NORD Drivesystems B1000 - Manual (Page 65)

www.nord.com A63 G1000 – Subject to Change Without Notice
INTRODUCTION
EXAMPLE for Helical-worm gearmotor:
A coiler operates 16 hours/day with 300 cycles/hour
with a calculated m
af
= 2.5. Ambient temperature is
120ºF and the unit operates 18 minutes per hour.
From the chart, fi nd 300 cycles/hour and follow the
axis vertically up until you intersect curve B. From the
intersection point, move horizontally left to fi nd the
service factor f
B
= 1.5 based on 16 hours/day opera-
tion.
The service factor f
B
for helical-worms must be modi-
fi ed for the ambient temperature factor f
B1
and duty
cycle factor f
B2
.
The combined service factor
f
Bcombined
= f
B
x f
B1
x f
B2
To fi nd the ambient temperature factor f
B1
use the
following chart based on ambient temperature.
To fi nd the duty cycle factor f
B2
use the following
chart based on how many minutes per hour the unit
is running.
In this example,
f
Bcombined
= (f
B
= 1.50) x (f
B1
=1.30) x (f
B2
= 0.90) = 1.76
When selecting worm gear reducers, multi-thread
(multi-start) worms must be used where shock load-
ing exists and where the driven machine may back-
drive the gearbox for short periods. Multi-thread
worms have z
1
(number of threads) greater than or
equal to 2.
m
af
≤ 0.25 all numbers of worm threads (z
1
) are possible
m
af
≤ 3.00 z
1
≥ 3 is recommend
m
af
≤ 10.00 z
1
≥ 6 is recommend
Refer to the worm reducer selection pages in this cat-
alog (pages and fi nd the any ratio with z
1
≥ 3. Then
refer to the gearmotor selection pages and choose a
gearmotor with a service factor of 1.76 or greater.
Engineering
NORD
Service Factor
Temper
atur
e F
a
c
tor f
B1
Ambient Temperature °F
1.4
1.3
1.2
1.1
1.0
50 68 86 104 122 32
1.0
0.9
0.8
0.7
0.6
0 12 24 36 48 60
Run Time Minutes/Hour
Dut
y C
y
cle F
a
c
tor f
B2