Ping-Pong Ball Launcher
A Ping-Pong ball launcher designed for entry into this years Meccanuity challenge. Unfortunately I had to cancel attendance to the event due to a family bereavement, so it was never tested in earnest!
The challenge was a firing range consisting of a board, 2 feet wide and 4 feet high, nine feet away from the model, with three holes in it of 60, 140 and 195mm diameter, represented by circular Meccano parts, into which the balls must be shot. Either 38 or 40mm balls could be used.
An initial idea to use angle girders in a cruciform arrangement, so as to guide the balls between the heels of the angle girders, showed real promise in mock-up form. So this became the basis of the launcher.
The ball striking energy is stored in the compression of two H/D spring assemblies 120c/d in series. A long axle rod with a collar on the leading end forms the striker, a second collar on this rod is latched between two pivoted couplings (63) when the rod is retracted manually. The trigger mechanism uses two pawls, the back edges of which act as cams to separate the couplings and release the axle rod (firing pin). The residual stroke energy of the firing pin (after striking the ball) is absorbed by rubber tyre elements to minimize shock and damage.
Initially a steel axle rod was used as a firing pin, but after thinking about the kinematics, this was substituted by an aluminium rod, which increased acceleration of the rod (lower inertia) and improved the projectile performance considerably. An aluminium axle rod is within the rules that required the use of Meccano parts, because the № 2 Meccano clock kit uses an aluminium rod as a pendulum.
Elevation is adjusted manually or by Meccano motor if quicker adjustment were necessary. A period of testing and adjusting of the “sights” established that one in two shots would put a ball through the smallest target hole.
An attempt to silence our chairman during the meeting narrowly missed from 15 feet away!