TILT Mechanism

The Pinball Machine Tilt Mechanism was an important development in Pinball History...

Pinball machines didn't have tilt mechanisms until 1932. Up to this point in time, you were free to "nudge" the machine as much and as often as you liked.

Seeing the need to prevent damage to a machine, and to prevent people from cheating to win prizes, Harry Williams (who later co-founded Williams Manufacturing) invented a device to sense this movement and stop the machine's current play.

This new device was called a "Stool Pigeon" and consisted of a small metal ball resting on a non-conductive pedestal above a metal ring. Excessive nudging of the pinball machine shook the ball off the pedestal and onto the metal ring, thus completing the circuit and causing the play to end.

But the Stool Pigeon proved to be unreliable, and took too long to reset. A new way had to be found...

Plumb Bob

The Plumb Bob was first used as a Tilt Mechanism in 1935. This new design (also by Harry Williams) was far more reliable, easier to adjust, and didn't have to be reset.

The idea of a Plumb Bob has been around a long time, and is used in construction, surveying, and measurement, to name a few. Basically it is a peice of string that is attached to a weight at one end, while hanging from the other. This gives you a perfectly vertical line that is vertically level.

The Plumb Bob Tilt works on this principle, but is a metal rod attached to the pinball machine cabinet at one end (top), with the weight at the other (bottom). It has a metal ring surrounding the weighted end.

The Plumb Bob works as a switch contact. The metal rod is attached to one half of the switch wiring, while the metal ring is attached to the other half. When the Plumb Bob swings due to movement of the pinball machine, it eventually touches the metal ring, closing the circuit (switch), and tells the pinball it has been "tilted".

This process causes the pinball machine to shut down until the ball has returned to its start (drained). Modern Pinball Machines give Warnings (which are usually adjustable from 0 to 5) before they shut the machine down, and wait for the ball to be returned.

Harry Williams called this new version "Tilt" after he overheard some players saying that the machine had "Tilted" after nudging it too much.

The Plumb Bob can be adjusted to determine how it reacts to nudging. If the Plumb Bob (or weight) is moved up on it's shaft, it becomes closer to the metal ring. This means that it takes less movement for the Plumb Bob to make contact. Similarly, moving it further down the rod increases the amount of movement required before the machine will tilt.

The Plumb Bob Tilt when activated causes modern pinball machines to stop play on the current ball. Once the ball has drained, a new ball is started, and play is allowed to continue.

But you can cause the machine to end the current game, loose that credit, and have to start over again...

 

Slam Switch

You may have seen "SLAM TILT" written on the display of a modern Pinball Machine. This occurs when you hit the front door reasonably hard.

The reason the Slam Switch exists is due to people trying to gain free credits on a pinball machine. Older coin mechanisms used a set of contacts to register that a coin had been accepted. These contacts would then let the machine know that a credit should be issued.

If you hit the front door hard enough and in the right place, you could get free credits due to the coin acceptor contacts closing from the shock to the machine.

This had obvious concequences, as the owner or operator of the pinball would see that the machine had alledgedly taken a certain amount of money (from reading the counters / meters in the machine), but the cash box had a smaller amount inside.

The solution to this problem was the Slam Switch.

The Slam Switch, is a set of contacts attached to the front door (Coin door) of the pinball, and are designed to sense the hitting of the front door. One of the contacts has a weight on it which bounces back and forward on the other contact once it has been hit.

This bouncing of the contact causes it to open and close rapidly. On the first instance of this bouncing, the pinball goes into Slam Tilt. This shuts down the machine completly, and it then waits for the balls to be returned to the start. Once the balls have returned, it ends the current game and cancels the current credit.

This feature has now been removed from the latest Pinball's manufactured by STERN (although it is still an option). This does not mean you can get free credits now though. The new Pinball Machines use electronic coin mechanisms in place of the old mechanical ones, and are not susceptable to giving free credits by hitting them.

 

Roll Tilt

The Roll Tilt has a special reason for being in a Pinball Machine... It detects when the front of the machine is being lifted!

The lifting of a pinball wasn't so much to do cheating (although if the Plumb Bob was disabled then you certainly could), it was more to do with stealing!

Yes, stealing.

So how can lifting a machine be stealing? Well, in the 1970's Pinball's accepted Dimes and Quarters in America, they accepted 20¢ coins in Australia, and other various coins around the world.

Due to the popularity of Pinball at the time, they made a lot of money. This led to people figuring out that if they lifted a pinball machine and dropped it, the cash box would literally fall out the bottom!

So the idea was to try to stop people from doing this by tilting the machine before they dropped it. Which hopefully alerted other people around that something was up.

Of course, the best method to prevent this was to empty the cash box regularily so there wasn't enough weight in it to fall through the bottom...

The Roll Tilt is a metal cradle which allows a small metal ball to roll along it if the front of the machine is lifted. The ball will rest against a metal contact when it reaches the other end, closes the circuit and tilts the machine.

 

Other Tilts

The other main variations of tilts are based on the Slam Switch. The same type of contact switch setup is placed in different locations in the Pinball Machine for different reasons.

The Playfield Tilt is a Slam Switch, but located on the pinball playfield. It mainly senses left and right motions, but can sense nudging.

The Cabinet Tilt is again a Slam Switch, but located on the base of the pinball cabinet. It mainly senses nudging, but also up and down motions.

Of all the different variations of Tilt Mechanisms, the Plumb Bob is the most widely used. While most of the others were created to solve a specific problem, the Plumb Bob was designed to solve all problems, and is still in use today.

 

The Tilt Mechanism was an important development in Pinball.
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