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  #1  
Old 05-18-2011, 05:10 PM
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Bill.Peyton Bill.Peyton is offline
 
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Location: St. Louis, MO
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Default Rudder Springs

Ok, here is what I am trying to do. I would like to have springs attached to the rudder cable ends to help in protecting the rudder from wind and to also eventually develop a rudder trim system similar to the piper aircraft. I test installed two rudder return springs which attached at the base of the Pilot Right peddle and the Co-Pilot Left peddle. The spring is attached at the other end to a bracket on the side of the tunnel next to the firewall. The issue is, now there is tension on the cables at all times, it is amazing how much friction the cables have as they thread there way from the front to the rear of the aircraft. The lack of pulleys really shows. My concern is the rudder cables will eventually wear right through the snap bushings. I am now looking at strategically installing pulleys in three different locations to get rid of a lot of the binding a wear issues.

For those of you flying, have you ever inspected the snap bushings for wear?
Has anyone else tried a return spring arrangement?
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  #2  
Old 05-18-2011, 05:44 PM
Moura Moura is offline
 
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Location: Uberaba, MG, Brazil
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Wouldn?t you be looking for this? http://www.mlblueskunk.com/Rudder_Trim_System.html

Moura
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  #3  
Old 05-18-2011, 05:53 PM
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Bill.Peyton Bill.Peyton is offline
 
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I don't think there will be enought force to return the peddles and protect the rudder with the small springs and short lever arm. I had looked at this system before, Thanks
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  #4  
Old 05-18-2011, 06:19 PM
Wayne Gillispie Wayne Gillispie is offline
 
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Location: USA
Posts: 1,499
Default Have not thought about springs but...

I have thought about installing a phenolic friction block setup on each side of tunnel encapsulating the rudder cable. For those long climbs tighten the left block. For those long descents tighten the right block. For parking for more than just fuel or a quick bite to eat tighten both blocks. I will probably do it after flying. Possibly a good winter job.

Also on the bushings vs pulleys. Our Blackhawks had cables ran over phenolic pulleys all the way to the tail rotor gearbox where they connected to dual hydraulic cylinders(primary and backup). Very little friction in that set up but very heavy too. Angles were much greater than on our RV, so it was a requirement.

You might also be able to run them through pieces of 1/4" thick phenolic. Lubrication of plastic bushings with some boelube may help keep the friction down. Fly over and I'll give you some 1/4" phenolic. I have plenty left after making my own terminal blocks.

Just about finished with panel wiring, then I'll be getting it up on the gear soon. Work picks up when the temps are above 85F.
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  #5  
Old 05-18-2011, 06:31 PM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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I don't know if springs are a viable solution for the gust lock issue, but I can tell you that the snap bushings in my RV-6 look almost new after 10 years and 750 or so hours. Even if they wear out after 20 years, replacing them is cheap and easy. I can't imagine that pulleys would be a better solution if you use cost, weight, and complexity as your metrics. Beyond that, the pulleys would probably need more maintenance than the bushings will.
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  #6  
Old 05-18-2011, 06:39 PM
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My snap bushings show no wear at 18+ years.
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  #7  
Old 05-18-2011, 07:38 PM
gasman gasman is offline
 
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Location: Sonoma County
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And if you think that wear will be a problem, a smaller bushing will snap into the existing bushings. Just split them with a razer and slip them over the cabal and press into place.

A piece of tubing split on one side and tapered on one end will push out the smaller bushing if you ever need to replace it.

Like Mel said....... this is not a problem. And drag on rudder pedals are not a problem compared to aileron drag.
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  #8  
Old 05-18-2011, 07:46 PM
Bob Axsom Bob Axsom is offline
 
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Default Adding the springs seem to be adding problems

I don't want to start an argument on this so just think of this as a caution. I wouldn't do it. As others have said the existing design is wear free on my RV-6A after 7 years also. The springs load up the system and lead to the need for other changes. I use two inverted square "U"s with ~3" legs made of 1/8" piano wire on each side of the rudder in holes in the rudder stops and the rudder horn. They are so solid that if you accidently leave them in on takeoff you have a fixed rudder. If you have one on one side only it can be overcome by you or the wind but not on both sides. When our plane was parked on the ramp at St. Simons Island, GA a couple of months ago the wind blew the tail one way and the breakout force on the nose gear was exceeded, the main gear went over my special 3/4" aluminum angle chocks and the plane was sitting askew to the limit of the tail tiedown rope but the rudder remained locked as straight as an arrow.

Bob Axsom
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  #9  
Old 05-18-2011, 08:14 PM
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Bill.Peyton Bill.Peyton is offline
 
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This is why this forum is great! I wasn't sure on the bushings, but it sounds like they are a non-issue. I still like the idea of centering springs. I don't like the idea of always having to put blocks in the rudder or a bar on the peddles for just a short time. I have read several posts regarding rudder damage and personally seen two different 10's with dented rudders from contact. Today I went out to my Archer to see how hard it is to move the rudder from the rear. It is amazing how stiff the springs are and yet, I have never felt like I was pushing on a spring.

Wayne, I just got my aircondx installed in the workshop. 2.5 tons should keep it cool this summer! Ill pick a good weekend and give you a call and swing by.
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Last edited by Bill.Peyton : 05-18-2011 at 08:17 PM.
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  #10  
Old 05-18-2011, 08:32 PM
gasman gasman is offline
 
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Quote:
Originally Posted by Bill.Peyton View Post
Today I went out to my Archer to see how hard it is to move the rudder from the rear. It is amazing how stiff the springs are and yet, I have never felt like I was pushing on a spring.
You were not just pushing on a spring, the rudder on a Archer is connected to the steerable nose wheel. Don't expect to flip the rudder side to side with the nose wheel on the ground.

With springs connected to the rudder pedeals on an RV, you will not feel them during normal use. But they will coushion the effect of side loads when tied down. And with less flat surface for the wind to push against, your RV might not shift from It's tie down spot.
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