NORD Drivesystems B1000 - Manual (Page 54)

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INTRODUCTION
G1000 – Subject to Change Without Notice
Engineering
OHL & Thrust
d
o
y + x y + x
f + x f + x
OVERHUNG LOADS
Maximum values for output shaft loads are given in
pounds of radial capacity as shown in the gearmotor se-
lection pages under the F
R
column. Input shaft capacities
are given on pages 58 - 59 as F
R1
.
The listed maximum loads are
• to be applied at the midpoint of the shaft
• calculated in the least favorable loading direction
• without thrust loads.
Keeping the operational loads at or below the rated ca-
pacity will ensure bearing performance for approximately
5,000 hours of service or greater.
The permissible overhung load values listed are based on
the least favorable loading direction. For higher overhung
load values please contact NORD with the exact loading
direction and life requirements.
OHL CAPACITY FOR REDUCERS
If a C-face reducer or solid input shaft reducer is used, the
Gearmotor Selection pages should be used to determine
the maximum overhung load F
Q
. Assign the HP value of
the motor driving the system to the reducer. Turn to the
Gearmotor Selection pages and match the HP, gear unit
and ratio to one shown in the table. Select the OHL capac-
ity (F
Q
) from the appropriate column.
CALCULATING OHL
When an in-line coupling is mounted on a shaft to connect
power then no overhung load exists. However, if power
transmission components such as sprockets or sheaves are
mounted directly onto the shaft they will deliver a rotating
load at a right angle to that shaft. The effective overhung
load on that shaft will be determined as follows:
F
OHL
=
2 x T x f
z
Where:
F
OHL
= Calculated OHL on gearbox shaft [lb]
T = Load torque on shaft [lb-in]
d
0
= Pitch diameter of overhung component [in]
f
z
= Power transmission component factor
Table for f
Z
factor
Transmission
Component
Factor f
z
Notes
Gear 1.00 17 teeth or less
Gear 1.15 18 teeth or more
Chain Sprocket 1.40 13 teeth or less
Chain Sprocket 1.20 13 to 20 teeth
Chain Sprocket 1.00 21 teeth or more
Timing Belt Pulley 1.50
V-Belt Pulley 1.70
Flat Belt Pulley 2.50
After calculating OHL actual compare to the overhung
load capacity found in the tables.
F
OHL
≤ F
R
or F
R1
If F
OHL
exceeds the rated capacity (F
R
or F
R1
) of the speed
reducer, either heavy-duty bearings or a larger gearbox
must be selected.
LOAD NOT AT MIDPOINT OF SHAFT
If the load is not applied to the midpoint of the shaft, the
maximum overhung load capacity F
Q
or F
Q1
must be modi-
fi ed. The new permissible overhung load F
QX
or F
Q1X
must
be calculated at a point on the shaft (x) by
F
RX
=
F
R
x z
F
R1X
=
F
R1
x z
Shaft strength must also be considered by these equations:
F
RSS
=
c
F
R1SS
=
c
Where:
F
R
= permissible OHL from gearmotor tables [lb]
x = distance from shaft shoulder to the point
where the load is applied [in]
c = factor from table [lb-in]
f = factor from table [in]
y = factor from table [in]
z = factor from table [in]
F
RX
= new permissible OHL at ‘x’ distance from
output shaft shoulder [lb]
F
R1X
= new permissible OHL at ‘x’ distance from
input shaft shoulder [lb]
F
RSS
= output shaft strength capacity [lb]
F
R1SS
= input shaft strength capacity [lb]
After calculating the above the lower of the two will be
the adjusted permissible overhung load (OHL
adjusted
) at ‘x’
distance from the shaft shoulder and is compared to the
F
OHL
value.
F
OHL
≤ F
RX
Unit sizing with this method takes into consideration non-
midpoint Ioad location and ensures acceptable bearing
and shaft strength.
THRUST LOADS
Loads that are directed towards or away from the gear-
box aIong the axis of the shaft are considered to be AXIAL
loads. Commonly this loading is called THRUST. Output
shaft THRUST capacity (FA) can be found in the Gearmo-
tor Selection tables adjacent to the OHL values. Input shaft
capacity is given on pages 58 - 59 as F
A1
:
• Capacity shown is the lowest value of either a load
directed into or away from the unit.
• Loads cannot exceeded the values shown in the tables
• Capacity listed is for pure axial loads with no overhung
load. If loads are kept at or below the rated capacity,
reasonable bearing life can be expected. Contact
NORD for combination load or a more exact
examination of the application.