Geoff Builds A Giant Marble Run For The Mechanical Subcamp Gateway:We wouldn’t just stop with one of these, if we had it so the balls filled a hopper which tipped when full and had one of each of these contraptions either side of the entrance then they could have a race. A few more details in terms of size and layout and the specification was agreed. Then it was time for the hard work, it is easy to say let’s have a set of buckets on a loop to carry the balls to the top, it is however somewhat more difficult to create. The first problem is that each bucket only wants one ball in it so something that looks a bit like a water wheel was created. The balls push on this causing it to spin, however that spin is halted by a couple of pivots that move in and out of the top of the fins. The pivots are in turn controlled by a paddle that the bucket strikes as it comes round the bottom drum. Next issue is that when the bucket gets to the top the ball needs to exit the bucket and enter the ‘marble’ run. So a sheet of polypropylene was cut to guide the balls out of the bucket and into a top hopped. On the face of it this looks fairly simple, but like many of the components in the system required a number of iterations before it worked reliably, in this case, it was version 4 that worked nicely. Another potential problem was that if you loaded the buckets up with balls and then turned the wheel in the wrong direction the balls would be emptied on the floor and the paddle that controlled the release of balls could be damaged. Given the project was all about the theatre of the contraption, it was a no brainer to go for a ratchet mechanism on the steering wheel shaft as this would not only stop it being driven the wrong way but would make a noise every time the ratchet dropped down. With access to the Kitronik laser cutting room and the stack of slightly damaged laser material, it was time to get on with the build. In all 61 unique laser cut components were designed cut, glued, screwed and assembled into modules and then mounted into the whole contraption. A further 30 individual items such as timber, screws, bolts, hooks, pulleys, ball racers, axels, axel brackets and let’s not forget the truck steering wheel were then needed to complete it. Although the design called for two marble runs one on each side of the gate the dry run consisted of just one side and without the marble run section being in place. Having built the contraption at the back of the Kitronik warehouse and spent much time debugging issues and making tweaks to the design it was the whole lot was dismantled into modules. Once everything was dismantled, everything was shrink-wrapped and loaded onto a truck ready for transportation to Charnwood. On-site it was the hottest day of the year to date when the whole lot was unloaded and the build began in the sweltering heat. Some warehouse racking was used as the Gateway frame that everything else would be built around. So, the first step was to put that up and to build the mechanisms off to the side. Then it was time to begin to assemble the sides. There were a few minor glitches as it was all put together, but after two days of assembly we had everything up and running and for the first time could see the complete gateway in all its glory ready for the campers to arrive the next day. Meet the Author: This blog was written by: Geoff Hampson – One of the founding directors of Kitronik
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