I often get asked why the octocopter has eight propellers. Why not 1 or 3, 4 or 6 or 12? As a result I shall continue this post in the (rough) style of Rudyard Kipling.
In the beginning of technology when aircaft were so new and all, there existed a helicopter with a single rotor that spun most rapidly and beauteously and was most ‘scruciating loud. Now the helicopter could fly in a manner unlike the other aircraft and they were most jealous of his hovering.
Now the problem with his rotor was that, what with it spinning always in the same direction, his body wanted to spin the other way and so he had to have a tail rotor blowing windy and sideways to prevent himself spinning in spirals and crashing most tremendously. And to top it all, Best Beloved, in order to allow flight forwards and backwards and sideways and all kinds of combinations, a complex series of linkages and socketses and swashes, and all kinds of other things ending in -es — that I dare not get into now for fear of falling foul of fysiks — had to be introduced, making the helicopter the most complicated and tricksy of all the aircaft (other than maybe the Harrier jump jet that may be likened to balancing an elephant most solemn and grey on top of a pole vaulter’s pole).
And so, Best Beloved, one day a man most geeky and pale from lack of sunlight from sitting at his workbench so long, emerged blinking into the daylight holding aloft his tricopter with three tiny propellers so buzzy and fine. And he said to the helicopter, “your work here is done for, with three tiny propellers, I have eliminated the need for all the linkages and socketses and swashes and all kinds of other things ending in -es, that I dare not get into now for fear of falling foul of fysiks.”
But the helicopter said, “ah, yes, but I see you have added something ending with -o, for you have added a servo, why is this so?”
And the man blushed and explained that with three propellers the tricopter still wanted to spin in spirals and crash most tremendously so the servo ending in -o was necessary. And the man returned to his workbench and grew paler and more geeky.
After a long time – things took ever so long in those days – the man emerged, blinking, into the dawn light, carrying before him another ‘copter with blades so buzzy and fine and he said to the helicopter, “your work here is done for, with four tiny propellers, I have eliminated the need for all the linkages and socketses and swashes and all kinds of other things ending in -es, that I dare not get into now for fear of falling foul of fysiks. I have also eliminated the need for a servo ending in -o.”
And the helicopter was most impressed, for the quadcopter – this was its name with its four blades spinning so buzzy and fine – did indeed fly forwards and backwards and sideways and all kinds of combinations with only its four props spinning so buzzy and fine. So many possible points of failure had become four and the helicopter sat glum swishing his tail rotor unhappily in the dawn light.
“I am done for,” said the helicopter, but the man raised his hand. “Not so,” said he, “for although my quadcopter has four propellers so buzzy and fine with two that buzz clockwise and two that buzz anticlockwise so that it doesn’t spin in spirals and crash most tremendously; it can only carry a fraction of the weight we need.” And so the helicopter flew off with his rotor so ‘scrutiating loud for his day’s work, happy in the knowledge that he was the strongest of the hovering aircraft. And the man returned to his workbench and became paler and more geeky.
One evening as the sun was setting and the elephant was chatting with the pole vaulter by the banks of the great grey-green, greasy Limpopo River, all set about with fever-trees, and keeping an eye out for crocodiles, the man emerged from his workshop and sat down beside the helicopter who had just returned from his day’s work.
“Your work here isn’t done, helicopter, but I have built you an assistant. I have tried all manner of combinations of even numbers of propellers. Four was to few and ten was too many, but six or eight seem fine and if one buzzy prop stops there are just enough to stop the copter spinning in spirals and crashing most tremendously. With eight props I can carry my nicest camera and fly through the air with the greatest of ease.”
So, having avoided fysiks for the whole of that long day, the man decided to get out in the sunshine more and sent his octocopter to take snappy photos of crocodiles and elephants in rivers and racing cars racing most ‘scrutiatingly loud. And, O my Best Beloved, the helicopter went to sleep, safe in the knowledge that he was the most complicated and tricksy of all the aircraft and could safely look down on all the other ‘copters, be they quad or hex or octo, because he was the original and the best and knew what to do with a swash.
HexCam and The Aerial Academy 