have finally arrived.
We no longer have motors with deficient power, overweight batteries, and inappropriate controllers. The overwhelming popularity and increasing demand in RC areas has called forth a rapid technical progress which we can happily benefit from. Several electric airplanes are already flown - and quite successfully, at that. What is still giving us headaches is that little tool which is capable of telling the controller what this should persuade the motor to do.
|Manufacturers are not very enthusiastic about listening to control line needs. Small production runs are not exactly what can make them rich in a short time. So it was a great pleasure to hear that some people were willing to accept the challenge and develop suitable tools for us. Products from Z-tron ( USA ) and JMP ( France ) have helped us to arrive at where we are now. State of the art of these so called “timers” is the possibility to set a few different features:|
set RPM if required
b) total motor run time
c) a short period ( say 10 to 20 seconds ) at low power to allow the pilot to walk to the handle, and at the same time save some battery capacity. This is sometimes called “run up” time.
flight speed. Depending on the product we can even choose two different
speeds. The first phase covers the time up to the Horizontal Eight. Before
beginning the Square Eight the motor will switch to a higher power level
= the second phase ( of course we’ll have to precisely program the
correct time parameters beforehand ). It’s also possible to program
a slight but continuous RPM increase during the second speed phase until
final motor stop.
e) We can set “ warning burps” to warn us of the soon to be expected motor stop.
this equipment high performance aerobatics is possible and is already a
reality. However clever minds among the electronic whizzes have instantly
found out that this need not be the end. Using all the possibilities that
modern technology can offer, much more can be achieved. Exactly that has
Being myself an “electronic Zero” , full credit of what follows must go to Wolfgang Nieuwcamp. A Dutch living in Germany Wolfgang doesn’t belong to the world top of stunt flyers, but he’s one of those creative minds who like to brood over unconventional ideas and make them come alive. Being comfortable with electronic devices he quickly discovered what we need.
|As experienced stunt flyers we know that an IC engine can be set to react on different flight conditions. The well known 4-2-4 regime can almost perfectly take care of two different situations: climb and dive. In addition the engine is able to “sense” whether the airplane is in horizontal flight at “eye level” ( in rule terms: 5 feet ) or up there somewhere on the hemisphere ( 45 degrees line angle or higher ). What it cannot do is care much about our Number 1 problem: line tension. This is slowly but irreversibly|
|decreasing with increasing line angle, because gravity starts claiming its rights here. Also, depending on airplane design, airplane weight, weather conditions ( wind ), and elevation line tension can be reduced quite drastically. Our OS-PA-Tiger was never designed to sense centrifugal forces, but it could be tuned to respond to flight altitude and position. An occasional, sudden, and unwanted loss of line tension was not “felt” by the engine.|
Now there are electronic devices which can do just that. They can “feel”
lateral acceleration - and they can react accordingly. They can be set to
a fixed value . This is the amount we need for sufficient line tension.
As soon as we have less tension, a sensor has to measure the missing amount
of “G force” and immediately tells the controller to increase
motor RPM. And that’s exactly what Wolfgang incorporated in his new
gadget. The “G sensor” is about as big as an M3 nut, and the
whole apparatus is about 5 x 3 centimeters big and weighs 8 gramm. Because
centrifugal force acts in one direction, the unit will be programmed accordingly
and must be installed in a certain position.
Seeing this mystic tool, my instant question was: “ how quick does it react?” For demonstration Wolfgang had rigged up a test unit with motor, controller, timer, and battery, all mounted on a board. The sensor was programmed so that “ in flight” was simulated by steady quiet holding of the unit. By turning the timer in the hand would easily simulate “acceleration”. The demonstration was overwhelming! Even the slightest movement of the hand instantly caused the motor to “ rev up” or brake down!
Wolfgang has intentionally renounced on adjustable RPM. With his gadget it’s no longer necessary to adjust to different manoeuvres, situations, or parts of the flight schedule. Since line tension is the only indication, this governor will automatically find the correct setting - everytime, instantly, reliably ! Thus the controller can easily be set for “full power” ( which at the same time prevents motor heat problems ). The right airspeed for the model then will have to be found by propeller choice ( diameter and pitch ). This may take a few test flights, but may safe us some frustrating “beep-beep” moments for programming the controller. Wolfgang used a menue card to adjust the controller to the motor. It’s available for the brand of controller he uses. This card is not absolutely necessary,since the controller can be handled “manually”; means: operated by several short and long clicks
|on a button depending on controller brand. Once this is done, there’s no further programming necessary. Imagine this: we no longer need to care about different power requirements in different parts of the schedule. The sensor feels how much line tension we have at the moment. If this is less than what was programmed into it, it instantly reacts and controls the motor accordingly. There’s no need to fly faster than what we’d like in order to keep sufficient line pull in all situations. The governor keeps care of that. In horizontal flight we have enough line tension at slower speed. So the timer can reduce power to the minimum required level, thereby saving lots of Am/h . Which again saves battery capacity which means savings in battery weight !!|
|I asked Wolfgang to give me a demonstration of his drive set and at the same time explain to me how the whole unit is set and used and how the whole process is running down. With the unit mounted on a board he could easily show how it’s done, what first steps are necessary, and how the timer is programmed. In the pictures you can see the setup ( without propeller ) which is used for demonstration purpose only. It’s quite helpful to build such a test rig ( after all it really isn’t much work ). A propeller of your choice is fitted to the motor; as to the size it’s wise to get some information from people who have some experience already. An amperemeter must be connected to the circuit. This must have a slightly wider range than what the controller and the motor is built for. With the motor running we can easily check the current draw. Of course this must not exceed the limit of motor and controller. That way we can find a suitable propeller. If this is the correct prop for the airplane is another story which we’ll have to find out in test flights. Now we can check if the whole drive unit works just as it should. The motor can be stopped by pressing a button on the timer at any time.|
|With an ampere-friendly propeller we can finally start the test cycle - means some test flights. Of course it’s helpful to have a number of props of different size handy. It’s recommended to connect the battery on the circle only. A short click on the timer’s button doesn’t cause anything. This is also for safety reasons, but the controller will already realize the motor. The button must be pressed and held down for a few seconds. Only this will start the program which is shown in the graphic.|
|. Now the timer tells the motor to start running, going up to max power = revolutions, hold this for a short moment, and then go back to Zero RPM for only an instant. This phase shows us that the system is working. After this very short “stop” the motor will run at very low power for about eight seconds. This time will allow us to walk to the handle; at the same time the reduced A draw will save us battery capacity. After these 8 seconds the motor again bursts into full power again, and our helper can release the airplane; of course after a wave of the pilot only|
|( if we fly alone with a stooge, this is the moment to pull the string !). From now on the timer starts to feel G loads; that’s what it was programmed for. It will sense centrifugal force and “ control the controller” hence the motor. According to requirements RPM ( means air speed ) is controlled to guarantee sufficient line tension. Shortly before the pre set end of flight time the timer will force the motor to imitate two hiccups before it will finally stop.|
|Wolfgang’s armament at the moment is a typical 40 size airplane, a Plettenberg Orbit 15-18 motor, Kontronic Pix 4000 BEC controller, a 4S 3200 battery, Graupner CamProp 12,5 x 6 , and his timer. He’s still waiting to get some additional flight results from a friend who’s playing around with his timer. Because of the nature of this micro processor G loads can only be felt in one direction. This direction is marked on the board ( a little arrow ). It’s in the direction of the longer dimension of the unit. So the timer has to be installed with the longer edge parallel with the lateral axis of the airplane; means across the longitudinal axis. Of course it can be turned around in any desired position - as long as its longer distance runs spanwise !!! ( just as Ford’s Model T was available in all colours provided this was black ).|
Wolfgang’s timer will be delivered with two micro processors. One of them is programmed for “simulated G” as mentioned above. With this you can run the garage or kitchen table tests which require a simulated centrifugal force. This is then replaced with the original “flight” processor. So far Wolfgang expects to be able to sell the timer for about 50.00 Euro. If you are interested you may contact him at wnieuwkamp"at"gmail.com .
|They say a picture is worth a thousand words. Well then - in order to remove possible doubts about his product Wolfgang has just produced a short movie to show how his gadget works. Just hit the button below and see for yourself.|