Joerg Sprave lives in Kronach, Germany and owns The Slingshot Channel. His livelihood comes from the consumer electronics industry but one of his greatest passions is slingshots. He specializes in building different types of frames, focusing on crossbow type slingshots and using energy from rubber under tension to power his devices.
Today his chainsaw powered machine gun is getting a lot of attention. The device uses a chainsaw motor to fire marbles and emulate a mechanized slingshot. Two thousands marbles per minute is the stat that’s being thrown around.
https://www.youtube.com/watch?v=hyuvojHyh0w
This is definitely a hobbyist maker doing things in his garage, but this maker and this garage are remarkable. The Slingshot Channel website shows off the engineering and design that has gone into several of Sprave’s designs. A rubber band calculator gives aspiring builders the exact material and band sizing that should be used based on draw length, desired band life and desired taper using Thera Band Gold, Sprave’s preferred rubber. Assembly methods and configurations are also discussed in an online manual.
The fact that the organization and the hobby are non-profit is communicated throughout the site. Joerg builds the designs and then gives them to manufacturers to mass produce for the love of the sport. There’s definitely an open source mentality on display in the information available online.
Strength of materials, mechanics, kinematics, and physics are all on display in this video where Sprave talks about the different design changes and improvements being made to his slingshot. The video of Joerg dressed as Team Fortress’ Heavy Weapons Guy is seeing a lot of page views today but the construction and problem solving to get to the finished product is far more interesting to me. Frame reinforcements, handling considerations and the ball feed mechanism are all issues solved through design improvements and modifying current components.
https://www.youtube.com/watch?v=hyuvojHyh0w