcontoller and the servos follow the potentiometer  

position.



A commercially available (R/C Hobby Shops) servo exorciser could be  

used or perhaps better would be the General Purpose Non-Mac Servo

controller offered by Eric Jones at http://www.PerihelionDesign.com



Jim



On 3-Nov-07, at 9:35 PM, Guy Buchanan wrote:



 	  Quote: 	
		  

 Jim,

         How do you drive them? I mean, what electrical signal do  

 you supply and how do you control it?



 Thanks,

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Sun Nov 04, 2007 7:37 am Post subject: Electronic Rudder Trim

At 09:16 PM 11/3/2007, you wrote:

 	  Quote: 	
		  Variable potentiometers are used to input a

signal to the microcontoller and the servos follow the potentiometer

position.


	


So then is the control a knob? Or can you do the "push to move" 

switch typical of trim systems?

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

jcorner(at)shaw.ca
Guest

Posted: Sun Nov 04, 2007 9:35 am Post subject: Electronic Rudder Trim

The control is a knob..... I initially started with a slide  

potentiometer for better visualization of the servo position but they  

are very scarce.

Since the servo always follows the pot position I think it is  

superior to the "push to move" switch systems.  With a dot or other  

marking  on the rotary knob

you always know the trim position.

JIm

Model 2, 582,  IVO med IFA, 1100 hrs

Model 5 under construction

Calgary AB

On 4-Nov-07, at 8:28 AM, Guy Buchanan wrote:

 	  Quote: 	

 At 09:16 PM 11/3/2007, you wrote:

> Variable potentiometers are used to input a

> signal to the microcontoller and the servos follow the potentiometer

> position.

 So then is the control a knob? Or can you do the "push to move"  

 switch typical of trim systems?

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Sun Nov 04, 2007 12:54 pm Post subject: Re: Electronic Rudder Trim

What servo do you use?  Is it a digital servo?



Thanks



DO NOT ARCHIVE

_________________
DO NOT ARCHIVE
Leonard Perry aka SNAKE
Soldotna AK
Avid "C" / Mk IV
582 (147 hrs and counting on the rebuild)
IVO IFA
Full Lotus 1450
#1 snake oil salesman since 1-22-2009

I would rather die trying to live, than to live trying not to die....

john(at)leptron.com
Guest

Posted: Sun Nov 04, 2007 2:37 pm Post subject: Electronic Rudder Trim

Hi Guys,

When I built my fox I bought a pot and digital box that I mounted a wheel to

that made it look just like a Cessna trim wheel. You set it where you want

it and it goes to that spot and stops. It also has a led system that is a 10

or 12 dashes to show the position of the trim. I use it on my elevator and

cowl flaps.

 I will be at the hanger in the morning and get the info off the box.

I used a mac servo cause that was what I had.



John Oakley

Speedster looking for a helicopter



--

jcorner(at)shaw.ca
Guest

Posted: Sun Nov 04, 2007 4:59 pm Post subject: Electronic Rudder Trim

On 4-Nov-07, at 1:54 PM, akflyer wrote:

 	  Quote: 	
		  --> Kitfox-List message posted by: "akflyer" <akflyer_2000(at)yahoo.com (akflyer_2000(at)yahoo.com)>What servo do you use?  Is it a digital servo?



	




I use a standard type R/C servo that has been around for at least 10 years.  Specifically a Hitec HS-805BB  1/4 Scale.

There is also a newer type servo that uses improved digital technology, but they are more expensive and I am quite satisfied 

with the above.



 Jim Corner

Model 2, 582,. Ivo med !FA, 1100 hrs

Model 5 under construction

Calgary, AB

 



 [quote][b]

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Sun Nov 04, 2007 5:16 pm Post subject: Re: Electronic Rudder Trim

thats the info I needed... a standard RC servo puts out ~42 oz. in of Tq.  The 805 is 343 oz. in



I have a few HS5955-TG that I will have to try out.



Thanks for the reply



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