Any flying model rocket (Fig. 1) has the following main parts: body, stabilizers, parachute, guide rings, fairing and engine. Explain their purpose.
The housing serves to accommodate the parachute and the engine. To it is attached the stabilizers and guide rings. Stabilizers are necessary for the sustainability of the model in flight, and a parachute or any other system of salvation is to slow the free fall. With the help of guide rings model set on the bar before the start. To give the model a good aerodynamic shape of the upper part of the body starts the payload fairing (Fig. 2).
The engine is the “heart” of the model rocket, it creates the required thrust for flight.
For those who wish to join the rocket modeling, own hands to make a working model of a flying machine called the rocket, here are a few samples of such products. I must say that this work will need available material and minimal tools. And, of course, this is the most simple, single-stage model under the engine pulse of 2.5 — 5 B. C.
Based on the fact that the sporting code of the FAI and our “competition Rules” minimum case diameter is 40 mm, select the appropriate mandrel for the body. For it fit an ordinary round rod or tube with a length of 400 — 450 mm. It can be constituent elements (tubes) hose from a vacuum cleaner or end-of-century fluorescent lights. But in the latter case needs special precautions because the bulb is made of thin glass.
Consider the technology to build simple model rockets. The basic material for making simple models, recommended to novice designers, paper and foam. The housing and the guide ring of glue drawing paper, parachute or brake band is cut from long-fiber or color (crepe) paper. Stabilizers, fairing, clip under the MRD is made from foam. For bonding it is desirable to use PVA glue.
Production models should start with housing. For the first model better to make it cylindrical. We agree to build the model under the engine MRD 5-3-3 with an outer diameter of 13 mm (Fig. 3). In this case, its mounting in the aft will have to carve a clip length of 10 — 20 mm.
Important geometric parameters of the shell model are the diameter (d) and elongation (X), which represents the ratio of the length of the body (I) to diameter (d): X = l/d. The elongation of most of the models for steady flying with the tail should be about 9 — 10 units. On this basis, we define the size of paper procurement for housing.
Fig. 5. The attaching lanyard:
1 — shelter; 2—suspension lines; 3—tab (paper or tape)
Fig. 6. Laying chute
If we take a mandrel with a diameter of 40 mm, the width of the workpiece compute the formula for circumference: C = πd the result Obtained should be multiplied by two, because the case is two layers of paper, and add 8 — 10 mm allowance for the seam. The width of the workpiece was equal about 260 mm.
Those who are not yet acquainted with geometry, the guys in second and third classes, we can recommend another simple method. Take a mandrel, wrap it two times with a string or strip of paper, add 8 — 10 mm and see what will be the width of the workpiece housing. It should be borne in mind that the paper needs to have fibers along the mandrel. In this case, it is well twisted, without kinks.
The length of the workpiece is calculate by the formula: L = πd or stop for $ 380 -400 mm.
Now about the bonding. Wrapped a piece of paper-the blank around the mandrel once, the rest of the paper we coat with white glue, give it a little bit to dry and wrapped a second time. Zagladin seam, placing the mandrel with the shell at the heat source, e.g. radiators, after drying, trimmed the seam with fine emery paper.
In a similar way and produce the guide ring. Take a normal round pencil and wrap it a strip of paper of width 30 to 40 mm in four layers. Get a tube, which after drying cut into rings with a width of 10 — 12 mm. Subsequently sticking them to the hull. They are the guide rings for the start of the model.
The shape of the stabilizers may be different (Fig. 4). Their main purpose — ensuring the sustainability of the model in flight. The preference can be given that, where part of the square is cut in the aft (bottom) of the hull.
Choosing the right form of the stabilizers, make it a template from heavy paper. Template cut out the stabilizers from the plate of foam thickness 4 — 5 mm (it is possible to apply foam ceiling). The smallest number of stabilizers 3. Adding a stack on top of each other in the package, skalyvaniem them with two pins and holding the fingers of one hand, treated the edges with a file or whetstone with glued sandpaper. Later rounds or draw all sides of the stabilizers (after dismantling the package) except the one which they will be attached to the housing. Next — glue the stabilizer PVA in the bottom of the hull and covered the sides with white glue — it smooths the pores of the foam.
Fairing machined from foam (better brand PS-4-40) on a lathe. If this is not possible, it can be also cut from a piece of foam and handle with a file or sandpaper. Similarly make the clip under MRD and pasted it in the bottom of the case.
As a rescue system model, ensuring its safe landing, use a parachute or brake band. The dome cut out of paper or thin silk. For the first launches of the diameter of the dome should choose the order of 350 — 400 mm, — thereby to limit the flight — you want to keep your first model memory. After attaching a sling to the dome produced by repacking of the parachute (Fig. 6).
After manufacturing all parts of the model hold its Assembly. Fairing connected by rubber thread (shock absorber) with the upper part of the body of model rockets. The ends of the sling of the parachute canopy associate in a harness and fasten it to the middle of the absorber. Next, paint the model in bright contrasting colors.
The starting weight of the finished model with the engine of MRD 5-3-3 about 45 — 50 g. Similar models can be carried out first competitions for the duration of the flight. If the runs are limited, we recommend you to choose as a rescue system brake band dimensions 100×10 mm.
Starts out entertaining and dynamic. After all the flight time in this case will be about 30, and shipping of models is guaranteed, which is very important for themselves “rocket scientists”.
A model rocket for demonstration flights (Fig. 7) is designed to start with a more powerful engine with a total impulse 20 n. s., It can carry on Board and payload — leaflets, pennants. Flying such a model in itself spectacular: the start is reminiscent of the start of this rocket and the ejection of leaflets or of colorful pennants add to the entertainment.
Fig. 7. A model rocket for a launch:
1—fairing: 2 — loop suspension system of salvation; 3 — chute; 4 — body; 5—stabilizer; 6—yoke under the PRD; 7 — guide ring
Fig. 8. Electrical control panel system running
Case sticking of thick drawing paper in two layers on the mandrel with a diameter of 50-55 mm and its length is 740 mm. Stabilizers (four of them) cut from a plate of foam with a thickness of 6 mm. After rounding three sides (except for the long — 110 mm) to the lateral surface covered with two layers of PVA glue. Then, on their long side, which is then fastened to the hull, make a groove round file for a snug fit of the stabilizers to the round surface. Guide Wycliffe method on a round mandrel (or pencil), cut into rings with a width of 8 mm to 10 mm and is mounted on the PVA to the hull.
Fairing machined on a lathe out of foam. From the same make and race under MRD width of 20 mm and insert it in the bottom of the case.
The outer surface of the head fairing, two to three times daubed with white glue — to remove roughness. Connected to the upper portion of the housing rubber damper, for which the fit of ordinary underwear elastic band width 4 — 6 mm.
The dome of a parachute with a diameter of 600 — 800 mm is cut from fine silk, the number of lines 12-16. The free ends of the filaments are connected by the node in a harness and attached to the middle of the absorber.
The interior of the housing at a distance of 250 — 300 mm from the lower edge of the paper the insert grille of thick paper or strips, which prevents the parachute and useful cargo to fall during the takeoff to the bottom of the model, breaking it alignment. The content of the payload depends entirely on the imagination of the designer model. The starting weight of the model is around 250 — 280 g.
For safe launch and flight models need a reliable starter equipment. It consists of a starter, remote start, conductors for power supply and igniter.
The starter should ensure that the model moves up until, until the speed required for a safe flight along the planned trajectory. Mechanical device built into the launcher and help you start to use forbidden by the Rules of competition model rocket sporting Code.
The most simple starter — guide rod (pin) diameter 5 — 7 mm, which is fixed in the starting plate. The angle of the rod to the horizon should not be less than 60 degrees.
The starter sets model rockets a specific direction of flight and provides it with sufficient stability at the time of descent to the guide pin. However, note that the larger the length of the model, the greater must be its length. The rules require a minimum distance from the top of the crown model before the end of the rod in one meter.
The control run represents an ordinary box size 80x90x180 mm, make it yourself out of plywood with a thickness of 2.5 — 3 mm. On the top bar (it is better to make removable) establish a pilot light, locking key and the start button. It is possible to mount a voltmeter or ammeter. Schematic diagram of the remote control run is depicted in figure 7.
As a current source in the remote control are used batteries or other batteries. In our circle for many years used for this purpose, four dry cell type KBS voltage of 4.5 V, connecting them in parallel to two batteries, which, in turn, are interconnected in series. This power is enough to launch model rockets during the sport season. It is about 250 — 300 launches.
For power supply from the control panel to the igniter, it is desirable to use stranded copper wire diameter not less than 0.5 mm with moisture proof insulation. For reliable and quick connections on the ends of wires install the connectors. In the joints of the igniter attached “crocodiles.” The length of the lead wires should be more than 5 m.
Igniter (Electrosoul) engines model rockets — it’s a spiral of 1-2 turns or length of wire with a diameter of 0.2 — 0.3 mm, length 20 — 25 mm. the material for the igniter is a nichrome wire having a high resistance. Electrosoul inserted directly into the nozzle of the MRD. When current is applied to the spiral (Electrosoul) produces a large amount of heat needed to ignite the engine fuel. Sometimes, to enhance the initial thermal pulse, the spiral cover powder pulp, pre-dip it in nitrocellulose lacquer.
When launching model rockets it is necessary to strictly observe safety measures. Here are some of them. Start models are only remotely, the remote start is placed at a distance of at least 5 m from the model. In order to prevent unintentional ignition MRD lock-up key of the remote control should be responsible for the start. Only with his permission on command “Key to start!” is a three-second pre-launch countdown in reverse order, ending with the command “start!”.
V. ROZHKOV, honored coach of Russia