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Rudder springs

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Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Wed Jul 15, 2009 7:34 pm Post subject: Rudder springs

While flying this evening I reflected on the fact that the rudder pedal 

forces seem disproportionately higher than the other control forces.  Part 

of this is due to the fact that I moved the rudder cable attach point from 

the original position midway up the pedal (per the plans) to the top of the 

pedal.  This gives more rudder deflection for a given amount of pedal 

deflection, which makes it more comfortable to turn on the ground, but also 

increases the pedal force.



However, another reason for the force is the heavy springs in front of the 

pedals.  These are necessary, of course, to keep the cables taut, but the 

also exert a fairly heavy centering force.  My thought was to replace the 

springs with an additional cable around a pulley (or two pulleys) to 

complete the circuit and keep the tension, without the centering 

tendency.  There might need to be a short spring in line with the new cable 

to take up any total length variation due to the geometry as it moves 

through the range of motion (I haven't analyzed it to see if this would be 

necessary), but it wouldn't provide the heavy centering force the original 

setup gives.



Thoughts?  Anybody seen this done before?



-Dana

--

  Never be afraid to try something new. Remember, amateurs built the ark. 

Professionals built the Titanic.

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Thu Jul 16, 2009 3:28 am Post subject: Rudder springs

My thought was to replace the

 	  Quote: 	
		   springs with an additional cable around a pulley (or two pulleys) to 

 complete the circuit and keep the tension, without the centering tendency.

 -Dana


	




Some Kolb rudders will slowly begin a shuffle, the beginning of rudder 

flutter, if there is not enough tension on the cables to prevent it.  Of 

three airplanes I built, only the Ultrastar was immune to this problem.



Normally would not happen on local flights, but on longer cross country 

flights if my feet relaxed pressure on the rudder pedals, I'd start to 

pickup a little shuffle, usually noticed at a wing tip moving slightly fore 

and aft.  Sometimes, if not detected and ignored for a while, it could get 

very active.



Holding a lot of pressure on the pedals gets tiresome real quick.  I 

remedied my problem by doubling up with stronger springs on each pedal.  Now 

I can fly feet off the pedals without going into flutter.



I don't know if your idea will work without return springs, unless your 

rudder is not prone to shuffle.  Short local flights it would by applying 

enough pressure on the pedals to keep them stable.



Why Kolb rudders do this could be for several reasons, the way the rudder is 

hung on the tail post, the way the prop blast hits the rudder, flexibility 

of the tail boom, etc.  Who knows, but they do.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Richard Pike

Joined: 09 Jan 2006
Posts: 1670
Location: Blountville, Tennessee

Posted: Thu Jul 16, 2009 8:45 am Post subject: Re: Rudder springs

As far as I know, there is only way to stop the Kolb rudder from developing it's flutter when you ease the foot pressure off, and that is to add a bird roost to it. Guaranteed to work, and also to cause bird poop to appear on your horizontal stab. Using the counterbalance, the springs need only be heavy enough to enable the pedals to keep the cables snug.



Richard Pike

MKIII N420P (420ldPoops)

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WhiskeyVictor36(at)aol.co
Guest

Posted: Thu Jul 16, 2009 6:39 pm Post subject: Rudder springs

In a message dated 7/15/2009 11:35:09 P.M. Eastern Daylight Time,  d-m-hague(at)comcast.net writes:

   	  Quote: 	
		     My thought was to replace the 

springs with an additional cable    around a pulley (or two pulleys) to 

complete the circuit and keep the    tension, without the centering 

tendency.  There might need to be a    short spring in line with the new cable 

to take up any total length    variation due to the geometry as it moves 

through the range of motion (I    haven't analyzed it to see if this would be 

necessary), but it wouldn't    provide the heavy centering force the original 

setup    gives.



Thoughts?  Anybody seen this done before?

   Dana,

    

   Before I became a Kolber, I was building a Scamp Bi-plane, which    was designed by Harris Woods (along with the Quail, Rail and the    Woody Pusher).  The Scamp rudder cables were done exactly as you    described.  Cables from the rudder terminated on the rudder pedals.     Then a lighter cable ran from one pedal to the other, through two pulleys    mounted on the firewall.  There was no spring.  I never completed    the Scamp.  Sold it and built the Kolb FireStar.

    

      Bill    Varnes

Original Kolb FireStar

Audubon NJ

Do Not    Archive



	


 Snoop, Lil Wayne, Lady GaGa -- land the tix you need for this summer's biggest tours. Tourtracker.com

  [quote][b]

slyck(at)frontiernet.net
Guest

Posted: Thu Jul 16, 2009 6:59 pm Post subject: Rudder springs

not a bad idea.  If I replace the puny springs that hold my rudder pedals forward I'll try a single bungeearound a point in front.  Might have to replace it with age but they are cheap.

BB

On 16, Jul 2009, at 10:28 PM, WhiskeyVictor36(at)aol.com (WhiskeyVictor36(at)aol.com) wrote:

[quote]  In a message dated 7/15/2009 11:35:09 P.M. Eastern Daylight Time, d-m-hague(at)comcast.net (d-m-hague(at)comcast.net) writes:

   	  Quote: 	
		    My thought was to replace the 

springs with an additional cable  around a pulley (or two pulleys) to 

complete the circuit and keep the  tension, without the centering 

tendency.  There might need to be a  short spring in line with the new cable 

to take up any total length  variation due to the geometry as it moves 

through the range of motion (I  haven't analyzed it to see if this would be 

necessary), but it wouldn't  provide the heavy centering force the original 

setup  gives.



Thoughts?  Anybody seen this done before?

  Dana,

   

  Before I became a Kolber, I was building a Scamp Bi-plane, which  was designed by Harris Woods (along with the Quail, Rail and the  Woody Pusher).  The Scamp rudder cables were done exactly as you  described.  Cables from the rudder terminated on the rudder pedals.   Then a lighter cable ran from one pedal to the other, through two pulleys  mounted on the firewall.  There was no spring.  I never completed  the Scamp.  Sold it and built the Kolb FireStar.

   

    Bill  Varnes

Original Kolb FireStar

Audubon NJ

Do Not  Archive



	




 Snoop, Lil Wayne, Lady GaGa -- land the tix you need for this summer's biggest tours. Tourtracker.com

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[b]

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Mon Jul 20, 2009 6:34 am Post subject: Rudder springs

> As far as I know, there is only way to stop the Kolb rudder from 

developing it's flutter when you ease the foot pressure off, and that is to 

add a bird roost to it. Guaranteed to work, and also to cause bird poop to 

appear on your horizontal stab. Using the counterbalance, the springs need 

only be heavy enough to enable the pedals to keep the cables snug.

 	  Quote: 	
		  

 Richard Pike


	




Richard P:



I found another way to do it, as I mentioned a while back.



Doubling up rudder springs does not balance the rudder, but it will prevent 

shuffling/flutter from initiating.  The double springs place enough pull on 

the cables to keep the rudder stable.  Also, the double springs don't add 

any more resistance to the rudder pedal when actuating.  They cancel each 

other out.



This also reminds me of the way I locked my rudder (gust lock).  I don't 

need it now with the Maule Tundra Tailwheel and heavy rudder pedal springs, 

but on the Firestar I would carry a bungee cord to wrap around the rudder 

pedals several times, locking them together.  That kept the rudder from 

beating itself to death.  This worked well.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Mon Jul 20, 2009 6:33 pm Post subject: Rudder springs

At 10:32 AM 7/20/2009, John Hauck wrote:



 	  Quote: 	
		  Also, the double springs don't add any more resistance to the rudder pedal 

when actuating.  They cancel each other out.


	


Well, yes and no, depending on the spring rate and length.  As you press a 

pedal, the spring on the side you're pressing shortens, lessening the force 

and the opposite side lengthens, increasing the force.  The imbalance is 

small near center, but the centering force increases with greater 

deflection.  My rudder always tends to return to center, and the reason for 

my original post was to reduce this centering tendency.



-Dana

--

  The most useful tool for dealing with management types is, of course, an 

automatic weapon.

apilot(at)surewest.net
Guest

Posted: Mon Jul 20, 2009 6:40 pm Post subject: Rudder springs

Someone told me a while back that I could increase rudder spring tension on one side instead of having a trim tab on the rudder.  Is this a good idea?   Vic Mark III Classic

ronlee

Joined: 25 Dec 2006
Posts: 141

Posted: Tue Jul 21, 2009 5:51 am Post subject: Re: Rudder springs

Sounds like a design problem. Has anyone tried VGs on the rudder?

_________________
Ron Lee
Tucson, Arizona

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Tue Jul 21, 2009 7:45 am Post subject: Re: Rudder springs

Dana,



Your idea of completing the rudder circuit with pulleys and a cable is a good one.   I have seen that system used on another aircraft with good results.  As you suspect, you will need a heavy compression spring like you would find on a tailwheel to go between the short cable between the rudder pedals, this will keep your cable tension constant and will compensate for the small changes in geometry as you deflect the rudder pedals...   I really like this system as it keep the rudder cables properly tensioned with zero centering force, so the rudder pedals can be easily moved to each stop and the only feedback you get are due to the air loads, just as it should be     Remember this system is something from another airplane type, but it is good design, works well, and is what I would do if I was trying to improve a Kolb.



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Tue Jul 21, 2009 8:17 am Post subject: Rudder springs

Remember this system is something from another airplane type, but it is 

good design, works well, and is what I would do if I was trying to improve a 

Kolb.

 	  Quote: 	
		  

 Mike


	




Mike B/Gang:



The reason I shared with the Kolb List the way I have my rudder pedals set 

up was because it works well, it has been thoroughly tested over many long 

hours sitting in the pilots seat, and it is a very simple fix.  Add a couple 

heavy rudder pedal springs to what you already have and...BINGO!!!  you have 

the problem solved.



No need to install a rudder counterbalance weight system, or a complicated 

cable and pulley system.  My philosophy is KISS, keep it simple.



However, I know there are folks on the List that like to experiment as much 

as I do.  So...maybe you all can reinvent a better wheel.  



BTW:  My system does not progressively load up the rudder pedals, even 

though the engineers on the List will argue with me on that point.  All 4 

springs are stretched in the neutral position.  Full pedal deflection 

sitting still on the ground has no more resistance than the standard Kolb 

soft rudder pedal springs.



The large rudder trim tab works perfectly, keeping the slip/skid ball 

centered at all cruise speeds.  I challenge the perfectionist to measure the 

amount of inefficiency produced by this system over twisting the engine 

every which a way.  Even if it costs a few cents more to fly my mkIII the 

way it is configured, by God it works, and it works good.  I fly for fun.



I think I'll keep my systems for now.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

cristalclear13

Joined: 19 Sep 2007
Posts: 363
Location: Southeast Georgia

Posted: Wed Jul 22, 2009 5:38 am Post subject: Re: Rudder springs

 	  John Hauck wrote: 	
		  

The reason I shared with the Kolb List the way I have my rudder pedals set 

up was because it works well, it has been thoroughly tested over many long 

hours sitting in the pilots seat, and it is a very simple fix.  Add a couple 

heavy rudder pedal springs to what you already have and...BINGO!!!  you have 

the problem solved.



No need to install a rudder counterbalance weight system, or a complicated 

cable and pulley system.  My philosophy is KISS, keep it simple.



john h

mkIII 	




I "snuck" a picture of John's rudder pedals when he flew into Douglas this year.  It is attached.

John Hauck's rudder pedals.jpg

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_________________
Cristal Waters
Kolb Mark II Twinstar Rotax 503 DCSI Sept 2007 - sold Sept 2012
Private Pilot Aug 2008
ELSA Repairman for N193Y April 2008
Rotax 2 stroke maintenance April 2009

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Wed Jul 22, 2009 5:52 am Post subject: Rudder springs

> I "snuck" a picture of John's rudder pedals when he flew into Douglas 

this year.  It is attached.

 	  Quote: 	
		  

 --------

 Cristal Waters


	




Thanks, Cristal.



I had forgotten exactly how I had done it.



Had to offset one side to make them neutral.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

russ(at)rkiphoto.com
Guest

Posted: Wed Jul 22, 2009 10:41 am Post subject: Rudder springs

Cristal

Did you attach that pic? I didn't get anything

Russ K

On Jul 22, 2009, at 9:51 AM, John Hauck wrote:

 	  Quote: 	

 > I "snuck" a picture of John's rudder pedals when he flew into  

 Douglas this year.  It is attached.

>

> --------

> Cristal Waters

 Thanks, Cristal.

 I had forgotten exactly how I had done it.

 Had to offset one side to make them neutral.

 john h

 mkIII

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