POWER TRANSMISSION SYSTEMS

• Mechanical power can be transmitted from one shaft to another by using four methods– Belt drive– Rope drive– Chain drive– Gear drive

• The shaft from which power is transmitted is called driver shaft and the shaft to which power is transmitted is called driven shaft

BELT DRIVE1. A belt is a looped strip of flexible material, used to

mechanically link two or more rotating shafts.

2. They may be used as a source of motion, to efficiently transmit power, or to track relative movement. Belts are looped over pulleys.

3. In a two pulley system, the belt can either drive the pulleys in the same direction, or the belt may be crossed, so that the direction of the shafts is opposite.

TYPES OF BELTS

OPEN BELT DRIVE

• It is used with shafts arranged in parallel and to be rotated in same direction.

• The driver pulley pulls the belt from one side and delivers the same to the other side.

• Side where tension is more is called tight side and the other side is called slack side

CROSS BELT DRIVE

• It used with shafts arranged in parallel and to be rotated in opposite direction.

• At the point where belts crosses, it rubs against itself and wears.

• Shafts are placed at a minimum distance of 20b to minimize the wear.

Length of belt

CHAIN DRIVE

• It consists of an endless chain running over toothed wheel. Toothed wheel is called sprocket.

• The smaller sprocket is called pinion and the bigger one is called wheel.

• Based on application we can classify chains as

1) Power transmission chains

2) Pulling chainsUsed in elevators

3) Hoisting chains Used in lifting loads

CLASSIFICATION OF CHAINS

TYPES OF POWER TRANSMITTING CHAINS

1. ROLLER CHAIN

2. SILENT OR INVERTED TOOTH CHAIN

1 Outer plate 2 Inner plate 3 Pin4 Bushing 5 Roller

ROLLER CHAIN

• It consists of rollers, bushes, pins, inner plates and outer plates.

• The pin passes centrally through the bush and the roller surrounds the bush.

• The bush moves freely on the roller and the roller moves freely on the bush.

• Bushes are held together by outer plates.

• Rollers are held together by inner plates.

• To prevent the lateral movement of the outer plates the pin ends are hammered in the shape of a rivet head.

Inverted tooth chain

• It is employed when heavier loads are to be transmitted and maximum quietness is desired

GEAR DRIVE

• Gear is a term used to generally denote toothed wheels.

• For transmitting power one gear will be mounted on driving shaft and the other will be mounted on driven shaft.

• The teeth's of the gears will be meshed with each other

• The distance between the shafts must be sufficient to enable meshing of the gear tooth.

Gear materials

• For heavy duty – cast steel and alloy steel

• For corrosive environment – Non ferrous materials (phosphor bronze, nickel, manganese)

• The cheapest material – Grey iron

SPUR GEARIn this the teeth will be cut parallel to the shaft

Used to transmit power between parallel shafts