Step 4: The cam
In this step we will be creating the main cam. This is one of the most important parts of the gun and is very tedious to construct.
Cutting and grinding:
Find a fairly thick piece of metal (about 3-4 millimetres), be sure that the metal is easy to work with because you will be drilling tiny holes. Cut a piece about 1 Â½ cm long and 6-7 mm wide. Grind the corners round to avoid it interfering with other parts of the gun.
Drill a 1mm hole in the center and then another about 4mm above it. Find yourself a fairly powerful motor to use in your gun, and take a measurement of its shaft width. Then re-drill the center hole to fit the shaft.
Welding the shaft:
This part is a bit of a bastard, on my first attempt at welding the motor to the cam I discovered that the shaft was die cast and it snapped when I welded it. But with some trial and error I got it in the end. If you want to use an alternative method to welding there are many. You could use brass and heat it to expand over your shaft, drill a side hole for a worm screw or even just hammer it on. Whatever works for you!