Transmit rotary power between shafts

1
Belts and Chains

• Transmit rotary power between shafts
• Flexible power transmission elements
• center distance can be adjusted

2
Belt Drives

• Good for high speeds (2500 - 7000 fpm) and low
  torques.
• Uses friction to transmit power

Velocity Ratio
3
V-Belt Size

• Size selected based on hp rpm

3V
5V
8V
4
V-Belt Length

• To avoid belt fatigue and vibrations, the center
  distance should be
• D2 lt C lt 3(D1 D2)
• Belts are available in standard lengths

or
where
5
Belt Selection

• 1. Select belt based on power service factor
• 2. Select driver sheave to achieve desired linear
  velocity
• 3. Select driven sheave based on ratio
• 4. Determine required belt length
• 5. Determine the number of belts required
• We will neglect secondary correction factors
  (for now)

6
Example

• Select a v-belt drive

AC Motor
25 hp 870 rpm
Target 310 rpm
Hammer Mill
7
Chain Drives

• Good for low speeds (600 - 1500 fpm) and high
  torques.
• Has positive engagement of sprocket teeth into
  chain links

8
Chain Size

• Size selected based on hp rpm

9
Sprocket

• Integer number of teeth (N)
• Pitch diameter (D)

10
Chain Length

• To avoid excessive sag and fatigue stresses, the
  center distance should be
• 30p lt C lt 50p
• Chain length must be an integer multiple of the
  pitch

or
both expressed in pitches
11
Chain Selection

• 1. Select driver sprocket size (Ngt17)
• 2. Select chain pitch size based on power
  service factor
• 3. Select driven sprocket based on ratio
• 4. Determine required chain length (number of
  links)
• 5. Specify lubrication
• We will neglect secondary correction factors
  (for now)

12
Example

• Select a chain drive

AC Motor
25 hp 310 rpm
Target 160 rpm
Hammer Mill