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Rudder Trim - Spring Bias

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rj_todd(at)yahoo.co.uk
Guest

Posted: Fri May 09, 2008 12:42 am Post subject: Rudder Trim - Spring Bias

Hi Jason,



I was wondering how you are going with the development of the rudder trim?



Best wishes,



Rodger

--- On Fri, 22/2/08, jason.kreidler(at)regalbeloit.com <jason.kreidler(at)regalbeloit.com> wrote:



 	  Quote: 	
		   From: jason.kreidler(at)regalbeloit.com <jason.kreidler(at)regalbeloit.com>

 Subject: Rudder Trim - Spring Bias

 To: rv10-list(at)matronics.com

 Date: Friday, 22 February, 2008, 6:55 PM

 I have 'developed' a spring bias rudder trim system

 for the RV-10.  After 

 sharing this idea with Deems he encouraged me to do the

 same with the rest 

 of the group.  So here goes, but before I get into any

 details let me 

 preface this whole conversation with a few thoughts.  This

 is all in 

 theory, I have absolutely no actual flight testing to back

 up any of the 

 'claims', or assumptions.  Just good old common

 sense and a tiny bit of 

 engineering.  Our airplane is not in the air yet, I had

 hoped to get in 

 the air, prove out the system, then share with the world. 

 To prevent 

 anyone else for possibly needlessly cutting into their

 rudder to add a 

 trim tab, I have decided to bear the scrutiny of an

 unproven, theoretical 

 system.  Please be gentle...

 

 I will attempt to verbalize the system.  I used two torsion

 springs, one 

 mounted / wrapped around, each rudder bar (the bar that

 connects the 

 rudder pedals).  One of the springs is fixed on both ends

 providing a 

 torsional force on the rudder bar.  The other springs free

 end is hooked 

 to a servo motor that allows approximately 30 degrees

 deflection.  The 

 theory is that the two springs will seek equilibrium (OK,

 that's not much 

 theory, that's more fact), here is where the testing

 needs to happen.  If 

 I deflect the one springs free arm 30 degrees, will it

 create enough force 

 to put the airplane in trim.  The springs apply about an 8

 pound force to 

 the rudder cables (pre-load if you will), assuming they

 will want to 

 maintain in equilibrium a 30 degree deflection should be

 more than enough 

 to trim the airplane.  The servo will act as sort of a fine

 tuning 

 mechanism, the course adjustment will be accomplished by

 winding more or 

 less tension in one spring or the other during flight

 testing.

 

 I like a few things about this method.

 1) It can be installed to any flying airplane with no

 modifications 

 required other than wiring.

 2) There is a chance that this system could be made manual

 and eliminate 

 the RAC servo if desired.

 3) This system provides tension to both rudder cables, no

 more 'flopping 

 rudder'.

 4) Keeps the rudder 'clean'.

 5) Doesn't add much extra rudder input force.

 

 I sent pictures of this system to Deems, I will

 'attempt' to post some 

 pictures to this forum if there is interest.  Comments

 welcome, I 

 apologize for the extremely long post, but I have added

 Deems questions 

 below, I figured if he asked, many more will have the same

 questions....

 

 

 1. How did you determine which spring type/size/strength to

 use?

 OK, you busted me!!  I didn't do the math, I feel

 extremely guilty about 

 this, as an engineer, I should probably go back and figure

 the forces 

 here.  Here is what I did; since I grew up in the business

 of garage doors 

 (my Dad owned his own company doing this), I went to Fleet

 Farm (one of 

 our local supply houses, similar to most lumbar yards) and

 found a garage 

 door spring that had an ID that would slide over the rudder

 bar with room 

 to spare, and would fit between the two rudder bars (I will

 measure this 

 for you).  I then cut lengths of the spring until I got

 what I 'thought' 

 was a reasonable amount of force with two turns of

 pre-load, and bent some 

 custom ends on them.  With torsion springs you have two

 options to 

 increase the reaction force.  You can add turns of

 pre-load, or you can 

 shorten the spring with the same number of turns.  I just

 went until I 

 reached what I 'felt' was a happy medium.  Remember

 that as you wind a 

 torsion spring more and more the inside diameter decreases,

 until it 

 eventually binds on the shaft (rudder bar).  What mostly

 drove me not to 

 do the math, was I had absolutely no idea what sort of

 corrective rudder 

 pressure was required to put the ball in the middle.  My

 plan all along 

 has been to get it in the air and do some experimenting, I

 installed the 

 system so that modification of the spring force should be

 simple.  I just 

 need to start dating a contortionist 

 

 2. I assume that you can 'adjust the torsional load

 somewhat by moving 

 the collar/s, Is that true?

 Correct, I started out with each spring wound an equal

 amount.  If I find 

 that I need additional trim to one side or the other I will

 wind one of 

 the springs to compensate.  The servo will just provide the

 'fine tuning'.

 

 3. One of the pictures shows the center support brace minus

 the delrin 

 bushings, I'm assuming that leaving those out is not a

 requirement of 

 your approach and was just the result of taking the picture

 before they 

 were installed?

 Correct, in fact there isn't a single modification to

 the airframe, if I 

 remove the system no one could ever tell it was installed. 

 I built the 

 mount so that it could be used in either the forward or aft

 rudder 

 mounting positions, my pedals are mounted in the aft

 position.  But I 

 drilled and prepped the airframe to mount the rudder pedals

 in either 

 position.

 

 4. What about the mount for the RAC servo, do you have a

 picture of it 

 before the servo is mounted.

 See attached....  The angle was determined by something, I

 just don't 

 recall what anymore.  I know it has to be at an angle to

 work though.  I 

 can measure if you decide to attempt this.

 

 5. Also it' looks like you used a small section of SS

 cable to connect 

 the servo arm to the spring coil, correct? Picture?

 Correct, see attached.  One end is run through the servo

 arm, the other 

 gets hooked by the spring.  The spring on the pilot side is

 hooked over 

 the opposite rudder bar.

 

 I gave some thought to your desire to have a manually

 operated system, I 

 think this system could be done manually with very little

 pain.  You may 

 be able to add a knob that would come out of the sub panel,

 really 

 anywhere along its length.  What would have to happen is a

 bracket would 

 need to be made that slid over the rudder bar with a nut in

 it.  Then a 

 threaded shaft running from the rudder bar to the sub panel

 would be used 

 to adjust the free arm of the spring.  It may be best if

 the spring were 

 pushed by the shaft instead of pulled, as this would make

 the mechanism a 

 bit simpler.  I could do a drawing of what I am thinking if

 you are not 

 following.

 

 While it was not my intention to begin producing kits, if

 there is enough 

 interest, I could be persuaded to fabricate a few.

 

 Thanks, Jason

 

 Jason Kreidler - 40617 Finishing

 (4 Partner Build)


	




      __________________________________________________________

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jkreidler

Joined: 13 Feb 2008
Posts: 151
Location: Sheboygan Falls WI

Posted: Mon May 12, 2008 4:09 am Post subject: Rudder Trim - Spring Bias

All, I have received several off-line inquiries as to the status of the development of the spring bias rudder trim system.  The work continues however, it has gone down an unexpected path.  Since receiving so many requests for kits, I decided it would be best to put pencil to paper and actually calculate the trim forces we could expect to see.  Well, numbers don't lie (if you ask the right question), and the numbers didn't look good.  The maximum trim force I could accomplish given the limits of the servo motor both in stroke, and thrust, is 2lbs. 

 

This is far below the value required to effectively trim the aircraft through a wide range of the flight envelope.  Van's estimated the required forces to be 5-10 lbs for 'standard' trim, and 25 lbs for takeoff measured at the bottom of the rudder pedal.  I had a conversation with Ken from Vans at Sun-N-Fun, I asked him "If you were going to design a rudder trim for the 10 what would it look like?".  Long answer short, he would design a spring bias system, he would not add a movable trim tab to the rudder due to the potential to put the rudder out of balance.  Please note, I am not trying to start a war here on the better way to add trim, just relaying what I was told.  He liked a spring system because it holds a bit of pressure on the rudder, which could eliminate some adverse yaw in turbulence.  I asked him why they haven't designed a system yet, and he first replied, we really don't think it is necessary, he then said that he has tried a few times and couldn't come up with a simple enough solution. 

 

So, what does this all mean?  After seeing the post by Albert Gardner I started to rethink the concept.  I liked the idea of using extension springs, as they would allow the forces acting on the servo to stay within limits, while providing 10+ lbs of trim force.  I still like the idea of keeping the rudder cables under tension throughout the system, this means the springs still need to be connected up-front.  I have some ideas, but have not assemble the complete concept yet.  Unfortunately it will not be as simple, which is a big negative in my book, I really like simple! 

 

All is not lost, if a person does not want rudder trim, but is tired of 'floppy rudder syndrome' the torsion springs provide enough force.  They can be wound during installation to accomplish a certain fixed trim force, eliminating the need to glue a trim block to the rudder.  I will let everyone know how this all turns out.  Sorry for not sending an update earlier, but I have been trying to get a complete answer before posting something again. 



 Thanks, Jason Kreidler 

N44YH - #40617 - Finishing 

4 Partner Build 

Jason Kreidler, Tony Kolar, Kyle Hokel, and Wayne Elsner 

Sheboygan Falls, WI [quote][b]

_________________
Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617

pitts_pilot(at)bellsouth.
Guest

Posted: Mon May 12, 2008 5:14 am Post subject: Rudder Trim - Spring Bias

I was going to reply off-line but decided that maybe more ideas can be generated as a group:

 jason.kreidler(at)regalbeloit.com (jason.kreidler(at)regalbeloit.com) wrote:  	  Quote: 	
		  

   All, I have received several off-line inquiries as to the status of the development of the spring bias rudder trim system.  The work continues however, it has gone down an unexpected path.  Since receiving so many requests for kits, I decided it would be best to put pencil to paper and actually calculate the trim forces we could expect to see.  Well, numbers don't lie (if you ask the right question), and the numbers didn't look good.  The maximum trim force I could accomplish given the limits of the servo motor both in stroke, and thrust, is 2lbs.   

 	
 I assume, from the statement below that this only applies to the torsion spring design .....  so why not a small jackscrew instead of a trim servo?

 SNIP

  	  Quote: 	
		  So, what does this all mean?  After seeing the post by Albert Gardner I started to rethink the concept.  I liked the idea of using extension springs, as they would allow the forces acting on the servo to stay within limits, while providing 10+ lbs of trim force.  I still like the idea of keeping the rudder cables under tension throughout the system, this means the springs still need to be connected up-front.  I have some ideas, but have not assemble the complete concept yet.  Unfortunately it will not be as simple, which is a big negative in my book, I really like simple!   

 	
 Simple is always good!  I think if there was a simple solution, it would have shown up already.  There are a lot of great minds out there so there should have been something pop up .... even if it wasn't a really great solution, it would be a start.

  	  Quote: 	
		  All is not lost, if a person does not want rudder trim, but is tired of 'floppy rudder syndrome' the torsion springs provide enough force. 	
 I've never had an airplane with the 'floppy rudder syndrome' ..... and really don't want to start now.  I own a Grumman AA-1B with rudder springs ...... the only problem with them is that they're really strong springs and they break ...... but folks smarter than me have devised a 'washer' tool to aid in changing them out.  The springs really cure the 'floppy rudder syndrome' which means we have to incorporate a good rudder gust lock to tame the beast.  I've modified my rudder pedal attach point to be inside the tunnel, (don't like sand and dirt on my cables) and have thought of a pulley attached to the firewall to make a closed loop system .... or extension springs to the firewall ...... after I find a good spot and beef it up a little.  Alas, I just don't have a good answer.

   	  Quote: 	
		    They can be wound during installation to accomplish a certain fixed trim force, eliminating the need to glue a trim block to the rudder.  I will let everyone know how this all turns out. 	
 Thanks for your time/effort.  Other than the jackscrew solution, I'm not much help.

  	  Quote: 	
		    Sorry for not sending an update earlier, but I have been trying to get a complete answer before posting something again.

 	
 Rome wasn't built in a day (although I wasn't there to figure out why   ) and the solutions to difficult problems take time ..... and I'll really be thinking of a solution before I get too far down the assembly path where it's nigh on impossible to install a mod.

 Linn

 do not archive

 

 [quote]

 Thanks, Jason Kreidler   

   N44YH - #40617 - Finishing   

   4 Partner Build   

   Jason Kreidler, Tony Kolar, Kyle Hokel, and Wayne Elsner   

   Sheboygan Falls, WI    	  Quote: 	
		  



 href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List

 href="http://forums.matronics.com">http://forums.matronics.com

 href="http://www.matronics.com/contribution">http://www.matronics.com/contribution



	
 [b]

dlm46007(at)cox.net
Guest

Posted: Mon May 12, 2008 5:38 am Post subject: Rudder Trim - Spring Bias

What kinds of problems have been seen with the glued tab or  the riveted tab other than it has only a cruise airspeed  setting?

   From: owner-rv10-list-server(at)matronics.com  [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of linn  Walters

Sent: Monday, May 12, 2008 5:51 AM

To:  rv10-list(at)matronics.com

Subject: Re: Rudder Trim - Spring  Bias

I was going to reply off-line but decided that maybe more ideas can  be generated as a group:

jason.kreidler(at)regalbeloit.com (jason.kreidler(at)regalbeloit.com)  wrote:   	  Quote: 	

All, I have received several    off-line inquiries as to the status of the development of the spring bias    rudder trim system.  The work continues however, it has gone down an    unexpected path.  Since receiving so many requests for kits, I decided it    would be best to put pencil to paper and actually calculate the trim forces we    could expect to see.  Well, numbers don't lie (if you ask the right    question), and the numbers didn't look good.  The maximum trim force I    could accomplish given the limits of the servo motor both in stroke, and    thrust, is 2lbs. 

I assume, from the statement below that  this only applies to the torsion spring design .....  so why not a small  jackscrew instead of a trim servo?

SNIP

  	  Quote: 	
		  So, what does this all mean?     After seeing the post by Albert Gardner I started to rethink the    concept.  I liked the idea of using extension springs, as they would    allow the forces acting on the servo to stay within limits, while providing    10+ lbs of trim force.  I still like the idea of keeping the rudder    cables under tension throughout the system, this means the springs still need    to be connected up-front.  I have some ideas, but have not assemble the    complete concept yet.  Unfortunately it will not be as simple, which is a    big negative in my book, I really like simple! 

Simple is  always good!  I think if there was a simple solution, it would have shown  up already.  There are a lot of great minds out there so there should have  been something pop up .... even if it wasn't a really great solution, it would  be a start.

  	  Quote: 	
		  All is not lost, if a person does not    want rudder trim, but is tired of 'floppy rudder syndrome' the torsion springs    provide enough force. 	
I've never had an airplane with the  'floppy rudder syndrome' ..... and really don't  want to start now.  I own a Grumman AA-1B with rudder springs ..... the  only problem with them is that they're really strong springs and they break  ..... but folks smarter than me have devised a 'washer' tool to aid in changing  them out.  The springs really cure the 'floppy rudder syndrome' which means we have to incorporate a good rudder  gust lock to tame the beast.  I've  modified my rudder pedal attach point to be inside the tunnel, (don't like sand  and dirt on my cables) and have thought of a pulley attached to the firewall to  make a closed loop system .... or extension springs to the firewall ..... after  I find a good spot and beef it up a little.  Alas, I just don't have a good  answer.

  	  Quote: 	
		   They can be wound during    installation to accomplish a certain fixed trim force, eliminating the need to    glue a trim block to the rudder.  I will let everyone know how this all    turns out. 	
Thanks for your time/effort.  Other than the  jackscrew solution, I'm not much help.

  	  Quote: 	
		   Sorry for not sending an update    earlier, but I have been trying to get a complete answer before posting    something again.

Rome wasn't built in a day (although I  wasn't there to figure out why   ) and the solutions to difficult problems take time ..... and I'll  really be thinking of a solution before I get too far down the assembly path  where it's nigh on impossible to install a mod.

Linn

do not  archive

 [quote]

Thanks, Jason Kreidler    

N44YH - #40617 - Finishing 

4 Partner Build 

Jason Kreidler, Tony Kolar, Kyle Hokel, and Wayne Elsner    

Sheboygan Falls, WI  	  Quote: 	

 href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List

 href="http://forums.matronics.com">http://forums.matronics.com

 href="http://www.matronics.com/contribution">http://www.matronics.com/contribution

href="http://www.matronics.com/Navigator?RV10-List">http://www.matronics.com/Navigator?RV10-List

href="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/c

[b]

MauleDriver(at)nc.rr.com
Guest

Posted: Mon May 12, 2008 6:12 am Post subject: Rudder Trim - Spring Bias

I haven't been following this real closely but am very interested in 

working solution ... excuse me if this has been covered.



Since servo force required is an issue, have you considered a totally 

manual/mechanical system?   For example, actuation via a pull on 

T-handle with a  twist to lock mechanism.  This is what my Maule uses 

though I am only familiar with the operation of it, not the design.



Bill "bonding doors" Watson

Durham

do not archive

ogdenk

Joined: 05 Feb 2007
Posts: 41
Location: Syracuse, NY

Posted: Mon May 12, 2008 6:22 am Post subject: Rudder Trim - Spring Bias

Jason,

  

 Although I am quite early in the build, I have followed the rudder trim threads with interest and I thought that the torsion spring was a great idea.  I was afraid that the linear servo approach might not work though, and am sorry to hear your results.  The reason it doesn't work, as you found, is that the torque gradient (amount of torque per unit angular displacement) of the torsion spring is too low, so the linear servo can't produce enough displacement to generate the required force.  The thing is, the low torque gradient is necessary or a large force from the pilots leg will be required to fully displace the rudder pedal.

  

 I think this could be made to work in the same way that my garage door tensioner works.  It uses a worm gear to drive another gear that is fixed to the end of the spring.  You stick a hex driver in the end of the worm gear and turn it with an electric drill to tension the torsion spring.  The amount of rotation of the spring is essentially unlimited using this method.  The ratio of the worm gear rotations to torsion spring rotations is high, so any typical electric drill can provide enough torque to tension the spring.  

  

 The analog for the rudder trim would be a 'rotary' servo (not sure if this is correct terminology, I don't see this kind of thing on the Ray Allen web site) that could spin a worm gear in either direction, driving a second gear that is coaxial to and attached to the torsion spring, to tension the spring.  Much more complicated than what you tried, but I still like it better (at this point at least) than chopping up my rudder to add a trim system.  Nothing beats the simplicity of a trim tab though!

  

 Kent Ogden

 #40710  Tailcone 



 	  Quote: 	
		  >> <jason.kreidler(at)regalbeloit.com> 5/12/2008 8:03 AM >>>


	


All, I have received several off-line inquiries as to the status of the development of the spring bias rudder trim system.  

  

 <<SNIPPED>>

  

  

 Thanks, Jason Kreidler 

N44YH - #40617 - Finishing 

4 Partner Build 

Jason Kreidler, Tony Kolar, Kyle Hokel, and Wayne Elsner 

Sheboygan Falls, WI 

 	  Quote:

Deems Davis

Joined: 09 Jan 2006
Posts: 925

Posted: Mon May 12, 2008 6:47 am Post subject: Rudder Trim - Spring Bias

I just returned from The NW RV-10 builders semi annual dinner/get 

together. There were 6-7 RV-10's that flew in for it. Among them was 

Bill & Susie DeRouchey's plane from So Calif. Bill showed us his 

solution for rudder trim. I was blown away !!!!! It is similar in 

concept to what Bill Watson is suggesting, it is _elegantly simple_, 

easy to implement and very effective. and has some benefits beyond trim. 

I don't want to steal Bill's thunder so I'll wait for him to respond 

directly. Bill and Susie are probably flying back home and it may be a 

day or two before he's back on the list. When he reads this I'm hoping 

he'll post some pictures and additional information. (I left my camera 

in the bag in my room and couldn't take any pics).

MauleDriver wrote:

 	  Quote: 	
		  

 considered a totally manual/mechanical system?   For example, 

 actuation via a pull on T-handle with a  twist to lock mechanism. 


	


PS. You should also see what the artistry and engineering of Paul 

Grimstad has developed?  (I'm salivating over it!!!!!!!!!)

 Deems Davis # 406

'Its all done....Its just not put together'

http://deemsrv10.com/

jkreidler

Joined: 13 Feb 2008
Posts: 151
Location: Sheboygan Falls WI

Posted: Tue May 13, 2008 5:36 am Post subject: Rudder Trim - Spring Bias

A few response rolled into one. 

 

"so why not a small jackscrew instead of a trim servo?" 

If I could find something light, inexpensive, and simple, it would certainly be an option.  Anyone have a source? 

 

"What kinds of problems have been seen with the glued tab or the riveted tab other than it has only a cruise airspeed setting?" 

Absolutely no problems at all, rudder trim may not be high on some lists, but it is on mine.  The fixed trim offers great benefit (extremely simple), at of course a price (fixed trim).  I know others have decided not to install trim, still others have cut into a perfectly good painted rudder to add trim.  Like any option it is a personal choice. 

 

"Since servo force required is an issue, have you considered a totally manual/mechanical system?" 

Yes, just haven't found a cute, light way of doing it.  However, electric means it can be buried in any orientation at any location, opening up more mounting options.  A manual system would be a real benefit, as I know a few are looking for a manual system. 

 

"I think this could be made to work in the same way that my garage door tensioner works." 

This would be an great approach, the question is where to get something like this? 

 

The great thing about sharing ideas is the collaboration.  Many of us have obviously been thinking of different approaches to this 'problem'.  In looking over Bill DeRouchey's approach I got to thinking... 

 

I think the secret to making this really simple is to start with a completely closed loop system.  So what would happen if we mounted a pulley to the firewall centered between the left and right rudder pedals on either the pilot or copilot side of the aircraft.  Then connect a cable to the two pedals routed through the pulley.  This gets us a closed loop system. 

 

Next we use Bill's concept, with a few changes.  Since we now have a closed loop, we only need to act on one of the rudder cables.  So instead of clamping the cable, we clamp two springs to the cable (about 12 inches apart), these two springs are then hooked in the middle to the knob that passes through the tunnel wall.  The tunnel wall is slotted, allowing the knob to move fore and aft.  So to adjust the trim you would loosen the knob slide it back until you center the ball, then re-tighten the knob.  The springs would still allow full use of the rudder, and the world is in perfect harmony.  Well, at least the ball is in the center. 

 

I wonder if the cable needs to be supported between the springs, I keep thinking that the springs would just want to pull together leaving the cable slack between the springs.  Maybe since the system is now closed, the two trim springs would act as a 'slack take-up'.  Also, not sure if there is enough room to fit the forward spring, and still keep the knob where it can be reached. 

 

What I like is the fact that we can now have either manual or electric trim.  In addition this certainly meets the simple, and relatively easy to install criteria.  Any thoughts? 

 

Thanks, Jason Kreidler

 N44YH - #40617 - Finishing

 4 Partner Build

 Jason Kreidler, Tony Kolar, Kyle Hokel, and Wayne Elsner

 Sheboygan Falls, WI [quote][b]

_________________
Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617

pitts_pilot(at)bellsouth.
Guest

Posted: Tue May 13, 2008 9:35 am Post subject: Rudder Trim - Spring Bias

jason.kreidler(at)regalbeloit.com (jason.kreidler(at)regalbeloit.com) wrote:  	  Quote: 	
		  

   A few response rolled into one.   

   

   "so why not a small jackscrew instead of a trim servo?"   

   If I could find something light, inexpensive, and simple, it would certainly be an option.  Anyone have a source?   

   	
 I'll google and see what I can find ..... after all, it was my suggestion.

  	  Quote: 	
		  

   "What kinds of problems have been seen with the glued tab or the riveted tab other than it has only a cruise airspeed setting?"   

   	
 None that I know of.  I'm operating in the dark here so just giving it some thought ..... the fixed trim works best at one cruise speed  .... and at one density altitude ..... 

  	  Quote: 	
		  Absolutely no problems at all, rudder trim may not be high on some lists, but it is on mine.  The fixed trim offers great benefit (extremely simple), at of course a price (fixed trim).  I know others have decided not to install trim, still others have cut into a perfectly good painted rudder to add trim.  Like any option it is a personal choice.   

   	
 Absolutely.  That is, I guess, the crux of my problem ..... the decision on what path to go is purely subjective on the part of the builder taking that path.  I felt that any good autopilot should be able to handle the trim problem, but others tell me the autopilot will either disconnect or the servo's will, at swome point, lock up or slip.

  	  Quote: 	
		  "Since servo force required is an issue, have you considered a totally manual/mechanical system?"   

   Yes, just haven't found a cute, light way of doing it.  However, electric means it can be buried in any orientation at any location, opening up more mounting options.  A manual system would be a real benefit, as I know a few are looking for a manual system. 	
 A simple solution is hampered by the fact the pedals flop.  the closed loop solution (below) really makes the difficult part go away.

  	  Quote: 	
		  "I think this could be made to work in the same way that my garage door tensioner works."   

   This would be an great approach, the question is where to get something like this?   

   

   The great thing about sharing ideas is the collaboration.  Many of us have obviously been thinking of different approaches to this 'problem'.  In looking over Bill DeRouchey's approach I got to thinking...   

   

   I think the secret to making this really simple is to start with a completely closed loop system.  So what would happen if we mounted a pulley to the firewall centered between the left and right rudder pedals on either the pilot or copilot side of the aircraft.  Then connect a cable to the two pedals routed through the pulley.  This gets us a closed loop system.   

   

   Next we use Bill's concept, with a few changes.  Since we now have a closed loop, we only need to act on one of the rudder cables.  So instead of clamping the cable, we clamp two springs to the cable (about 12 inches apart), these two springs are then hooked in the middle to the knob that passes through the tunnel wall.  The tunnel wall is slotted, allowing the knob to move fore and aft.  So to adjust the trim you would loosen the knob slide it back until you center the ball, then re-tighten the knob.  The springs would still allow full use of the rudder, and the world is in perfect harmony.  Well, at least the ball is in the center.   

   

   I wonder if the cable needs to be supported between the springs, I keep thinking that the springs would just want to pull together leaving the cable slack between the springs.  Maybe since the system is now closed, the two trim springs would act as a 'slack take-up'.  Also, not sure if there is enough room to fit the forward spring, and still keep the knob where it can be reached.   

   

   What I like is the fact that we can now have either manual or electric trim.  In addition this certainly meets the simple, and relatively easy to install criteria.  Any thoughts?   

   	
 A simple (in my mind, anyway) would be to make the rudder system closed loop.  This will allow the two-springs on one cable possible.  Next we put the end of a vernier control cable on the center of the two springs .... and we can adjust the tension on the springs to bias the rudder.  How well it works is dependent on the tension and length of the springs.  I have to admit I'm not a fan of the 'gripped cable' mod but I do admire it's simplicity.

 Linn

 do not archive

 [quote]

   Thanks, Jason Kreidler

 N44YH - #40617 - Finishing

 4 Partner Build

 Jason Kreidler, Tony Kolar, Kyle Hokel, and Wayne Elsner

 Sheboygan Falls, WI    	  Quote: 	
		  



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 [b]

Albert Gardner

Joined: 10 Jan 2006
Posts: 455
Location: Yuma, AZ

Posted: Wed May 14, 2008 9:13 pm Post subject: Rudder Trim - Spring Bias

I have been doing a little testing of my spring bias trim system. I did not

measure rudder pedal forces required but the spring bias system has almost

enough force on take off so that only a little right rudder pressure is

required and the same for slow flight. Otherwise for normal climb, cruise

and descents the trim system will center the ball. It was easy to install as

Vans aileron trim servo is used as is and 4 holes drilled in the bottom of

the tail cone to install it. The turn around pulley bracket is simple to

fabricate and bolts to the elevator bell crank housing assy. The hardest

part was pulling additional rudder cables from the trim servo arm back to

the rudder horn. Also, having 2 rudder cables attached to the rudder horn is

the one thing I don't like about the system. I already had a 5 wire cable

installed in the tail come anticipating rudder trim at some later point when

I built the plane and a Ray Allen LED trim indicator and switch on the panel

with wiring completed. The trim forces are fairly easy to overcome so run

away trim doesn't seem to be a big worry. All in all I'm very happy with the

system. Frankly, the idea of clamping the rudder cables to effect trim seems

difficult for me to accept.

Albert Gardner

N991RV

Yuma, AZ

_________________
RV-9A N872RV
RV-10 N991RV

pitts_pilot(at)bellsouth.
Guest

Posted: Thu May 15, 2008 4:56 am Post subject: Rudder Trim - Spring Bias

I'm sure there are  more than a few that would like to see some pictures!!!

Linn

do not archive



Albert Gardner wrote:

 	  Quote: 	
		   



 I have been doing a little testing of my spring bias trim system. I did not

 measure rudder pedal forces required but the spring bias system has almost

 enough force on take off so that only a little right rudder pressure is

 required and the same for slow flight. Otherwise for normal climb, cruise

 and descents the trim system will center the ball. It was easy to install as

 Vans aileron trim servo is used as is and 4 holes drilled in the bottom of

 the tail cone to install it. The turn around pulley bracket is simple to

 fabricate and bolts to the elevator bell crank housing assy. The hardest

 part was pulling additional rudder cables from the trim servo arm back to

 the rudder horn. Also, having 2 rudder cables attached to the rudder horn is

 the one thing I don't like about the system. I already had a 5 wire cable

 installed in the tail come anticipating rudder trim at some later point when

 I built the plane and a Ray Allen LED trim indicator and switch on the panel

 with wiring completed. The trim forces are fairly easy to overcome so run

 away trim doesn't seem to be a big worry. All in all I'm very happy with the

 system. Frankly, the idea of clamping the rudder cables to effect trim seems

 difficult for me to accept.

 Albert Gardner

 N991RV

 Yuma, AZ

Tim Olson

Joined: 25 Jan 2007
Posts: 2881

Posted: Thu May 15, 2008 12:18 pm Post subject: Rudder Trim - Spring Bias

Don Orrick sent me some photos and info on a rudder trim setup

that he's using in his RV-10.  It's got a vernier control and

doesn't lock any cables anytime.  He admits it to be slightly

crude as it's a proof-of-concept that he actually has flying,

but it could be cleaned up to be pretty nice if someone wanted

it different.  I'm just passing on the info to you all in case

you like the idea.



It's in my Tips area at: (with photos)



http://www.myrv10.com/tips/mods/RudderTrim/DonOrrick.html

I'm surprised at how long the rudder trim thread lasts. It

seems to me that there are just so many ideas to ponder.

Personally, the electric servo trim tab seems pretty

simple and straightforward and actually took very little

effort and time to install...and I left the rudder on

the plane to do it, so I'm not sure why people spend tons

of time and effort on other ideas, but it's showing to be

a good thinking exercise at least.  And between Albert

and Don, these systems are pretty true to the simple

rudder trim concept, without affecting rudder pedal function.



For me, a static wedge was pretty good for a long time.

The adjustable trim is very nice to have...and I personally

feel it's hard to beat a quick tap of a button to center

it...with no cable involvement at all.



Tim Olson - RV-10 N104CD - Flying



Albert Gardner wrote:

 	  Quote: 	
		   

 

 I have been doing a little testing of my spring bias trim system. I did not

 measure rudder pedal forces required but the spring bias system has almost

 enough force on take off so that only a little right rudder pressure is

 required and the same for slow flight. Otherwise for normal climb, cruise

 and descents the trim system will center the ball. It was easy to install as

 Vans aileron trim servo is used as is and 4 holes drilled in the bottom of

 the tail cone to install it. The turn around pulley bracket is simple to

 fabricate and bolts to the elevator bell crank housing assy. The hardest

 part was pulling additional rudder cables from the trim servo arm back to

 the rudder horn. Also, having 2 rudder cables attached to the rudder horn is

 the one thing I don't like about the system. I already had a 5 wire cable

 installed in the tail come anticipating rudder trim at some later point when

 I built the plane and a Ray Allen LED trim indicator and switch on the panel

 with wiring completed. The trim forces are fairly easy to overcome so run

 away trim doesn't seem to be a big worry. All in all I'm very happy with the

 system. Frankly, the idea of clamping the rudder cables to effect trim seems

 difficult for me to accept.

 Albert Gardner

 N991RV

 Yuma, AZ

Albert Gardner

Joined: 10 Jan 2006
Posts: 455
Location: Yuma, AZ

Posted: Thu May 15, 2008 2:42 pm Post subject: Rudder Trim - Spring Bias

OK, here they are. Installation in the tail cone is straight forward. Bolt

the pulley bracket behind the elevator bellcrank using the aft 3 screws.

Build Vans aileron trim unit and locate the servo unit about half way

between the aft baggage bulkhead and the next one aft straddling the floor

stiffener. Fabricate 2 3/32" cables, one long enough to wrap around the

pulley. I left a 12" gap that the springs would bridge and provide bias

tension. Attach the cables to the rudder horn. Hook up the servo to the

switch and indicator. Fly. I added a keeper to the pulley bracket to insure

the cable could not  come off the pulley. It adds some small security for

gust protection on the ground but not enough to replace a gust lock.

Albert Gardner

N991RV

Yuma, AZ



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_________________
RV-9A N872RV
RV-10 N991RV

billderou(at)yahoo.com
Guest

Posted: Thu May 15, 2008 5:02 pm Post subject: Rudder Trim - Spring Bias

Albert-

  That is a very clean and foolproof installation.

   

  Bill DeRouchey

  N939SB, flying



Albert Gardner <ibspud(at)roadrunner.com> wrote:

  [quote]OK, here they are. Installation in the tail cone is straight forward. Bolt

the pulley bracket behind the elevator bellcrank using the aft 3 screws.

Build Vans aileron trim unit and locate the servo unit about half way

between the aft baggage bulkhead and the next one aft straddling the floor

stiffener. Fabricate 2 3/32" cables, one long enough to wrap around the

pulley. I left a 12" gap that the springs would bridge and provide bias

tension. Attach the cables to the rudder horn. Hook up the servo to the

switch and indicator. Fly. I added a keeper to the pulley bracket to insure

the cable could not come off the pulley. It adds  some small security for

gust protection on the ground but not enough to replace a gust lock.

Albert Gardner

N991RV

Yuma, AZ



--

sam(at)fr8dog.net
Guest

Posted: Fri May 16, 2008 5:09 am Post subject: Rudder Trim - Spring Bias

Let's see the pic!

 

 Bill DeRouchey wrote: [quote]   Albert-

   That is a very clean and foolproof installation.

    

   Bill DeRouchey

   N939SB, flying

   

   Albert Gardner <ibspud(at)roadrunner.com> (ibspud(at)roadrunner.com) wrote:

   [quote]OK, here they are. Installation in the tail cone is straight forward. Bolt

 the pulley bracket behind the elevator bellcrank using the aft 3 screws.

 Build Vans aileron trim unit and locate the servo unit about half way

 between the aft baggage bulkhead and the next one aft straddling the floor

 stiffener. Fabricate 2 3/32" cables, one long enough to wrap around the

 pulley. I left a 12" gap that the springs would bridge and provide bias

 tension. Attach the cables to the rudder horn. Hook up the servo to the

 switch and indicator. Fly. I added a keeper to the pulley bracket to insure

 the cable could not come off the pulley. It adds some small security for

 gust protection on the ground but not enough to replace a gust lock.

 Albert Gardner

 N991RV

 Yuma, AZ

     

 --

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