The baby onager, first try:
(See also: Second try)

Design objectives:

1. Build a catapult as fast as possible
2. Throw 10 gram nails as far as possible.

Specs: Weight:   780 gram Dimensions:   width: 0.15 m, length: 0.39 m, height: 0.05 m Shot: up to 10 gram pebbles and bended nails Range: 35 m Length of arm: 0.24 m Skein:   14 mm, nylon Maximum torque: 10 Nm Muzzle velocity: >20 m/s (72 Km/h), estimated Acceleration: about 1000 to 1500 m/s2 (100 to 150 g)
The beam The beam is made of hardwood, about 3 mm thick. The beam should be as light as possible, especially since the design does not use a release pouch.
A detail of the skein,
The washer The washer is made from a piece of 18 mm plywood, a 32 mm thick pvc tube to hold it in place, and a 4mm nail to hold the rope. This configuration is not very good; after a few shots, the nail first broke trough the wood of the washer, than it bended seriously. The nail is now replaced by a 7 mm steel bar.

The skein (rope) has the power to break everything in the construction.

This problem is addressed in The baby onager, version 2