Fun With Pinball


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

Tuning the Field Mechanism

Once the Tilted Field Disc Problem is resolved the entire mechanism will still likely need a fair bit of tuning.  The mechanism is very elaborate and sensitive to even minor adjustments.  Getting it to work smoothly and reliably will take plenty of investigation, disassembly, correction and reassembly.  Each time through the process you will likely learn something new about it.

Given the limited energy held in the Field Segment Spring to rotate the Field Disc, friction and inefficiency will need to be chased out of the system.

Clockspring for Field RebounceClockspring for Field Rebounce Clockspring for Field RebounceClockspring for Field Rebounce

An easy thing to change is to back off the tension on the 654 Clockspring for Field Rebounce.  I had initially installed it so that it was dragging slightly on the bottom of the Field Disc.  This made a grinding noise I didn't care for and put unnecessary drag and wear on the Field Disc.  I ultimately adjusted it so that it rides just below the Field Disc without actually touching it.  That has no effect on how well it holds the Field Disc in place once it stops.

Field Stop and Field Stop BumperField Stop and Field Stop Bumper Field Stop and Field Stop BumperField Stop and Field Stop Bumper Field Stop and Field Stop BumperField Stop and Field Stop Bumper

Field Stop (right) and Field Stop Bumper (left)Field Stop (right) and Field Stop Bumper (left)

The Field Stop and Field Stop Bumper control when the Field Disc rotates and where it stops. When the Field Disc is stopped the Field Stop Bumper is pinched between the Field Stop and the Field Disc tooth by all the torque waiting to rotate the Field Disc.

When a ball drops into a hole in the Field Disc, the weight of the ball pushes down on the Field Stop Bumper to push it out of the way of the tooth on the bottom of the Field Disc and allow it to rotate.  The weight of the ball has to overcome any friction holding the Field Stop Bumper in place.

I found that the weight of the ball wasn't enough to push the Field Stop Bumper out of the way so the ball would land in the hole but nothing would happen.  Upon closer inspection I discovered that there was too much friction between the Field Stop Bumper and the Field stop on one side and the Field Disc tooth on the other.  All of the surfaces had some amount of wear or unevenness so when they were all pinched together it took too much force to dislodge the Field Stop Bumper.

Polished Field Disc ToothPolished Field Disc Tooth Polished Field Stop (right) and Field Stop Bumper (left)Polished Field Stop (right) and Field Stop Bumper (left) Polished Field Bumper StopPolished Field Bumper Stop Field Stop and Field Stop BumperField Stop and Field Stop Bumper _MG_6587_MG_6587

The solution was to grind and/or polish all four surfaces (both sides of the Field Stop Bumper and one side of the Field Stop and Field Disc tooth.  I used sharpening stones and a small buffing wheel to remove the nicks and burrs and to polish the surfaces.  Once reassembled the ball was usually able to get the Field Disc to rotate as it should.

Adjust the playfield pitchAdjust the playfield pitch Adjust the Wire RailAdjust the Wire Rail

There are two other adjustments that can be made to improve the basic problem of the ball having trouble overcoming the friction of the locked Field Disc.  The first is to increase the playfield pitch by lowering the front leg levelers and/or raising the back leg levelers.  By increasing the playfield pitch, the ball should roll through the Hit runway with more speed and momentum which should help unlock the Field Disc when it falls into the hole.

The other adjustment is to bend the green 638 Wire Rail at the end of the Hit runway so that it strikes the ball above its mid section.  If the ball hits the Wire Rail with its mid section or equator the ball will tend to bounce straight back before dropping into the hole.  If instead the Wire Rail is raised a bit so that the ball hits the Rail above its mid section the ball will be deflected downward when it hits the Rail.  That downward deflection should give the ball more downward momentum and a better chance of unlocking the Field Disc.

Adjusting the Trap Door

Trap door before adjustmentTrap door before adjustmentBall is hung up on the front lip Trap door before adjustmentTrap door before adjustmentBall is hung up on the front lip

You may discover that the 621 Trap Door that pivots under the 604 Trap-door Die Cast, to drain balls after an out or a hit, rises slightly above the playfield to create a lip or curb.  This may not be an issue when the Strikes and Balls runways are empty because the Trap Door might tip down under the weight of the incoming ball enough to let it pass.  But when there are balls trapped in the runways an incoming ball can't overcome the weight of the trapped balls and may not be able to ride over the lip at the front edge of the Trap Door.

In the 4th Ball scenario shown above the last ball to arrive lost its momentum as it collided with the 3rd ball in the Balls runway.  It should roll over into the Hit runway but without any forward momentum it hangs up on the lip created by the front edge of the Trap Door.

Trap Door bracket before adjustmentTrap Door bracket before adjustmentBracket is level with the Die Cast below Trap Door bracket after adjustmentTrap Door bracket after adjustmentBracket is tilted back slightly Trap Door after adjustmentTrap Door after adjustmentNo more front lip

To eliminate the lip at the front of the Trap Door the 620 Bracket for Trap-Door Lock must be tilted back slightly to effectively lower the level of the Trap Door.  In the photo on the left above the Bracket is mounted level with the Die-Cast just below it and the Trap door sits just proud of the playfield creating the lip.  In the center photo the Bracket has been tipped back slightly which lowers the Trap Door and eliminates the lip.  The adjustment is made by loosening the two mounting screws on the left in the center photo and advancing the adjustment screw on the right.  Once the Bracket is at an appropriate angle the two mounting screws can be tightened to hold the Bracket in place.

The photo on the right shows the adjusted Trap Door with no leading lip.  Balls effectively drop slightly onto the Trap Door from the playfield and will no longer get hung up on the transition.

Adjusting the Kickout Stamping

1st Base Kickout1st Base Kickout 2nd Base Kickout2nd Base Kickout 3rd Base Kickout3rd Base Kickout

You may need to adjust where the fingers of the 667 Kickout Stamping rise through the holes in the 601 Field Disc when a new game is started.  If they're too far off center the ball may not get reliably ejected from the hole. The Kickout Stamping is made from fairly thin sheet metal so adjustments are not a problem.

Improving the Field Segment tension

Once the game has been reassembled you may notice that the 601 Field Disc rotates slowly or has trouble completing extra base hits or home runs.  If there's not enough tension on the 629 Field Segment from the RWS13 Segment Spring the Field Segment may not be able to complete the required Field Disc rotation.

Field Segment mostly wound
Field Segment mostly wound Field Segment fully woundField Segment fully wound

You may discover as I did that the Elevator lift mechanism is not resetting the Field Segment completely.  The photo on the left above shows where the Elevator lift would set the Field Segment after raising a ball to the playfield.  If you look closely you can see that the Field Segment has only been reset about 3/4 of the way to its full reset position.  The Elevator lift doesn't extend far enough to reset the Field Segment completely - there are still several teeth on the Field Segment that could be pushed past the brass 669 Pinion for Base Control.

The photo on the right shows what a complete reset of the Field Segment looks like.  In this position the Segment Spring is fully extended and is able to apply more torque to the Pinion and Field Disc.

Field Segment partially resetField Segment partially reset Field Segment fully resetField Segment fully reset Field Segment with fender washerField Segment with fender washer

Here are other views of the same issue.  The bottoms of these photos show the end of the Field Segment that is pushed to the left by the Elevator lift. In the left photo the Field Segment pushed as far back (left) as the Elevator lift can reach.  In the center is the Field Segment completely reset. Notice that the end of the Field Segment is roughly 1/4" further back when it is completely reset.  On the right is a fender washer that will effectively extend the end of the Field Segment so that the Elevator lift can push it all the way back to it's fully reset position.

Field Segment extension partsField Segment extension parts Field Segment extendedField Segment extended Field Segment extended by ~1/4"Field Segment extended by ~1/4"

To extend the end of the Field Segment a 1" fender washer can be added.  Once the washer is positioned (as shown in the 3rd photo in the previous group) mark and drill a hole in the end to accommodate a small bolt and nylon insert lock nut or similar fasteners. The photo on the right shows how the fender washer extends the Field Segment so that it is roughly 1/4" closer to the Elevator lift mechanism.

Extended Field Segment installedExtended Field Segment installed

With the fender washer installed on the Field Segment the Elevator lift is able to completely reset the Field Segment and the Field Disc should rotate with a bit more force.

RWS13 Segment SpringRWS13 Segment Spring

Another option to improve the Field Segment tension is to move the 679 Stamping for Segment Spring further away from the Field Segment to stretch the RWS13 Segment Spring a little more.  This would keep the entire mechanism under greater tension which might have long term effects on the casting so it probably shouldn't be the first adjustment made.

Adjusting the Outs Counter

603 Main Push Bracket603 Main Push Bracket 603 Main Push Bracket lever603 Main Push Bracket lever

When I reassembled my game I found that when the game was reset by the coin chute the Outs Counter would not reset all the way back to 0 outs. This was because the lever on the 603 Main Push Bracket that is pushed by the coin chute was bent too far back.  Bending the lever forward a bit was all that was needed to get the Main Push Bracket to travel the full distance when pushed by the coin chute.

Adjusting Game Play Percentages

Adjust the JS6 Bumper SpringAdjust the JS6 Bumper Spring Adjust the playfield pinsAdjust the playfield pins

The original game instructions indicate that the angle on the JS6 Bumper Spring at the end of the top arch can be bent to affect where the ball will likely enter the playfield.  It goes on to mention that the likelihood of getting hits, outs, etc. can be changed by bending the first pin in the rows leading into those features.  So for example to make hits more likely, bend apart the first pin in each row leading into the Hit Runway to increase the size of the alley leading into the Runway.

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