rudder peddle spring tension.

[labrador_cub]

I'm currently in the middle of getting my annual done on the pa12 for the summer and the AME doing it was walking around the tail and tugged on the rudder cable where it connects to the rudder and of course it moved pulling back the peddle in the cabin, so he said we need to tighten the cables because they are "way to loose" ( my pa12 has all the rear controls removed so just 2 rudder cables straight to the front pedals with turn buckles connecting the cable to the peddle) so after I explained they are a spring returned setup not a continuous loop he now wants me change the springs, I think the springs are just fine they have no problem keeping the peddles up and the slack out of the cable's , I will say the hinge point of the peddles is a bit gummy with years of grease dried up but that's about it. so if anyone has any insight on how I can convince him they are good ,like somewhere that does a lot of cub work I can get him to call, I would appreciate it! its already July 9 float season up here is almost 1/2 over and I have 0 hrs flown, last thing I want is to loose 2 more weeks of flying changing 2 springs that are fine.

you can kinda see the rudder cables/ turn buckles in this old picture, its the best I got.

 

[skywagon8a]

My first response would be to find an AME who knows something about airplanes, particularly PA-12s. The only reason those springs are there is to keep the pedals forward until you place your feet on them. They have nothing to do with the tension on the cables which is totally controlled by the pilot's foot pressure.

 

[labrador_cub]

I don't have much choice on the AME he's the only one around for more then 300 miles and up until this summer we had no one, he knows Cessna's and helicopters but new to cubs. there's a J3,PA-18 and another PA-12 in my area so I guess between us 4 he'll get to know cubs, well to an extent after all no 2 cubs are alike haha.

 

[mike mcs repair]

Find a new mechanic


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[stewartb]

How is it not a closed loop? Push one pedal down and try to hold the other down. Then try the same with the opposite pedal. Cub rudder pedal spings are mostly along for the ride. They don't do much.

 

[S2D]

Just help educate him. He'll catch on if hes a competent mechanic.

 

[Stew]

How is it not a closed loop? Push one pedal down and try to hold the other down.

You would need to complete the circle to have a closed loop, this is a U arrangement with return springs.

If you take your foot off and pull one front pedal back on the ground or in flight and the only thing that will return it towards upright is the pedal spring.

In response to labrador_cub's thoughts about replacing the front rudder pedal return springs, if you have removed the rear controls then the cables are being tensioned on the ground by just one pair of rudder return springs, the front pair instead of both front and back pairs. It follows that replacing the front ones is probably not going to fix the issue and you don't want to be replacing those without a good reason.

 

[stewartb]

I'll give you that. But I've never used my toes to pull an opposite pedal to actuate a rudder. I generally keep a little pressure on both feet and use more pressure on one or the other to control rudder. If I didn't have rudder springs I wouldn't miss them. s far as taking up cable slack it'd make better sense if the rudder springs were turned around.

 

[Stew]

I'll give you that. But I've never used my toes to pull an opposite pedal to actuate a rudder.

Think that is the issue, it wouldn't actuate the rudder, it would just make the cable slack as it is not a closed loop

I generally keep a little pressure on both feet and use more pressure on one or the other to control rudder.

Absolutely agree with that.

As far as taking up cable slack it'd make better sense if the rudder springs were turned around.

You got me there.

 

[labrador_cub]

Just help educate him. He'll catch on if hes a competent mechanic.

he understands how the system works after I showed him, but it seems to me like he thinks the cables should have as much tension as say the aileron cables for example. my cables are not slack or sagging , when you pull the peddles back and let them go they return fine. its just when the mechanic pulls sideways on the cables they're not tight like the other control cables are so hes saying the springs are bad, but they are doing exactly what they're supposed to do they're keeping the peddles from falling back on the floor. so changing them is going to be a waste of my money and more importantly another wasted week of flying. I just need to find a way to convince him they are okay without replacing them and it being the same.

 

[S2D]

Hand him the phone number of a couple supercub mechanics like Pierce and tell him to call someone that's familiar with Cubs before he messes with it. If he won't even do that, I would take my cub and run.

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[RaisedByWolves]

he understands how the system works after I showed him, but it seems to me like he thinks the cables should have as much tension as say the aileron cables for example. my cables are not slack or sagging , when you pull the peddles back and let them go they return fine. its just when the mechanic pulls sideways on the cables they're not tight like the other control cables are so hes saying the springs are bad, but they are doing exactly what they're supposed to do they're keeping the peddles from falling back on the floor. so changing them is going to be a waste of my money and more importantly another wasted week of flying. I just need to find a way to convince him they are okay without replacing them and it being the same.

I like my aileron cables pretty loose.

Why does he want the rudder cables tighter?



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[labrador_cub]

That's what I'm looking for, he's willing to call around and get educated on it I just need some phone number's and this place is the best to get them. he said the other day he was going to call univair and ask them and last night he emailed me the link to they're springs and told me to order them because mine are to weak. I don't know for sure if he did call them after but if he did univair is in the parts business so it would make sense for them to recommend new springs.

 

[Stew]

I understand it that your rear controls are removed, that presumably includes the rear pedals. If the front pedals are returning when you pull them back the springs are certainly ok as normally there would be the front and back pedal return springs pulling on the cable.

Not seeing this tension issue, the only tension on the rudder cable is what you put on it with you feet and a little bit of pull from the return springs when your feet are off the pedals,

May be wrong but I would not be changing the front rudder pedal return springs with all that involves, it won't achieve what is being currently asked of you. Best get dialing Mr Pierce.

 

[labrador_cub]

you are correct stew the peddles are removed, stick gone, throttle gone, and the break cylinders are moved to the front which you can see in the picture I posted. this was all done in 1989 so just the front springs have been doing there job for 29 years without issue, I don't want to go messing with it now.

 

[TurboBeaver]

The real question here that has not been answered was, if in fact the rudder springs are really only to hold the pedals
forward, and are not tensioners for the rudder cables per say. Then how "tight" should the rudder cables really be??
My 12 shows a saggy cable as it comes out of the fuselage either way when fully deflected???? Are the cables too " loose" or too long ??? Bet your IA wouldnt
like mine either. This has new springs on rudder pedals 50
Hrs ago??? What say you all ???

 

[Stew]

Rudder Pedal Spring Tension

Are the cables too " loose" or too long ???

My personal unqualified opinion to the "too long" suggestion. If you deflect the rudder pedal to the front stop on one side and the rudder is then at full deflection then the cable is certainly not too long that side, repeat with the other side to check that as well.

Then how "tight" should the rudder cables really be??

When you jump in a Cub and place your feet on the pedals, you automatically apply minimal and equal pressure to both pedals without giving it a thought and that takes up the excess slack on each cable that the return springs are not holding. Short answer is the cable tension will be as much as the equal pressure you apply plus a bit more on one side or other as you use the rudder to keep the ship balanced.

If you are talking about a plane with a rudder bar, both pedals are physically connected and move as one and the connecting cables would be tensioned just as the elevator/ailerons are, that is a closed loop.

As regards changing front rudder pedal return springs that have done 50hrs, I believe that it will change absolutely nothing in a setup.

Kind regards

Stew

 

[supercrow]

All the springs do is keep the pedal upright and off the floor so your feet can find them when you get in. Your feet then become the "tensioners".

 

[skywagon8a]

My 12 shows a saggy cable as it comes out of the fuselage either way when fully deflected???? Are the cables too " loose" or too long ??? Bet your IA wouldnt
like mine either. This has new springs on rudder pedals 50
Hrs ago??? What say you all ???

E, Are you saying that when your rudder pedals are pushed as far forward as possible and the rudder is manually pushed to it's stop that there is still some sag in the cables? IF SO then the cables are too long. IF SO you might have directional control problems during take off and landings. IF SO you might have difficulty in recovering from a spin.

In this type of installation the control surface is supposed to hit it's stop before the pedal (or stick) hits it's stop. This allows for cable stretch when the pilot applies force to the controls thus ensuring that the control surface makes it's full travel limits. If there is sag in the cable as I think you are saying, your rudder is not moving to it's full travel in flight. Have someone sit in the cockpit holding the rudder pedal to it's stop. Then you push the rudder in the opposite direction. How much deflection do you have? Wouldn't you be surprised if it was straight back? Thus no travel at all.

The only reason for the pedal springs is to prevent the pedal from falling to the floor when you lift your foot off it. What would happen if you lifted your left leg when landing in a left cross wind with the flaps down to move the stick under your knee for full aileron travel and the rudder pedal fell on the floor? Think about that.

If the airplane design required a certain cable tension there would be a mechanical connection between the left and right pedals.

 

[Steve Pierce]

I talked to the original Poster's mechanic on this. He was making a mountain out of a mole hill. Sent him a lot of pictures and hope he got the just of what I was trying to tell him.

 

[n40ff]

Get in the airplane, put your feet on the pedals and apply tension, then let the mechanic check and see that the cables now have proper tension.

Oliver,
I edited it and you can do likewise. Good point!

Jack

 

[Oliver]

Hmm..
I was going to suggest that you email your mechanic a link to this thread.

 

[TurboBeaver]

Pete,
I will take a picture of how much slack it shows and you tell me what you think....... And I am refering to slack on the opposite side of the one pulling tension on the rudder.

 

[cruiser]

Pete,
I will take a picture of how much slack it shows and you tell me what you think.......

I knew there was a good reason why I passed on that airplane LOL

 

[tempdoug]

maybe the rudder horn is bent, or one of the guide pulleys missing, or, or, or,.

 

[n40ff]

FWIW my Acroduster2 has a "closed loop" cable between the rear rudder pedals while the Spezio Tu-holer has springs on the front pit pedals. Push rods between the front and rear pedals on the Acroduster(no brakes in front)

No practical difference, both keep them off the floor until your toes do the job. OTOH there was a relative huge difference in time/effort to fabricate the Acroduster system....did I say HUGE

Of coarse the Tu-holer doesn't actually need springs at all since the rudder pedals hang down/pivot from the top. Springs are not needed, when one broke I didn't know it until the next preflight when I noticed the slack cable and rudder slightly off center. I say not "needed" only because there is nothing in the front pit for the slack cables to hang-up on. That could be a concern in some airplanes so I'd say that there shouldn't be any slack. Tension? Only enough.

Jack

 

[flywhatever]

rudder peddle spring tension

I've been building a cub up from scratch, been installing the springs on the rudder pedals, not a fun job, but a lot funner when the airplane is completely uncovered, so I hear. Anyhow, thanks for al the answers to this fellows thread... I too, believe that these springs are solely for keeping the pedal from falling on the floor. Piper built according to KISS...Keep it simple stupid. It's not rocket science...seems this fellows mechanic needs an education and/or this fellow needs a more knowledgeble mechanic...

 

[algonquin]

I've seen a light spring attached to the firewall and one outside peddle on each side of a Pacer. That keeps the cables tensioned in static, that might make him happy. There are basically two adjustments eddles together and the rudder centered with your feet on the peddles and each peddle forward to the rudder hits the stop each side. It's important to do this with your feet on the peddle to ensure your foot doesn't stop the peddle travel short of the rudder stop, just pushing the peddle with your hand can mess you up.

 

[kcabpilot]

You could show him the PA-18 Pilot's Manual that lists control cable tensions on page 43. It says rudder cable tension should be "taunt" I'm not kidding, that's what it says....:???:

 

[skywagon8a]

Pete,
I will take a picture of how much slack it shows and you tell me what you think....... And I am referring to slack on the opposite side of the one pulling tension on the rudder.

Was this done with someone sitting in the seat pushing the pedals with his feet? OR just reaching in the door while pushing the pedal by hand? When done as algonquin describes there would be no slack.

...It's important to do this with your feet on the peddle to ensure your foot doesn't stop the peddle travel short of the rudder stop, just pushing the peddle with your hand can mess you up.