Brake/Rudder pedals - part 10

General law of relativity (4.0 hrs)

You are going to have to picture this in your mind a bit. 

As my foot presses forward on the brake pedal, the force is going to be transmitted to the bracket, and its plywood base. This force is an order of magnitude greater in the forward direction than in any other, and would peak during maximum breaking.

With only two things attaching the plywood base to the floor, namely 3 plies of fiberglass laid over the top (primary), and some flox underneath (secondary), does it really make any sense having the front edge of the plywood as sharp as a knife? 

I didn’t think so, since repeated brake applications might force the plywood base to act like a blade trying to slice the fiberglass bond. Not good.

The sharp ramp I cut into all sides of the plywood was designed to ease the laying of fiberglass, so I decided to blunt its leading edge, and make the forward ramp out of flox instead (flox fillet).

This will eliminate the slicing tendency of the once sharp plywood base, and create a hardened abutment to contain it, as well as the gentle transition for the fiberglass I was looking for. A win win win situation.

Plywood base leading edge proposed change

Squaring the front edge of the plywood base

The bond between flox and wood is very good, but the one between flox and metal is very weak. So, in order to reduce the chances that the flox might loose its grip on the base during shear load applications (aka "using the brakes"), I decided to drill the steel base from below. This will allow flox to penetrate the base from below, and act the way a motocross tire would in the dirt, grabbing hold of the base with upward fingerlike protrusions, in addition to flox’s already excellent adhesive qualities (with the wood at least).

The holes were drilled to a depth of ⅛” (3.2 mm) through the steel plate, and into the hardened flox. The steel plate will thus be completely embedded in flox, gripping it from both sides.

I hope I will never need to remove this!

New set of holes drilled into steel and flox (bottom of part shown)

That means I’d better find the perfect position for the pedal assembly, because there will be no turning back.

Spending most of the day trying out multiple pedal locations, the one position I kept going back to was the one right against the sidewalls, sometimes a little more forward, sometimes a little more backward, depending on what shoes I was wearing.

This created a "small" problem for me, because the rudder cable attaching point rubbed against the sidewall, and if left this way it would eventually wear through the structure. Definitely not good. 

The issue is pretty obvious

"This ain't gonna work!"

I obviously jinxed myself two posts ago when I said: "It seems that I always end up building at least 3 versions of everything I design...". 

That statement is fast becoming like "the EZ shop's general law of relativity", and since I had only modded the pedals twice... guess what?

"Yes Virginia, there is only one cure for this… shorten the stick-out of the rudder cable attaching point!"

Version #3 would involve more cutting, grinding, machining, and welding. I wouldn't expect any less at this point.

Separation is always painful

The middle piece is headed for the recycling bin

Machining a chromoly sleeve (later divided into two shorter ones)

Sleeve inserted, and all surfaces prepped for TIG welding.

Dry fitting parts (gap is intentional)

TIG welding in progress

Pedal version #3 is 0.420" (10.7 mm) narrower than version #2

Old and new side by side

Much improved clearance

Here's the math behind the re-engineering

With all said and done, this mod went pretty fast (a couple of hours per side), and will improve positioning flexibility by eliminating any chance of contact with the sidewalls.