|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
PERSONAL TRANSPORT: GROUND, WATER, AIR
The main rotor of the autogyro. Personal transport
Directory / Personal transport: land, water, air It can be said without exaggeration that the main thing in a glider-autogyro is the main rotor. The flight qualities of the autogyro depend on the correctness of its profile, mass, centering accuracy and strength. True, a non-motorized apparatus in tow behind a car rises only 20 - 30 m. But even flying at such an altitude requires mandatory compliance with all the previously stated conditions.
The blade (Fig. 1) consists of the main element that perceives all loads - a spar, ribs (Fig. 2), the gaps between which are filled with foam plates, and a trailing edge made of a straight-layer pine lath. All these parts of the blade are glued together with synthetic resin and, after proper profiling, covered with fiberglass for extra strength and tightness. Materials for the blade: aircraft plywood 1 mm thick, fiberglass 0,3 and 0,1 mm thick, epoxy resin ED-5 and polystyrene PS-1. The resin is plasticized with dibutyl phthalate in the amount of 10-15%. The hardener is polyethylenepolyamine (10%). The manufacture of the spar, the assembly of the blades and their subsequent processing are carried out on a slipway, which must be sufficiently rigid and have a rectilinear horizontal surface, as well as one of the vertical edges (their straightness is ensured by gouging under a ruler of the type curved, at least 1 m long). The slipway (Fig. 3) is made from dry boards. To the vertical longitudinal edge (the straightness of which is ensured) for the time of assembly and gluing of the spar, metal mounting plates are fastened with screws at a distance of 400-500 mm from each other. Their upper edge should rise above the horizontal surface by 22-22,5 mm.
For each blade, 17 strips of plywood should be prepared, cut according to the drawing of the spar with the outer layer along, with processing allowances of 2 - 4 mm per side. Since the dimensions of the plywood sheet are 1500 mm, in each layer it is inevitable to glue the strips at least 1:10, and the joints in one layer should be 100 mm apart from the joints in the other, following it. Pieces of plywood are arranged so that the first joints of the lower and upper layers are 1500 mm from the butt end of the spar, the second and penultimate layers are 1400 mm, etc., and the joint of the middle layer will be at a distance of 700 mm from the butt end of the blade. Accordingly, the second and third joints of the harvested strips will be distributed along the spar. In addition, you need to have 16 strips of fiberglass with a thickness of 0,3 mm and dimensions of 95x3120 mm each. They must first be processed to remove the lubricant. The blades should be glued in a dry room at a temperature of 18-20°C. Spar manufacturing Before assembling the blanks, the slipway is lined with tracing paper so that the blanks do not stick to it. Then the first layer of plywood is laid and leveled relative to the mounting plates. It is attached to the slipway with thin and short nails (4-5 mm), which are driven in at the butt and at the end of the blade, as well as one on each side of the joints to prevent displacement of plywood pieces along the resin and fiberglass during assembly. Since they will remain in layers, they are hammered randomly. Nails are driven in in the indicated order and to secure all subsequent layers. They must be of sufficiently soft metal so as not to damage the cutting edges of the tool used for further processing of the spar. Layers of plywood are abundantly moistened with a roller or brush with ED-5 resin. Then a strip of fiberglass is successively applied to the plywood, which is smoothed by hand and a wooden trowel until resin appears on its surface. After that, a layer of plywood is placed on the fabric, in which the side that will lie on the fiberglass is first smeared with resin. The spar assembled in this way is covered with tracing paper, a rail measuring 3100x90x40 mm is laid on it. Between the rail and the slipway with clamps located at a distance of 250 mm from each other, along the entire length of the rail, the stacked package is compressed until its thickness is equal to the upper edges of the mounting plates. Excess resin must be removed before it hardens. The spar blank is removed from the slipway after 2-3 days and processed to a width of 70 mm in the profile part, 90 mm in the butt, as well as a length between the ends - 3100 mm. A necessary requirement that should be met at this stage is to ensure the straightness of the surface of the spar, which forms the leading edge of the blade in the process of further profiling. The surface to which the ribs and foam core will be bonded must also be reasonably straight. It should be processed with a planer and always with a hard alloy knife or, in extreme cases, with bastard files. All four longitudinal surfaces of the spar blank must be mutually perpendicular. Pre-Profiling The marking of the spar blank is produced as follows. It is placed on the slipway and on the end face, front and rear planes, lines are applied that are 8 mm away from the surface of the slipway (~ Un max). At the end end, in addition, a complete blade profile is drawn using a template (Fig. 4) on a scale of 1: 1. Special precision in the manufacture of this auxiliary template is not required. On the outer side of the template, a chord line is applied and two holes with a diameter of 65 mm are drilled on it at the toe of the profile and at a point at a distance of 6 mm from it. Looking through the holes, combine the chord line of the template with the line drawn on the end face of the spar in order to draw a line on it that defines the profiling boundary. In order to avoid shifts, the template is attached to the end with thin nails, under which holes arbitrarily located along their diameter are drilled in it. The spars are processed along the profile with a simple planer (rough) and a flat bastard file. In the longitudinal direction, it is controlled by a ruler. After completing the processing, the ribs are glued to the rear surface of the spar. The accuracy of their installation is ensured by the fact that a chord line is applied to them during manufacture, which is aligned with the chord line printed on the rear plane of the spar blank, as well as by visual verification of the straightness of their location relative to the auxiliary template. It is again attached for this purpose to the end face. The ribs are located at a distance of 250 mm from each other, with the first being set at the very beginning of the spar profile or at a distance of 650 mm from the end of its butt part. Assembly and processing of the blade After the resin has hardened, foam plates are glued between the ribs, corresponding to the profile of the rear part of the blade, cuts are made along the protruding ends of the ribs in the rail forming the trailing edge. The latter is glued on resin to the ribs and foam plates. Next, rough processing of foam plates is carried out, the curvature of which is adjusted to the curvature of the ribs, and excess wood is removed from the lath to form a trailing edge with some allowance for subsequent precise processing according to the main template (Fig. 5). The basis of the template is first made with an allowance of 0,2-0,25 mm for the UV and UN values indicated in the template in order to obtain a profile smaller than the final size for gluing with fiberglass. When processing the blade using the main template, its lower surface is taken as the base. For this purpose, the straightness of its generatrix is verified with a curved ruler at a distance Xn = 71,8 mm, where Yn = 8,1 mm. Straightness can be considered sufficient if in the middle of a ruler 1 m long there is a gap of no more than 0,2 mm. Then, guide rails made of hard wood or duralumin 500 mm high are attached to the long sides of a well-aligned duralumin plate measuring 226x6x8,1 mm. The distance between them for the upper half of the main template should be equal to the width of the blade, or 180 mm. The latter is laid on a slipway on 3 - 4 linings, the thickness of which is equal to the thickness of the fixture plate, and pressed with clamps. Due to this, the straightened plate can move between the slipway and the lower surface of the blade along the entire length in a rectilinear plane, which ensures the stability of the blade thickness and the correspondence of its surface to a given profile. The upper surface of the blade can be considered machined if the upper half of the template moves along its entire length without a gap along the profile and at the points of contact of the template with the guides. The lower surface of the blade is checked with a fully assembled template, both halves of which are rigidly connected together. The upper and lower surfaces are profiled using bastard files with a coarse and medium notch, and the depressions and irregularities are sealed according to the template with ED-5 resin putty mixed with wood flour, and again filed according to the template. Blade pasting The next operation is pasting the profile and butt parts of the blades with fiberglass 0,1 mm thick in two layers on ED-5 resin. Each layer is a continuous fiberglass tape, which is superimposed with its middle on the leading edge of the blade. The main requirement that must be observed in this case is that after the fabric is well saturated with resin, the excess resin must be carefully squeezed out with a wooden float in the transverse direction from the front edge to the back so that air bubbles do not form under the fabric. The fabric should not tuck or wrinkle anywhere to avoid unnecessary thickening. After pasting the blades, they are cleaned with sandpaper, and the trailing edge is brought to a thickness close to the final one. Also check the profile of the toe of the spar. For now, this is done using the main template with some allowances, as indicated above, to ensure the quality of the profiling of the upper and lower surfaces.
The main template is brought to the required size and with its help the profile is finally adjusted using putty, and the lower surface of the blade is again taken as the basis, for which, using a curved ruler, the straightness of its generatrix is again checked at a distance Xn = 71,8 mm from the toe. After making sure that it is straight, the blade is placed on the slipway with the bottom surface down on linings 42 mm high (this value is the rounded difference between the height of the lower half of the template and Un = 8,1 mm). One of the linings lies under the butt part of the blade, which in this place is pressed against the slipway with a clamp, the rest along the blade at arbitrary distances from each other. After that, the upper surface of the blade is washed with acetone or a solvent and covered along the entire length with a thin layer of ED-5 resin putty and tooth powder of such density that it is easily distributed on the surface and does not flow down along the curvature of the profile (consistency of thick sour cream). A firmly fastened main template slowly and evenly moves along the blade with a chamfer forward along the movement so that its edge rests all the time on the horizontal surface of the slipway. Removing excess putty on the convex areas of the profile and leaving the right amount of it in the depressions, the template thus ensures the finishing of the profile. If it turns out that the cavities in some places have not been filled, then this operation is repeated after applying a thicker layer of putty on them. Excess putty should be periodically removed when it begins to hang from the leading and trailing edges of the blade. When performing this operation, it is important to move the template without distortion and perpendicular to the longitudinal axis of the blade, moving it non-stop in order to avoid uneven surfaces of the blade. After allowing the putty to reach full hardness and smoothing it slightly with sandpaper, the final puttying operation is repeated on the lower surface, using pads 37 mm high. Blade finish Having made the blades, they are treated with sandpaper of medium grit, paying special attention to the formation of the toe of the profile, washed with acetone or solvent and covered with primer No. 138, except for the place where the trimmer is attached (Fig. 6). Then all the irregularities are sealed with nitro putty, making sure that no excessive thickenings form on the profiled surfaces. The final finishing work, consisting in the careful removal of excess putty with water-resistant sandpaper of different grain sizes, is carried out in accordance with the advancement of the closed template along the surfaces of the blade without excessive pitching and gaps (no more than 0,1 mm). After gluing the blades with fiberglass 0,1 mm thick and before they are covered with soil, on the butt of the blades on the top and bottom of the ED-5 resin, oak or ash plates measuring 400x90x6 mm are glued, which are cut so that the blades acquire an installation angle enclosed between the chord and horizontal plane and equal to 3°. It is checked using a simple template (Fig. 7) relative to the front surface of the butt, as well as controlling the parallelism of the surfaces formed in this case from below and above the butt. This completes the formation of the butt of the blade, and it is pasted over with 0.3 mm fiberglass on ED-5 resin to make the blade airtight. The finished blade, except for the butt, is painted with nitro enamel and polished. For advice on determining the actual position of the center of gravity of the blades, their balancing and mating with the hub, read the following issues of the magazine. Assembly and adjustment We have considered the technological process of manufacturing the rotor blades of an autogyro. The next step is balancing the blades along the chord, assembling and balancing the main rotor along the radius of the blades. The accuracy of the installation of the latter depends on the smooth operation of the main rotor, otherwise increased unwanted vibrations will occur. Therefore, the assembly must be taken very seriously - do not rush, do not start work until all the necessary tools, fixtures are selected and the workplace is prepared. When balancing and assembling, you must constantly control your actions - it is better to measure seven times than to fall at least once from a small height. The process of balancing the blades along the chord in this case is reduced to determining the position of the center of gravity of the blade element.
The main purpose of necessitating blade chord balancing is to reduce the tendency for flutter-type vibrations to occur. Although these oscillations are unlikely to occur in the described machine, they must be remembered, and when adjusting, every effort should be made to ensure that the CG of the blade is within 20 - 24% of the chord from the nose of the profile. The NACA-23012 blade profile has a very small displacement of the center of pressure (CP - the point of application of all aerodynamic forces acting on the blade in flight), which is within the same limits as the CP. This makes it possible to combine the lines of the CG and the CP, which practically means that there is no pair of forces that cause the rotor blade to twist. The proposed design of the blade provides the required position of the CG and CP, provided that they are manufactured strictly according to the drawing. But even with the most careful selection of materials, compliance with the technology, a weight discrepancy may occur, in connection with which balancing work is performed. It is possible to determine (with some allowable errors) the position of the CG of the manufactured blade by making the blades with an allowance at the ends of 50-100 mm. After the final filing, the allowance is cut off, a tip is placed on the blade, and the cut element is balanced.
A blade element is placed on a trihedral, horizontally located prism with its lower surface (Fig. 1). Its sectional plane along the chord must be strictly perpendicular to the edge of the prism. By moving the element of the blade along the chord, its balance is achieved and the distance at the profile toe to the edge of the prism is measured. This distance should be 20-24% of the chord length. If the CG goes beyond this maximum limit, an anti-flutter weight of such a weight must be hung on the profile nose at the end of the blade so that the CG moves forward by the required amount. The butt of the blade is reinforced with overlays, which are steel plates 3 mm thick (Fig. 2). They are attached to the butt of the blade with caps with a diameter of 8 mm and sunken rivets on some kind of glue: BF-2, PU-2, ED-5 or ED-6. Before installing the pads, the butt of the blade is cleaned with coarse sandpaper, and the pad itself is sandblasted. The parts to be glued, that is, the butt of the blades, linings, holes for the caps and the caps themselves, are degreased and thoroughly lubricated with glue. Then the caps are riveted and rivets are placed (4 pieces for each lining). After this operation, the blades are ready for marking for installation on the hub. The main rotor of a gyroplane (Fig. 3) consists of two blades, a bushing, a propeller axis with rolling bearings, a horizontal hinge bearing housing, and a deflection angle limiter for the main rotor axis. The sleeve consists of two parts: a U-shaped truss and a bottom plate (Fig. 4). It is desirable to make a farm from a forging. When making it from rolled products, special attention must be paid to ensuring that the direction of the rolled metal is necessarily parallel to the longitudinal axis of the truss. The same direction of rolling should be on the bottom plate, which is made from a sheet of D16T grade duralumin 6 mm thick. The farm is processed according to the operation in the following order: first, the workpiece is milled, leaving an allowance of 1,5 mm per side, then the farm is subjected to heat treatment (hardening and aging), after which the final milling is performed according to the drawing (see Fig. 4). Then, with a scraper and sandpaper on the farm, all transverse risks are removed and a longitudinal stroke is applied. The axis (Fig. 5) is mounted on a pylon on two mutually perpendicular axes, which allow it to deviate from the vertical at specified angles.
Two rolling bearings are mounted on the upper part of the axle: the lower one is radial No. 61204, the upper one is angular contact No. 36204. The bearings are enclosed in a housing (Fig. 6), which, with its lower inner side, perceives in flight the entire load from the weight of the gyroplane. In the manufacture of the case, special attention should be paid to the processing of the mating of the side with the cylindrical part. Undercuts and risks at the interface are unacceptable. In the upper part, the bearing housing has two ears, into which bronze bushings are pressed. The holes in the bushings are processed with reamers after they are pressed in. The axis of the bushings must pass through the axis of rotation of the housing strictly perpendicular to it. Through the holes in the ears of the bearing housing and the bushing, which are pressed into the cheeks of the truss, a bolt passes (Fig. 7), which is a horizontal hinge of the main rotor of the gyroplane, relative to the axis of which the blades perform flapping movements. The angle of deviation of the axis and, accordingly, the change in the position of the plane of rotation of the disk are limited by a plate fixed on the pylon (Fig. 8). This plate does not allow the main rotor to deviate in excess of the allowable angles that provide controllability of the gyroplane in pitch and roll. Authors: B.Barkovsiky, Yu.Rysyuk
▪ Bicycle cart for two surfers
The existence of an entropy rule for quantum entanglement has been proven
09.05.2024 Mini air conditioner Sony Reon Pocket 5
09.05.2024 Energy from space for Starship
08.05.2024
▪ Verbatim SSDs Verbatim Vi3000 and Vi560 S3 range ▪ Beats Electronics Powerbeats2 Wireless Headset ▪ Satellite-controlled mushroom picking
▪ site section Tone and volume controls. Article selection ▪ article Write only when you can't stop writing. Popular expression ▪ article Chebrets. Legends, cultivation, methods of application ▪ article Dynamics - a second life. Encyclopedia of radio electronics and electrical engineering
Comments on the article: Igor Everything is fine, but 1 mm aviation plywood can no longer be found.
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
We recommend interesting articles Section 
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page