UNUSUAL ELECTROLET

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UNUSUAL ELECTROLETWith a slight rustle of the blades of the propeller model took to the air. Passed one circle, two, three. All this is familiar today in many circles of our country guys raise flying model aircraft with electric motors. However, some features of this device are forced intently follow him. Whether unusual for a rechargeable element wing — flaps, or confidence, a kind of reliability of the flight. After all, we are accustomed to the fact that the power of the motor just enough to keep the model in the air.

But here’s the completed base, finished the tenth circle. Probably followed by a “pipeline” — intermediate landing and subsequent takeoff, and then the boy gently put your model and turn off the power. But no! She suddenly roaring engine (if you can say that about sagadevan stronger than the electric motor, which could hardly be heard sooner), performs a loop, a true loop the loop! Applause of the audience, and “pilotage” she was indeed worthy of the name — confidently demonstrates almost all complex acrobatic figures.
 
To make a machine that helped not only the Golden hands of modelers, but also knowledge of fundamentals of electrical engineering and aerodynamics.
 
Work began on the project future elektroperedachi with the choice of engine. Mainly used to put motors type DK-5-19. Easy, resourceful, they made almost triple overvoltage. But this perekal made itself felt. Powerful sparking at the brushes, and a large operating current heated the motor so that the melted plastic housings of collectors and otpaivali album from the brush holders. Struggled with it, putting textolite instead of nylon and has been crafting brushes. But still power is not enough: easy model was made only horizontal flight.
But someone brought up a view taken from neighbors-modelers motor installation, manufactured by our industry for floating models under the brand A-287. Solid feel immediately scared off — it’s too heavy. Still connected to power and… was that a motor with almost no sparking and no appreciable heating allows four to five times perekal voltage at short-term inclusions. Measurements showed that the power consumption is 30 W or more (at a voltage of 13.5 V the current is 2.2 A load). It’s not a few watts DC-5-19! Then weighed the engine. Weight — 62 g When removed the stern tube and thruster, shortened the long shaft, there are only 46 grams (for information: DK-5-19 weighs 25 grams). It became clear that you can get to work. Nylon plastic body was replaced by a thin-walled Cup made of magnesium alloy MA-8. It is lighter, heat resistant and allows you to replace the bearings friction on the ball.
 
Fig. 1. Aerobatic model with a motor
 
Fig. 1. Aerobatic model with electric motor:
 
1 — spinner, 2 — body, 3 — keel, 4 — keel, 5 — th, 6 — propeller 7 — wing 8 — flap 9 — rod 10 — stabilizer, 11 — Elevator.

 
Fig. 2. The design of the fuselage
 
Fig. 2. The design of the fuselage:
 
1 — motor, 2 — flexible conductor, 3 — outlet of the cooling air, 4 — light (celluloid 0.3 mm), 5 — polik (Whatman), 6 — the pilot (foam), 7 — frame, 8 — screw M2 wing mounting, 9 rocking chair (fiberglass 0.5 mm) 10 — wall of the cooling channel (Whatman) 11 — hood-intake (celluloid 0.6 mm or fiberglass 0.3 mm), 12 — slot motor (balsa), 13 — the frontal frame (plywood 1 mm).

 
Fig. 3. Mount the landing gear
 
Fig. 3. Mount landing gear:
 
1 — copper tube (wrapped with thread and glued in the wing), 2 — clamp rack, 3 — plywood panel, 4 — front, 5 — panel.

 
The revision was subjected to the collector — casing for reliability machined from the PCB, and plate brushes with the edges duct-taped to the holders of the thinnest copper wire. The holders mounted on the metal wall of the motor through insulating textolite cups. Note that the holes in the ends of the shell and the wall is not only to facilitate: they are the part of air, which drives the propeller to cool the highly stressed engine. And it after all the modifications are “thin” and began to weigh only 38 g. some of these motors of a horseshoe stator over time, lose their magnetic force, in such cases, we recommend to podmanivaya them using a simple fixture. Propeller find themselves depending on the speed of the shaft reworked engine. Just do not use COC large diameter: holes the cooling of the engine will be obstructed and it will overheat. When the good and cooling time of about 3 minutes modified motor allows you to bring the power consumption up to 40 watts.
 
Taking the efficiency of the installation is 40%, and screw to 70%, you can try to determine the main parameters of the model. First of all on the speed of flight.
Small, of course, attractive. However, the flight model should not be too slow. Otherwise it does not hold tension cord at the points of the hemisphere close to the Zenith. We agree that the length of the wire cord is 5 m and the centrifugal force balances the weight of the model. This tension is enough, as electroanalyt fly in the hall where he is not afraid of the wind and the extra effort will give a series of measures, applicable only pilots: mowing the axis of the engine out of the circle, loading the outer end of the wing, the deflection of the rudder shift conclusions a cord from a wing-back and differential flap deflection. Under these conditions minimum flight speed of about 7 m/s. Circle the airplane will be held for 5 (including arm’s length “pilot”). The angular velocity turned out slightly different from the terms “big” maneuvers. And what will give the engine? Its thrust (in Newtons) is equal to:
 
 
where NIn is the shaft power of the engine equal to its power consumption multiplied by efficiency of the electric motor, W;
η — the efficiency of the propeller;
V — airspeed, m/s.
 
After calculating get the value of the thrust is 1.6 N, or about 160, So in a lot of need to “meet” during the construction of the apparatus. Flight characteristics will improve) if the model will be able to make lighter, weighing approximately 100 g, the Excess power will help her become more flexible.
 
What is the value of the specific load on the bearing surfaces make for elektroperedachi? Given the relatively short cord of about 10-15 g/dm2. Then the minimum turn radius will allow not only round but also square loop.
 
The result is the total area of the bearing surfaces 7-10 DM2. Divide it so. The wing is 85%, the horizontal tail — 15%. Now you can draw the entire model. The only snag in what to build. Because the design is not so much: the engine with the propeller and spinner weighs about 40 g, control system — 5 g, and chassis, even a single Bicycle, is hardly easier 5 years is only 50 g.
 
Possible ways several. Balsa will be able to create a lightweight case design, you can fit long-fibre paper on Amalia. You can take graph paper and from it to glue the whole model, the pre-coloring of patterns of detail in watercolor. Wing flaps will weight about 28 g, as this paper has a specific surface weight of 1.8 g/DM2.
 
But the most attractive and rewarding material — melkosortnyj packing foam (specific weight of 0.016 g/cm3, or 0.32 g/dm2 with a thickness of 2 mm). The special exterior finish is not required, enough to stick on the white plane cut from thin coloured paper letters, stripes or emblems. Can be cut from foam and the wing on the metal and the plywood templates, and then to pierce it along a spoke, insert in the hole nichrome wire and to facilitate the wing from the inside. This “product” is surprisingly easy — with flaps it weighs 5-6 g.
 
Fig. 4. Engine
 
Fig. 4. Engine
 
Fig. 4. Engine:
 
1 — housing 2 — ball bearing 3X7, 3 — the rotor Assembly, 4 — brush holder, 5 — insulating glass, 6 back wall, 7 — ring, the stator magnet.

 
Stabilizer with Elevator easier to manufacture from a single piece, as well as the vertical tail. If you have scraps of balsa, turn over all the planes and rudders along the perimeter with strips of wood. Treat the outside of the fuselage, then cut along the vertical axis with a hot string, hollow inside, and seal it with PVA emulsion.
 
Drawing the nodes of the control system, try to place the model in a rocking chair with a maximum swing arms of the suspension cord. Many people make the mistake of installing korotkovichi rocking control, and they are for light microplane are not suitable. Small lever — small torque. As a result of moving poorly stretched cord, if transmitted to the handlebars, or inaccurate, or late. When extreme deviations rocking the elevators should go up and down 40°, flaps — 30° in the opposite direction.
For cord better to use wire marks PEL. Some use stranded wire in Teflon insulation MGTF. It is long, but the model fly worse. The fact that the same cross-sectional area of a core of the latter larger outer diameter, and this extra air resistance. Thick cord as if wrapping the plane in a circle, reducing the tension of the wires.
 
At a current of 2.5 A, you can use a wire of PEL with a diameter of 0.25 mm (current its melting point 10 A), the voltage drop across the two wires with a length of 5 m is approximately 9 In, heat recommend joining a gym with Konami wire greater in 1.5—2 times the diameter. Thin could if not to burn out in the wing, at least, podpravit foam. Note that all connections of the electric circuit can only be performed by soldering, in any case, a simple twist lived!
 
Fig. 5. Control system
 
Fig. 5. Control system:
 
1 — wire-leash, 2 — rocking chair 3 — flexible conduit, 4 — retainer flaps, a 5.7 — thrust (chii), 6 — pylon rudder, 8 — tube-hinge (straw).

 
The current source any if only it provided on the approach to Kardam voltage of 24 V. This set of round batteries, and a basic rectifier of alternating current. On the handle of management mount variable resistor to reduce the input voltage to Kardam at least twice, and switch.
 
Sending a microplane in the first flight, be sure to check if there are distortions planes, easily deflected rudders, whether the venue is center of gravity. If you have no experience of piloting models of cord, slide it forward 5-7 mm, loading nose of the device.
 
Novice modelers can be recommended to build a school. Alterations of the engine it is not required, the propeller is attached to the shaft coming out of the stern tube. Just do not forget that in this embodiment, when the vertical manoeuvre of the model and the engine power is limited by heating of its elements, it is permissible for him to bring the voltage up to 8 V. since the line current is 1.4 A, the voltage drop in the cords 5, to the handle it is necessary to bring the 13 Century.
 
Y. PAVLOV, engineer

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