Fun With Pinball

 

The Restoration and Photographic Study of a 1934 Rock-Ola World's Series Pinball Machine (continued)

The Field Disc Mechanism

The Field Disc Mechanism is the most elaborate part of the game.  When a ball drops into the top hole from the upper part of the playfield the Field Disc rotates counterclockwise to simulate another base runner running through the bases.  The Field Disc rotates through one or more 90 degree increments to represent singles and extra base hits.  This mechanism and the entire game runs without any electricity, relying solely on spring tension.

601 Field Disc 601 Field Disc 601 Field Disc 601 Field Disc

Part 601 is the green Field Disc which dominates the playfield.  Balls that get through the 604 Trap-door Die Cast above land in the top hole on the disc and advance from one base to the next as hits are made and the Field Disc rotates.

607 Die-Cast for Mechanism 607 Die-Cast for Mechanism 607 Die-Cast for Mechanism

Part 607, the "Die-Cast for Mechanism", supports the rotating 601 Field Disc above and other related devices under the playfield that determine when and how far the Field Disc rotates.

642 Base Control Gear 642 Base Control Gear

Part 642 is the Base Control Gear which determines what kind of base hit will be scored (single, double, triple, or home run).  Some games apparently have cast gears while this one is made from thick stamped sheet metal.

646 Base Control Die Casting 646 Base Control Die Casting 646 Base Control Die Casting

The 646 Base Control Die Casting mounts to the shaft on the 601 Field Disc and helps rotate it and the 642 Base Control Gear shown above when hits are made.  The 650 Field Ratchet Pawl is riveted to the Base Control which allows the Field Disc to rotate in just one direction.

629 Field Segment 629 Field Segment

The 629 Field Segment is what drives the 601 Field Disc above.  Each time a ball is lifted into the plunger lane the Field Segment is pushed to one end of its range of travel which stretches a spring that holds the energy required to turn the Field Disc.  Whenever a hit is scored the Field Disc is released and the rack of teeth on the Field Segment drives a pinion (or gear) on the Field Disc shaft to turn the Disc. The Field Segment is essentially just a small wedge shaped portion of a much larger gear.

Installing the 607 Die-Cast for Mechanism Installing the 607 Die-Cast for Mechanism Installing the 607 Die-Cast for Mechanism

Installing the 607 Die-Cast for Mechanism Installing the 607 Die-Cast for Mechanism

The 607 Die-Cast for Mechanism is mounted to the playfield with four 6-32 x 5/8" oval head slotted machine screws run through the top of the playfield into tapped holes at the ends of the casting.

Installing the 667 Kickout Stamping Installing the 667 Kickout Stamping

Installing the 667 Kickout Stamping Installing the 667 Kickout Stamping Installing the 667 Kickout Stamping

The 667 Kickout Stamping is made from a formed strip of sheet metal.  When the 603 Main Push Bracket slides forward at the beginning of a game it raises the Kickout Stamping which kicks balls out of their holes in the 601 Field Disc to return them to the ball reservoir below the playfield.

The Kickout Stamping is attached on the outside of the 607 Die-Cast for Mechanism mounting holes with a pair of 3/16" shank diameter grooved clevis pins and hairpin clips.  The shorter clevis pin under the 1st base side has a shank length (cap to groove) of .18". On the 3rd base side the 648 Bumping Safety is mounted with the Kickout Stamping to the Die-Cast for Mechanism with a longer clevis pin that has a shank length of 1/2".

RWS18 Bumping Safety Spring Installing the RWS18 Bumping Safety Spring

The RWS18 Bumping Safety Spring mounts between the 624 Three Outs Lockwire and a hole in the corner of the 648 Bumping Safety.

The Bumping Safety is intended to discourage cheating.  If the game is lifted and dropped to influence ball travel the inertia of the relatively heavy Bumping Safety will cause it to lift the 667 Kickout Stamping which in turn will eject any balls resting in the Field Disc.

Patent Illustration of the Kickout Stamping

Figure 4 from the patent illustrates the Kickout Stamping, Bumping Safety and parts of the Outs Counter.

Installing the 628 Field Stop Bumper Installing the 628 Field Stop Bumper Installing the 627 Field Stop Installing the 627 Field Stop

The 628 Field Stop Bumper rests loosely in a pair of holes in the 607 Die-Cast for Mechanism.  The 627 Field Stop mounts above it with a shoulder bolt so that it can pivot between the stops on the back edge of the Die-Cast for Mechanism.  The shoulder bolt has a 6-32 thread and a 3/16" shank.

These two parts move out of the way to allow the 601 Field Disc to rotate.  When they return to their positions they serve as a brake to stop the Field Disc so that the holes are always at the compass points when the Field Disc stops.  Tabs under the holes in the Field Disc come to rest against the Field Stop Bumper to await the next hit.

Installing the 642 Base Control Gear 642 Base Control Gear installed

The 642 Base Control Gear mounts to the 607 Die-Cast for Mechanism with the 645 Shoulder Screw for Base Control Gear with the internal teeth pointing towards the 601 Field Disc (or down in these photos).  The Shoulder Screw has a 1/4" diameter shank about .44" long followed by about .37" of 8-32 threads.

The internal teeth interact with the 628 Field Stop Bumper above, pivoting it up and down to allow the 601 Field Disc to rotate. Be sure to clean both the hole in the Base Control Gear and the shoulder bolt well to allow the Gear to turn freely.  I added a bit of graphite to the shoulder bolt for good measure.

Field Disc shaft Field Disc shaft with shim

Shim between Field Disc and Die-Cast Shim between Field Disc and Die-Cast

Base Control Gear and Field Disc installed

The 601 Field Disc mounts from the top side of the playfield down through a hole in the center of the 607 Die-Cast for Mechanism.  A 1/4" ID x 3/8" OD x .01" shim is added to the Field Disc shaft before it is inserted into the Die cast to minimize the contact and friction between the two.

Patent Illustration of the Field Bumper

Figure 11 from the patent shows how a ball that falls into a hole in the Field Disc pushes down on the Field Stop Bumper.  Also shown are the Base Control Gear, Base Control Die Casting, Pinion an Field Disc.

Installing the 646 Base Control Die Casting Installing the 646 Base Control Die Casting

The 646 Base Control Die Casting mounts to the shaft of the 601 Field Disc.  A cotter pin through holes in the casting and the shaft holds the two together.  Don't bend the ends of the cotter pin right away.  You'll likely need to remove the Field Disc several times as you make adjustments.

Installing the 669 Pinion for Base Control Installing the 669 Pinion for Base Control Patent Illustration of the Pinion and Base Control

The 669 Pinion for Base Control is a large brass gear that sits on top of the 646 Base Control Die Casting on the shaft of the 601 Field Disc.  I cleaned the Field Disc shaft and the hole in the Pinion well and added some graphite to make sure that the Pinion can rotate freely on the shaft and against the Casting.

If you look closely at the upper extremities of the brass Pinion you can see evidence of wear from the 650 Field Ratchet Pawl (or click spring) as it rubbed against the Pinion.  I installed the Pinion upside down so the worn parts of the teeth no longer interact with the Field Ratchet Pawl.

Installing the 629 Field Segment Installing the 629 Field Segment

The 629 Field Segment mounts onto a pivot at the end of the extended arm of the 607 Die-Cast for Mechanism.  Once in place it should easily turn the 669 Pinion for Base Control as it swings back and forth if the 650 Field Ratchet Pawl is not locking the Pinion in place.

Be sure to install the Segment with the small hole towards the rear of the game.  That hole will hold a spring that draws the Field Segment across the Pinion.

Installing the 608 Bearing for Field Shaft Installing the 608 Bearing for Field Shaft Installing the 608 Bearing for Field Shaft

The 608 Bearing for Field Shaft has a tooth that supports the 629 Field Segment as it swings back and forth.  The tooth must be threaded into the arced slot in the Field Segment.  Once properly set into the Segment the Bearing can be mounted to the 607 Die-Cast for Mechanism with an 8-32 round head machine screw and lock washer (not shown) at each end.  The screw threaded into the Segment pivot point is 3/8" long and the other screw closer to the brass Pinion is 1/2" long.

The assembled mechanism

Here's what the assembled mechanism looks like so far.  Note that none of the springs have been installed at this point.

RWS13 Segment Spring Installing the RWS13 Segment Spring

The RWS13 Segment Spring holds the energy required to rotate the 601 Field Disc as balls drop onto it.  It mounts between the 679 Stamping for Segment Spring and a small hole in the 629 Field Segment.

Each time a new ball is lifted onto the playfield the Field Segment is reset which stretches the Segment Spring.  The stretched spring provides torque to the brass Pinion through the Field Segment.  When the Field Disc is unlocked by a ball dropping onto a hole it rotates due to the torque provided by the Segment Spring.

RWS16 Dog for Pinion Spring Installing the RWS16 Dog for Pinion Spring

The RWS16 Dog for Pinion Spring mounts between a tooth on the 646 Base Control Die Casting and the hole in the 650 Field Ratchet Pawl.  Note that the spring pictured here is not an original but something I found in my parts stash that fits.

The Dog provides a ratcheting mechanism that allows the Pinion to rotate freely when the 629 Field Segment resets but locks the Pinion to the 601 Field Disc as the Field Disc rotates.

RWS15 Field Stop Bumper Spring Installing the RWS15 Field Stop Bumper Spring

The RWS15 Field Stop Bumper Spring mounts between small holes in the 627 Field Stop and the 607 Die-Cast for Mechanism.  The Field Stop and 628 Field Stop Bumper are the braking mechanism for the 601 Field Disc.  As it rotates the Field Disc develops a significant amount of angular momentum that has to be overcome when it stops suddenly at one of the four base positions.  The Field Stop and Field Stop Bumper have to stop the Field Disc suddenly without causing damage by moving into the path of the tooth on the bottom edge of the Field Disc.

To do this both the Field Stop and Field Stop Bumper rotate a short distance along with the Field Disc as the Field Disc over rotates past it's final stopping point.  The Field Stop Bumper Spring stretches as the Field Disc slows down and pulls the Field Stop, the Field Stop Bumper and the Field Disc back to the correct stopping point after they've over rotated.

Field Stop Bumper Spring Field Stop Bumper Spring Installing the Field Stop Bumper Spring

Field Stop Bumper

Just below the 601 Field Disc is a piece of slightly curved blue spring steel that pushes down on one end of the 628 Field Stop Bumper.  I don't think this part is listed on the original parts list.  It's held in place on the 607 Die-Cast for Mechanism, concave face down, with a 6-32 x 3/16" round head slotted machine screw mounted into a threaded hole.  Note the guide in the Casting that helps align the spring steel to the proper angle.

This piece of spring steel returns the Field Stop Bumper to its blocking position after a ball on the playfield had pushed it down to allow the 601 Field Disc to rotate.

654 Clockspring for Field Rebounce Installing the Clockspring for Field Rebounce Installing the Clockspring for Field Rebounce

The 654 Clockspring for Field Rebounce is a similar piece of blue spring steel mounted to the first base side of the 607 Die-Cast for Mechanism. It is meant to keep the 601 Field Disc from rotating too far backwards when it is stopped suddenly by the 628 Field Stop Bumper.  When the Field Disc comes to a full stop the Field Stop Bumper keeps it from rotating any further forward and the Clockspring keeps it from rotating or bouncing back.  The Field Disc becomes essentially locked in both directions.

Originally the Clockspring was riveted to the main casting and had a 6-32 round head slotted machine screw to adjust its tension on the underside of the Field Disc.  As the Disc rotates (clockwise in the center photo above as seen from below) the Clockspring rides up over the green tooth and drops down behind it to keep it from backing up.

The Clockspring on this game had been removed at some point perhaps because it had broken off.  This replacement was cut to size, drilled and fastened to the casting with a small machine screw, star washer and nut.  From the top you can see that the casting has guides on either side of the spring steel to help align it.

Spring steel installed

With the 601 Field Disc removed you can see where the two pieces of spring steel are installed.  The one near the center pushes down on the 628 Field Stop Bumper to stop the turntable  from rotating forwards.  The one near 1st Base keeps the Field Disc from bouncing backwards when it does stop.

Field Disc Mechanism

This short video shows how all the pieces work together to turn the Field Disc for a single and extra base hits.  Once cleaned and reassembled the Field Disc mechanism will likely need some tuning to get it to work reliably.  Details are on the Tuning page.

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