helicopter cable runs
The power cable runs from the State applied to various control channels. As a rule, it is duplicated, which increases the reliability of control and rigidity of the wiring. Cable runs with large strokes easier, it has less mass and dimensions than with rigid rods and rocking. As a self-locking actuators used Screws, located directly at the 'PB and stabilizer. These couples exclude loading cable runs alternating efforts. Furthermore, they provide a reliable fixation of the propeller blades and the stabilizer at a predetermined position. This facilitates the solution of problems relating to flutter.
To increase the stiffness of the control wiring without increasing the weight of its design can be achieved by the use of wire rope with a strong increase in strokes - 1000 mm or more. This accordingly reduces the load on the wiring.
Typically, the fuselage of the helicopter and wires made of different materials, so the pre-tension the cable affects the temperature change. With this in mind, Pq should be chosen with the maximum permissible negative
In order to design at positive temperatures wire tension was too great for helicopters like nevysotnyh JIA, we can recommend the seasonal adjustment of the tension cables (summer and winter). In this case, the maximum temperature difference will not exceed 60 ° C, and the change in cable tension will be determined by the formula.
General recommendation on the design elements of the wiring can be formulated as follows:
- Should strive to replace components operating in bending and torsion elements perceive only longitudinal forces. Especially avoid transmission via rocking motion (or sectors) connected with long shafts working in torsion. In addition, you must pay special attention to ensure the rigidity of mounting and wiring design of the helicopter - this is largely dependent on the overall stiffness of the wiring.
Friction in the wiring worsens its frequency response and handling characteristics. If more friction in the wiring, causing the need for the application to the arms control large enough for their breakaway forces, control of the helicopter may not be possible. Therefore, in the general technical requirements to the helicopter, depending on their type, specifies the maximum permissible friction force wiring given to the control lever.
The use of combined types of wiring due to the desire of designers to maximize the benefits of each of the species, as far as possible avoid the pitfalls of each. For example, the undisputed advantage of being hard wired to the reciprocating rods compared to cable runs is easy to use and less friction with repeated changes of direction on the rocker. At the same time, the cable runs on the straights it turns lighter and takes up less space, making it easier to layout. Cable runs easily duplicated. So frequently used hard wiring in places where conditions for ensuring the kinematic relations between the elements of the management system and layout of the helicopter need multiple connections and changing the direction of the route of wiring (for example, in the cockpit). The long straight sections without changing direction frequently performed using the cable runs.
Screw mechanism in the mechanical control
Winding mechanisms used to convert rotary motion into linear. They consist of a screw and nut, in which there is a mutual displacement of sliding friction (screw mechanisms) or rolling friction (ball screw mechanism).
The driving member is rotated in such arrangements, and the slave performs translational motion. The helical gears are mainly used and trapezoidal buttress thread with a small angle of the profile. The parameters are determined by the thread load and displacement of the output level. The efficiency of helical gears is determined by the conditions to ensure minimum wear of the mating surfaces of the screw and nut thread:
Screw transmission work in slozhnonapryazhennom condition. Their performance is determined not only by the condition of strength, but of conditions of stability for axial compression force F.
Ball mechanisms compared with screw have higher accuracy, stiffness, efficiency, withstand high speeds and loads, are subject to less wear and friction losses. Rolling friction in ball-screw mechanism is created when moving steel balls arranged between the screw and nut in special precision grooves of a closed loop in the bypass channel (A-A). Screws and nuts are made of stainless steel, and the sleeve is made of aluminum alloy. It should be noted that the ball mechanisms have a large mass and dimensions than the screw mechanism. This sometimes limits their use in the control mechanism.
Selecting bearing swivel control units
Bearings hinges control wiring work when rocking motion. Their durability determines the local wear of the raceways, known as "false brinelling".
The control rods used ball bearings light series gated tucked grease for the entire life of the bearing. Permissible bearing load management mechanisms, for which the total number of oscillations does not exceed the 100 000, and the amplitude of the oscillation is 20 ° or more, determined by the empirical formula
They can be used swiveling spherical plain bearings. By the material of plain bearings to meet the following requirements: minimum coefficient of friction and wear in the starting materials and steady modes; high heat resistance and thermal conductivity; The minimum coefficient of linear expansion; high stability properties; manufacturability and cost. The bearings control mechanisms used bronze, and composite materials.
Forecast durability of concrete bearing should be carried out taking into account the variety of factors acting on it, and all the complexity of their interaction (a kind of lubricant, load, speed, bearing installation method, the criterion of failure, and other factors).
Pressures on AG1 are dynamic. With this complexity of loading any recommendations on the calculation of bearing joints AP will inevitably be very provisional. Nevertheless, some of them help designers navigate the issues of selection of bearings for these critical units.
Allowable load bearing joints AP directly related controls are usually determined experimentally. For this purpose, special stands, allowing to create all kinds of forces acting on the AP in flight produce long-term tests.
Preserving the bearing units in the mechanisms of control
Used four types of seal bearing housing: Type A - continuous seal by rolling balls or rollers obkatyvanii without grooves in the housing; type B - sealing the solid rolling by obkatyvanii balls or rollers by a special groove in the body, b); Type B - without grooves seal by crimping punch; Type D - seal snap rings.
Terminations of type A is used for the shells from materials with a tensile strength of not more than 600 MPa type B - by up 600 1300 MPa. Sealing type B is recommended for cases of materials with a tensile strength up to 1300 MPa and is not recommended for cases of non-ferrous metals with elongation less than 4%. Termination type D is used for units with a periodically dismantled bearings and housings made of materials with maximum tensile strength of more than 1300 MPa.
To eliminate the jamming in the bearing assembly management mechanism used swiveling bearings. The width of the fork of the bearing assembly is chosen so that when turning the eyes to the angle + 5 ° excludes its contact with the inner surfaces of the fork. Necessary gap created washers or the inner ring of the bearing.
- Aviation and literature
- A uniform
- Military aviation
- Civil Aviation
- Helpful information
- The calendar
- Aviation and music
- game air
- Plane Crash
- Aviation and cinema
- Educational establishments
- Author's articles
- Assemblies and units of air equipment
- The probability of catastrophes
- Online Timetable
- The calculation of the distance
Best in the world of aviation