• If You Are Having Trouble Logging In with Your Old Username and Password, Please use this Forgot Your Password link to get re-established.
  • Hey! Be sure to login or register!

Cub Rudder Pedal Friction..how much is too much?

Thanks, interesting. Last year we ordered new FAA/PMA pedals from Wagaero and couldn’t get the springs to fit. We pulled out the Piper drawings and determined they had welded the spring stops on in the wrong position (so much for PMA’s). They refunded our money and we ordered from Univair and had no problem with them.
 
Were you using the original Piper springs or were they Univair replacement springs?
 
Have measured the Univair return spring.

The wire guage is spot on at 0.095in as per the Piper drawing.

The main difference is the pitch of the coils and the absence of a bend to keep the two "legs" parallel and at 90deg to the axis of the spring coils.

Result is that the spring is approx 0.25in wider than the Piper original and the legs are not parallel.

I can fit the Univair spring, it is a tight fit but the problem is the distortion to the coil axis such that the individual coils bind on the bottom tube of the rudder pedal. That is confirmed by the gouges in the old pedals I took off.

I removed the welded wire stop from an old rudder pedal and re-assembled everything to give the Univair spring the extra space and it all worked as advertised, the fundamental finding is that the axis of the coils has to be true as any lateral pressure on the "legs" will distort the coil axis and cause binding of the rudder pedal lower tube.

If you are "experimental" then you have the option of removing the wire stop and shifting the pedal along by approx 0.25in to get enough space to easily fit the Univair spring. The other option is to source a spring that is a true replica of the original Piper part and I am fairly confident that they will work just as they were intended.

Attached are a couple of annotated drawings and also a blank .pdf file if there is any kind soul that would have the time and inclination to measure their Univair spring for comparison.
 

Attachments

  • 40941_Spring-Rudder Pedal Torsion_Piper Measurements.jpg
    40941_Spring-Rudder Pedal Torsion_Piper Measurements.jpg
    176.1 KB · Views: 166
  • 40941_Spring-Rudder Pedal Torsion_Univair Measurements_actual.jpg
    40941_Spring-Rudder Pedal Torsion_Univair Measurements_actual.jpg
    148.7 KB · Views: 166
  • 40941_Spring-Rudder Pedal Torsion_Univair Measurements_blank.pdf
    92.4 KB · Views: 176
Cub rudder pedal springs never made sense to me. The depression of one pedal returns the other pedal equally. What good do springs do?
 
As far as I can see, the only function is keeping the pedals back and cables taut when feet not resting on the pedals.
 
It's a looped cable system. If you want the left pedal to return up? Push on the right pedal. One can't move unless the other moves equally in the opposite direction. It you park with the rudder deflected? The pedals reflect the rudder position. The springs don't do anything useful that I can see.
 
Last edited:
On the ground, air loads do that in flight.

It would only work like that if the rudder cable system was a complete loop

If there were no springs fitted and you applied full right rudder in flight, clearly the left pedal would travel to the back stop. Release the right rudder pedal and the airload will centralize the rudder and the right pedal will be pulled back to central by it's cable but the left pedal will stay where it is, fully back towards you, with the cable slack (unless you push it forward with your boot).

I reckon that the primary function of the spring is to return the pedal upright and take up the cable slack in this situation.
 
Last edited:
What cable slack?

As the full right rudder deflection mentioned above comes back to central, the right cable attachment tab/cable on the rudder pulls the right rudder pedals back to central, the left cable attachment tab/cable on the rudder comes forward as the rudder centers and without return springs or you boot them, the left rudder pedals go nowhere and stay fully aft, that slack in the cable.

Just try pulling back on the front right rudder pedal, the left one stays put as it is not a looped system, it is a "U" arrangement with pedal return springs.
 
Last edited:
maybe it just needs used a little
mine are starting to loosen up alittleIMG_0170.JPG
 

Attachments

  • IMG_0170.JPG
    IMG_0170.JPG
    233.8 KB · Views: 150
Does anyone know what length the AN bolt is on the front pedals? I’ve had to replace a rudder pedal and I can get the spring to function but not enough thread showing through the nylon nut. What are the stock length of the bolts I need to order some longer bolts. Thanks.
 
Depends on floorboard, thickness. Wood/aluminum/composite???

(last time i used wood for floor boards was in 2004, and then i added a layer of fiberglass on top with black gel coat....)


Sent from my iPhone using SuperCub.Org
 
Last edited:
This kind eliminates that problem


camera_pics.jpg

Old thread but does anyone have a source for this spring currently?

DENNY
 
Old thread but does anyone have a source for this spring currently?

DENNY
I was going to suggest to get some piano wire at a local hobby shop and make your own. Then I looked at hobby shops in Anchorage.....they aren't the old type of hobby shops I remember. They seem to only sell premade parts. You could ask them though.
 
I think I found some wire on Amazon that would work. My MOREBETTERDISEASE is getting the best of me trying to change most every part so I was looking for a ready made part. I have the stock style springs already in but what a major pain. I say some threads with a simple spring from to the firewall which would make life easy down the road. Just hoping someone had a bunch on a shelf.
DENNY
 
I say some threads with a simple spring from to the firewall which would make life easy down the road.
DENNY
Some airplanes used a screen door spring forward for this purpose. There isn't enough room on a Cub to do this. Remember the only purpose of the spring is to prevent the pedal from flopping down onto the floor, just so you can get your feet back onto the pedal easily. Some planes use a balance cable which goes forward, around a pully, across to the other side, around another pulley and back to the other pedal. Another option would be to connect the front and back rudder pedals with a rod instead of a cable and run a screen door spring forward from the rear pedal.
 
IMG_7286.jpg
This is what I have. If you want them give me your address and I’ll send them to you. I am using a different spring set up so don’t need these.
 

Attachments

  • IMG_7286.jpg
    IMG_7286.jpg
    476.2 KB · Views: 18
.... Another option would be to connect the front and back rudder pedals with a rod instead of a cable and run a screen door spring forward from the rear pedal.

In 2002 I recall there were three FAA Maintenance Inspectors (the PMI and associates) staring at that particular interconnection. My PA-11 had an ancient heavy strand cable, and it WAS NOT to be replaced if still airworthy. To this day I don't understand the importance but we complied. Even when the Airworthiness Certification was conducted that was confirmed. Anybody know why the focus on that?

https://www.univair.com/piper/piper-pa-11/view-all/10865-000-piper-rudder-cable/

Gary
 
My PA-11 had an ancient heavy strand cable, and it WAS NOT to be replaced if still airworthy. To this day I don't understand the importance but we complied. Even when the Airworthiness Certification was conducted that was confirmed. Anybody know why the focus on that?
Gary
Piper used 1x19 (1 strand...19 wires) cable for the rudders. It is considered nonflexible and is used for straight pulls only...no pulleys. The cable you are used to is 7x19 (7 strands of 19 wires each) flexible cable. The 1x19 is higher. breaking strength. https://www.lexcocable.com/resources/downloads/wire-rope-spec-sheets/
 
Back
Top