Worm gearing . remely doubtful if a suffi-cient number of examples were taken whether this differencewould as an average exist at all. ^ The Brown & Sharpe experiments referred to have recently (Nov., 1912)been confirmed by a very careful test on a Daimler worm driven axle,carried out by the National Physical Laboratory, London, of which areport has been published by the Daimler Motor Car Co. of Coventry,England. CHAPTER VISTRENGTH OF WORM-WHEEL TEETH The behavior of a worm wheel, considered as a structure, isexactly analogous to that of a spur wheel; that is to say, thestresses upon the teeth
Worm gearing . remely doubtful if a suffi-cient number of examples were taken whether this differencewould as an average exist at all. ^ The Brown & Sharpe experiments referred to have recently (Nov., 1912)been confirmed by a very careful test on a Daimler worm driven axle,carried out by the National Physical Laboratory, London, of which areport has been published by the Daimler Motor Car Co. of Coventry,England. CHAPTER VISTRENGTH OF WORM-WHEEL TEETH The behavior of a worm wheel, considered as a structure, isexactly analogous to that of a spur wheel; that is to say, thestresses upon the teeth have precisely similar effects in theirtendency to shear off the teeth, and therefore, apart from thespecial nature of worm gear and the effects of rubbing, whichhave to be provided against by special proportioning of theteeth, it becomes necessary to design them from this point ofview in the first instance, afterward modifying the form of theteeth if necessary to suit the other considerations of the Fig. 12. The stresses in the worm wheel caused by the tangentialpressure between it and the worm are limited, not by the horse-power of the motor but by the maximum tractive resistancebetween the car wheels and the road, thus V R (28) The tooth of the worm wheel is a cantilever on which the loadw is applied at a point near the center of the tooth on the pitchline pi (Fig. 12). 34 STRENGTH OF WORM-WHEEL TEETH 35 Let Z = length of thread of worm per . revolution through 360 = angle of worm circumference subtended by worm ;l = actual length of-tooth. P T =-- thickness of tooth on pitch line = — Then >l = ^ (29) The length of the cantilever k is the dedendum of the toothwhich may be taken as .3683P. Let a = permissible stress in metal, say 7000 lb. per squareinch. Then the safe load applied to the cantilever = W = — (where Z = modulus of the section) (30) K and ^^T ^^^^ If x = safe load on tooth in pounds ^6^360^^ (32) X
Size: 2128px × 1174px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublishernewyo, bookyear1916
