F-16 Engine Panel

Introduction

One of the reasons of the intriguing mixture of sensations the F-16 cockpit provides is possibly due to its long history. The first design is of the late seventies and has been updated eversince.

This in turn implies that old-fashioned analog gauges share their valuable spot in the cockpit with digital displays. It has to be remarked that each update the F-16 cockpit layout went through, analog gauges have been moved more and more far away from first scene, but are still present. The attraction to that (past) world of gauges and needles is the main reason that moved me to build the F-16 engine panel.

The panel contains 4 gauges: namely , top to bottom:

• OIL: oil temperature gauge (%).
• NOZ POS: nozzle position (%).
• RPM PERCENT : spool rpm (%).
• FTIT : turbine inlet temperature (ºFx100).

Parts needed

PSCockpit MainBoard handles a quite comprehensive variety of input, and can drives different stepper / servos or aircores. In my design, I was looking for something cheap, and with a decent response; therefore I went for the servo option. If someone wants performance I believe aircores is the best way out, while due to the speed of the needles, I would discart stepper motors (such as the X-27 or X-40 motors), at least when commanded direclty from the boards, since they are really slow.

A brief list of the parts needed to build the panel is herein under reported:

• 4 microservos (MG90)
• 2 sets of plastic gears (to be used to extend the servo angular range)
• 1 Stainless Steel Shaft Toy Car Gear Axle DIY Accessories G08 Drop ship
• black screws M2x40mm
• nylon spacers
• 30 3mm green LEDS.
• 30 120ohm resistors.
• Dupont cables.
• ON/OFF switch
• acrilic black, transparent and white (3 mm, 2 mm and 1.5 mm respectively).
• acrilic with two colors (engraving), 3 mm.
• MDF 3 mm.
• One-side, fiberglass PCB copper plate
• Adafruit 16-channel 12-bit PWM servo controller.
• last but not least a mini CNC 3018 !

Design

Today there are several commercial options available to buy more or less realistic F-16 panels replicas, I would say that the final result is always better if you buy the replicas, but the fun to learn an understand the different softwares and tools required to build your own design was too exciting for me.

Therefore I bought a (rather) cheap mini CNC, it comes in kit, so you have to do your own assembly, and since the CNC is capable of reaching some pretty good tolerances, well, the weak link here, was my building skills.

It would defenitely require a post for itself, so I skip the details about building the CNC, anyway once one experiences a little bit (and throws a way a good number of drill bits), I would totally recommend the experience of building your own mini CNC.

The machine’s versatility really surprised me, and there are a lot of things that it can do quite decently. I used it for practically everything in the build:

• cutting MDF
• cutting acrylic
• engraving the panel
• printing the PCB

The result is really impressive, and several task would have been simply impossible to be accomplished without the CNC (e.g. panel engraving, and servo “gearboxes”).

It is not all peaches and dandelions, there are different softwares that need to be learned, ones for the engraving, ones for cutting and others for the PCB, finally the G-Code (the language the CNC relies on) is not the most friendly thing on earth.

Luckly there is an always growing community of generous people out there which is sharing their experiences (some of them with really a huuuuuge experience), so if one has time and patiente to try fix learn search ask, I’m sure will find the solution.

Adafruit assembly

Adafruit board comes with some pins and other components, that shall be welded on the board. I’m not an expert on that topic, but was (and is) the most difficoult soldering I had to do. For the purpose I bought a cheap soldering lens bench, which really helped me in the task. I also added a condenser even if due to the relatively modest number of servo I have to drive (4), and almost with no load, I’m still confused whether it was necessary or not.

Servo gear box

The servo design is cheaper, nevertheless requires a gearbox, so to increase the gear ratio of the servo. Several options are available, more or less intrusive, a rather easy approach is explained by Moon in this viperpits post.

I built a set of spacers which create the space to fit the smaller gear.

The precision one can achieve with the CNC is quite remarkable. The spacers are screwed directly to the servo.

Backlight

Sofar in my previous design, backlight, was quite a time consuming activity. The electrical scheme is quite straight forward, but there are many weldings, and wires, which ultimately generate almost always quite a lot of mess behind the main panel.

This time, by having the possibility to use it I chose to design my backlight panel as a PCB.

The schematic is quite straight forward, but the CNC allows quite tight tolerances (engraves some 0.2 mm of the PCB surface so to print the tracks). Therefore a very important requirement for your CNC is to support probing in the Z axis.

The one I bought initially was not provided with this feature, but luckily there was a PIN available on the board of the CNC that fullfills this purpose.

There is plenty of articles describing in detail what Z probing is, but to summarize, and simplify, is a technique which senses where the layer you want to mill is, in CNC coordinates, on several points of the board, taking advantage of this information, the CNC corrects its path so to always keep the 0 where it actually is. Due to bad assembly, not perfectly parallel boards, and geometrical imperfections in general, the 0 in Z axis in one point of the board may not be the one on the otherside.

Below there are some pictures indicating Z probing (of a different part). Milling, and engraving of the board, soldering of resistors and LEDs, and final assembly.

GRBL Height Map

Panel

The real character of this design is the panel, which is obtained by the assembly of different layers of acrylic, starting top to bottom:

1. External black layer .
2. Transparent layer (the “glass”).
3. Internal black layer (creates a chamber where the needles are free to rotate).
4. white on black engraved panel.
5. backlight panel.

Panels 1 to 3 are quite conventional, and starting from a raw material it is quite straight forward to mill some simple shapes in it.

The engraved panel is quite a different story, it relies on GCODE to run the CNC but since there are quite a lot of informations to engrave, i think that the easiest way to deal with it was to take advantage of one of the (many) free online services which allows converting an image to vectorized image and then translate it to GCODE.

The result, as you can see, is quite surprising (it was my first attempt, and didn’t even use Z probing). The material I used is one I found in a local shop, and possibly was the most difficult item to find. It is ment to be milled, so behaves really nice (doesn’t melt).

The Mini CNC is just for DIY and hobbist purposes, and is quite slow, nevertheless, being this my first attempt I would say the result is decent, there are commercial options which provide for a fair price a panel which comes possibly with higher standards of quality, but the satisfaction of having something purely designed from yourself, is quite rewarding.

Case

For the case design I opted for something simple, similar to the one I designed for the F-16 MISC Panel. I used MDF and I glued, painted it with a primer and then with a grey paint.

Finally I added as cover a black ABS sheet (which I shaped by using a conventional hoven, to achieve a better result it would have been better to use a heat gun).

PSCockpit

The settings to use the Adafruit with pscockpit are very well described in the website, nevertheless JShep, the author of the boards suggested me to switch the USB poll type from MainBoard to PC in the communication panel, and the servo communication improved considerably.

Final result

The pictures herein under show the final result, predicted and realized, of the design.