Page 165 - The Tribology Handbook

Roller chain drives B2

SELECTION OF CHAIN DRIVES Driven Sprocket
Z7
The following selection procedure gives guidance for In-
dustrial applications for the selection of chain drives
comprised of roller chains and chain wheels conforming to
IS0 606.
Chain selected using this method will have a life expec-
tancy, with proper installation and lubrication, of 15 000
hours.

c
Basic information required Centre Distance P

In order to select a chain drive the following essential Z1 - No of teeth on drive sprocket
information must be known:- Z2 - No of teeth on driven sprocket
(a) The power, in kilowatts, to be transmitted. C - Centre Distance mm
(b) The speed of the driving a.nd driven shafts in rev/min. P - Chain Pitch mm
(c) The characteristics of the drive. i = Drive Ratio
(d) Centre Distance. L = Chain Length Pitches
From this basic information, the driver sprocket speed Table 2.1 Drive ratios i, relative to one, using
and selection power to be applied to the ratings charts, are preferred sprockets
derived.
No. of No. ojteeth on
teeth on drive sprocket Zl
driven
sprockel
z2 15 17 19 21 23 25

Step 1 Select drive ratio and sprockets 25 - - - - - 1 ,oo
38 2,53 2,23 2,OO i,80 1,65 1,52
57 3,80 3,35 3,OO 2,7I 2,48 2,28
Table 2.1 may be used to choose a ratio based on the 76 5,07 4,47 4,OO 3,62 3,30 3,04
standard wheel sizes available. 95 6,33 5,59 5,oo 4,52 4,13 3,ao
It is best to use an odd number of teeth combined with 114 7,60 6,70 6,OO 5,43 4,96 4,56
an even number of chain pitches.
Ideally, chain wheels with a minimum of 17 teeth Drive ratios can otherwise be calculated using the
should be chosen. If the chain drive operates at high speed formula
or is subjected to impulsive loads, the smaller wheels
should have at least 25 teeth and should be hardened.
It is recomimended that chain wheels should have a
maximum of 114 teeth.
For large ratio drives, check that the angle of lap on Z is
not less than 120". Step 3 Select drive

From the rating charts, Figure 2.1 and Figure 2.2, select
the smallest pitch of simple chain to transmit the SELEC-
TION POWER at the speed of the driving sprocket Z,.
This normally results in the most economical drive
selection.
Step 2 Calculate selection power Should the SELECTION POWER be greater than that
shown, then consider a multiplex chain selected from the
SELECTION POWER = Power to be transmitted X f, X ratings charts.
.h (kW) Chain manufacturers should be consulted if any of the
Wheref, andj; are given in Tables 2.2 and 2.3 following apply.
This selection power can then be used in Figure 2.1 and (a) More than 1 driven sprocket
Figure 2.2 to select a suitable drive arrangement (b) Power or speeds above or below chart
(c) When volume production is envisaged
(d) Ambient conditions other than normal
This section has been compiled with the assistance ofRenold Chains
B2.1