4.1.2 Coefficients Used in Selection

Multiple strand factor
In multiple strand power transmission chains, the loading is unequal across the width of the chain, therefore, the transmission capability is not a direct multiple of the number of chains. You must use a "multiple strand factor," which is shown in Table 4.1, to determine the correct value.
Service factor, Ks
The chain transmission capability is reduced if there are frequent or severe load fluctuations. You must apply the appropriate factor based on the type of machine or motors (Table 4.2).

**Table 4.1** Multiple Strand Factor
Number of Roller Chain Strands	Multiple Strand Factor
2	1.7
3	2.5
4	3.3
5	3.9
6	4.6

**Table 4.2** Service Factor
Type of Impact	Machines	Source of Power
		Electric Motor or Turbine	Internal Combustion Engine
		Electric Motor or Turbine	With Hydraulic Drive	Without Hydraulic Drive
Smooth	Belt conveyors with small load fluctuation, chain conveyors, centrifugal blowers, ordinary textile machines, ordinary machines with small load fluctuation.	1.0	1.0	1.2
Some impact	Centrifugal compressors, marine engines, conveyors with some load fluctuation, automatic furnaces, dryers, pulverizers, general machine tools, compressors, general work machines, general paper mills.	1.3	1.2	1.4
High impact	Press, construction or mining machines, vibration machines, oil-well rigs, rubber mixers, rolls, general machines with reverse or high-impact loads.	1.5	1.4	1.7

Chain speed coefficient, Kv; sprocket tooth coefficient, Kc
Adjust the transmission capability according to the chain speed and number of teeth in the small sprocket (Figure 4.6). The sprocket coefficient is labeled Kc.
Impact coefficient, K
This coefficient (Figure 4.7) is based on the inertia ratio of the driving machine and driven machine (ratio of I, ratio of GD²) and the amount of play in transmission equipment. When the inertia ratio is less than 0.2 or greater than 10, use the value of 0.2 or 10, respectively.

Figure 4.6 Speed Factor (Kv) and Sprocket Factor (Kc)

Figure 4.7 Shock Factor (K)

**Table 4.3** Unbalanced Load Factor (Ku)
Lifting Strands	Factor
2	0.6
4	0.36

Unbalanced load coefficient; Ku
When you use two or four chains in a hanging application or shuttle traction setup, the tension of each chain is not equal. This must be accounted for by using the coefficient found in Table 4.3. The example assumes an unbalanced load ratio between two chains of 60/40 (percent) [i.e., 60 + 40 = 100 percent].