Rudder pedal assemblies

The very first time I read Chapter 13, I remember thinking, "Wait, what do you mean you can't adjust the pedals?!" The original plans has you build pedals out of 4130 tubing and install them about a fixed pivot point on the fuselage which you can't adjust. I kept thinking - there's gatta be a better way!

So I thought about various designs and finally settled on the following:

I'm cheating here by letting you see the final product at the beginning of the post - but what the heck.. sometimes it's nice to get straight to the point!

So now let me explain how I built them - I started out by making pedals out of 4130 steel tube 5/8" dia (.035" wall). Height measures about 7" and the foot rest is 3" wide. I then took some 4130 steel sheet (6" x 12" x .125") and cut out the webs and tabs. The pedals were primed after everything was welded up. The pushrods will get attached to the web and the rudder cables will get attached to the upper tabs.

I then drilled a hole through the base of the pedal and inserted a stainless steel unthreaded spacer (5/16" OD, 3/4" length, #10 screw size) McMaster-Carr part #:92320A220.

I thought a little tack weld to hold the spacer in place couldn't hurt...

This serves as the pedal pivot point.

Here I am playing around... test fitting it onto the fuselage... looking good...
The U-channel is aluminum 6063T52 1.25x1.25x1.25 (about 1.5 ft per side).

So now to get the pedal to actuate the master cylinder... I went with standard Matco MCMC-4 master cylinders.

I had to come up with a plan so that the first half of the pedal push will actuate the rudder, while the second half of the pedal push actuates the brake. To do this, I have a cylinder go inside of a tube which acts as the pushrod for the pedal.

Let me explain:

Here is the rudder pedal assembly in its neutral state:

When the pilot steps on the rudder pedal, the pushrod slips along the cylinder that is attached to the master cylinder until it hits the stop (the large area washer) - at this point, the pilot has actuated the rudder, but not the brake.

Pressing the rudder pedal in further, the pushrod hits the stop and forces the master cylinder to actuate - applying the brake.

So now that you get the concept, let me show you how I made the pushrod and master cylinder extension rod.

First I purchased a 1' rod from McMaster-Carr part #: 8920K155 (low-carbon steel rod, 1/2" diameter, 1' length). I cut it into two rods (3.75" each) and used a grinding wheel to taper one end.

In order to attach it to the master cylinder, I bored out a 7/8" deep hole on the other end (the flat end)...

...and then tapped it so that it would match the thread of my master cylinder....

I then applied a AN970-5 washer to act as the stopper...

And bolted the 3.75" rod extension onto the master cylinder. Notice how I kept the nut on the back so that I can later fine tune the position - it will also make sure the rod does not come loose.

Hopefully you are starting to get the picture... the rod extension gets inserted inside the pushrod like this:

The pushrod is made out of 4130 steel tube 5/8"x .049 wall (5" long each). One side has a 1" long slit (about 3/16" thick) to allow for the rudder pedal web to be inserted into it.

I rotated it 90 degrees and drilled a hole through it so that I can insert a bolt to act as a pin to attach to the web.

Ok... so now we have the following parts:

   2 rudder pedals
   2 U-cahnnels
   2 master cylinders (with extension rods and stoppers)
   2 pushrods

I then cut the U-channel to 14" long each and made a hole 1" inside from the forward lip (0.5" down from the top edge) - this is the forward hole which the pedal will pivot on. I then made another hole 0.75" in from the aft face (0.5" down from the top edge) - this is the hole which the master cylinder will pivot on. So the holes are 12.25" apart.

I then used a AN3-14A bolt to install the redder pedal onto the U-channel. I used AN960-10L washers on the outsides and AN960-10 washers as spacers on the inside (note that I used two AN960-10 on the left and two on the right - it looks like three in the picture because it is a reflection off of the aluminum wall).

I then used a AN3-14A bolt to attach the master cylinder... again using AN960-10L washers on the outsides with a MS21042-3L nut.

I then inserted a washer style bolt on the pushrod to connect to the rudder pedal web...

And there you have it... two rudder pedal assemblies complete with master cylinders attached!

I will later have to drill a hole on the tabs, but I will do that when I install the rudder cables.


Capt Meatballs said...

Great job Ary, they look terrific.

Unknown said...

Great job so far, those look great. What is your plan to fasten the channel to the floor pan.??
Also, I assume that the only adjustment to be made to length extension of the "throw" is with the nut, adjusting it out.?? Again, nice work..

Ary said...

Thanks guys!

Warbird fan - to answer your questions:

I am planning on installing three t-nuts to a piece of plywood which will be glassed onto the nose floor pans (similar to the process I did when installing the speed brake actuator bracket to the back of the pilot's seat - I will then make equally spaced holes along the U-channel of the rudder pedal assemblies. The pilot can then place the assembly at the desired location.

I should have been more specific when I mentioned "adjustable". So although this design does not allow the pilot to adjust the pedal distance on the fly, he or she can at least adjust it while on the ground by simply using a socket wrench (as opposed to the original design which would involve re-glassing the pivot point).

The nut behind the large area washer allows me to fine tune when the pushrod comes in contact with the washer - hence allowing me to adjust the point in the pedal press that the master cylinder gets actuated.

All this will be covered in a later post when I install the assembly to the floor pans and when the rudder cables are installed.

Let me know if this answers your questions...


mdmbkr said...

Does this design allow you to use both brakes at the same time?

Ary said...

mdmbkr - absolutely! They are not connected in any way - so the left pedal controls the left rudder and left master cylinder to control the left caliper to brake the left main wheel. The right pedal controls everything on the right. So pressing both at the same time actuates both rudders outward (which act as speed brakes on the ground) and then actuates both the left and right brakes on the main wheels.

Keep in mind that the Long-EZ rudders only deploy outward (not inward). The reason for this is because if you were to deploy a rudder located on the wingtip inward - the drag of that rudder would create a moment large enough to rotate the aircraft in the opposite direction than what the pilot intends.

So to make the aircraft nose turn left, only the left rudder is actuated. To make the nose turn right, only the right rudder is actuated.