If you have been to a science center, it is likely you've seen some kind of ball machine or ball wall before. The basic idea is that you can assemble a pathway for a ball to travel along using some combination of ramps, tubes, funnels, etc. There are many toys and kits our there from Kinex, Fridgits and many others - just Google "rolling ball machine" and enjoy surfing.

The purpose of this project is to build parts for a rolling ball machine of sorts for a science center. We have a 4'x15' framed piece of steel sheeting onto which the parts are attached with magnets. You could do something like this for a large space, your garage or whatever, or just as easily apply these ideas on a smaller scale and do one for your fridge or smaller metal bulletin board.

I will focus most of the instructable on building the main ball-duct part, 8 of which are shown in the picture.

I'd appreciate any ideas and feedback as I expect to tweak this for many months to come.

Step 1: Materials

For one ball-duct:

Materials
1x 2ft section of 2 in PVC
2x #6-32 x 3/4" flat head screws w/ nuts
4x #6 lock washers
2x Neodymium Magnetic Cup Holder /w 23 lb Holding Force (i tried several different kinds of magnets, and these were the strongest and have a good price point - several vendors on the web)
Balls - I use practice golf balls

Tools
circular saw
drill w 3/4 bit (i used a Forstner bit)
clamps
rotary tool
sand paper
safety glasses (electric saw + PVC = flying plastic!)
philips driver

Step 2: Cut the PVC

With my first prototypes, I tried to cut the PVC lengthwise in identical halves (3 3/4" on the circumference) but the outside lip was not high enough to catch the balls when they jump from duct to duct so I decided to cut each piece with a little higher wall, effectively creating only one duct per length of PVC.

1. measure 4 1/2" on the circumference and draw cut lines.

With safety glasses on (seriously)

2. Clamp the ends of the PVC to a work table or board. I used some pretty strong spring style clamps (see pic 3)

3. retract the circular blade guard and saw 3/4 of the PVC.

4. spin the PVC around, reclamp and complete the first cut

5. move to the next cut line and cut 3/4 of the way

6. reclamp and complete cut 2

7. sand the edges (there is a lot of splintering)

I read a lot of stuff about cutting PVC and much was mentioned about the sawblade binding. During my prototypes it happened a bit but with a full charge of my drill there weren't many problems except with the first cut.

I would imagine that a table saw, band saw or a large scroll saw would make quicker and more accurate work of this, but the circular saw is all I have.

Step 3: Drill for Magnet Assembly

1. From each end, measure in 4" and down 1/4" and mark

2. drill 2 holes as marked

3. with magnet side facing away from the PVC, insert the flat head screw into the magnet face, then add lock washer and insert into PVC hole

4. on the inside edge of the PVC, add a second lock washer and nut and tighten

5. trim extra screw length with shears, circular tool, etc and sand or grind down rough edges

This completes the construction of the ball-duct part

Step 4: Other Ball Wall Parts

Here are the parts I have built so far using the same magnet assembly described for the ball-duct part:

1. Feeder Cone: used a sports drill cone, clipped off the end and added one magnet on a flat edge of the base (2 of them shown at the top)

2. Plastic Funnel (red topped part): attached an auto funnel to a 3" to 2" PVC step-down using screw+nut, cut about a 1/4 pie section of the funnel to allow it to flush up against the wall, also added a 45 degree PVC joint to the end to allow adjustments

3. PVC Funnel: attached 1 magnet assembly to a 4" to 2" PVC step-down

4. Drum: cut and stretched a surgical glove over a 3" to 2" PVC step-down, fastened with a steel strap and attached one magnet assembly