Game Build Details
|Atomic Pinball Clock
Atomic Clock Build Details
Game Design Example
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These are more elaborate assemblies that help define and control the behavior of the pinball machine.
The Score Motor is the heartbeat of the pinball machine. It rotates periodically during the game when sequences of events need to happen in a specific order. As the motor turns cams open and close switches in a specific, repeatable order similar to the way the drum in a music box plucks the fingers that play the tune.
The first time the Score Motor runs is when a new game starts. All the features need to be reset, score reels returned to zero and the first ball kicked out to the shooter lane. During the game the Score Motor might run to score 50 points (advancing the 10s score reel five times) when a single switch closes for example.
This score motor is from a D. Gottlieb & Co. pinball machine and is wired to a set of score reels to show how scoring five points might work:
The video below demonstrates the D. Gottlieb & Co. score motor which uses two cams and a set of pins mounted to the cams to open and close the switches. The video also demonstrates how the switches operate according to the Motor Sequence Chart shown in the instruction card above and often found on the schematic diagram of a D. Gottlieb & Co pinball machine.
This score motor is from a pinball machine made by Williams Electronic Manufacturing Company and uses a set of cams but no pins to operate the switches. A switch from each cam is used to light one of the bulbs in front to show the timing of the various cams.
The following video demonstrates the Williams Electronics score motor.
Most pinball machines make sounds of one sort or another. Electromechanical games used chimes, bells and knockers. Chimes and bells of different tones were used for different point values (e.g. 10 point chime, 100 point chime, etc.) while the knocker was typically used when a free game or special was awarded.
A set of chimes and a knocker are demonstrated in the following video. (An example of a bell can be seen in the video for the captive ball unit below.) In the chimes, solenoids are mounted below a set bars of different lengths similar to the bars in a xylophone and the plungers strike the bars when the solenoids are activated. The knocker works the same way, but the plunger strikes a plate typically mounted to the pinball machine cabinet which makes the entire cabinet a sort of resonant chamber.
Note that the motion of the plungers is the same as shown in the video for the solenoid, just much faster.
More detail and animations explaining how chimes generate different pitches is on the Chimes, Vibrations and Pitches page.
Most early pinball machines required the player to manually lift the ball from inside the cabinet into the shooter lane where it would be shot onto the playfield with the plunger. In the 1960s the ball lifter was replaced by an automated kicker powered with a solenoid.
When the lower plunger is pushed in, a lever swings up that carries the ball above the playfield and into the shooter lane as shown in the following video. In this demonstration the ball falls below the playfield as soon as it is launched. In a real pinball machine the ball would be routed back to the ball lifter from the drain between the flippers and from any other hole where the player might lose the pinball.
Large electromagnets like this were used in some games to change the path of the ball without touching it from below the playfield. Electromagnets have no effect unless they're powered so turning them on and off can have interesting effects.
When the electromagnet is powered, the ball is attracted to the center of the electromagnet. If the electromagnet stays on the ball will oscillate around the center and eventually stop. Powering the electromagnet intermittently on the other hand can accelerate the ball if done at the right times.
For a more in depth explanation of why the ball in the video behaves as it does, visit the Electromagnets and Acceleration page.
The Disappearing Post, or Up Post, is an obstacle that would appear and disappear periodically during a game. Typically it was installed between the flippers and could prevent the ball from draining between them when in the up position.
The post is lifted into the up position by a spring wrapped around its shaft. The spring is compressed when the post is lowered by the bottom solenoid. The post is held in the lower position by a plastic latch mounted to the shaft. The smaller relay activates to release the latch and let the post lift to the up position as shown in the video below. Switches mounted to the back of the unit turn the lights on when the post is in the up position.
Targets are some of the playfield objectives the player has to hit with the pinball during the game.
A Drop Target disappears into a slot in the playfield when hit by the ball. After points are scored, the solenoid below the playfield resets the drop target to its starting position.
The drop target is held in the up position by a notch on its shaft that rests on a small ledge just below the playfield. When struck by the ball (or by a finger in the following video) the target is pushed back and falls off the ledge, pulled down by the outstretched spring. When the solenoid is activated, it pulls the target back up, stretches out the spring again and props the drop target notch back up on the ledge.
There are three switches mounted to this assembly. The bottom two switches tell the game whether the drop target is up or down. In this demo the two switches are wired to lights instead to indicate the target's position. The top switch opens when the drop target is reset to its up position. It is used to cut power to the solenoid.
The spring loaded Vari Target registers how hard it was hit by the ball. A soft hit only pushes it back a little bit while a harder hit will push it back further. The points awarded vary according to how far back the Vari Target was pushed.
Once the points have been scored, the relay fires to reset the Vari Target to its starting position.
The video below demonstrates how the Vari Target works. The armature on the relay acts like a ratchet to let the target swing back and hold it at its last position. Switch blades attached to the back of the target arm connect an upper and lower contact together to complete a different circuit for each position. In this board, each circuit lights a bulb to show how far back the Vari Target was pushed.
The relay armature is pulled out of the way to let the target reset to its starting position. A switch in the lower left is closed whenever the target is not in its reset position. This tells the pinball machine that the target has been hit and points should be awarded. In this board, the switch is used to cut power to the reset relay once the target has been reset.
A Roto Target only presents three targets at a time above the playfield, but during the game the wheel spins periodically to expose a different set of three targets. Regardless of its position, the Roto Target can tell which of the targets was hit (1, 2 or 3) and award points accordingly. It does this with a set of rotating contact switches on the back of the roto target similar to those shown in the video for the stepper.
The Roto target uses a double ratcheting mechanism to spin in one direction, then roll back a bit in the other direction to center the target as the spinning stops. This mechanism is shown in the video below.
Toys are often incorporated into the playfields and backboxes of pinball machines to entice and entertain. Players don't usually much control over these devices but they do offer a chance to win more points or specials of various sorts, and they're fun to watch.
The Captive Ball Unit was a feature in the backbox of a few games in the mid 1960s (e.g. Pot 'O' Gold, Casanova and Apollo). It would fire a ball vertically through a pachinko-like maze and award points based on which lane the ball ultimately fell through. The player had no control over the ball in the captive ball unit. It was just a fun diversion from what was going on on the playfield.
The lights near the bottom were added to highlight which lane the ball falls through as was the bell that rings when the ball drains through the middle lane.
The Doodle Bug assembly is a captive ball mechanism that appeared below a window in the playfield of just three games (Doodle Bug, Dipsy Doodle and Love Bug) in the early 1970s. The captive ball travels back and forth through a track awarding the player with points for each pass. The player could activate the mechanism by hitting the appropriate playfield objectives but had no control over its operation.
When the assembly is activated, an electromagnet immediately below the track draws the captive ball towards the center of the track. The ball accelerates towards the center until it rolls over a button switch in the center of the track. The button switch momentarily deactivates the electromagnet and the ball's momentum carries it over the switch to the other side. When the ball passes the button switch the electromagnet reactivates and draws the ball towards the center again, but the ball's momentum carries it nearly the length of the track before slowing down and changing direction back towards the center. The visual effect is a ball traveling on its own back and forth across its track.
This assembly has been configured to operate a bit slower than it would have in the game to give you a better view of what's happening. A small stepper unit on the right side was added to flash the lights on the end of the track back and forth as the ball passes. On the left side a pair of motor driven cams control the assembly's operation. The top cam keeps the demonstration running for a short period while the bottom cam provides a minimum time between demonstrations. The cams effectively limit the duty cycle to prevent the electromagnet from overheating.
The Spinner Unit is another captive ball mechanism that appeared first in A-Go-Go in 1966 and in several other games through the early 1970s. When activated by hitting other objectives on the playfield, the Spinner Unit briefly spins a platter like a roulette wheel and awards the player based on where the ball comes to rest.
The platter of the Spinner Unit is driven by a motor like those used in score motors. Each hole in the platter has a switch that closes when the ball lands in the hole. The underside of the spinning platter has several concentric rings which connect to switch contacts that are fixed to the base. Together the rings and contacts form a slip ring that allows the switches on the spinning platter to be used in the scoring circuit without any wires to get twisted or tangled.
The grey spoked wheels at the back of this board are cams driven by a small motor that are used to control the demonstration. The top cam turns on the platter motor for short period while the bottom cam disables the black start button to allow the demo to proceed uninterrupted for a short time.