Friday, May 26, 2017

Arduino and FSX - Update for Rudder Pedals and Brakes

Update for Rudder Pedals and Brakes — 
'Arduino and FSX' blogs, Part 3 and Part 4 discussed using an Arduino UNO as a joystick with buttons and axes. In Part 4, rudder and brake pedals were built using plans from Bruce May (How To Build Rudder Pedals, 2006). My experience with those pedals as constructed was less than desired, so a rebuild was in order. The problems that required fixing were: 1) sticky movement of the pedals; and, 2) the pedals did not self-center the rudder as foot pressure was released. The toe brakes worked very well and did not require changes to the original design. The Arduino joystick wiring and programming did not require any changes, other than recalibration of the X, Y, and Z axes in FSUIPC since the rebuild changed some of the sensor positions.



Photo 1: Original Pedal Design: a metal bracket was added to limit toe braking when moving rudder.   
 
Photo and Figure 2: Revised Pedal Design: Toe brake hinged above rudder pedal.
The revised plan was to place each pedal and toe brake on a drawer-slide trolley to provide metal tracks for the trolley wheels to move without binding or dragging. The second change was to fix the lower part of the pedal in place so pushing the rudder pedal did not also cause braking. The third change was to move the toe brakes above the rudder pedals. And lastly, to modify the return springs so the pedals would have good tension while providing improved self-centering.


Photo 3: Pedal Trolley rolls between side rails and is centered by tensioner spring fastened to center of trolley base and each end is fastened to base plate. Trolley must be mounted to provide space for tensioner spring.




Photos 4, 5, 6: Trolley Side Rails are cut to 20" length. Trolley Roller Slides are cut to 12" length. A second 3/4" roller is mounted in cut-out on the 12" Trolley Roller assembly. The 4" x 12" Trolley plywood base is mounted between the Left and Right Trolley Roller assemblies. The Trolley Side Rails are snugged to the Trolley Roller Slides to give a smooth fit (See Photo 3).


The base plate of the pedal platform is 20"x20" plywood. The revised pedal trolley platforms are 4"x12" plywood, mounted between two modified drawer slides (think of a kitchen cabinet drawer with just the bottom piece of the drawer that slides front to back). The 4" wide by 12" long trolley can move forward 4" and backward 4". Centered under the trolley is a 10.25" spring that is stretched and secured 1" from the front and rear of the base plate. The center of the spring is attached to the bottom of the trolley with a figure-8 of wire and a small screw. The trolley side rails must be mounted sufficiently high to allow space for the tensioning spring under the trolley. The trolley can then move fore and aft with the desired pressure and return to the center position (with some dead space error) as foot pressure is released.
Attaching the pedal spring to the bottom of the pedal trolley fixed several problems. In the previous design, the return spring had been connected between the angle bar that rotated as the pedals were moved. The spring pulled on the angle bar tending to twist the bar against its center pivot pin causing friction, gouging, and wear of the aluminum bar. The result was tension on the bar that led to sticky and erratic pedal movement. In the new design, the spring tension is inline with the pedal so that foot pressure is easily transferred between the foot, the pedal, the spring, and the base, and the spring can stretch fore and aft without binding.
The earlier design had a flat pedal that served to move both the rudder and toe brake. I found that design difficult to use while taxiing since movement of the rudder for steering usually caused one or the other differential brakes to also be applied. In the revised design, the toe brake is moved to a separate hinged piece at the top of the pedal assembly. The rudder pedal is now a 4"(W)x6.5"(L) piece of plywood mounted at a 35-degree angle with a 4"(W)x3"(L) piece of plywood toe brake mounted edge-to-edge with a 3" cabinet hinge. The toe brake rotates forward and down by pressing forward and down with the toes while rudder control and steering is provided by fore and aft movement of the pedal and trolley by the heel of the foot. I find this design works well for me.
Construction Materials -
1 - 24" x 48" x 5/8" or 3/4" plywood
4 - 20" x 1-5/16" x 3/4" slide rail support (or 20" x 1-3/8" (as needed) x 3/4")
2 - 20" x 1.5" plywood rear bumper strip
2 - 7/16" x 10.25" x 0.041" springs (Everbilt SKU 683-948 from Home Depot)
2 - 3" cabinet hinges
4 - 3/4 in. nylon sliding shower door rollers, #8x32 screws, 11/64" drill hole
2 - sponge balls
assorted #8 3/4" and 1 1/4" wood screws
Other parts as specified by Bruce May (2006)
Base plate: 20" x 20" plywood
Pedal trolleys: 4"(W) x 12"(L) plywood
Pedals: 4"(W) x 6.5"(L) plywood
Toe brakes: 4"(W) x 3.5"(L) plywood, rounded as desired
Pedal supports: 5.5" x 5.5" plywood, cut to shape, see Figure 2
Pedal support cross member: 2" x 3" plywood

Useful references -
 (May 26, 2017)

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