Desktop trebuchet from bicycle frame

Step 5 Sling release pin and trigger

By now all "heavy" work is done and the rest is just tinkering. The first small part is the sling release pin.

I made the sling release pin from a discarded bicycle chainguard. All it needs is a smooth pin and holes for the trigger pin and sling fastener. The ring used to fasten the sling to the pin is normally used for attaching fishing hooks to lures. Fishing equipment is really good for all kinds of things.

After the sling release pin I built the trigger. The trigger design is simple, a metal ring, attached to a wire, is placed over the screw that holds the sling release pin in place. To fire the trebuchet, pull the ring off the screw and the throwing arm is released. Fishing equipment is again used extensively here.

The sling release pin can be adjusted by loosening the nut a bit and tilting the pin. The more the pin points forward, the later the sling is released and the lower the trajectory will be. You need to adjust the pin angle every time you change the ammo weight, sling length or weights.