1. The support
2. The torsion spring
3. The cradle
The support provides a means of suspending the cradle and allows the torsion spring to develop its force. A sawhorse makes a convenient support.
The torsion spring is a piece of spring steel wire (heavy gauge music wire - about 18 inches long and 1/10 inch in diameter works). The wire is rigidly attached to the support and the cradle so that when the gun and cradle are given a bit of rotation, the wire is twisted and develops its torsional spring force.
The cradle is simply a convenient carrier for the gun, and allows the torsion spring’s force to act on the gun.
All components, with perhaps the exception of the spring steel wire, are available at local hardware and craft stores. Spring steel wire may be ordered from one of the big industrial supply houses (McMaster-Carr Supply Company, 630-833-0300).
A piece of one-inch drill rod, three feet long, makes an excellent calibration bar, and is also available from the industrial supply house, although less expensive options will work.
Pencil
Ruler
Carpenter's Square
Drill and Drill Bits
Screwdriver
Hammer
Hot Glue Gun
Utility Knife
Wrenches
Wood Saw
Hack Saw
Although not absolutely necessary, a bench vice is very handy.
Materials include:
Wood
1/2" x 1/8" iron bar stock
Wood Screws
Wood Glue
Scrap leather & moleskin
Bubble level
Nuts, bolts, washers
Spring steel wire
Calibration and use also require:
Stopwatch
Postal Scale
Calibration Bar
