We know that the torque transmitted by the pinion,Īnd formative or equivalent number of teeth for the pinion, T E = T P / cos 3 α Thus the design will be based upon the pinion. cast steel), therefore the pinion is weaker. Since both the pinion and gear are made of the same material (i.e. Let m = Module in mm, and b = Face width in mm. Width from static strength considerations and check the gears for wear, given σes = 618 MPa. If the gears are made of cast steel having allowable static strength of 100 MPa determine a suitable module and face The teeth are 20° stub in diametral plane and have a helix angle of 45°. A pair of helical gears are to transmit 15 kW. Now using the Lewis equation for the pinion, we have tangential load on the tooth (or beam strength of the tooth), Since (σOP × yP) is less than ( σOG × yG), therefore the pinion is weaker.
#SPUR AND HELICAL GEAR DESIGN FULL#
We know that for 20° full depth involute teeth, tooth form factor for the pinion, We know that pitch circle diameter of the pinion, Find the power that can be transmitted from the standpoint of strength. The face width of both the gears is 90 mm. The pinion has 16 standard 20° full depth involute teeth of module 8 mm. The allowable static stresses for the bronze pinion and cast iron gear are 84 MPa and 105 MPa respectively. drives a cast iron spur gear at a transmission ratio of 4 : 1. A bronze spur pinion rotating at 600 r.p.m. We know that the radial load on the bearings due to the power transmitted,Ģ. Since the normal pressure between teeth is 175 N per mm of width, therefore necessary width of We know that the torque acting on the pinion, We know that number of teeth on the pinion, Since the nearest standard value of the module is 8 mm, therefore we shall take We know that minimum number of teeth on the pinion in order to avoid interference, Nearest standard module if no interference is to occurĭP = Pitch circle diameter of the pinion, and The load on the bearings of the wheels due to power transmitted.ġ. The nearest standard module if no interference is to occur ģ. Involute teeth of standard proportions (addendum = m) with pressure angle of 22.5° Permissible normal pressure between teeth = 175 N per mm of width. The following particulars of a single reduction spur gear are given : Gear ratio = 10 : 1 Distance between centres = 660 mm approximately Pinion transmits 500 kW at 1800 r.p.m. Manufacturing and designing cost of helical gears will be more as compared to spur gear designing and manufacturing cost.1.Power loss in case of helical gear train operation will be more as compared to spur gear train operation.One pair of mating helical gear will have less efficiency as compared to efficiency of mating spur gears of similar size.Therefore helical gear requires good quality of lubrication. There will be sliding movement between mating gear teeth in case of helical gear and heat generation will be more as compared to spur gear application.When a pair of helical gear meshes with each other, there will be creation of axial thrust load on gear due to helix angle of gear teeth and therefore gearbox designer has to select such bearings those are able to absorb and support this axial thrust load.There will be less wear and tear in case of helical gear during operation as compared to wear and tear in case spur gears operation as if we consider helical gears operation, load will be distributed between several teeth at any time and that is why there will be less wear and tear in operation of helical gears.Helical gears will have more capability to transmit load between two parallel shafts as compared to similar module and equivalent width of spur gears.Helical gears could be used to transmit the motion and power between two parallel shafts and also between two non parallel shafts.Helical gears are preferred for heavy load applications.Such gradual engagement of helical gear will provide the silent and smooth operation. As we have discussed in our previous post that in case of helical gear, engagement of helical gear teeth will be gradual and engagement will start from one end of a tooth of helical gear with the other tooth of mating helical gear and spread continuously throughout the tooth as gear rotates.