2015 Designer's Notebook - 4

Engineering Application and Web Tension Information
Clutch Sizing:

Clutch or Brake Placement

Maximum torque required = 2.4 lb-ft
Minimum torque required = 0.4 lb-ft

Application Data:

- 265) = 509 watts
Slipwatts = 2.4 lb-ft (1750
7

Rewind a material with constant tension
Tension = 40 lb

NOTE: Tentative selection would be a C-3A

Full roll diam. = 3 feet

Notice that the heat dissipation required has not changed,
but it looks like a smaller clutch can be used. The major
disadvantage is in the ability to control tension at the
rewind roll. Now, a 1 lb-ft change in torque through the
clutch will result in a 25 lb-ft change in torque at the roll.
Relating this change to a change in tension at the core of
the roll, the tension change due to 1 lb-ft in clutch torque
is 100 lbs of tension change! This situation could result in
stability problems when trying to control tension.

Core diam. = 0.5 feet
Velocity = 100 fpm

Calculating Requirements at the roll:
Torque (max) = Tension x Radius (full roll)
Torque (max) = 40 lb x (3/2 ft) = 60 lb-ft
Torque (min) = T x R (core) = 40 lb (0.5/2 ft) = 10 lb-ft
fpm = 10.6 rpm
RPM (full roll) = 100
(3 ft)π

Conclusion: Whenever possible, place the clutch as close
to the load as possible.

RPM (core) = 10.6 (3/0.5) = 63.6 rpm

Use the C-100, Case 1

Taper Tension

Case 1: Clutch is directly coupled to the rewind roll
RPM1
1.0 HP
1750 rpm
Motor

RPM2
25:1
Speed
Reduction

Tq 1

In taper tension winding, two factors control the torque
level. First, the torque must be increased in proportion to
roll radius to provide constant tension, and second, at the
same time the torque must be modified to decrease the
tension as the roll builds. As a result of this, the actual
peak torque requirement may occur at some intermediate
point in the roll. The point of peak torque is determined
by the percent of taper desired, and by the diameter ratio
of the core to full roll. In the examples below, we see
graphs of constant tension (0% taper), 50% taper tension,
and 67% taper tension. These graphs are for a 3 inch core
to a 15 inch OD, with 100 lbs starting tension.

RPM3
Clutch

Roll

Tq 2

Tq 3

RPM1 = 1750
RPM2 = 70 rpm
RPM3 = 63.6 to 10.6 rpm
Tq 1 = 3 lb-ft
Tq 2 = 75 lb-ft
Tq 3 = 10 to 60 lb-ft

Control

Slipwatts: Tq (max) (RPM in7- RPM out) =
60 lb-ft (70 - 10.6) = 509 Watts
7
Therefore you should choose a C-100
NOTE: In this case a 1 lb-ft change in torque through
the clutch will result in a 1 lb-ft change in torque
at the roll.

Torque (lb-ft)

Clutch Sizing: Maximum torque required = 60 lb-ft
Minimum torque required = 10 lb-ft

RPM2

50.0

25.3

37.5

19.0

25.0

50% taper
6.3

0

0
0

3

6

9

12

15

Diameter (in)

Tq 1

25:1
Tq 2

Roll
Tq 3

Control
RPM1 = 1750
RPM2 = 1590 to 265 rpm
RPM3 = 63.6 to 10.6 rpm

Torque (lb-ft)

Clutch

10.2
PEAK

5.1

Tq 1 = 3 lb-ft
Tq 2 = 0.4 to 2.4 lb-ft
Tq 3 = 10 to 60 lb-ft

Engineering Application and Web Tension Information

0
0

3

6

9

Diameter (in)

3

6

9

12

NOTE: The torque requirement and
the peak torque point changes for
each change in taper tension.
Drives, however, must be sized for
constant tension, as this is the
most demanding situation from a
torque or power standpoint.

15.3

67% taper

0

Diameter (in)

25.4

RPM3

PEAK

12.7

0% taper

20.3

1.0 HP
1750 rpm
Motor

4

31.65

12.5

Case 2: Clutch is placed between the motor and the
speed reducer.
RPM1

62.5

12

15

15



Table of Contents for the Digital Edition of 2015 Designer's Notebook

Table of Contents
2015 Designer's Notebook - Cover1
2015 Designer's Notebook - Cover2
2015 Designer's Notebook - Table of Contents
2015 Designer's Notebook - 2
2015 Designer's Notebook - 3
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2015 Designer's Notebook - Cover3
2015 Designer's Notebook - Cover4
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