Page 166 - The Tribology Handbook

B2 Roller chain drives

Table 2.2 Application factor f,

Characterisfics of driver
Smoofh Slighf Moderate
running shocks shocks
Driven machine Electric motors. Internal combustion Internal combustion
characferisfics Steam and gas engines with 6 cyls. or engines with less than
turbines. more with mechanical 6 cyls. with mechanical
Internal combustion coupling. coupling.
engines with Electric motors with
hydraulic coupling. frequent starts.
(2+ per day)
Smooth Centrifugal pumps and compressors. I .o 1.1 1.3
running Printing machines. Paper calenders.
Uniformly loaded conveyors. Escalators.
Liquid agitators and mixers. Rotary driers. Fans.
.Ifoderufe Pumps and compressors (3+ Cyls) I .4 1.5 1.7
shocks Concrete mixing machines.
Non uniformly loaded conveyers.
Solid agitators and mixers.
Heaiy Planers. Excavators. Roll and ball mills. 1.8 1.9 2.1
shacks Rubber processing machines. Presses and shears.
I & 2 cy1 pumps and compressors.
Oil drilling rigs.
Factorf, takes account of any dynamic overloads depending on the chain operating conditions. The value of factorf, can be
chosen directly or by analogy using Table 2.2.

Table 2.3 Tooth factor f2 for standard wheel The tooth factor f2 allows for the choice of a smaller
sizes diameter wheel which will reduce the maximum power
capable of being transmitted, since the load in the chain
will be higher.
Tooth factorh is calculated using the formula
15 1.27
17 1.12 19
19 1 .o h=-
21 0.91 ZI
23 0.83
25 0.76 (Note that this formula arises due to the fact that selection
rating curves shown in Figure 2.1 and Figure 2.2 are those
for a 19 tooth wheel).

Recommended centre distances for drives
3 1 5 3 1 1; 1; 1; 2 2; 3
-
Pitch (in) s 2 8 4
(mm) 9,525 12,70 15,875 19,05 25,40 31,75 38,lO 44,45 50,80 63,50 76,20
______ ~~______
~ ~~
Centre
Drttance (mm) 450 600 750 900 1000 1200 1350 1500 1700 1800 2000
Chain length calculation Selection of wheel materials

To find the chain length in pitches (L) for any con- Choice of material and heat treatment will depend upon
templated centre distance of a two point adjustable drive shape, diameter and mass of the wheel.
use the following formula:-
(y)2 Piniodwheel Steady Medium impulsive Highhly impulsive

z, -+ z, 2c x P
+
+
Length (I.) = - Up to 29T EN8 or EN8 or 9 hardened EN8 or 9 hardened
-
2 P C EN9 and tempered or and tempered or
case-hardened case-hardened
The calculated number of pitches should be rounded up to mild steel mild steel
a whole number of even pitches. Odd numbers of pitches 30T and C.I. Mild steel Hardened and
should be avoided because this would involve the use of a over meehanite tempered steel
cranked link which is not recommended. or case-hardened
If a jockey, or tensioner sprocket is used for adjustment mild steel or flame-
purposes, two pitches should be added to the chain length hardened teeth
(L).
Cis the contemplated centre distance in mm and should
generally be between 30-50 pitches. e.g. for a 1; P chain Through hardened EN9 should be oil quenched and
C = 1.5 X 25.4 X 40 = 1524 mm. tempered to give a hardness of 400 VPN nominal.
B2.2