these are mainly use when a large amount of power is to be transmitted from driver pulley to driven pulley when these pulleys are 8 meter apart.these are basically used in workshop,factories,where the large amount of power is transmitted.when the very large amount of power is being transmitted from one place to another place one rope is not sufficient so in that case we use number of rope to transmitting the power from one place to another.
Gear is used transmit the power from one shaft to another shaft or also gears can increase or decrease the speed or power according to the user requirement.
earlier we use cylinders or discs to transmitting the power but at high power transmission there is losses in power when we use cylinders or discs.but in modern way to increase the power transmission efficiency recesses or projections are provided over the periphery of the cylinders or discs to produce the Gears.
classification of gears
when shafts are intersecting
1.straight bevel gears
2.spiral bevel gears
when the shafts are skew
When the shaft s neither parallel nor intersecting …is known as skew assembly shafts
Advantage of spur gears
1.they are easy to install
2.they have high power transmission.
3.velocity ratio is constant.
4.they are reliable than the belts because gear does not slip like as belts.
5.power transmission range is about 50000 kW.
Disadvantage of spur gear
1.they are more expensive than the belt drives.
2.they can only be used for limited center distance.
3.they make noise during high speed performance.
Application of spur gear
metal cutting machine
rack and pinion mechanism
in this type the teeth are inclined with the axis of rotation of the gear.they are use where the power transmitted between two parallel shaft similar as the spur gear.
rubber and plastic industry
clay working machinery
compressors and in oil industry.
1.more costly than spur gear.
2.they have axial component(thrust force) along the rotation axis of the rotation.so they requires more reliable
Rack and Pinion
pinion is the small gear which is mash with a rack .rack is a gear which has infinite radius .rack and pinion assembly is used to transform the rotation motion of the pinion into the linear motion of the rack.
rack and pinion gearing is mostly use in rack railway.rack railway is the railway to overcome the steep grade railway. steep grade railway is the railway which include slope up and slope down railway track . so to overcome these difficulty maximum traction is require which is provided by rack and pinion assembly.
A picture is shown below to understand the rack railway system.