For the pinball table project, we’d like to have more active elements that interact with the ball in some physical way. I thought I’d throw the challenge up to anyone interested - come up with some other playfield toys.
Design Requirements -
Physically interacts with the ball in some way.
The ball is a standard pinball - 1-1/16" steel ball bearing. It can travel at significant speed, and any mechanism above the playfield must be strong enough to take impacts.
The ball is ferrous - electromagnets can interact with it
the playfield is 1/2" wood. we’ll be cutting it out on a shopbot, routing out pockets is possible.
Can be made in quantities of at least 3 (one per side).
target cost <$25/unit [1]
appropriate size/dimensions. [1]
We have 5V and 48V power supplies already planned - 12V or whatever can probably be arranged, but ideally use those two.
a ball can’t get hung up on it
[1] - Exception - if it’s cool enough to justify it, we’ve got more flexibility.
Using a short length of belt ($1), two pulleys ($2), a motor ($5-15, depending on how sophisticated you want to get with it), and a large magnet, you can invisibly slingshot balls around.
You hide that assembly underneath the playfield, and then as the belt rotates, the BFM (the large magnet) that’s glued to the belt grabs the ball and slings it off in a different direction.
A stepper will give you the ability to control speed, direction, and position, but are probably minimum $12 or so. A beefy DC motor should be much cheaper ($5) and will hurl the ball pretty much at random, but will work fine.
Going the DC motor route, you could put a magnetic reed switch ($1) on the bottom of the assembly and be able to tell when the magnet is down and in a “parked” position.
This has the advantage of basically being a single axis of the type of CNC platform that several of our members are working on, so there will be spare materials and expertise kicking around.
What about a magnet and grippy (rubber) surface mounted on the axle of a high RPM motor? A ball is trapped, the motor spins it up, and then it’s released somehow. For the next few collisions, it may ricochet very strangely. Depending on how it’s mounted, it could create spin parallel to the table plane (like a spinning top), or perpendicular to it (like sonic the hedgehog).
Or you could have a ball bearing on the end of a rod that pivots about a point. Think of it as something like a Newton’s Cradle, but only with one ball, and the ball can do a full loop. Of course the weight on the end doesn’t need to be a ball bearing, but it should weigh <= a pinball so that it has the opportunity to be hit, spin around the axis, and hit the pinball back into motion before it goes anywhere else.
Hopefully this makes sense. The dark circle is the pinball. The light circle is the bearing on a rod around a pivot point:
