http://cdn.instructables.com/FC4/PS2T/IDFSOFML/FC4PS2TIDFSOFML.LARGE.jpg

What I used with optional substitutes:Parts:

1 10 foot 3/4 inch conduit ~1 foot of 3/4 inch schedule 40 pvc ~1 foot of 1 inch schedule 40 pvc 4 LASCO 3/4-in x 1/2-in Dia 90-Degree PVC Sch 40 Side Outlet Elbow 4 LASCO 1/2-in Dia x 3/4-in Dia PVC Sch 40 Adapter 1 5/16 inch 6 foot threaded rod 4 5/16 inch bearings (optional) 2 3 inch aluminum beams

clothespin ~1 foot of Kiln-Dried Poplar Board (Common: 1-in x 6-in x 24-in;

Actual: 0.75-in x 5.5-in x 24-in) any type of wood will wook

1 Camera mount 1/4 inch 20 thread size bolt

1 K'NEX motor

any motor 1 Medium K'NEX gear

any gear to fit the threaded rod 1 Small K'NEX gear

any gear to fit your motor 4 Hose clamps Paint Motor controller Wire Normally on contact switch Small hinge Wood screws #6 32 thread machine screws of varying lengths Rubber bands Lubricating oil

The cost of the required parts was about $100. I had many of the parts, as you might also, so your cost could be lower.