# MECHANICAL ENGINEERING Subject name: Design of Transmission Elements Course code

MECHANICAL ENGINEERING

Subject name: Design of Transmission Elements Course code: 11ME401

Course co-ordinator: Poliraju Tentu

Note: Data books are allowed

Part-B

Q no Sub Qno Question Comp

Level Cognitive level

2 i A shaft running at 500rpm carries a pulley 100 cm diameter which drives another pulley in the same direction on with a speed reduction of 2:1 by means of ropes. The drive transmits 250 HP angle of groove is 400. The distance between pulley centers is 200cm. the coefficient of friction between rope and pulley is 0.2. The rope weights 1.2Kg/m and has safe allowable stress of 175 N/mm2. It is recommended that initial tension in the rope should not exceed 800N. Find no. of ropes required and rope diameter. Also the length of the rope. C1 apply

ii A v-belt of 6cm2 cross section has a groove angle of 400 and angle of lap of 1500, µ=0.1. The mass of the belt per meter run is 1.2 kg. The maximum allowable stress in the belt is 850 N/m2. Calculate horse power that can be calculated at speed of 30m/s. C1 apply

iii A rope pulley is designed to transmit 30KW. Diameter of pulley 360mm. speed= 120rpm, angle of groove=450,angleof lap on smaller pulley= 1700, µ=0.27, number of ropes = 10, mass of rope = 55C2 Kg/m, working tension of rope is limited to = 125 C2 KN where C is circumference of rope in m. find 1) initial tension 2) diameter of each rope C1 apply

iv A flat belt drive is required to transmit 10KW from a motor running at 1000rpm. The belt is 15mm thick and has mass density of 0.001 gm/mm3. Permissible tensile stress for the belt material is 2.5 N/mm2. Diameter of the driving pulley is 250mm where as speed of driven pulley is 367 rpm. Driving and driven shafts are 1.75m apart. The coefficient of friction between belt and pulley may be taken as 0.25. Determine width of the belt for safe working. C1 apply

v An open belt system is transmitting 10KW power. Driving pulley of the diameter 200mm and driven pulley of diameter 480 mm. center distances between pulleys is 2m. Maximum stress in the belt is not to exceed 2.2MPa. Thickness of the belt is 8mm. determine breadth and length of the belt. Given that density of belt material = 950Kg/m3, µ = 0.3, driving pulley is rotates at 1000rpm. Neglect bending stress in the belt. C1 apply

vi A V- belt operates on two sheaves having pitch diameters of 250mm and 800mm. The groove angle of the sheaves is 36° and the contact angle of of the small sheave is 140°. The maximum allowable belt load is 900N and the V- belt mass is 0.523 kg/m. The smaller sheave rotates at 1150 rev/min, and 26 kW is to be transmitted. For a coefficient of friction of 0.2, how many V-belts should be used, assuming each one takes its proportional part of the load? C1 apply

vii A flat belt 8mm thick and 100mm wide transmits power between two pulleys, running at 1600m/min. the mass of the belt is 0.9 Kg/m. the angle of lap in the smaller pulley is 1650 and the coefficient of friction between the belt and pulleys is 0.3. if the maximum permissible stress in the belt is 2MPa. Find

Maximum power transmitted

Initial tension in the belt

C1 apply

viii A V-belt transmits 20KW from a 250 mm pitch diameter sheave to a 900 mm diameter pulley. The centre distance between the two shafts is 1000 mm. the groove angle is 400 and the coefficient of friction for the belt and sheave is 0.2 and the coefficient of friction between the belt and flat pulley is 0.2. the cross-section of the belt 40mm wide at top, 20mm wide at bottom and 25mm deep. The density of the belt is 1000Kg/m3 and the allowable tension per belt is 1000N. Find number of belts required. C1 apply

ix

A V-belt is driven on a flat pulley and a V-pulley. The drive transmits 20KW from a 250mm diameter V-pulley operating at 1800 rpm to a 900 mm diameter flat pulley. The center distance is 1 m, the angle of groove 400 and µ = 0.2. if density of belting is 1110 Kg/m3 and allowable stress is 2.1 MPa for belt material, what will be the number of belts required if V-belt having 230 mm2 cross-sectional area used. C1 apply

x A belt 100 mm wide and 10 mm thick is transmitting power at 1000 m/min. the net driving tension is 1.8 times the tension on slack side. If the safe permissible stress on the belt section in 1.6 MPa, calculate the maximum power that can be transmitted at this speed. Assume density of the leather as 1000 Kg/m3. Calculate the absolute maximum power that can be transmitted by this belt and the speed at which this can be transmitted. C1 apply

3 i In a 50mm long journal bearing arrangement the clearance between the two at concentric condition is 0.1mm. the shaft is 2mm in diameter and rotate at 3000rpm. The dynamic viscosity of the lubricant used is 0.001 Pa.s and the velocity variation is linear. Considering the lubricant to be Newtonian, calculate the frictional torque the journal has to overcome and the corresponding power loss. C2 apply

ii In a 50mm long journal bearing arrangement the clearance between the two at concentric condition is 0.1mm. the shaft is 2mm in diameter and rotate at 3000rpm. The dynamic viscosity of the lubricant used is 0.001 Pa.s and the velocity variation is linear. Considering the lubricant to be Newtonian, calculate the frictional torque the journal has to overcome and the corresponding power loss. C2 apply

iii The following data is given for a 3600 hydrodynamic journal bearing:

Journal diameter = 100mm

Bearing length = 100mm

Radial load = 5-KN

Journal speed = 1440rpm

Radial clearance = 0.12mm

Viscosity of lubricant = 16cp

Minimum film thickness

Coefficient of friction

Power lost in friction

C2 apply

iv A journal bearing is loaded with a bearing pressure of 1.5 MPa. The journal diameter and length both are 50mm and it rotates at 600rpm. The heat is dissipated from the surface at rate of 12 J/m2/sec/0C. The bearing housing is 10times the projected area. If the coefficient of friction is 0.0015, determine the surface temperature of the bearing? Note that there is no artificial cooling.

A journal bearing is proposed for a steam engine. The load on the journal is 3KN, diameter 50mm, length 75mm, speed 1600rpm. Diametrical clearance is 0.001mm ambient temperature 15.50C. oil SAE 10 is used and the film temperature is 600C. Determine

The heat generated

The heat dissipated

Take absolute viscosity of SAE 10 at 600C = 0.014Kg/m-s C2 apply

v A full journal bearing of 50mm diameter and 100mm long has a bearing pressure of 1.4 N/mm2. The speed of the journal is 900 rpm and the ratio of journal diameter to the diametrical clearance is 1000. The bearing is lubricated with oil whose absolute viscosity at the operating temperature of 750 may be taken as 0.011Kg/m-s. The room temperature is 350. Find

The amount of artificial cooling required

The mass of lubricating oilrequired, if the difference between outlet and inlet temperature of the oil is 100C. Take specific heat of the oil = 1850J/Kg/0C. Take heat dissipation coefficient as 280W/m2/0C

C2 apply

vi A shaft is supported as shown in fig. The weight of the pulley is 1000N and tensions in the belt in horizontal direction are 3000N and 1500N on tight and slack side respectively. Calculate dynamic load capacity for shaft diameter of 50mm. There is an axial thrust of 2000N. Life of bearing should be 5000hrs at 400 r.p.m ( take axial load factor X = 0.56, radial load factor Y = 1.5) C2 apply

vii a) Explain film wedge action in journal bearing with neat diagram

b) A bearing for an axial flowcompressor is to carry a radial load of 2.5KN and a thrust of 1.5KN. The bearing is used for 40hrs/week for 5 years. The speed of the shaft is1000 rpm. And diameter 50mm. Calculate dynamic load capacity. X = 0.56, Y = 1.4 C2 apply

viii A shaft made of steel receives 7.5KW at 1440 rpm. A pulley mounted on the shaft has a diameter of 0.4m and ratio of belt tensions is 3.5. the teeth on gear of 250mm pitch circle diameter has a 200 involute profile. Shaft diameter at bearing B1 is 25mm and 20mm at bearing B2. What is life of bearing in hours? And find dynamic load carrying capacity. C2 apply

ix

Calculate dynamic load rating of a single row deep groove ball bearing for a radial load of 4000N and an axial load of 5000 N, operating at a speed of 1600 rpm. For an average of 5 years at 10 hours per day. Take radial factor as 0.56, axial load factor as 1 C2 apply

x A journal bearing is proposed for steam engine. The load on the journal is 3KN, diameter 50mm, length 75mm, speed 1600 rpm. Diametral clearance 0.001 mm. ambient temperature 15.50C. oil SAE 10 is used and film temperature is 600C. Determine the heat generated and heat dissipated. Take absolute viscosity of SAE10 at 600C = 0.014Kg/m-s C2 apply

4 i Figure shows a 32 mm wide band brake with the drum rotating in a clockwise direction. The brake utilizes a woven lining with dynamic coefficient of friction u = 0.55. All dimensions are shown in mm. The maximum force that the actuating mechanism can provide is F=300 N. (i) what angle of wrap (?) is necessary to obtain a brake torque of 800 Nm? (ii) What is the corresponding maximum lining pressure when the brake operates? C3 apply

Ii A torque of 300 N-m acts on the brake drum as shown in Fig. (a). If the brake band is in contact with the brake drum through 240° and the coefficient of friction is 0.25, determine the force ‘P’ applied at the end of the brakelever for the position as shown in fig. C3 apply

Iii A band brake is used to control the speed of a flywheel as shown. The coefficient of friction is 0.25. Determine the magnitude of the couple being applied to the flywheel, knowing that P = 65 N and that the flywheel is rotating counterclockwise at a constant speed. C3 apply

iv The band brake as shown in fig. has wrap angle of 2150 and cylinder radius 60mm. calculate the brake torque when coefficient of friction is 0.25. C3 apply

v For the band brake as shown in fig. the following conditions are given

d= 350mm, Pmax = 1.2MPa, µ = 0.25, and width b = 50mm. determine the following

The braking torque

The actuating force

Reactions at the hinge point ‘o’

C3 apply

vi The block type hand brake as shown in fig has a face width of 45mm. the friction permits maximum pressure of 0.6 Mpa and coefficient of friction of 0.24. Determine

i) Effort F

ii) Maximum torque

Heat generated if the speed of the drum is 100rpm and the brake is applied for 5sec. C3 apply

vii The double brakes is as shown in fig. has a torque of 250N-m at 600 rpm. The drum diameter is 200mm and the angle of contact of each shoe is 1200. The coefficient of friction may be assumed as 0.3. Determine spring force F. C3 apply

viii A simple band brake operates on a drum 0.6m in diameter rotating at 200 rpm. The coefficient of friction is 0.25 and the angle of contact of the band is 2700. One end of the band is fastened to a fixed pin and other end to 125mm from fixed pin. The brake arm is 750mm long

i) What is minimum pull necessary at the end of the brake arm to stop the wheel if 35KW is being absorbed?

ii) Find the width of 2.4mm thick steel band if the maximum tensile stress is not to exceed 55N/mm2 C3 apply

ix A band brake as shown in fig uses V-belt. The pitch diameter of the V-grooved pulley is 400mm. the groove angle is 450 and the coefficient of friction is 0.3. Determine the power rating. C3 apply

x The block brake as shown in fig. has the drum of diameter 750mm. a = 1m, b = 400mm, and c = 50mm. the coefficient of friction is 0.3. The torque capacity of the brake is 225 N.m. find the normal reaction and the force to be applied at the end of lever for clockwise and anticlockwise rotation of drum at 600rpm C3 apply

5 i A single plate friction clutch of both sides effective has 300 mm outer diameter and 160 mm inner diameter. The coefficient of friction o.2 and it runs at 1000 rpm. Find the power transmitted for uniform wear and uniform pressure distributions cases if allowable maximum pressure is 0.08 Mpa. C4 apply

ii A car engine develops maximum power of 15 kW at 1000 rpm. The clutch used is single plate clutch both side effective having external diameter 1.25 times internal diameter µ = 0.3. Mean axial pressure is not to exceed 0.085 N/ mm2. Determine the dimension of the friction surface and the force necessary to engage the plates. Assume uniform pressure condition. C4 apply

iii A single plate clutch transmits 25kw at 900 rpm. The maximum pressure intensity between the plates is 85KN/m2. The outer diameter of the plate is 360mm. both sides of the plate being effective & the coefficient of friction is 0.25.determine

a) Inner diameter of plates.

b) The axial force to engage the clutch. C4 apply

iv A single plate friction clutch of both sides effective has 300mm outer diameter and 160mm inner diameter. The coefficient of friction is 0.2 and it runs at 1000 rpm. Find the power transmitted for uniform wear and uniform pressure distribution cases if allowable maximum pressure is 0.08 Mpa. C4 apply

v A multi plate clutch must transmit 20KW of power without slipping at 4000rpm. The coefficient of friction is 0.28. the inner and outer diameters are 80 and 160mm respectively. The axial force applied to the plates is 460N.

Determine the number of plates required using

i) uniform pressure theory

ii) uniform wear theory C4 apply

vi A car engine develops maximum power of 15KW at 1000 rpm. The clutch used is single plate clutch both side effective having external diameter 1.25 times internal diameter. m = 0.3. mean axial pressure is not to exceed 0.085 Mpa. Determine the dimension of the friction surface and the force necessary to engage the plates. Assume uniform pressure condition. C4 apply

vii A multi plate clutch having effective diameter 250mm and 150mm to transmit 60KW at 1200 rpm. The end thrust is 4.5KN and m = 0.08. Calculate the number of plates assuming

i) Uniform wear theory

ii) Uniform pressure theory C4 apply

viii An engine developing 30KW at 1250 rpm is fitted with a cone clutch. The cone face has an angle of 12.50. The mean diameter is 400 mm, and coefficient of friction is 0.3. The normal pressure shouldn’t exceed 0.08Mpa. Design the clutch (find inner and outer radius of clutch plate). C4 apply

ix A cone clutch is to transmit 7.5 KW at 600 rpm. The face width is 50mm, mean diameter is 300mm and the face angle is 150. Assume m = 0.2, determine

i) The axial force necessary to hold the clutch parts together and

ii) The normal pressure on the cone surface C4 apply

x An engine developing 30KW at 1250 rpm is fitted with a cone clutch. The cone face has an angle of 12.50. The mean diameter is 400 mm, and coefficient of friction is 0.3. The normal pressure shouldn’t exceed 0.08Mpa. Design the clutch (find inner and outer radius of clutch plate). C4 apply

6 i A pair of carefully cut spur gears with 200 stub involute profile is used to transmit a maximum power 22.5 KW at 5 Hz. The velocity ratio is 1:2. The material used for both pinion and gear is medium cast iron whose allowable static stress is 60 MPa. The approximate centre distance may be taken as 600mm. determine module and face width of pinion and gear. Also check the gear for dynamic and wear loads

Take The dynamic factor as 80, load stress factor as 1.4. C5 apply

ii a) Explain “law of gearing” in gears with neat sketch

b) Derive “Lewis beam strength equation”. C5 apply

iii a) Write a note on interference in gears

b) A pair of Spur gers is to transmit 20KW when the pinion rotates at 300 rpm. The velocity ratio is 1:3. The allowable static stresses for the pinion and gear are 120 MPa and 100 MPa respectively. The pinion has 15 teeth and it’s face width is 14 times the module.

Determine a) module b) face width and c) pitch circle diameters for both pinion and gears. C5 apply

iv a) Derive an expression for beam strength of a spur gear tooth ( lewis equation) using standard notations.

b) In a pair of spur gears, the number of teeth on the pinion and the gear are 20 and 100 respectively the module is 6mm. calculate:

1. The centre distance

2. The pitch circle diameters of the pinion and the gear C5 apply

v In a spur gear drive the diameter of pinion is 80 mm and the centre distance 160 mm. the power to be transmitted is 4.5KW at 800 rpm of pinion. Using 200 full depth teeth and material for pinion a steel with permissible static stress of 200 MPa,and for gear a steel with permissible static bending stress of 150 MPa. Determine the necessary module and face width of the teeth using lewis equation. C5 apply

vi A pair of spur gears for a crane hoist drive is to be made of the following specifications:

200 full depth teeth, pinion static stress = 80MPa, gear static stress = 55MPa, pinion teeth = 20, gear teeth = 80. The pinion is to be transmitted at 5KW at 200 rpm.

What standard module and face width will satisfy these conditions

If the dynamic load for this pair is 3.8 KN determine whether or not the design is safe?

C5 apply

vii A spur drive is required to transmit 18KW power at 1440 rpm from motor to a low speed shaft with speed ratio of 4:1. The pinion has to be designed for the most compact size with 200stub teeth. Material for pinion is steel having strength of 100 MPa and the gear is cast iron with strength of 55 MPa. Determine circular pitch (????) and face width. C5 apply

viii A spur gear pair is used to transmit 18KW power at pinion spedd of 300 rpm. The pinion has 18 teeth of 200 pressure angle and it’s face width is 12.5 times the module. The required velocity ratio is 3:1. Take permissible static stress for pinion and gear as 120 MPa and 100 MPa. Design the gear using lewis equation. C5 apply

ix A spur gear drive is used to transmit a power of 5kW. The pinion rotates at 900 rpm and has diameter of 80 mm. the profile of the teeth is 200 full depth involute. Take material for pinion and gear having static stress of 200 MPa and 150 MPa. Calculate the module and width of the teeth. Take gear ratio as 3. C5 apply

x A 15kW and 1200 rpm motor drives a compressor at 300 rpm through a pair of spur gears having 200 stub teeth. The centre distance between the shafts is 400mm. the motor pinion is made of forged steel having an allowable static stress of 210MPa. While the gear is made of cast steel having allowable static stress of 140 MPa. from the strength stand point of view find,

i) Module

ii) Face width

iii) Number of teeth and pitch circle diameters of each gear

iv) Check gears for wear. Take endurance limit as 700MPa. C5 apply

7 i A pair of helical gears is to transmit 15KW. The teeth are 200 stub in diametral plane and have a helix angle of 450. The pinion runs at 10,000 rpm and has 80mm pitch diameter. The gear has 320mm pitch diameter. If the gears are made of cast steel having allowable static strength of 100 MPa. Determine the suitable module and face width from static strength considerations and check for dynamic and wear loads. Given ??es = 618MPa. C6 apply

ii A helical gear with 300 helix angle has to transmit 35KW at 1500 rpm with a speed reduction of 2.5. If the pinion has 24 teeth, determine the necessary module, pitch diameter and face width for 200 full depth teeth. Assume bronze material for both pinion and wheel.( static stress 84 Mpa) C6 apply

iii A single stage helical gear reducer is to receive power from a 1440 rpm 25 KW induction motor. The gear tooth profile is involute full depth with 200 normal pressure angle. The helix angle is 230 number of teeth on pinion is 20 and the gear ratio is 3. Both gears are made of steel with allowable stress of 90MPa and hardness 250 B.H.N. design helical gears from bending strength and wear strength point of view C6 apply

iv A pair of helical gears is to transmit 14 KW. The teeth are 200 stub and helix angle is 450. The pinion runs at 10,000 rpm and has 80mm pitch circle diameter. Wheel has 320mm pitch circle diameter. Both gears are made of cast steel of 140 MPa strength. Determine module and face width and also check for wear loads, given ??es = 618 MPa. C6 apply

v a helical cast steel gear with 300 helix angle has to transmit 35KW at 2000 rpm. If the gear has 25 teeth, find the necessary module and pitch circle diameters and face width for 200 full depth involute teeth. The static stress for cast steel may be taken as 100MPa. The face width may be taken as 3 times the normal pitch. The tooth form factor is given by the expression

C6 apply

vi Design a pair of helical gears to transmit 30kW power at a speed reduction ratio of 4:1. The input shaft rotates at 2000 rpm. Take helix and pressure angles equal to 25°and 20°respectively. The number of teeth on the pinion may be taken as 30. Assume the material and necessary parameters. C6 apply

vii A helical gear speed reducer is to be designed. The rated power of the speed reducer is 75 KW at a pinion speed of 1200 rpm. The speed ratio is 3 to 1. Determine the module, face width, number of teeth in each gear. The teeth are 200 full depth in the normal plane. Both gears are made of case hardened alloy steel of 350MPa strength. C6 apply

viii A helical cast steel gear with 300 helix angle has to transmit 20KW at 15Hz. If the gear has 24 teeth, determine module, pitch diameter and face width for 200 full depth teeth. Static stress for cast steel is 56MPa. The width of the face may be taken a 2.5 times the normal pitch. C6 apply

ix A helical cast steel gear with 300 helix angle has to transmit 35 kW at 1500 r.p.m. If the gear has 24 teeth, determine the necessary module, pitch diameter and face width for 200 full depth teeth. The static stress for cast steel maybe taken as 56MPa. The width of face maybe taken as 3 times the normal pitch. What would be the end thrust on the gear? The tooth factor for 20o full depth involute gear maybe taken as, 0.154-(0.912/TE) , where TE represents the equivalent number of teeth. C6 apply

x A pair of helical gears is used to transmit 15Kw. The teeth are 20ostub in diametral plane and have a helix angle of 45 degree. The pinion has an 80mm pitch diameter and operates at 10000RPM. The gear has a 320mm pitch diameter. If the gears are made of cast steel (??0=100MN/ m2), determine a suitable module and face width. The pinion is heat treated to BHN of 300 ( es =525MPa) and the gear has a BHN of 200 ( ??es = 350MPa). C6 apply

8 i Two cast iron bevel gears having pitch diameters of 80 mm and 100mm respectively and to transmit 11/4 KW at 1100RPM of the pinion. The tooth profiles are of 20 degree full depth. Take (Static stress=55MN/ m2)

(a) determine the face width and the required module from stand point of strength

(b) Check the design for wear , take modulus of elasticity of cast-iron as 84 Gpa and surface endurance limit as 630 MPa. C7 apply

ii A pair of cast iron bevel gears connects two shafts at right angles. The pitch diameters of the pinion and gear are 80mm and 100mm respectively. The tooth profiles of the gears are of 14 ½ 0 composite form. The allowable static stress for both the gears is 55 MPa. If the pinion transmits 2.75KW at 1100 rpm, find the module and number of teeth on each gear from the strength point of view and check the design for wear. Take surface endurance limit as 630MPa and modulus of elasticity for cast-iron as 84GPa. C7 apply

iii A 25 KW motor running at 1200 rpm drives a compressor at 660 rpm through mitre type bevel gear arrangement. The pinion has 30 teeth. The pressure angle of the teeth is 200 full depth involute. Both pinion and gear are made of heat treated cast iron having static stress of 190 MPa. Determine module and face width of the gears. Face width may be taken as 0.25 of slant height of pitch cone. C7 apply

iv A pair of straight bevel gears is required to transmit 10 KW at 500 rpm. From the motor shaft to another shaft at 250 rpm. The pinion has 30 teeth. The pressure angle is 200. If the shaft axes are at right angles to each other, find module, face width and slant height. The Gears are capable of withstanding a static stress of 60 MPa. The tooth form factor may be taken as 0.154-0.912/TE where TE is the equivalent teeth. Assume velocity factor as where v is pitch line velocity in m/s. The face width may be taken as ¼ th of the slant height of the pitch cone. C7 apply

v A 40KW motor running at 1440 rpm drives a compressor at 780 rpm through 900 bevel gear arrangement. The pinion has 24 teeth. The pressure angle of the teeth is 200. The working stress of the gears are given as 140 () MPa, where v is the pitch line velocity in m/min. the face width may be taken as ¼ th of the slant height of the pitch cone. Determine for the pinion, the module and face width. Also find slant height C7 apply

vi A triple threaded worm teeth of 6mm module and pitch circle diameter of 40mm. If the worm gear has 30 teeth of 141/20 and the coefficient of friction of the worm gearing is 0.05. find

The lead angle of the worm

Velocity ratio

Centre distance

Efficiency of the worm gearing

C7 apply

vii A worm drive transmits 20KW at 1200 rpm to a machine carriage at 75 rpm. The worm is triple threaded and has 50mm pitch diameter. The worm gear has 90 teeth of 6mm module. The tooth form is to be 200 full depth involute. Coefficient of friction may be taken as 0.01 for mating teeth. Calculate:

Tangent force acting on the worm

Axial thrust and separating force on worm, and

Efficiency of the worm drive

C7 apply

viii A double threaded worm drive is required for power transmission between two shafts having their axes at right angles to each other. The worm has 14 ½ involute teeth. The center distance is approximately 250mm. If the axial pitch of the worm is 30mm and lead angle is 230. Find:

Lead

Pitch circle diameters of worm and worm gear

Helix angle of the worm

Efficiency of the drive if the coefficient of friction is 0.05

C7 apply

ix Design 200 involute worm and gear to transmit 10KW with worm rotating at 1400 rpm and to obtain a speed reduction of 12:1. The distance between the shaft is 225mm. ( design of worm and design of worm gear) C7 apply

x Design a speed reducer unit of worm and worm wheel for an input of 1KW with a transmission ratio of 25. The speed of the worm is 1600 rpm. The worm is made of hardened steel and wheel of phosphor bronze for which the material combination factor is 0.7 N/mm2. The static stress for the wheel material is 56 MPa. The worm is made of double start and the centre distance between the axes of the worm and wheel is 120mm. The tooth form is to be 14 ½ involute. Check the design for strength, wear and heat dissipation. C7 apply