My best friend died on Saturday.


I’d like to introduce you folks to someone. The guy in the photograph at the bottom is Robbi Hommel, and after my wife, he is the most important person in my life. Or he was. Robbi died over the weekend of a heart attack. He was 67 years old. Until I got the call yesterday, the absolute worst day in my entire life was the day I had to tell Rob that his mother had been killed in a car accident.

For nearly 30 years, this guy has gone along with all my crazy plans and projects, and more than a few silly things. He was the kind of “enabler” you wanted on your side.

We first met while working at a little hole in the wall electronics store called Supertronix in Kent, WA. We made fast friends and spent a great deal of time doing all kinds of nerdy things. From collecting Commodore computers, to pulling a VAX 8250 from the machine room at Mannesmann Tally, carting that sucker home and re-assembling it in the upstairs of my house. (That was in 1994 – when Jennifer & I moved in 2006, there was still a visible bow in the ceiling from that VAX! It’s not really surprising – that was a FULL VAX 8250 system. Four RA81 hard disks, a TU-81+ 9 track tape drive, and the main cpu rack, and the house was built in 1948…)

Rob could get along with just about anyone – he’d be instant buddies with complete strangers the instant he met them. Sometimes that drove me to distraction, especially when I was in a Home Depot trying to get something done. He’d be off talking to someone about whatever, enjoying himself immensely.

He enjoyed puns – the more eye roll-inducing, the better. He knew very odd people (me included!). He played Frisbee once with Three Dog Night at a hotel in Colorado. He didn’t care who they were, he just wanted to enjoy himself.

He’d regale me with stories about is friend Lloyd, who got himself (and Rob) into trouble more than once. Lloyd once worked at a hotel in Colorado where Betty Ford was staying after (it was rumored) some kind of detox. Lloyd had been directed to deliver room service to her room, and he arrived, apparently banged on the door and yelled, “Betty! It’s me, Lloyd! I’ve got your Scotch and Quaaludes!” The door was swiftly opened by a Secret Service agent, and he was escorted off the property. 🙂 Rob loved telling these stories about his odd friends, and I sincerely hope he was able to tell stories to others about his weird friend, Gene.

He worked at Ampex as a tech, doing field service repairs on the huge TV tape systems that they produced in the late 70’s and early 80’s. He and a friend created a huge model train layout they called “The Minnefats-Weehawken Train Line” and all the trains & switches were controlled with a SYM-1 single board computer.

He had a love of science and all things Nerd. He knew a little bit about just about everything and was most certainly a genius in his own right. He’s the only person I could honestly describe as a polymath. I have no doubt that Adam Savage would consider Robbi a peer.

He was right by my side when I was up to my neck in flight simulator things – often times egging me on to greater accomplishments and getting doors opened to places people normally didn’t get to see. He once talked his way into getting us a personalized tour of Seattle Center – the main hub of air traffic control for the Pacific Northwest. It was amazing, and it’s an experience I never would have been exposed to without him. We spent hours there talking to the controllers. The lead meteorologist LOVED his job. I’d never met a Weather Nerd before. That was an experience.

If it wasn’t for Rob, I never would have found the F-15 that we both enjoyed working on. It was his idea that we head out to the Olympic Air Museum on the day we found that fuselage section sitting outside the main hangar. If it wasn’t for Robbi dragging me out of the house to go visit that place, this project would have never existed.

There were times when something would go awry with whatever project was in process at the time, and we’d somehow point at each other and yell, “YOU!” while laughing hysterically at whatever it was that went (usually predictably) pear shaped.

Rob is the reason that I’ve got a rolling electronics bench named Martha Stewart. I once handed him a drawing of the kind of rolling bench I wanted to build and it consisted (charitably) of three lines. He looked at me and said, “Who do you think I am, Martha Stewart?” That bench got built, and it’s fucking awesome – if you look at it side on, you can see the three lines I drew that was the whole genesis of it.

We built a LOT of stuff together. I can’t look inside either one of my workshops without seeing something we worked on together. That’s going to make for some rough days ahead I think.

Rob was all at once, a father figure, a brother, a mentor, a best friend, and an equal.

The last time I got to see Rob was a few months ago – previously to that, it was a couple of years – because of this fucking human malware that paste-eating retards refuse to take seriously. You selfish cunts cost me time with my friend, and I’ll never forgive you for it.

We got to talk on Friday about the work I needed to do on the wood shop that he and I built together out of the run down pole barn/stable that was on our property when we moved here. I had just gotten the roof replaced and we had plans to Get Shit Done, post human malware. By Saturday, he was gone. Now, there’s a lot of things that probably won’t get done, but the things that do, will remind me of him. It will make them all precious to me.

The photo below is of Rob, sitting in the F-15A a the McChord AFB Museum (long before this “JBLM” nonsense). You can tell just by the look on his face that hilarity was going to ensue, and it was going to be soon. That day he managed to get the docent to open it up so I could take tons of research photographs for our work on the F-15C. (Robbi could talk his way into just about any place – that’s how we managed to get some “stick time” in the MD-85 flight simulator at the Alaska Airlines training facility in the mid-90’s.)

I don’t know that I ever thanked him enough for the things he did for me, but I hope he understood how much I appreciated him.

There won’t be any new hijinks, so I’ll have to treasure the memories of the ones that were.

Thank you Robbi. For everything.

Robbi Lee Hommel – 1955-2021

APG-70(V) Radar panel rebuild is complete!


This took a completely unacceptable time to finish. 🙁 I tore down the original panel probably close to three years ago. Life and other projects conspired to push work on the F-15C to the background. Yesterday (9/19/20) I got out of bed with my task for the day to get this panel knocked out. I didn’t get it done in a single day, but damn near. 🙂

I disassembled the APG-70(V) radar panel and stripped down all the switches of the original wiring and carefully de-pinned the Cannon connector. I worked out the connection positions on the switches and got new leads attached. When I originally started this rebuild, I got as far as a single switch and then SQUIRREL!…

Here’s what the panel components look like prior to final assembly:

WordPress screws with the aspect ratio for some stupid reason…

And after installing & pinning the interface connector:

The channel selector is kind of a neat switch. It consists of two 8 position rotary switches. The first is labeled “A” through “H” and the second is “1” through “8”. The switches are BCD – Binary Coded Decimal. There’s a common wire on each and then three terminas, “1”, “2”, and “4”. Those three wires in combination can represent 8 different switch positions.

Now the back plate gets mounted. In rewiring the panel, it uses 52 pins on the original Cannon connector:

Now it’s ready for the edge-lit panel and knobs to be installed. Maintainers may spot a problem in this view. 🙂

This particular APG-70(V) radar happens to be serial number 0009…

With the knobs back on…

Finally, here it is with the rear shell cover back on:

Here’s a pile of the extra bits that I didn’t need…

The next thing I need to do is craft the wiring harness that connects the APG-70(V) panel to the main bulkhead Cannon plug. I’m going to look into either building or buying some kind of automated wire measuring/cutting tool. There’s 52 wires for this panel – it makes for a very tedious work session when most of your time is consumed by measuring and cutting wire…

BTW, if anyone knows how to force WordPress to stop imposing 1:1 aspect ratios on images, please let me know in the comments.

Something new!


If you look above this post, you’ll see a new tab – “Library”. This is where I’m starting to put scans of “official” documentation and literature that I’ve got on the F-15. The first two volumes of Eagle Talk are up already. I’ve got vols III and IV to scan, and those will go up as soon as I can get them scanned. It may be a slow process as running the book scanner enrages my carpal tunnel something fierce. 🙁

[Update 03May19]

Volumes III and IV are scanned and available for download. If you have later volumes, please contact me! I’d love to add them to the collection.

Upcoming live stream!


I’ve been looking into doing live streaming of the panel rebuild work on the F-15.  Basically this would be a live stream of me working out the panel wiring, wiring up the connectors and adding the harnesses to the main side console harness.

I’d be narrating what I’m doing as well as answering questions from folks over chat – I’ll be using Twitch to handle the stream.

I’ll likely start doing this on Saturdays at noon(ish) and the stream will run until I get tired of working on the “panel of the day”. 😉

When I firm up a schedule, I’ll post information here as well as in the “usual” places, such as SimHQ, the simpits-tech mailing list and likely Facebook.

See you then!

CAS panel rebuild & wiring harness is complete.


Last Saturday I took some time do de-pin the cannon plug in preparation for rebuilding the CAS panel.  This weekend I finally got around to getting that panel rebuilt and wired into the left side console harness.

Here’s a few pics of the rebuilt panel assembly:



The CAS panel is interesting in that it’s got a pair of magnetically held toggle switches.  It’s essentially a relay that’s designed with a very heavy spring to keep it open unless the coil is holding it closed.  Here’s what one looks like:

mag-switch-1Fingertip for scale. 🙂

At some point I’ll post the little video I did that shows how the switch operates.

It turns out that I may have a pretty special CAS panel.  I noticed the manufacture date & serial number on the back of the edge-lit panel:


The date is November 5th, 1971 with a serial # of 2.  This makes me think that the panel may be from one of the original test articles that MD built, but I’m not sure.  I’ll update this post if I find out more information.


New gauge design!


I spent quite a while working on getting the air core motors to work properly.  The biggest issue was the sound they made due to the PWM signal resonating in the instrument shell.  I did get the sound to go away, but at the required frequency the motor would no longer move properly.  This lead me to look into other methods I could use that would still fit into a 2″ MS33639 instrument shell.

Many years ago I briefly looked into the micro stepper motors made by Switec.  They were fairly new on the scene and were nice, but expensive motors.  Fast forward about 12 years and I find that you can obtain these motors for as little as $2.50 each! (lot of 25 on eBay)  My search for more information on the motor led me to an Arduino project where the goal was to use these steppers in various projects.  The cool thing is that due to the low power consumption of the coils, they could be directly driven from an Arduino without the need for an h-bridge chip! (20mA per coil) The blog entry that I found is here: – I’d recommend you read the rest of his blog – there’s a ton of great information on using Switec motors, including with a Raspberry Pi.

I did a bit more research and found a demonstrator project on Tindie that used a Switec motor –  The board allowed for easy connection to an Arduino and included clamping diodes to prevent back-EMF from doing damage to the Arduino.  Since the board was way too large for my needs, I re-designed it to use surface mount diodes (LL4148) and reduced the size of the board to match the diameter of a Switec motor.


The 4 pin connector along the bottom is for the two coils in the motor and the 2 pin connector at the top is for the 5v reference voltage for the diodes.

I revised my gauge code to use the Switec X25 library and it works great!  The motor I’m using is the X27.168 and has an internal stop.  The 2″ gauges in the F-15 don’t require more than 300 degrees of rotation at the most, so this is a perfect choice – it allows me to rotate backwards to hit the stop and then start from a known point.  The idea being to use the stop in lieu of a “home” position detector.

Unfortunately, changing to the Switec motor required that I completely re-design the “middle” section of the gauge.

Here’s the result of that redesign:

v2-gauge-iso-1-sm v2-gauge-iso-2-sm

The resulting assembly is going to be roughly 3/4″ shorter than the original, air-core based design.  I’m currently printing the new components as I write this.  The photo below is the new center mating clip.

center mating clip

This part attaches to the back half of the instrument using two screws.  It is connected to the motor and instrument face using a pair of 0-80 screws that pass through the stepper motor and end up in heat-set inserts installed in the standoffs on the instrument face.



I also got the chance to get the finishing touches done on the gauge face graphics.  I had them printed up on 120lb card stock at Staples:

gauge facesThe plan is to cut them out on the laser and then glue them to the gauge faces after assembly.  I had enough made to ensure that I’ll have spares when I inevitably screw one up. 🙂 I really like how they turned out!

Thanks for reading!

Update on the 2″ gauge.


I finally had the time to come back to the gauge and get the firmware finished!

I had somehow managed to do damage to the Arduino Nano such that you couldn’t upload firmware to it using the “normal” method in the Arduino IDE.  Turns out I’d blow the rxdata line going into the ATMega 328 MCU on the board. 🙁  The good news is that I’ve got it replaced and the firmware is done.  Next step is to make some high quality faces, new needles and new instrument shells.

Here’s an interesting bit of trivia for you – the F-15C can consume up to 150,000lbs of fuel per hour at low altitude and in full afterburner.  That’s right around 22,000 gallons of fuel per hour!  Those F100-PW-220 engines are hungry! 🙂

2in. Gauge design is complete and tested.


So the printed circuit boards mentioned in the previous entry have been put to work!

The gauge shown here is the core that I’ll build the six 2″ engine gauges out of.

Here’s what the gauge looks like on the inside.  All the plastic components (the white bits) are 3D printed on my SeeMeCNC Rostock MAX v1, Orange Menace.

gauge interior, side

gauge interior, side 2

Here’s how it looks with the “test” case on it:

gauge front

Finally, here’s a short video of the gauge in operation:

Once I have the time, a properly sized case will be printed (the blue one is too short) and I’ll get a good laser engraved face on the gauge.

It’s coming along! 🙂

[Here are the gauge electronic components, sans header connectors]


A side trip to engine gauges…


I’ve recently been working on getting the six engine gauges for the F-15 put together.  Since I’m not going to be using real instruments, I needed to scratch build them.  Last year I did a short demo that shows how I’m using a small OLED display to emulate the “odometer” style display that’s used in the Fuel Flow, Temperature and RPM gauges.  I finally got around to doing the software integration and did a short video that shows both the air core and the OLED display working together:

Some weeks later, the boards I ordered from Osh Park arrived and I got the first one soldered up.


This is the top of the new interface board.  The chip in the center is an LM293DD dual h-bridge chip.  This is the surface mount version of the LM293D that I bread-boarded the circuit on.  The header on the right goes to the OLED interface.

The bottom of the board has a four pin connector that will go to the air core motor.


This is what the final assembly looks like after the Arduino Nano has been mounted.

The USB connector is at the back end of the board and will be accessed through an opening in the back of the instrument.  I’m still working on the design for the instrument core, so I don’t have much else to show yet.

More soon!





I don’t know if this update qualifies as a “milestone” or not, but I finally finished and installed the wiring harness for the right side console!

The adventure started this morning with the construction of the wiring harness for the recently finished TEWS panel.  This consisted of cutting, stripping and adding pins & sockets to the 22 wires that are used by the TEWS panel.

Weapons of choice...

Weapons of choice…

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