Reconfiguring the Brake Pedals

07-07-2009, 10:44 AM

Mike | Reconfiguring the Brake Pedals

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Old 07-07-2009, 10:44 AM

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Mike Mike is offline

Flying, 6th Editor

Join Date: Nov 2008

Location: New York

Posts: 938

Default Reconfiguring the Brake Pedals

A while ago I posted a little blurb regarding the configuration of my brake pedals. This is what I came up with…..

One of the problems I noticed when I purchased 20W was poor braking. While trying to do a run-up my baby was rolling at 1000 rpm. The brakes would not hold! Over a period of time (from the time it was built) the brakes were pushed harder and harder to accomplish the needed braking.

Looking straight down at the pedals I noticed the pedals were bent back on the horizontal and the vertical. Since the vertical stalk was bent the MC-4 master cylinder piston rod was traveling at an angle which scored the master cylinder until it started leaking; therefore poor braking. I also noticed that the welds at the bottom of the vertical stalks were cracked.

The pedal stops were installed, however if the rudder pedals are even (rudder centered) they would not be at the stops so therefore most of the time the stops are useless. I assume the stops were there to rest the vertical stalk against when doing hard braking to make a turn.

So; I needed to change the geometry and do some welding.

I saw the Matco brake configuration that is on the seawind website http://seawindpilots.com/landing_gear.htm

(bottom of page) so I decided to call Matco and find out what the best configuration might be. They agreed that the best configuration is the same one that is on the website as well as the upgrade to the brakes themselves for $140.00 per side. They also mentioned that the brake system needs 450psi at the pads. I had 180psi.

I wanted to do the least amount of cutting to the existing structure as possible so………..

1- I started by removing the pedals. When I removed the “C” clip I was able to slide out one of the pedals. The other pedal had to be cut in order to remove it (go figure?) (Picture #1)

2- I added an extension to the pedal horizontal at the floor and then added a second vertical pedal shaft (Picture #2). The rod that went into the horizontal is 1/2" and about 8-10" long. It is chamfered on top to snugly fit into the tubing past the original vertical stalk weld.

3- I moved the brake cylinders so they are now centered in the rear of the pedal. The cylinder bottom is now attached to a cross plate that is held in place by the existing hardware (Picture #3).

This is really an easy fix without any massive rearrangement of original parts.

So what’s left to do….

1-Weld the vertical and horizontal pieces.

2-Swap out the brake line for braided line.

3-Send in brake assembly (rotor, pads….) for upgrade.

Before the reconfiguration, the plane started to move at 1000 rpm with brakes on. Now I can get the rpm’s up to 2600 before she starts to move.

With the existing (book) configuration; if you push the brakes hard you have the chance of snapping the pedal vertical shaft. Each annual should include checking for cracking on all 4 pedal vertical shafts.

Hopefully this will end the brake issue; at least it will for me.

PS – If anyone is interested in the actual size cad drawing; I can email it.

06-23-2010, 07:33 AM

Mike

I finally finished the mechanical part of the Brakes. The welding in place was a pain in the butt. The brakes are much stiffer now and won't bend as before. Check your brake stems for cracks in the tubing.

Next and final some SS hoses to clean up the poly flow tubing.