Typical Wichita clutch
and brake mounting
on a press
22Wichita Clutch 800-964-3262
Wichita Low Inertia Brakes increase tension control for
paper unwind stands.
Wichita Spring-Set
Air Release Brakes
insure accuracy and
high performance for
a metal shear.
P-1100-WC 1/12
Clutch sizes are affected by the
following variables:
Air Tube Disc Clutches and Brakes
Application Factors
1. Machines that operate under smooth
loads require smaller clutches. These
machines are driven by either
multi-cylinder high speed engines or
electric motors with reduced starting
current.
2. Drives that require high starting
current motors will require clutches
with sufficient torque to prevent
excessive slipping while starting.
3. Starting torque may be high, which
requires a fast clutch response time
to transmit the required torque; or,
extended clutch slip time is required
to protect the prime mover.
This chart gives application factors
ranging from light duty (the A group) to
extra heavy duty (the D group).
After initial usage is determined, see
4. Starting torques may be very low
compared to the normal torque,
which may result in the clutch not
being fully pressurized prior to the
time of full torque requirement. This
will cause the clutch to overheat from
slippage. Clutch inflation time in this
instance is very important.
5. Clutches on most machines are
designed to slip prior to damage
from shockloads. As a result, the
clutch may require periodic
main te nance; therefore, the clutch
should be located for easy access in
the power train.
Clutch es should also be located for
max i mum cooling air. In instances
“Selection Requirements” to com plete
the selection process. The in fla tion and
exhaust time should also be checked to
insure proper response.
where this is not pos si ble, forced air
cooling may be nec es sary for
extended clutch life.
6. Safe clutch operating speeds should
be maintained in product design.
Maximum Clutch Contact Velocity
FPM Material
(Recommended
6,000
9,000
upper limit for slip)
ductile iron
cast iron
12,000 steel
Dynamic balancing recommended when
peripheral speeds exceed 3500 FPM.
The maximum speeds shown are safe
op er at ing speeds based on years of
Wichita testing. Please do not exceed
these limits.
Application Guidelines
B
Field of Application Group A Group B Group C Group D
Pumps Centrifugal Reciprocating compressors Reciprocating compressors
compressors over 2 cylinders, one or two cylinders
centrifugal fans & blowers
Low Inertia and Very Low Inertia Clutches and Brakes
Very Low Inertia
Drive Plate Assembly
with Bonded or
Riveted Pads
Floating Plate
Grooved
Friction Disc
Demountable
Backplate
(Optional)
Hub
Ductile
Center Plate
Ring Shims
Multiple Spud
Airtube
Pressure
Plate
Airtube
Holding
Plate
Roto-Coupling
Spider
Operating Features
The Wichita Air-Tube Disc Clutch com bines
all the best features of the disc type clutch with
all the advantages of direct air engagement.
The simplest and most trouble-free method of
applying air pressure is through direct axial
pressure ap pli ca tion by com pressed air in a
special com po si tion full-circle tube.
Wichita Clutches engage smoothly without
noise, shock or impact and release com plete ly
in a fraction of a second. Extremely fast action
is possible because of the small volume of air
re quired.
Clutches may be slipped moderately to control
the acceleration rate.
When large inertia loads are powered from
electric motors, smooth, controlled slip starts
by Wichita Clutches can keep power demands
below the allowed max i mum.
Heat generated by controlled slipping or
high cycle rate operation is dissipated by
the cen trif u gal blower design of these units.
Wichita Low Inertia and Very Low Inertia
Clutches and Brakes are de signed to be
com plete ly free from effects of cen trif u gal
force and self energization.
Torque developed is in direct proportion to air
pressure ap plied.
These clutches and brakes interface well with
automated controls through simple air and/or
electric circuits.
Water cooled, copper disc clutches are
available for use when power trans mis sion
needs require excessive or con stant slipping
which demands higher heat
dis si pa tion.
Wichita Clutches operate perfectly when
teamed with Wichita Brakes in pro duc tion
situations requiring tension control, cyclic
duty, or positioning.
Wichita Brakes have the same outstanding
performance characteristics as Wichita
Clutch es.
24Wichita Clutch 800-964-3262
P-1100-WC 1/12
Air Tube Disc Clutches and Brakes
Low Inertia and Very Low Inertia Clutches and Brakes
Selection Requirements
The selection of a Low Inertia Brake is
based on:
1. Torque required to stop a load.
2. Friction area necessary to absorb
rotational energy.
3. Contact velocity of rotating discs.
4. Maximum bore capacity of unit.
Selection example
To properly select a Low Inertia Brake for
a controlled deceleration application, the
following information is needed:
As calculated, the torque required to stop the
load in 5 seconds is 14,547 lb.in. Wichita Low
Inertia Brakes are rated at 100 PSI.
This application has only 80 PSI available.
To determine the torque rating of a Low Inertia
brake at 80 PSI apply the following formula:
Application: Torque for a Low Inertia Brake
= Torque X Catalog Rated Pressure
Available Air Pressure
= 14,547 X = 18,183 lb.in.
100
80
Consult pages 26 and 36 for clutch and brake
spec i fi ca tions. A Low Inertia model 114 Brake
2
pro duc es 27,625 lb.in. torque at 100 PSI.
However, the bore capacity is 4.125 inches.
This application requires a 5 inch bore.
There fore, a Low Inertia 118 is to be
in ves ti gat ed.
Catalog Torque Rating = 64,500 lb.in.
@ 100 PSI
Maximum Bore Capacity = 5.25 in.
Catalog Swept Friction Area = 264 in.
2
Calculations show this application needs at
least 202 in.
2
to absorb the heat.
All of these ratings are acceptable for the given
application data.
Next, check contact velocity of rotating discs.
= Diameter of centerplate X RPM
3.82
B
P-1100-WC 1/12
Torque
25.5 x Stop Time
25.5 x 5
WR2x RPM
=
=
2.473 x 750
= 14,547 lb.in.
Using the above calculations, consult the
Low Inertia Specifications Chart on
pages 26 and 27.
=18" X 750
3.82
= 3,534 FPM
Standard material is sufficient up to 6,000 FPM
(see page 23). Balancing is recommended
above 3,500 FPM.
Therefore, a Low Inertia ATD-118 brake is
the optimum choice for this application.
A Spring-Set Air Release Brake is also
available (see page 58).
Note:
This application example is for pre lim i nary
sizing only. Contact a Wichita Sales Engineer
or the factory for final selection.
Clutch air pressure during inflation can
be closely estimated by the following:
Clutch pressure = P
(inflation)
1
1 – )PSI
1
u
Kt
(
e
This equation is accurate from 5% up
to 95% P
= Line pressure to clutch PSI
P
1
.
1
K and U = coefficients for specific
clutch and air pressure from
Spec i fi ca tion Table
e = Naperian base log
t
= Time at initiation of signal for
o
inflation sec.
t
= Time delay of air system – sec.
d
Clutch air pressure during exhaust
can be closely estimated by the
fol low ing:
Clutch pressure = (P
) (R) (E-t)vPSI
1
(exhaust)
R, E and V = coefficients for specific clutch
and air pressurefrom Spec i fi ca tion
Table
t
= Time to exhaust = E from
e
Spec i fi ca tion Table
t = Time variable – seconds. In the ex -
haust equa tion “t” cannot exceed
the value of “E” sec.
Shown are some of the air systems used
on Wichita clutches. These systems are
ac cept able for remote op er a tion where
clutch reaction time is not important.
Faster clutch re ac tion time is ac com
plished as in di cat ed in the
di a gram by lo cat ing the flow
control valve, if re quired,
and the so le noid valve as
close as possible to the
roto-cou pling. Where
clutches are located on long shafts, the
use of quick release valves on the clutch
will fa cil i tate faster clutch response.
A typical clutch-brake torque curve for
a single backshaft press (cyclic ap pli ca tion) would appear as shown below.
Time (sec.)
t
= time at which disengaged clutch
O
c
receives signal
t
= time of clutch en gage ment
C
c
= time of clutch full inflation
t
1
c
= time at which disengaged brake
t
O
B
receives signal
t
= time of brake engagement
B
c
= time of brake full exhaust
t
1
B
t2 = overlap time at which clutch and
brake are both engaged
28Wichita Clutch 800-964-3262
P-1100-WC 1/12
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