#4931004
Did I say it was a slow build? I mean slow. As in I started work on this prop in 1994.

But now, 26 years later, I think I'm in the home stretch, so I thought I might as well start a retrospective build thread culminating in a final prop replica that features:

  • Resin shells cast from two-part molds to capture the exterior AND interior detail of an Iona shoe polisher I've accurately reworked and detailed to match the PKE meter, mainly based on the photos my friend Bryan Ambacher took of the real prop while visiting Modern Props for his set decorator job around 1995.
  • Wings driven by dual servos, emulating the linkages of the real prop.
  • Electronics controlled by a Teensy 3.2 Arduino and Prop Shield to drive the LED chases, servos, and movie-accurate sound effects (weak and strong readings).
  • PCBs for the main electronics and LED display screen with multiple Molex Picoblade connectors to plug in the various outboard LEDs, servos, switches, speaker, and other components.
  • Two touch switches on the handle to activate the wings, lights and sounds at half and full deployment
  • Two touch switches on the panel (tied together) to activate various user-selectable modes:

    -DEFAULT MODE ties the LED chase speeds to the wings state. At half up the lights chase slowly. At full up the lights chase quickly.

    -CLASSIC MODE emulates the 1984 movie prop. The LED chase speed is controlled by the potentiometer at the top of the handle, independent of the wings state. This is activated by briefly touching one of the contract pairs on the flat panel of the prop. Briefly touching the switch again sets it back to DEFAULT MODE.

    -SILENT MODE turns the amp off for the sound effects. This is activated by holding one of the panel touch switches down for two seconds or more. Keeping contact on the switch for two seconds turns the amp back on.
  • Rechargeable NiMH batteries (5x 2/3A-sized cells, similar to the real prop) and a port in which to plug in an external charger.
  • Mode select switch below the display hood to switch the chase pattern on the display.
  • Master power switch at the bottom of the handle.
Here's a video showing a successful test of the PCB I designed and had fabricated by OSH Park:



And a photo of that setup:

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Here's a video of an earlier breadboard prototype showing the wing movement (we've matched the speed to the real prop in the Arduino code):



All in all, I think this will be a pretty cool replica. One reason it's taken me so long to get this together is I keep adding features like the various MODES and sound effects. Thanks to Patrick B. (GohstTarp) for doing the heavy lifting on the coding.

Once it's all done, hopefully within the next few months, I'll look into creating kits for this if there is any/enough interest.
Last edited by WShawn on March 15th, 2022, 11:39 pm, edited 2 times in total.
#4931020
I'm not 100% sure, but I think the touch switches on the flat panel in the original prop duplicated the functions of the ones on the handle below, triggering the lights and servos to go full or halfway up. (Doesn't Ray struggle with those controls while examining Oscar's room in GB2? I'm too busy to put in the Blu-ray at the moment.)

To clarify, the screen pattern (7 LED chases) is selectable by the physical slide switch under the display screen hood, as in the real prop. I'll have to fabricate the doohickey that disguises that switch. The one on the Matty prop is one of the few things on that toy that appears to be accurate, so I might see if I can pull a mold off of that. Otherwise it's simple enough to scratch-build.
NickFame13, Jimsy33 liked this
#4931036
Years ago, Cyland Props recorded a short bit of footage of the actual P.K.E. Meter prop. I'll have to see if I still have a copy of it, but until then, your recollection of the switches matches what I remember hearing about it.
#4931040
Kingpin wrote: February 10th, 2020, 3:30 pm Years ago, Cyland Props recorded a short bit of footage of the actual P.K.E. Meter prop. I'll have to see if I still have a copy of it, but until then, your recollection of the switches matches what I remember hearing about it.
I'd love to see that video if you still have it kicking around. I managed to grab some of the images off of his website just before he took it down. He had a few shots of the guts from angles that Bryan didn't get, though they're somewhat low-rez.
Alex Newborn liked this
#4931044
Here's some not-so-quick background on what led up to this build. Jump down if you'd rather just see photos and descriptions of the actual build.

1984: As I've written here before (and as detailed at marshall-arts.net/ProtonPacks) my friend Bryan and I were able to take photos and measurements of the Egon pack being displayed at the Scottsdale Center for the Arts in September. From those reference materials we were able to scratch-build pretty accurate packs in time for Halloween, 1984.

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1986-ish: While wearing our packs at a convention in SoCal (probably Pasadena) a stranger complimented us on the quality of our packs and invited us to tour Modern Props. There we got to see many of their famous props and hold the PKE meter (not charged up, sadly). We didn't have a camera on us, but I made a little sketch on the back of a business card I had on me. That scrawl says "7 ribs."

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1989: With Ghostbusters 2 on the horizon I set out to scratch-build a PKE meter. My only references were a lobby card of the publicity photo that shows the PKE in the pocket of Venkman's lab coat and a professional-quality NTSC videotape of Ghostbusters I recorded off of the ABC network feed at the TV station I was working at at the time.

I built a master from balsa wood, made two-part fiberglass molds for each half and then cast fiberglass shells for each shell half (yes, you can cast fiberglass in fiberglass molds with enough mold release and PVA.)

I built an aluminum mechanism housing an old Tamiya model tank motor and gear train to drive the wings, and an engineer at KGUN helped design the electronics that used microswitches and relays to control the wing positions and lights. I filed teeth into a little block of aluminum to translate the rotational spin of the tank motor gear into linear movement to push and pull the arms. The rollers on the microswitches would engage bumps I built into the sled to stop the motor when it hit certain points of the track. I didn't have the budget or knowledge to use servos.

The LEDs were driven by a mix of analog timers and counters. I misidentified the light chase on the wings, making it harder on myself to have several LEDs light at the same time on each wing. This was an artifact of transferring 24fps film to 29.97 fps interlaced TV video; that transfer process can blend two film frames. I had this replica done in time for the GB2 premiere.

Here's are some photos I took in the early 90s that show the guts of the unit:

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Here are photos taken around 2001:

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Here's a low-rez video shot around 2001:

https://youtu.be/ka0jnBN2T3Y

1990-1992?: Bryan had a brief career working as a set decorator on various movies that shot in Tucson and L.A. including Harley Davidson and the Marlboro Man, Madhouse, and several others. He brought my PKE Meter to one of those productions to show to his fellow crew members, and they were fairly impressed. A few weeks (or months?) later he brought me an Iona Shoe Polisher that one of his co-workers found at a yard sale. Bryan and his co-worker gave me permission to use it to build a new version of the prop.

1993-1994: While working on some production in L.A. Bryan was sent to Modern Props to pick up something. Walking by the workshop he saw the PKE Meter sitting on the workbench. Not being the shy type, and armed with a 35mm SLR camera this time, he proceeded to snap 12 photos of the prop, both opened with the interior guts visible and closed up and working. Those photos can be viewed here:

viewtopic.php?f=5&t=42356

Armed with an Iona shell and reference photos I set off to build a new replica. More below.
Kingpin, tobycj liked this
#4931047
1994: My plan was to make molds of the unmodified Iona polisher and pour resin copies that I could then chop up and modify to create the PKE prop. I'd then return the shoe polisher to Bryan's co-worker. By that time I had some experience creating flexible molds using RTV polyurethane rubber. In this pre-internet era the Polytek catalog offered good instructions on how to proceed.

First I mount the prop onto a flat board with registration pins:

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I mold clay around the buck to create a void where the mold rubber will live:

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I build a box to define the plaster mother mold:

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The mother mold and positive ready to pour in the RTV mold rubber:

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Carefully pouring rubber into the mold:

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The resulting molds didn't look too bad. This is a new photo of this mold I still had around:

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I had never tried resin casting before. I wasn't entirely satisfied with the results at the time. It didn't help that I was casting the resin in Tucson in August. My resin would solidify before I'd poured half the piece. Looking at the pieces now they don't look horrible. They could probably be sanded and filled to make workable pieces. I guess at the time I wanted something near perfect on which to build the prop:

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tobycj liked this
#4968068
So after a two-year layoff I've finally mustered up the creative energy to resume work on my Never-ending PKE project.

When we last left my sloth-like build, I'd decided that modifying a cast of the virgin PKE shell wasn't going to work, so I set about modifying the actual thing (with the permission of Bryan Ambacher, who acquired it).

I set out on this task around 2001.

It was a fairly straightforward process of cutting out the brush mount area, covering that with styrene sheet, filling other spots with styrene, and filling voids with Bondo and spot putty.

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#4968069
With the basic shape of the shell filled out I set about detailing it. This involved sanding the nose and sides to create sharper profiles, moving the screw holes, mounting strip styrene to create the ribs, and building a hump that transitions to the handle potentiometer knob.

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I fabricated an extension to the display platform which turned out to be a little too long:

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I composited various views from the photos Bryan took to help work out the dimensions and angles:

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I shortened the display base platform:

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And then fabricated the display panel unit from sheet styrene:

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#4968070
February-April, 2003:

With the exterior (mostly) in good shape I turned to fabricating the wings. My initial hope/plan was to create a mold of a single wing in which I could encapsulate the wiring and LEDs in resin. I drew up a plan, built a buck from styrene plastic, then cast a polyurethane mold around that.

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I sanded down the tops of yellow T1 LEDs and glued short bits of acrylic rod to each. I wired up the LEDs and slid the electronics into the mold.

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Unfortunately, the resulting casts weren't great. Sometimes the wires would protrude to the outside, but the main problem was the cast wings would tend to warp, rendering them unusable.

With that I turned to fabricating each wing from scratch.

To help position the LED/Rods I built a jig for my drill press to create consistent holes along the edge:

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I fabricated each wing from styrene:

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I glued in the electronics and wiring:

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And poured resin inside to add a bit of strength and seal the wiring:

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Jimsy33 liked this
#4968072
November, 2003:

My goal was to replicate the basic workings of the original prop with two servos driving the two wings via RC-type linkages.

I added supports inside the modified shell to support the aluminum plates for the wings and servos:

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An aluminum frame to hold the servos:

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Aluminum plate to support the wings:

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Finished wing on support plate:

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Rough placement of wing and servos:

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Jimsy33 liked this
#4968074
December, 2003:

I turned my attention to the electronics. I found a simple circuit to drive servos online. I combined that with an LED chase circuit I found in Forest Mims' Electronics books and the touch switch circuitry I was using in my 1989 PKE. This would be a completely analog setup.

I found some free circuit design software online (I don't remember its name) and came up with these:

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I then created a scale layout of the components in Adobe Illustrator:

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I drew the wiring on different layers, printing out each separately to help organize the wiring:

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At the time I was planning to include an internal charging circuit

I then set to wiring up this thing:

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Once again, more setbacks. For one, once this was all wired up I couldn't see a way to fit it all into the shell. Second, I kept having issues driving two servos at once with this setup. Driving a single servo worked fine, but trying to drive two would produce chatter and erratic movement. I tried adding a big capacitor to smooth out the signals, but that didn't work. I started attending meetings of a local robotics club, but they weren't much help, either. So with that I kind of let this project sit idle until 2014.
#4968076
After MANY years off, in 2014 I had the good fortune of a new neighbor (programmer and hobbyist) informing me of the existence of Arduinos, specifically the Teensy which is developed locally in Portland. So with his help, and the help of my friend Patrick (@gohsttarp) we started building code for a Teensy to drive the electronics. I also found a new circuit for touchswitches that uses fewer components and is more reliable.

In 2015 I decided to create molds of my master shells for several reasons. If I was going to be toting this around to conventions and appearances I didn't want to risk damaging this Iona-based prop. I'd had strips of the ribbing pop off while working on the shell. I also harbored a hope of maybe someday offering a kit.

Wanting to save resin, I created plaster mother molds to help hold the Polytek polyurethane molds. I used one of my original casts of the Iona, mocked up with a display panel, to work out those mold parts.

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I tried several types of resin including several from Polytek and one from Sharkthane

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The results from the polyurethane molds were so-so, so I re-did the molds with Smooth-On's Oomoo silicone resin. The results were much cleaner, though the Oomoo is very fragile.

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Jimsy33 liked this
#4968078
In the summer of 2017 I shifted my focus to building the most accurate set of Ecto Goggles I could, as seen in this thread: viewtopic.php?f=12&t=43597

June, 2018:

As we progressed on this project we succumbed to feature creep and decided to add sound effects to the prop. I incorporated a Teensy Prop Shield that could play back sound files and amplify them to a speaker.

The prospect of manually wiring up this circuit again was not appealing. In our research into building and programming our Arduino circuit I learned that it was now fairly easy and inexpensive to have custom PCBs fabricated. Once again I'd turn to a local company, OSHPark, to fabricate the boards.

Thanks to YouTube, other tutorials, and forums I learned enough KiCAD to design a schematic for the main board and then design and route a PCB.

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For $20 I had three prototype boards fabricated in around a week:

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I managed to fry two of these boards and destroy several Teensy 3.2s and Prop Shields by being careless with my component soldering and power supply. The third try worked, as seen in the first post in this thread.
Jimsy33 liked this
#4968079
September, 2018:

Working with the shells I'd cast in the Oomoo molds I found they weren't super-easy to assemble, so I decided to make some tweaks to the interior supports, this time casting the shells with Smooth-On's Moldstar silicon rubber. It's much more durable than the Oomoo. I re-used the plaster mother molds from before.

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I continued to experiment with different resins. Sharkthane was the easiest to pour, but I didn't like the feel of the finished cast. Smooth-On's Onyx Fast feels a lot like styrene (which is what I want), but I had trouble getting the mold filled before it would set up. The Onyx Slow cured to a horrible texture, full of bubbles or something. I don't have a pressure pot or vacuum system.

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A cast where the mold didn't fill.
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I also didn't do a great job of designing the molds, the result being the inner mold would frequently get stuck on the outer mold when I put the halves together, resulting in distorted and failed casts.
Jimsy33 liked this
#4968096
February, 2020:

I designed a small PCB for the display in KiCad. I'd wire this up to a Molex Picoblade harness to plug into the main PCB. Working out the LED spacing for the crossover was a challenge. OSHPark fabricated three boards for under $7. I later revised this to move the LEDs in the display up just a little bit.

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I redesigned the support plate, creating a template in Illustrator that I could print out and temporarily tack to the aluminum to form, drill, and tap the plate:

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I designed plans for the wiring in Illustrator:

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#4968098
March, 2022

I'm finally resuming actual work on this project, starting with fabricating new wings. I'm going to try the casting method again, but this time with the LEDs soldered to a PCB. The T-1 LEDs will straddle the PCB. I'm hoping this added stiffness, along with using silicone rubber for the molds, will produce non-warped wings I can semi-mass produce.

I designed the wing PCBs in KiCad. The file is currently at OSHPark, in the process of being fabricated.

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If this resin casting approach continues to produce poor results I'll try creating them with the 3D printer that arrived today. I'm excited to try this out (though I still have a lot of things to figure out like how I'm going to heat its workspace.)

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Last edited by WShawn on March 16th, 2022, 6:20 pm, edited 1 time in total.
Jimsy33 liked this
#4968099
I'm working to build a wing buck for casting. One thing I'm struggling with a bit is the spacing of the LED/rod assemblies. They're not perfectly spaced on the actual prop, and that's in conflict with my anal-retentive nature to make everything perfect. My inclination at this time is to replicate the original prop as much as possible, so my replica's lights will be a little uneven.

I was hoping to use my drill press to create holes in which to insert the acrylic rods, but it was just too coarse and uncontrollable to perfectly drill the holes. So I'm going to glue on each rod, creating a little jig to make sure they're positioned accurately. I'll use a CA gel to glue on longer rods, then trim them down to their correct length.

The divots in this photo were created with a smaller bit that I just twisted in by hand. The final buck will have a notch on the round end to reveal the contacts for the wing PCB.

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#4968101
wralex wrote: March 16th, 2022, 6:17 pm Mars 2 pro is a very good printer. I used a saturn and really love it.
I'm excited to play around with it. I wanted a solid but inexpensive starter printer. If I get a lot out of it I'll look to get something bigger like a Saturn. I have to decide whether I want to buy a wash/cure station or do a DIY approach.
#4968102
I bought their wash and cure Mercury X bundle. Love it too. Perfect for the saturn but will be perfect for the Mars too. Maybe check for the Mercury Plus kit.

Personnaly, I use water washable resin and don't regret. Almost odour less and no need to use isopropyl alcool.
#4988281
Is your teensy code publicly available anywhere? I'm interested on how you did the real-time sound effects. I stumbled upon a sears version of the Iona my dad had all this time and never new it. I modeled it and scratched built my own any have it running on a teensy 4.0 but I'm not happy with the way it sounds. Any help would be appreciated.
#4988284
I'd have to ask my friend Patrick who wrote that code whether he'd want to share it. Note that it was written for a Teensy 3.2 and Prop Shield.

Since the Teensy 3.2 is no longer available we've switched to an Adafruit Itsy Bitsy M0 Express with code Patrick wrote in Circuit Python.
#4988285
A year ago I finished my PKE Meter Mk 1 just in time for Rose City Comic Con. I've recently upgraded the unit to a Mk 2. Functionally it's very similar to the Mk 1, but I made a lot of internal changes.

The Mk 1 ran off of a PJRC Teensy 3.2 Arduino microcontroller which is no longer in production, so I’ve replaced that with an Adafruit Itsy Bitsy M0 Express. Patrick Benton did the coding again but this time using Circuit Python; it was a struggle getting everything to fit in its paltry 32 KB of RAM.

I’ve replaced the five 1.2V 2/3 C cell NiMH batteries with a single 3.7V 2200 mAh Lithium Ion battery that can just live in the handle, leaving space for a much bigger speaker in the main shell. I’m using a small Adafruit LiIon charger board to manage the charging (the NiMHs required an outboard charger).

A 3W Class D I2S amplifier board from Adafruit drives the 5 cm speaker.

I’ve switched to micro servos that also free up more space (though they’re somewhat noisy).

Using two shift registers I can change the chase pattern on the wings from the GB1 pattern to GB2 with the touch of one of the touchswitches.

This Itsy Bitsy has built-in capacitive touchswitches whereas I had to incorporate extra components for resistive touchswitches in the Mk 1. These capacitive ones seem to be working reliably, even in the rain (the old ones would get stuck in the FULL position when wet).

I designed in KiCad and had OSHPark fabricate a new main PCB along with a smaller board that combined the LiIon charger board and a Polulu boost converter to regulate and increase the battery voltage from 3.7V to 5V. This also includes a circuit to drive a charge status LED in the handle that glows red when charging and green when complete.

I modeled and 3D resin printed a thing to hold the speaker, for now just epoxied into the shell.

I’m looking to make some tweaks to my Iona buck at which point I’ll make new silicone molds to crank out more resin shells.

The Mk 2 behaved well at Rose City Comic Con this year and at multiple Halloween events with the Portland Ghostbusters. We're still tweaking the code a bit. I still hope to make kits, but as the name of this thread indicates, it's slow going.

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#4988295
I would appreciate it if you could ask. I'm sort of stuck. I'm using the same amp board with a teensy 4.0 and fasttouch library for the capacitive touch. Also using micro servos , but i would switch to an all metal geared MC90s servo if sound is an issue. Picked up a 5 set from Amazon. Night and day difference as far as how quiet they are.

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