Tham khảo tài liệu 'gear noise and vibration episode 2 part 3', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 180 Chapter 10 frequency Fig Tuned damped vibration absorber response. Although it is possible in theory to use steel springs and oil damping this is rare due to sealing and tuning problems. The device needs careful tuning to the correct frequency and is in general only worthwhile if the auxiliary mass can be about 10 of the effective mass of the resonance and the original dynamic amplification factor Q of the resonance was greater than 8. The absorber can then reduce the Q factor to below 4. Copyright Marcel Dekker Inc. All rights reserved. Marcel Dekker Inc. 270 Madison Avenue New York New York 10016 Improvements 181 Untuned Lanchester dampers which use only mass and viscous damping will work over a range of frequencies but require greater mass and give much less damping so they are little used except for torsional engine vibrations which occur over a wide range of frequencies as speed varies. Production control options When trouble strikes and the customer s installation cannot be altered there is a tendency to panic and to halve all drawing tolerances on principle to make sure that all the gears are being made better. This is of course no help if it is a faulty gear design or installation and is very expensive to achieve. On the assumption that development has investigated permissible loaded . and found that it must be kept below say 4 pm at once-per-tooth there are several options available. The first is the obvious one to run a model and to see how tolerant the design is to errors of profile helix and pitch. This should give a good idea of the sensitivity of the design which could decide how tightly manufacturing tolerances should be specified. If these tolerances are not economically sensible then the choices are a alter the design to make it less sensitive if possible b greatly reduce tolerances or c manufacture scrap. Option b though often used is usually far too expensive. Option c deliberately catering for a percentage of scrap is guaranteed
