Inertia dynamics wrapspring_selection_specsheet
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This document provides instructions for selecting the appropriate wrap spring clutch or clutch/brake for an application. It defines different types of clutches and their functions. It outlines the steps to determine the required torque capacity, which includes calculating the system's reflected rotational inertia and drag torque. Formulas are provided for different clutch types. An example selection problem is shown. Technical specifications and parameters for various clutch models are presented in a chart.
![J-32
Step 1—Determine function and series
Function: Overrunning
Series: SC-“OR”
An overrunning/one way wrap spring clutch generates torque
in one direction. The output hub freewheels or overruns after
the input hub stops.
Function: Start/Coast
Series: SC-“SS”
The start/coast wrap spring clutch is used to engage and
disengage torque on a random basis. Once disengaged, the
output coasts to a stop.
Function: Single revolution and start/stop
Series: SC-“SR”, DCB, or DCB Super
Single revolution and start/stop wrap spring clutches give
precise nonaccumulating error single revolution cycling.
Multiple stops can also be achieved through special design.
The output hub does not override.
Step 2—Calculate system WK2
Reflect WK2 to the Clutch or Clutch/Brake
Step 3—Select model by torque capacity
Choose from “Operating Parameters Chart.” Torque capacity
must exceed calculated requirements and RPM.
Torque Formulas
Wrap Spring Products engage almost instantly; Clutches .003
seconds and Brakes .0015 seconds. The greater the load,
the tighter the spring grips the hubs. Unlike friction products,
wrap spring units are not forgiving. System Inertia must be
calculated for proper selection.
Clutches and Clutch-Brakes use different formulas to calculate
required torque because of response times and torque capa-bilities.
Use the formula that applies to your application.
Overrunning, One Way, and Start/Coast
Series SC-“OR” and SC-“SS”
System drag torque must be added to the calculated torque
for unit selection. Drag torque is the force required to initiate
motion that is measured with a torque wrench.
Where:
WK2 = System inertia reflected to clutch (lb.in.)
N = Speed of shaft where clutch is located (RPM)
Td = System drag torque (in-lbs)
Example
A small conveyor requires a random positioning clutch and
has a reflected system WK2 of 36 Lb-In2 at 95 RPM. The
measured drag torque is 5 in-lbs. The conveyor is on an
incline. A backstop device is necessary.
Torque = [(36 x 95) ÷ 1.1] + 5 = 313 in-lbs
The SC-6 “SS” clutch is chosen from the “Operating Param-eters
Chart.” It exceeds the torque requirements (500 vs. 313)
and is operating within its speed range. Start-Coast (SS) is
where the output is allowed to coast to a stop.
Single Revolution and Start/Stop
Series DCB, DCB Super and SC-“SR”
System drag torque must be subtracted from the calculated
torque for unit selection. Drag torque is the force required to
initiate motion that is measured with a torque wrench. It is
important that the DCB and DCB Super operate within their
speed range. They require a minimum amount of rotational
force to ensure that the clutch and brake springs unwind and
or wind on their hubs.
Where:
WK2 = System inertia reflected to clutch or
clutch/brake (lb.in.)
N = Speed of shaft where clutch is located (RPM)
Sf = Stopping factor (listed below)
5.55 for DCB and DCB Super
1.1 for SC-“SR”
Td = System drag torque (in-lbs)
Example
A machine requires a single position clutch-brake for placing
one shipping label on a box as it passes by. The labeling head
has a reflected system WK2 of 80.5 Lb-In2 at 140 RPM. The
measured drag torque is 3 in-lbs.
Torque = [(80.5 x 140) ÷ 5.55] - 3 = 2028 in-lbs
The DCB-8 Clutch-Brake is chosen from the “Operating
Parameters Chart.” It exceeds the torque requirements
(2500 vs. 2028) and is operating within its speed range.
Mounting
Dynacorp® wrap spring clutches and brakes are factory
assembled and tested before you receive them. All wrap spring
products are to be mounted where they are fully supported by
a shaft going completely through the unit, normally parallel
shaft applications. They are secured to the shaft by pinning
or by the use of keys. The shaft must be properly supported
(Figures A & B).
When assembling sprockets, gears, or pulleys to the unit’s
hub, the radial bearing load capabilities must not be
exceeded. Counterboring or bearing mounting of the
sprocket, gear, or pulley may be required (figures A & B).
The side plate on the DCB and DCB Super series are not to
be rigidly bolted to anything. It must be restrained from move-ment
by a torque pin or arm through one of the mounting
holes. This precaution will eliminate internal bearing damage.
Wrap Spring Product Selection
WK2 Torque (in lbs) = N + T11.1 d
WK2 N
Torque (in lbs) = – TS d f
Wrap Spring Clutches
Sold & Serviced By:
ELECTROMATE
Toll Free Phone (877) SERVO98
Toll Free Fax (877) SERV099
www.electromate.com
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Inertia dynamics wrapspring_selection_specsheet
- 1. J-32 Step 1—Determine function and series Function: Overrunning Series: SC-“OR” An overrunning/one way wrap spring clutch generates torque in one direction. The output hub freewheels or overruns after the input hub stops. Function: Start/Coast Series: SC-“SS” The start/coast wrap spring clutch is used to engage and disengage torque on a random basis. Once disengaged, the output coasts to a stop. Function: Single revolution and start/stop Series: SC-“SR”, DCB, or DCB Super Single revolution and start/stop wrap spring clutches give precise nonaccumulating error single revolution cycling. Multiple stops can also be achieved through special design. The output hub does not override. Step 2—Calculate system WK2 Reflect WK2 to the Clutch or Clutch/Brake Step 3—Select model by torque capacity Choose from “Operating Parameters Chart.” Torque capacity must exceed calculated requirements and RPM. Torque Formulas Wrap Spring Products engage almost instantly; Clutches .003 seconds and Brakes .0015 seconds. The greater the load, the tighter the spring grips the hubs. Unlike friction products, wrap spring units are not forgiving. System Inertia must be calculated for proper selection. Clutches and Clutch-Brakes use different formulas to calculate required torque because of response times and torque capa-bilities. Use the formula that applies to your application. Overrunning, One Way, and Start/Coast Series SC-“OR” and SC-“SS” System drag torque must be added to the calculated torque for unit selection. Drag torque is the force required to initiate motion that is measured with a torque wrench. Where: WK2 = System inertia reflected to clutch (lb.in.) N = Speed of shaft where clutch is located (RPM) Td = System drag torque (in-lbs) Example A small conveyor requires a random positioning clutch and has a reflected system WK2 of 36 Lb-In2 at 95 RPM. The measured drag torque is 5 in-lbs. The conveyor is on an incline. A backstop device is necessary. Torque = [(36 x 95) ÷ 1.1] + 5 = 313 in-lbs The SC-6 “SS” clutch is chosen from the “Operating Param-eters Chart.” It exceeds the torque requirements (500 vs. 313) and is operating within its speed range. Start-Coast (SS) is where the output is allowed to coast to a stop. Single Revolution and Start/Stop Series DCB, DCB Super and SC-“SR” System drag torque must be subtracted from the calculated torque for unit selection. Drag torque is the force required to initiate motion that is measured with a torque wrench. It is important that the DCB and DCB Super operate within their speed range. They require a minimum amount of rotational force to ensure that the clutch and brake springs unwind and or wind on their hubs. Where: WK2 = System inertia reflected to clutch or clutch/brake (lb.in.) N = Speed of shaft where clutch is located (RPM) Sf = Stopping factor (listed below) 5.55 for DCB and DCB Super 1.1 for SC-“SR” Td = System drag torque (in-lbs) Example A machine requires a single position clutch-brake for placing one shipping label on a box as it passes by. The labeling head has a reflected system WK2 of 80.5 Lb-In2 at 140 RPM. The measured drag torque is 3 in-lbs. Torque = [(80.5 x 140) ÷ 5.55] - 3 = 2028 in-lbs The DCB-8 Clutch-Brake is chosen from the “Operating Parameters Chart.” It exceeds the torque requirements (2500 vs. 2028) and is operating within its speed range. Mounting Dynacorp® wrap spring clutches and brakes are factory assembled and tested before you receive them. All wrap spring products are to be mounted where they are fully supported by a shaft going completely through the unit, normally parallel shaft applications. They are secured to the shaft by pinning or by the use of keys. The shaft must be properly supported (Figures A & B). When assembling sprockets, gears, or pulleys to the unit’s hub, the radial bearing load capabilities must not be exceeded. Counterboring or bearing mounting of the sprocket, gear, or pulley may be required (figures A & B). The side plate on the DCB and DCB Super series are not to be rigidly bolted to anything. It must be restrained from move-ment by a torque pin or arm through one of the mounting holes. This precaution will eliminate internal bearing damage. Wrap Spring Product Selection WK2 Torque (in lbs) = N + T11.1 d WK2 N Torque (in lbs) = – TS d f Wrap Spring Clutches Sold & Serviced By: ELECTROMATE Toll Free Phone (877) SERVO98 Toll Free Fax (877) SERV099 www.electromate.com sales@electromate.com
- 2. J-33 Operating Parameters Chart Static Maximum Minimum* Anti-Back Anti-Overrun Input Hub Maximum Torque Input Input Torque Torque Bearing Load Model In.-Lbs. Speed Speed In.-Lbs. In.-Lbs. Lbs. DCB-2 25 1800 300 10 10 7.5 DCB-4 125 1200 200 80 25 14 DCB-5 250 750 150 160 45 32 DCB-5 SUPER 250 750 150 125 125 40 DCB-6 500 500 100 300 300 63 DCB-6 SUPER 500 500 100 300 300 65 DCB-8 2500 300 50 600 600 300 DCB-8 SUPER 2500 300 50 600 600 300 SC-2 25 1800 None — — 8 SC-4 125 1200 None — — 14 SC-5 250 750 None — — 32 SC-6 500 500 None — — 63 SC-8 2500 300 None — — 300 * When operating below minimum speeds, system inertias may have to be increased for proper performance. Consult factory for application assistance. Inertia Conversion Chart Inertia of Steel Shafting (per inch of length or thickness) In order to determine the inertia of a rotating member (shaft, disc, etc.) of a material other than steel, multiply the inertia of the appropriate steel diameter from the chart at right by: Dia. WK2 Dia. WK2 Dia. WK2 (Inches) (Lb.-In.2) (Inches) (Lb.-In.2) (Inches) (Lb.-In.2) 1/4 0.00011 7 66.816 13 803.52 3/8 0.00055 7-1/4 77.04 13-1/4 858.24 1/2 0.00173 7-1/2 87.984 13-1/2 924.48 3/4 0.00864 7-3/4 100.656 13-3/4 995.04 1 0.0288 8 113.904 14 1068.48 1-1/4 0.072 8-1/4 128.88 14-1/4 1147.68 1-1/2 0.144 8-1/2 144 14-1/2 1229.75 1-3/4 0.288 8-3/4 162.72 14-3/4 1317.6 2 0.432 9 182.88 15 1404 2-1/4 0.72 9-1/4 203.04 16 1815.84 2-1/2 1.152 9-1/2 223.2 17 2314.08 2-3/4 1.584 9-3/4 252 18 2910.24 3 2.304 10 277.92 19 361.52 3-1/2 4.176 10-1/4 306.72 20 4433.76 3-3/4 5.472 10-1/2 338.4 21 5389.92 4 7.056 10-3/4 371.52 22 6492.96 4-1/4 9.072 11 407.52 23 7757.28 4-1/2 11.376 11-1/4 444.96 24 9195.84 5 17.28 11-1/2 486.72 25 10827.36 5-1/2 25.488 11-3/4 529.92 26 12666.24 6 36 12 576 27 14731.2 6-1/4 42.624 12-1/4 626.4 28 17036.64 6-1/2 49.68 12-1/2 679.68 29 19604.16 6-3/4 57.888 12-3/4 735.84 30 22452.48 Material Multiplier Bronze 1.05 Steel 1.00 Iron 0.92 Powdered Metal Bronze 0.79 Powdered Metal Iron 0.88 Aluminum 0.35 Nylon 0.17 Wrap Spring Clutches Sold & Serviced By: ELECTROMATE Toll Free Phone (877) SERVO98 Toll Free Fax (877) SERV099 www.electromate.com sales@electromate.com