Page 164 - The Tribology Handbook

61 Belt drives

FllTlNG AND TAKE-UP ALLOWANCES

Fiiing allowance (mm)

A 19-25
E 25-40
C 38-50
0 50-75

SPZ 12-20
SPA 20-25
SPB 25-30 I l l
SPC 40-50 Take-up fitting L = total belt length

J 8-20 Take-up allowance
L 22-30
M 38-80
2-3% L

2-3% L

P,mm = 3 10-16'
5 16-21
8 24-35
14 38-60
L P J 20 49-80
"For flanged pulleys. For unflanged
pulleys, 2-5 mm issufficient for all sections
0.03-0.05% L

DESIGNING MULTI-DRIVE SYSTEMS
For each driven shaft and the motor shaft, write down its
transmitted design kW, its rev/min R, its approximate arc
= kW; + kW3 of contact 8, its recommended A (from Figure 1.10) and
kW*, the accumulated kW, as illustrated.
Select belt section from the power rating charts for the
most severe combination at any shaft of kW* and n. For
speed reduction drives, the motor shaft will always be the
most severe.
Estimate the number of belts (or belt width) and belt
kWl .nlI el, hl tension as for a 2-shaft drive based on kW, n, d, A for the
motor pulley.
kW; = kW1
The resulting tension may not prevent slip on one or
more of the driven shafts. Check this by calculating, for
each driven shaft, i, and the motor shaft m, the quantities
fi and fm below. Select the largest ratio of fifm. If this is
greater than 1.0, increase the number of belts (or belt
width) and belt tension by this factor.
It may be advantageous to drive the shafts by separate
belts. The complexity may be such that a specialist should
be consulted, particularly if any 8 < 90" or if, for a
kW, , n, . em, hrn
synchronous belt, less than 6 teeth are in mesh on any
kWL = kW, pulley.

91.10