Rudder Pedal Springs

[mswain]

Another local Bearhawk builder wanted me to ask what diameter wire springs are people using on their rudder pedal return springs? He feels his are too weak. He currently is using 1" OD springs.

[Battson]

Mine springs are 5/8" diameter, the wire itself is about 2mm in diameter.
They are very weak compared to the tailwheel steering springs for instance, but all they need to do is hold the pedals upright, and they achieve that. The pilot's feet do the rest.

[Helidesigner]

I found that stiff pedal springs improve yaw control. Without a stiff set of return springs I found my self overshooting where I wanted to be to center the ball. I actually measured the spring stiffness of several sets. I am currently using a set that is .75 in in diameter, a rod diameter of .105 in, and have an average stiffness of about 85 lb/in over 1 inch of travel. Coil springs are stiffest on initial extension and soften a bit as they extend. My springs start at 98 lb/in and drop to 75 lb/in at 1 inch extension. I'm looking for an even stiffer set. The tail wheel and rudder air loads create much higher pedal forces than the return springs.

[haribole]

Hi Helidesigner, do you have a part number and source for the ones that you are using?

[Enewton57]

Since we are talking about rudder return springs, one idea I picked up from Bob is this - if you need a rudder tab to center the ball when flying, you can instead use a stiffer or slightly shorter, rudder return spring on one side. Might take some experimenting to get it right, but no unsightly tabs on your rudder.

[Bcone1381]

Today I tried a rudder pedal spring that I thought was going to work pretty good. I did not like how the shape of the hook interacted with the rudder pedal and the attach point the Bob provides on the rudder pedal for the spring. It seemed like it might find it own way to detach. SO, I heated up the end and modified it, then quenched it in water to cool it down. When I reattached it, the end that was heated did not retain its shape. The tension force straighten it out.

Is there a specific rudder spring that people have found to be ideal? If I heated up my spring and cooled it down slowly would it be stronger? Is there a better material to us like a Piano Wire Spring that would allow one to gently make adjustments with heat and still retain its strength?

The spring I used was 3/4" DIA., 2-7/8 long, and made with .105 diameter wire. I do not know what material it was made from.

[Battson]

Today I tried a rudder pedal spring that I thought was going to work pretty good. I did not like how the shape of the hook interacted with the rudder pedal and the attach point the Bob provides on the rudder pedal for the spring. It seemed like it might find it own way to detach. SO, I heated up the end and modified it, then quenched it in water to cool it down. When I reattached it, the end that was heated did not retain its shape. The tension force straighten it out.

Is there a specific rudder spring that people have found to be ideal? If I heated up my spring and cooled it down slowly would it be stronger? Is there a better material to us like a Piano Wire Spring that would allow one to gently make adjustments with heat and still retain its strength?

The spring I used was 3/4" DIA., 2-7/8 long, and made with .105 diameter wire. I do not know what material it was made from.

I just cold-bent the spring after cutting it to length. It stayed like that, has done for a long time.

[whee]

I did the same as Battson.

[Bcone1381]

I followed your lead for round two and like the results. I stuck with the 3/4" diameter spring made out of .105 diameter wire. I was following Helidesigner's lead. A fellow Bearhawker at OSH may have described to me what Helidesigner experienced in post #3, but I don't know what he used for rudder return springs. Thanks for all your help.

[Bdflies]

Brooks, I spent a lifetime involved in welding, consequently involved with heat treatment of metals. When you mentioned heating and quenching a spring, I immediately went into 'hmmmmmmmm' mode. Welding can be considered a 'science'. If we know the metals and the process to be pursued, a viable fillermetal and procedure can be found, in most cases. Heat treatment, however, is something of magic and science, mixed with a big portion of alchemy. If a spring works, don't try to mess with the heat treatment.
Batson and Whee are right: bend it cold. If the spring is long enough to stretch and return, after bending, you're good. If it's too short and you 'yield' it at your bend, it'll fail. Just be sure it's long enough.

Bill

[Bcone1381]

Thanks so much Bill. You validated my experience, that the heated spring was unsatisfactory and went in the garbage. When it failed to hold its shape I wondered about the quench.

Yesterday I picked up a 9" spring. I cut it to length and bent it like Battson and Whee you suggested. I like what I have now.

[Wmilbauer]

I used the spring the same as is used on my Glasair sportsman after trying 5 different springs. They are expensive but they work and are strong enough to use the turnbuckles to adjust for trim in cruise.

[Mruffatto]

I know this is an old thread but I was wondering if the springs that were mentioned above are still working out ok? I have a 3” x .75” x .105” spring that may work if I can figure out a way to shorten a little bit. I haven’t figured out a way to bend a new hook in it.

Another thought I had that I’d like opinions on is to put a small pulley where the spring currently mounts and be able to mount a spring vertically. It’s more complex and would require welding but it would allow a variety of spring to be used. Maybe even a way to incorporate some rudder trim. Pretty similar to the rudder trim systems for pacers? I saw a thread with a pic but can’t seem to find it now.

Am overthinking all of this? It just doesn’t feel that great the way I have it installed now.

[AKKen07]

Seems like I’ve seen that suggestion before, the pulley, so I doubt you’d be the first! I couldn’t find the right kind of spring locally so I have a variety that I will try out in testing. For bending a hook I put the spring in a vice so the vice compressed the spring with the last half a turn exposed at the top. Then used a hand file, that I ground into a wedge point at the tip, and pried the half turn 90 degrees. A screwdriver might work? I may have used a big pliers and possibly a hammer to get it all the way bent, can’t remember.

[Gerd Mannsperger]

The rudder springs are just to hold up the rudder pedals.

If you want to help stability and a means to trim the rudder use 2 long cantering springs in the tail attached to the rudder cable. that will give a much more even pull over the whole rudder travel and only putt on the ruder cabe right before the rudder.
Maule has used that extensively and this can be used as a blueprint, (there are many around to look at just remove the rear cabin wall and you can see the whole set up) I can install the whole set up in an hour. It works perfect to trim your plane out for hands of cruise it also makes the plane more stable in rough air so it does not wallow around. One can accomplish the same by keeping slight pressure on both ruder pedals with your feet when in bumpy air, the springs can do that for you hands and feet off.

[N8doggaf]

Does anyone have a source for an effective spring that they are using? I am having a really hard time actually finding something that works. The one's I've tried from the hardware store are too long and stiff. After taking measurements, the free length is 2.5" and the fully extended length is 6". I can't seem to find any 1" diameter extension spring.

[gregc]

A little pricey but as I recall McMaster-Carr has a good selection.

[Mark Goldberg]

If a spring is too long sometimes it can be cut to a better length. A spring that is too stiff and doesn't allow the forward movement is bad. Bob has flown with NO springs at times. The springs really just keep your pedals from falling aft. I usually have bought a few cheap springs from the hardware store and use the ones that work best.

I have asked Bob to help me come up with a set of springs we could include with the kits. For rudder pedals, door latches, and inside the flap sticks. But it has never happened. Maybe you guys out there will help me come up with a set of all the springs needed for the different models. Mark

[Bcone1381]

Did Bob ever say if yaw stability or adverse aileron yaw was effected by spring strength? If I choose a spring with a Max load of 28 pounds over a 7 pounder it seems to me like it may strengthen it some.

[jaredyates]

Russ wrote up a nice article about his findings of yaw stability and its relationship to the springs.

https://bearhawk.tips/4172

[Mark Goldberg]

If you have the ball to one side and need to remedy that a stronger spring on one side is an alternative to putting a tab on the rudder trailing edge. Mark