By WShawn
#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, as in the 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 Kingpin on February 10th, 2020, 11:35 am, edited 1 time in total. Reason: Added youtube code
NickFame13 liked this
By WShawn
#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.
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By WShawn
#4931040
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
By WShawn
#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.
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By WShawn
#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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