Wednesday, July 20, 2016

Building a Homemade Pinball Machine

The following Post is not intended to be a set of plans showing how-to-build-yourself a copy of what I built.  Instead, this is a description of “how” I built a homemade pinball machine for my grandkids. 

I have intentionally omitted exact measurements, because, should you decide to build one, that will all vary based on what materials you may have on hand or can scrounge.  Most of the information you need to build your own can be gleaned from the photos and descriptions.

On occasion, my wife and I get to spend some quality “Grammy and Grampa” time with our out-of-state grandkids.  When we go we always try to take along some “hands-on” activities.  Sometimes we hit the ball out of the park with our choices…other times…well, not so much.  It is difficult to always match the varied interests and abilities of 4 young children who are rapidly growing, developing and evolving. 

I’m not exactly sure how this particular idea came to mind but my wife found this YouTube video of how someone else built his own Pinball Machine.  It seemed like it might be a good choice for a project for the kids.  The plan was to design and build a Pinball machine in my workshop, then disassemble it and then reassemble it at their house with the aid of 8 and 9 year old hands.  The thing does make noise and “could” provoke arguments so I needed to clear it first with their parents.  After receiving a green light from them, I began work.

I admit that I copied many of the features that I saw in the video but like practically everything else I do, I decided to modify the design to suit my tastes and my unusually large and varied junk box.  I decided to use small (1” dia.) rubber balls rather than the marbles the video showed.  Someone else suggested the rubber –coated roller balls out of computer mice, and I have to admit, they would be an excellent choice, but, my junk box was sadly lacking there.

Photo Number 1 is an overall view of my completed, ready to play, but as yet unpainted, pinball machine.

My unit happens to be about 24” x 36”.  The size was “strongly influenced” by the chunk of ¾” nice birch plywood that I happened to have.  I needed to get all four sides, the legs and the flippers out of that one piece and I just about used it all up.  The Pinball machine in the video was built around a piece of Melamine tabletop.  I didn’t have any of that but I did have a nice, new piece of “Peg-board” and decided to use that instead.
Using the table saw, I cut the four sides to width and length.  I then cut a 3/16”wide groove (to fit the Peg-board) near the bottom of all four pieces.  I then inserted the peg-board and drilled and screwed the four sides.  

It would have been “nice” to have nicely mitered corners to hide the grooves.  Unfortunately, my table saw isn’t very good and does not handle cutting miters very accurately, so I just used butt joints.  Admittedly, the slots are visible on the ends of the two side pieces, but I don’t think it would have been worth the additional effort to hide them.

I added two short legs at the back to put the playing field at about a 7°or 8° angle.  The exact angle isn’t too critical but make sure to make both legs exactly the same length and with the same angle.  I used three screws to ensure that the legs couldn’t wiggle loose with the excitement of play.  Not shown in this photo were two adjustable “feet” added to the bottoms of the legs.  I drilled and inserted them in the ends to allow for a means of leveling the table.  In retrospect, that was probably not a great idea.  The pinball machines size dictates that it must be played on a table and if the table is slippery (like the one at their house) it slides around way too much.  If I had it to do over, I would skip the adjustable feet and glue a piece of anti-slip/anti-scratch material on the bottom of each foot.  That would protect the table but still “grip it” and minimize the sliding.

Of course, the heart of any pinball machine is, for lack of a better name, “the shooter.”  The over all length of the “shooter channel” is about 18”.  I made mine out of some pine strips that I ripped from of a chunk of 2x4.  

Do yourself a favor.  Carefully cut and drill the cross pieces in the shooter so that they are square and exactly the same.  The same is true of the side pieces. Otherwise, you are likely to experience binding of the rod sliding through the holes (this is personal experience talking, here).

The first version used a ¼” wooden dowel rod as the shaft of the shooter.  However, when I was trying things out during my initial trial fitting, I noticed that the metal locking collar (used to push against the spring as the shooter is pulled back, see sketch below) tended to slip on the dowel rod because it always smacked the middle support whenever it was released.  Tightening the screw in the collar to prevent slippage only further damaged the dowel rod.  It was only a matter of time before something would break and by that time Grammy and Grampa would be several hours away making retrofits difficult to accomplish.  

So, I rooted around a little farther down in the junk box and found a length of ¼” mild steel rod.  I cut it to length and drilled two small dimples in the rod to accept the screws from the collar and the pull-knob so they couldn’t slip with use.  You could use a wooden dowel for the center rod, but I would go to at least 5/16”in diameter and would use some sort of locking screw or pin through the shaft to ensure that the knob and collar cannot slip.  I used odd pieces of ¾” and 1-1/4” dowel rod for the tip and knob of the shooter.  The dowel on the tip does not require the little dimple in the rod because in operation it is always being pushed “on to”, not “off of” the rod.

I screwed the shooter channel into the lower right hand corner of the frame from the bottom only.  CAREFULLY, measure to locate the hole for the shooter rod to come through.  You might want to make that hole a size or two larger through the frame to prevent any binding.  You really want that ball to fly out of there.

(Later note: I re-drilled the hole for the screw in the wooden knob clear through so that the screw would have a really solid hold on the steel rod and the knob couldn’t be pulled off.)

Bear in mind as you are building the “shooter channel” that the right-hand-flipper control rod also has to pass through it (either over or under the steel rod) to hit the right-hand-flipper. In this photo, you can see that mine passes over the rod.  It doesn’t really matter which path you use, but you want both flippers to be the same and you need to decide which path you want to use before you get too far into the project and certainly before you go drilling holes in the frame where they will really show. 
 With the channel firmly in place, drill the 3 holes (the frame and both sides of the channel) at the same time.  Here again, you “might” want to drill out the hole in the frame a size to two larger to prevent binding.  A little paste wax on the flipper dowel rod is a good idea, too.

I played around quite a bit with the design of the flippers.  What you see represents what was, I think, my third variation.  They consist of two pieces of ¾” plywood glued together and cut into an “L” shape.  I drilled a ¼” diameter hole in the corner of each “L” to act as the pivot point.  I also played around with where to locate the flippers.  That was one of the advantages of using the pegboard.  There are ¼” holes every 1” in both directions, so you can play around to decide on the best locations for the various bits and pieces without damaging anything. 

I made the pivot out of a 2-1/2”- ¼-20 machine bolt.  Since I expect that the flippers are going to get a real work out, I used two fender washers (1 on top and 1 underneath) and tightened the locking nut to prevent any “wiggling” or damage to the Masonite Peg board.

When installing the flippers, I used a flat washer on both and bottom of the flipper and their respective nuts.  I placed a second “jam” nut on top of the first.  Make sure that your flipper moves freely.  If not, loosen both nuts, hold the lower nut in place with an open-end wrench and retighten the jam nut.

In order to give the left flipper control rod the same sort of “bearing” surface as the right side (to prevent it from “wiggling” when smacked) I added a small additional block and drilled through the frame and the block at the same time.  I cut and drilled two small lengths of ¾” dowel to act as the contact blocks on the ends of the flipper control rods. The discs glued onto the outside ends of the control rods are wooden toy wheels from…you guessed it…the junk box!

These two photos show the left flipper in both the “open” and “rest” positions.  I hooked some heavy, “matched” rubber bands to big screw-eyes to retract the flippers and pull the control rod back into rest position.

You will notice that I added two straight blocks to stop and hold the flippers in their “relaxed” locations.

 I flexed and wedged a length of a wooden Venetian blind slat (~1/8” thick) between the top of the shooter channel and a small block in the middle of the back frame piece.  One inch wide Basswood slats (from the junk box, again) are flexible enough to form a nice arc to keep the ball from getting stuck in the upper right-hand corner.  Bear in mind that the Basswood will snap if you get too vigorous with the bending.  I fashioned a little triangular block with a little hook to hold the slat in place from the back side.  You can just make it out near the center of the arc in this photo.
For interest, I added 6 bumpers, made from 1-1/4” dowel about 1” long.  I drilled and inserted a piece of ¼” dowel to locate the bumpers at the desired locations on the peg-board.  I also cut two “C” shaped goals.  I spent quite a bit of time playing with the semi-finished game trying to find the best location for the bumpers.  Although I started out with a very non-symmetrical arrangement, I finally decided that the very regular “upside down face” arrangement worked pretty well.  The bumpers are glued down.  The goals have dowel rods to locate them but are screwed down from the bottom side.

I also added a few random angled pieces to deflect the ball from corners and the ends of the flippers.

Did the project work?  Did the kids enjoy their role as “assemblers”?  Judge for your self from the following video taken just minutes after the project was completed:


'Til Next time...Keep Makin' chips

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