Episode 4 of Gadget Geeks showed our Inventors at their brilliant best, as they designed, built and tested the remarkable Fast Food Cannon and iTrot horse controller. Here, Charles Yarnold and Tom Scott describe exactly how they did it.
FAST FOOD CANNON:
CHARLES: Colin's knowledge of firing things at high speed is awesome, and a little worrying! He took a air compressor (like a large version of what you use to pump up a car's tyres) and connected it to a pressure vessel. This meant he could fill the vessel with lots of highly compressed air, enough to fire several sausage rolls into the audience between pressure refills. This meant we got a reliable amount of 'oomph' behind each shot.
CHARLES: He then took this and put it inside an amazing wooden cannon he build from scratch, it looked the business!
TOM: Look, first of all, let me say: the maths worked. But like many theories, the real world got in the way.
After measuring the stadium, I worked out a formula that would describe the angle and distance to each seat. That used nothing more than high school geometry - sines, cosines and tangents - although dealing with the three-dimensional bleachers took some thinking about.
We used a commercial SMS service, with its number splashed on the side of the cannon. It forwarded incoming texts to a web service I wrote. (It's turned off since, by the way; text messages to that number are just ignored now!) Those requests were fed into the formula and converted into yaw and pitch - vertical and horizontal angles. When we were ready to fire, it sent one of the requests to Charles' electronics.
CHARLES: The electronics inside gave me detailed readings to give to Tom for his calculations, and they also fed into the automatic movement and firing we used on the day to aim it at the correct seat. Sadly you didn't get to see it work on the show, but aiming was all controlled by motors, we didn't have to touch a thing to have the cannon move into position, start the count down and fire the sausage roll (surely that was worth more than one star, even if mother nature got in the way a bit!)
Ingredients:
1 x Large air compressor
1 x Custom wooden cannon chassis
1 x Digital compass
1 x Wii Nunchuck
1 x 7 segment count down display
2 x netbooks
2 x arduinos
30 x wrapped sausage rolls
HORSE CONTROLLER:
CHARLES: Colin had some ideas for this one, so I let him go at it with a "if you can control it with switches, I can control it with an arduino". Sadly I didn't realise that out of the 3 geeks, I'm the only one who knows how to ride a horse... While Colin's steering was amazing, and the large wooden legs did start the mechanical horse... it wasn't the best of his ideas.
CHARLES: Once we had a working test robot I swapped out Colin's switches for relays so I could control his mass of motors and cables digitally. It was then onto the first test, we quickly ditched the legs for vibrating pads (designed for people who are hard of hearing) and Colin made the gadget more compact and stylish.
TOM: In hindsight, I should have made the control system using Processing for Android. If you ever have to build a remote control for a horse, do it that way. Instead, for some bizarre reason that I can't remember, I used PhoneGap. Don't get me wrong - PhoneGap's a beautiful system - but what's basically a mobile web page was a bit of a bodge for what we needed.
Still, it did work: ten times a second, it pulled in data from the phone's accelerometer and worked out how it was turning. If it detected that the phone was being tilted left, right, or forwards, it would make a call over a wifi network and update the netbook that was built into iTrot - in turn, that netbook (which was also sending back the webcam images to the phone) would cue Charles' electronics.
A side note: full marks to the Acer Aspire netbooks we used. Over the course of the series, they fell off horses, were put into freefall, disassembled, reassembled, and exposed to all sorts of demanding and dangerous conditions - and they just kept on going.
CHARLES: I love horses, best of all the animals, and throughout the build of the gadget I had the comfort and safety of the horse in mind at all times (as did Tom and Colin). We made sure to add in emergency stops, build it into a saddle for comfort and were ready to call off the gadget if we or the horse were unhappy at any time. To have all these nerves, and then to see Casey be totally chilled walking around normally, and then to actually respond properly to the iTrot was one of the most "warm fuzzy" gadget success's we had.
Ingredients:
1 x arduino
2 x Electric window motors
1 x Netbook
1 x Android phone
1 x Saddle
2 x vibrating pads
8 x Relays
8 x Flyback diodes
