Tham khảo tài liệu 'manual gearbox design part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 66 Manual Gearbox Design surface which create vibrations and consequently noise. Hypoid gears are almost free from the problem of differences in these sliding motions and the teeth also have a larger curvature radius in the direction of the profile. Therefore the surface pressures are reduced resulting in less wear together with quieter running. Hypoid gears are as much as times stronger than a spiral bevel gear of the same dimensions and made in the same material. Certain limits must be applied to the teeth of hypoid gears so that the tooth proportions can be calculated in the same way as for spiral bevel gears. The offset must not be larger than one-seventh of the ring gear outer diameter and the tooth ratio must not be much less than 4 1. Within these limits the tooth proportions can be calculated in the same way as for spiral bevel gears and the radius of lengthwise curvature can be assumed in such a way that the normal module is a maximum at the centre of the tooth facewidth and stabilized tooth bearings are obtained. If these limits are exceeded . if the offset is larger or the ratio is smaller a tooth form must be selected which is better adapted to the modified meshing conditions. In particular the curvature of the tooth length curve must be determined with other points in view. The limits are only guidelines as it is impossible to account for other factors which are involved including a the pitch line speed of the gears b the lubrication of the gears c the loads that the gears have to cope with d the gear shafts and their mountings e the general conditions under which the gears are used The calculation of Gleason spiral bevels and hypoid gears has been covered by the author in the Gear Handbook Butterworth-Heinemann 1992 but in the following pages it is intended to give the calculations which both Klingelnberg and Oerlikon use to calculate the dimensions of their gear forms. Klingelnberg palloid spiral bevel gear calculations Basic conception .
