Thomas Senkel became the first man to fly with an electric powered Multicopter named e-volo, paving the way in manned DIY electric flight. Senkel’s first manned flight took place in Germany in Late October 2011, after several successful unmanned test flights of the vehicle. The e-volo multicopter is a contraption made of aluminum tubing, an exercise ball, and lots of electric motors.
The pilot sits atop a seat strapped to an exercise balance ball while four spindly legs keep the whole affair from tipping over. Sixteen outrunner, electric brushless DC motors provide the power to easily lift the e-volo into the air (shouldn’t it be called a SEPTENDECIMCOPTER?). The light weight Lithium Polymer batteries should be capable of delivering flights of up to 20 minutes.
Essentially the e-volo is a larger, more complex version of a Quadcopter, a new type of flying vehicle which is becoming very popular in the R/C modelling crowd. Quadcopters are X shaped airplanes which use four electric motors and propellors to lift the Quadcopter into flight. By varying the amount of power to each motor the plane can be steered through some elaborate maneuvers which a helicopter would have difficulty duplicating. Advanced flight control systems make the Quadcopter flyable using Gyroscopes, accelerometer, compass and GPS. The e-volo has 4 times the motors of a Quad copter but works on the same basic principal. According to a press release from e-volo Syntern company the multicopter weight in at 80 kg (around 176 pounds) and can carry a payload of about the same weight. E-volo makes no mention of the amount of power needed to acheive this feat.
How a Modeler Might Make a Multicopter
Since I am an electric model airplane buff I thought it might be fun to try and figure out what a modeler would need to create his own e-volo style machine. Based on my experience with building and flying electrically powered aircraft since 1980, I would estimate (W.A.G. – Wild Ass Guess) that in order to pull this off, the electric motors would have to deliver a minimum of 150 to 200 watts per pound. Since the weight of the airframe and pilot add up to 300 pounds, that means you would need a minimum of 45,000 watts of power to accomplish hovering flight, though 60,000 watts would be better. This would mean that each motor had 3.75kw in size at the high end or 2.8kw for lower powered flight. Based on the largest easily available Lithium polymer battery pack having a voltage of 37V, this leads to about 76 amps per motor at full power. NOTE: Watts equals amps times volts. 76×37 = 2812 watt or 2.812kw.
What all that math means is that people could duplicate these results if they desire to. However, I suspect that the e-volo team may still have a few trick up their collective sleeves. You see, one of the team’s talents is to rewind motors to suit their needs. So I would be surprised if the motors in question are stock motors after all. In fact in a press release by e-volo, they mention that ” The existing standard engines were not ideal for the e-volo“, says Thomas Senkel. They did not have the adequate performance parameters and an inferior power efficiency, so they were adapted to serial models. The propellers were similar, ″as we have different specifications for such a hover flight“, says Senkel.
Thomas Senkel has been rewinding motors for quite some time. In fact, he recently unveiled a 20kw brushless DC motor motor he had just completed on youtube. If Thomas can make this monster motor work, winding 16 of his own custom 3.75kw motors should be child’s play. Also based on the low current draw displayed by his big motor, Thomas may have been able to wind the smaller motors so that they required less current than I estimated to do the same amount of work which would lead to longer flight times.
Additionally You would require 32 battery packs (two per Motor), sixteen Electronic Speed Controls capable of handling at least 100 watts each, a electronic flight control system for flight stabilization Miles of wire and quite a bit of Aluminum tubing. I would be really surprised if you could build the aircraft for less than $15,000. Which would still be a great bargain for a personal flight system.One last thing to consider is that all of these equations change based on how the motors and batteries are connected. If they are wired in series the values will change compared to if they are wired in parallel. To make matters even worse, it is quite common to have multiple wiring configurations within the same plane, it is not unusual to have one segment wired in series while another is wired in parallel. Isn’t this fun?
If the thought of building your own Multicopter is a bit too much to handle, have no fear. The e-volo team plans to sell multicopters in the not too distant future according to their website. “Simple flight for the average person would be a dream come to reality for us. In the next few years we would like to make more of these simple to fly devices available at an affordable price. The flyability of this device, the simple and straight forward piloting making the possibility of flight available to the average person is a goal that we strive towards”. Congratulations team e-volo. Well done.
Here is a bit of information taken from e-volo press release.
The e-volo measures approximately five by five meters, has four jibs (with 4 propellers each), a basic weight of about 80 kg (including batteries). So it is an ultra light aircraft, which already as a prototype allows for a payload of about 80 kg. 16 propellers provide it with the necessary uplift and at the same time guarantee the required security, because beside the impressively easy construction without a complex mechanism the aircraft can be landed safely even with a malfunction of up to four engines. The e-volo makes flying easy! A position sensor ensures the correct position in space and permanently balances position changes with rotary speed adjustment – and so the e-volo can stay still in the air! The specially developed steering and flight electronics make it as stable as necessary. Multicopters are already available as smaller models, but unmanned as toys. Amongst other applications they are used for spying purposes. They are controllable even with an iPhone – but now for the first time ever such an electrical powered aircraft has flown manned.
The electrical power is supplied by lithium batteries and enables a flight time of up to 20 minutes depending on payload.
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