Motor Selection/
Drive Design
For the drive selection, several factors must be
considered, including the timing belt (especially the
allowable belt pull strength and required stiffness)
and the motor (especially the starting torque, the revolutions
per minute and the resulting performance).
FAdditional = additional loads from the application
FDrive = m · (a+g) + FN · 0.05 + 100 N + FAdditional
For timing belt selection:
Indicated FDrive < Fu
For motor selection:
Mreq =
nreq =
Preq =
With DPitch in m of timing belt pulley h = 50 too 75%
387
11
Notes on the
Load Specifications
For information about load specifications for track
roller assemblies, refer to the information beginning
on page 352.
Notes on the Load Specifications for Timing Belts
The standard timing belts used are PU (polyurethane)
with steel cord tension members. Other types,
including conductive belts, are available on request.
The maximum track roller assembly travel speed
of v = 10 m/s can be achieved using timing belts
with no reduction of the load capacities.
From a > 10 m/s2 onwards, the values must be
reduced by the usual load factors (e.g. without load
peaks s = 1 to high load peaks s = 2.5).
The allowable tension loads are based on a 0.4%
elongation of the timing belt.
The breaking strength of the belts is significantly
higher. The normal usable belt pull strength (Fu)
and required pretension (Fv) is approximately:
Fallowable = Fv + Fu with Fv = Fu
The usable starting torque results from the maximum
usable belt pull strength, of the engaged teeth
and the pitch diameter of the timing belt pulley.
The most important consideration is the required
driving force. As a simple starting point for the
calculations, the transition point from acceleration
to constant speed can be used.
Constant acceleration
(a = constant):
v = a · t = 2 · a · s
Constant speed (v = constant):
v =
Max. driving force:
FDrive = Fa + FRoll + FEmpty + FAdditional
Fa = m · (a+g)
with m = moving mass in kg
a = const. acceleration in m/s²
g = 10 m/s², for vertical travel
g = 0 m/s², for horizontal travel
FRoll = FN · μRoll
with FN = FG for horizontal travel
μRoll = 0.05 for lightly preloaded track roller
FEmpty = 50 to 100 N depending on the module
st
and pre-tension of the timing belt
FDrive · DPitch m
2 · h
depending on selected drive (gearbox, motor,
etc.)
Linear Units and Modules
v in m/s
Timing Belts AT 5-16 5M-15 8M-30
Fbreaking 3900 N 3600 N 14900 N
Fallowable 1200 N 1150 N 4000 N
Fv = Fu 600 N 575 N 2000 N
The values for the mk LZR modules are:
Timing belt AT 5-16 5M-15 8M-30
DPitch 41.4 mm 50.9 mm 71.3 mm
Z 26 32 28
MDrive 12 Nm 15 Nm 70 Nm
v · 60
DPitch m· p
FDrive · v
h