Menstrie Meeting 2013

In May 2013 we held our annual Menstrie Meeting and Challange.
The Challenge this year was to construct a ping pong ball projector. See the Challenge Rules page for more details.

Menstrie Challenge - Report

Five members, Alistair Nicoll, George Roy, Douglas Carson, Gordon Stewart and Bill Jack brought entries for the 2013 Menstrie Challenge. The competition involved producing a mechanism to project ping pong balls into a bucket. The bucket was placed six feet from the projection point. Up to twenty balls had to be fired in a three minute period. After each round the bucket was moved back 3ft and so seven rounds were played in all at distances of 6,9,12,15,18,21 and 24 ft.

Three major approaches to projection were taken by the entrants:-

1. Acceleration produced by a rapidly moving conveyor belt (Alistair Nicoll)
2. An automated bat (Douglas Carson, Bill Jack)
3. A spring loaded firing mechanism (George Roy, Gordon Stewart)

Of these, the first never even got started. The ball was gripped by four driving bands (two upper and two lower) which were actuated by rapidly rotating 2" Pulley Wheels. The bands ran over a flat surface made of Flexible Plates. Obviously for such a device to work properly the distance between the plates is crucial and has to be accurately set. As it turned out the competition balls were of the order of 2mm larger than the one used in the development of the model. They would therefore not fit between the plates and the entry was withdrawn before the first round started.

The automated bat entries used a rapidly rotating strip or plate to impart motion to the balls. One example of this genre is shown above. It worked quite well as far as range was concerned but accuracy was poor and a wicket keeper and several fielders were required to field errant balls. Bill Jack’s entry was also of this type although on Bill’s case provision was made for automatic feeding of the balls. This machine was also inaccurate and managed to destroy at least one ball in the feed mechanism. Technically this should have meant disqualification but as another destroyed ball was found, the origin of which was uncertain, this was not enforced, and Bill went on although he came last in the overall ranking.

The two most successful entries were from Gordon Stuart and George Roy. Both were basically guns which fired the ball from some form of barrel/channel and were actuated by either Tension Springs or Driving Band. In Gordon’s case the tensioning was done by a motorised mechanism but in George’s model the springs had to be manually tensioned before each “shot”. The George Roy entry was a clear winner in spite of the fact that it imparted considerable and random spin to the balls which meant that, if they bounced before reaching the bucket, their subsequent path was somewhat random. Results are shown below. The figures in the main body of the table are for the number of balls entering the bucket in a 3 minute period at each range.

Final results are calculated by multiplying the number of balls by the range multiplier and adding.

Range (ft)	6	9	12	15	18	21	24	TOTAL SCORE
Multiplier	2	3	4	5	6	7	8
George Roy	16	1	17	9	6	4	0	212
Gordon Stuart	9	6	12	7	3	5	3	196
Douglas Carson	3	0	3	3	2	0	0	45
Bill Jack	8	4	0	0	0	0	2	44

---

Pictures from Menstrie 2013

High resolution versions of the photos are also available for download if desired.