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Ultimate Homebrewed Cockpit - Pt. 5, The Light at the End Of The Tunnel
by Gene BucklePrevious Installments:
- Part 1 - The Ultimate Homebrewed Cockpit
- Part 2 - Prequel or "Why am I doing this?"
- Part 3 - Cockpit Delivery - Hell on Earth
- Part 4 - The Face-lift Begins
Welcome to Part 5 of the Ultimate Hombrewed Cockpit Journal series! It has been a while since the last article, and BOY has it been busy around here! Rob & I have made a lot of progress towards the goal of a fully functional F-15 flight simulator. Last month a huge leap was made in identifying the airframe I have through inquiries made to the folks at Edwards Air Force Base in California. Starting in 1984, the Air Force began a program to develop a protective suit to be worn by flight crew members. This program was called TLSS or Tactical Life Support System. It was designed to protect an individual from a number of threats: positive acceleration up to 9G's, altitude exposure to 60,000 feet, cockpit thermal conditions up to 50 degrees centigrade, head protection from buffet, impact against the cockpit or the slam of ejection, protection of vision from laser hazards and nuclear flash, and chemical/biological protection against liquids & vapors.
Three sets of Boeing's first prototype of the system were put through laboratory tests at Brooks AFB in 1986. I believe that my airframe is one of the static test articles that were sent to Brooks. I'm still waiting for a response to my inquiries from Brooks AFB, so we still don't have the numbers of those test articles yet. I have to thank both Tech Sargeant Chris Ball of the Edwards AFB Public Relations Office and Dr. Raymond Puffer, a research historian also located at Edwards. Without their help, I never would have gotten this close to identifying my airframe.
After much hand-wringing, begging and sniveling, I finally have a genuine F-15C throttle quadrant to install! When I receieved it last month, I was totally shocked. The quadrant and been removed from service for rebuild and it was NEVER REINSTALLED. This TQ is in *mint* condition. There isn't even any bolt scratches on the mounting lugs!
Genuine F-15C throttle quadrant. Laying forward
F-15C throttle quadrant. Upright.
F-15C throttle quadrant. Upright from rear and above.
There are a series of five connectors that wire the buttons on the throttle quadrant into the airplane. As soon as the last one is removed, I'll be able to use a multi-meter to build a wiring schematic of the quadrant. The connectors are a nightmare to remove! Rob has done a wonderful job so far, but there are three screws yet to go. Since the cockpit was left outside uncovered before I got it, there is a lot of corrosion holding those screws in. They're VERY small and the space available to work on them is limited. It's averaged about an hour a screw so far to get them out. I thank Rob for his dilligence and patience in working them out without damaging the cannon plugs they're holding in place.
Maintenance Deck Installed
As you can see from the photo above, we've attached a maintenance "deck" to the side of the cockpit. This allows far easier access to tools and such as things are being done inside the cockpit. It's also handy for sitting on while working on the right side interior. Work has progressed quite well in getting the flight controls connected up and working. Work first started on the control stick which controls the pitch and bank controls. New Tool!
Sheet metal brake/shear
This is the new sheet metal brake/shear that I got. This is a "gotta have it" tool if you're doing any sheetmetal work. Using this shear, I'll be able to make the potentiometer mounting plates as well as all of the metal backing plates for the side console panels. It's no lightweight at 300lbs! Rob & I damn near gave ourselves a hernia getting it unpacked and up on to the bench.
The Flight Stick
Flight Stick Control Links
This is a picture of the control links as they pass through the cockpit floor just foreward of the left side console. The far left connection is a three fingered control arm that controls the bank controls. The silver object is a 1/2" diameter 5 foot long section of steel wiring conduit that has been made into a pushrod. Just to the right of that you can see the control arm for the pitch control. The white object is also steel wiring conduit. The other one will be painted white as well. I'm painting all the new hardware I install to both differentiate between what I install and what was already there as well as to make it look nice. The slide potentiometers for computer input will be installed foreward of these two control arms.
Stick Centering Mechanism
This is the stick centering mechanism I constructed. It's located about 5 feet aft of the control arms. I'm using two large springs on either side of a solid mount to provide roughly 10lbs of centering force to the stick. The one in the back is for the pitch motion and the fore unit is for the bank motion. While this arrangement works VERY well, it makes a great deal of noise and there are a few binding problems. I'm going to disassemble it soon so these issues can be resolved. A lot of the noise results from the springs & washers sliding along the control pushrods. This can be damped out by wrapping the washers with electrical tape as well as placing a length of heat shrink tubing around the pushrods to make the action smoother as well as prevent the steel on steel mechanical noise created by the moving parts. Many of you that fly remote control airplanes will recognize this mechanism right away. It's based on a little scratch built device known as a servo saver, although greatly scaled up. For those of you that are not R/C pilots, this device is used where ever you have a control servo (a radio controlled motor that translates stick motion to physical motion in the airplane) that has a greater travel than the control you've got it connected to. It allows the servo its full travel and since the springs will compress when the other end reaches its travel limit, it won't stall and possible damage the servo.
Rudder Pedals
Control Arm Ball Link Unassembled
This is the control arm end of the rudder pedal connection. It's a 1/4" bolt that's been drilled to accept a ball link. These ball links are quite often used in R/C airplanes, especially in throttle linkages where only one end of the pushrod needs to be adjusted.
Control Arm Ball Link Assembled
This is what it looks like with the nylon part of the ball link connected. The wire in the upper right of the image is a 2-56 threaded 1/16" steel pushrod. This screws directly into the nylon ball cup. The brass fitting will not be used.
Slide potentiometer Mounting Plate
This is the mounting plate that holds the slide potentiometer that will translate the mechanical motion of the rudder pedals into a value the computer can use. The plate itself is 1/16" aluminum that I cut a slot in with my CNC mill. The potentiometer is electrically identical to the pots that you have in your rudder pedals and joystick, but it slides instead of rotates.
All together now
This is how it all goes together. The bolt is installed in the rudder control arm that is located in the right rear avionics bay. The ball cup is connected to the bolt, and the wire pushrod will fit into a slide fitting on the potentiometer. This allows me to physically center the slide pot and then tighten the pushrod down. If any adjustments need to be made, I can do this easily by loosening the screw. If I had used a fixed length pushrod here, no mechanical adjustments would have been possible.
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