Home

Job

Pinball

Photo Album

Automotive

Press/Awards

Contact

The central toy on the Space Shuttle Pinball playfield is often beaten up and broken.  I have repaired several of these, but I have always wanted to modify one to light up.  Despite the white color, the plastic in the original toy is completely opaque, and therefore incompatible with this mod.  In 2008, Bob from Phoenix wrote me that he had started the process of vacuum forming them, and I assisted him as well as I could.  This write-up shows how the custom toy was made.

The first technical hurdle was applying a translucent coating onto the inside of the clear plastic.  I experimented with various viscosities, and settled on a four to one ratio of water and white acrylic paint (more water than paint).  Some Acrylic Flow Improver (by Winsor & Newton) was added to ensure that the paint particles stayed suspended.

The paint was applied by pouring some into the form, and then swishing it around.  I then let it drain and dry.  This was then repeated a total of five times to build a thin even coat of paint.  The result looked quite good except one could still see some unevenness when backlit.  However since the real Shuttle has blemishes too, I was not too concerned about it.  One important issue is that the coating is very soft and can easily be scratched.  So I always had to handle the form very carefully.

In my restorations of the standard Shuttle toy, I fasten an anodized aluminum sheet to the bottom of the unit for stiffness and stability.  This platform has always given me the idea of one day mounting LEDs on it to light up the toy from below.  However due to the original plastic's opacity, this would only be possible with a custom molded form. 

I first cut an aluminum sheet to cover the bottom completely.  The idea then was to nestle the plate into the bottom of the plastic (just like I do with the original toy), but I soon realized that the coating I had previously applied was too soft.  Eventually, the white would be scratched off the bottom edge, and it would not look very good. 

I changed the plan to have the aluminum extend all the way around, and bent small tabs to hold the outline of the toy.  This prevented all contact with the soft acrylic paint.  The aluminum sheet was also a good substrate to mount the switch that is activated when the ball ascends the ramp.

For the LEDs, I selected white low-profile ones that had a small hemi-spherical focusing lens.  I filed the lens flat, and the resulting pattern was very even.  I lined four of them up along the main long axis of the toy.  I then selected two high-brightness sharp focus units and laid them down flat to light up the wings.  This produces a long white path of light, which would hopefully shoot its way into the narrow and flat wings.

I used white hardware as much as possible.  This included white wires, and a white microswitch.  The microswitch is put on the starboard side so that its shadow would be cast on the side of the shuttle toy facing away from the player.  That strategy paid off extremely well as you will see later.

The white LEDs are connected to the GI circuit.  With a meter, I measured that the GI circuit is at 5.6Vac on my machine.  I then set up a 12V wall-wart transformer with a variable transformer dialed to the same voltage.  I could now test the white LEDs from my workbench.

The LEDs have a forward voltage of about 4V.  I placed the four middle ones in parallel, back to back.   Thus two conduct on each half wave of the GI waveform.  This is then in series with a 43 ohm 1/4 W resistor.  The steady state current is about 60mA, so each LED runs at 15mA rms.  The two narrow beamed LEDs are also back-back, and have their own 43 ohm resistor in series with them.  They consume 20mA, leading to a total load on the GI of 80mA (AC rms).  This is well below a single #44 bulb.

One problem that I only solved at the end was what to do about the Main Engines.  These are of course a very prominent part of the Shuttle.  My first idea was to simply have red LEDs fire upwards to cause the OMS (Orbital Maneuvering System) pods to glow and flash (these are the round bulbous parts in the back of the Shuttle).  However, I did not like this idea as an exhaust plume would look much better.  I then thought of how I could produce this plume, and hit on the idea of fastening red star posts to the back to form the nozzles of the main engines.  I could then simply put some bright red LEDs in the back to light them up.  These LEDs had to fire upwards into the star post for maximum effect, so embedding them into the star posts would not be preferred.

There are three ways to illuminate the red LEDs.  In the first, I could connect it to the flash bulb circuit.  These light up infrequently.  A better circuit are the two lamps on the lamp matrix (#39 and #40).  These flicker constantly during attract mode and game play.  In addition, #39 is very easy to reach on the playfield.  The positive line (Yellow-Green) is used by the '1000', '2000', etc lights, and the negative line (Red-Violet) is used by the 'A' light.  Both of these lines are within inches of the pass-through hole for the microswitch cable.

The red LEDs are wired in series, with a blocking diode, and a 43 ohm resistor in series.  This produces a bright red flicker effect in the exhaust nozzles.  It looks quite good.

Once that was done, I printed a set of graphics onto clear adhesive polyester, and applied that to the upper form as a final step.

Links

• Clay's page on how to vacuum form.
• Supplies and equipment to do your own forming.
  

Project Log

• March 2009 - Bob develops the process of vacuum forming the Shuttle toy.
  
• July 2009 - Using the vacuum formed sheet from Bob, I create the custom toy for my machine.