Calculation of inertia ratio (I R ) Calculate the inertia ratio (I R ) I R = I L /I M I L = Inertia of the load at the DISCO output shaft I M = Inertia of the motor rotor or input inertia (see chart)
DISCO Input Inertia (I M )
I M (in
2 ./lbs.)
HP 1/4 1/2 1 2 3 5 7 ¹⁄₂ 10
DISCO DK002 DK004 DK007 DK015 DK022 DK037 DK055 DK075
2.68 4.05 9.24
15.62 23.18 51.15
Refer to the “DISCO Input Inertia” chart for inertia guidelines for all DISCO units, including free input types.
102.30 131.20
DISCO Inertia Guidelines
Classification Inertia Ratio (I R )
Caution for Selection
Low Inertia
Less than 1 1 - 4 4 - 15
None Start a maximum of one time per hour, or select one size larger DISCO.* Select one size larger DISCO, and choose a reducer combination that allows the DISCO to run in the higher rpm range.* Contact U.S. Tsubaki, PTUC Division
Medium Inertia High Inertia
Very High Inertia
Above 15
*Slow Starting: Precautions may be necessary to avoid overloading the DISCO. One effective measure is to insert a powder coupling or fluid coupling between the variable speed drive and the load. In addition, start the DISCO at the lowest output rpm.
Input shaft speed check Faster input shaft speed yields more efficient operation. The maximum input is 1800 rpm. If the input rpm is low, it may be difficult to change the speed of the DISCO. Please contact U.S. Tsubaki when the input is below 100 rpm.
Allowable overhung load/allowable thrust load 1. Overhung Load When a sprocket, gear, or pulley is mounted on the high speed or low speed shaft of the DISCO, an overhung load is applied. Refer to the “Table of Standard Characteristics” (pages D55~D56) for the allowable overhung load. The value is given for mounting in the center of the shaft length.
Load Connection Factor (C f )
Type of Connection
Factor
Sprocket/Chain Gear/Pinion Toothed Belt/Pulley V-Belt/Pulley Flat Belt/Pulley
1.00 1.25 1.50 2.00 2.50
T • C f • L f R
Allowable Overhung Load (lbs.) ≥
T = Required torque (in./lbs.) C f = Load connection factor L f = Load location factor R = Pitch radius of the sprocket, gear, etc. (in.)
Load Connection Factor (L f )
I/Q L f
0.25 0.8
0.38 0.9
0.50 1.0
0.75 1.5
1.00 2.0
Confirm the overhung load.
2. Thrust Load Refer to the “Table of Standard Characteristics” (pages D-55~D56) of the selected DISCO to confirm that the thrust load is within the design limits. Thrust load is a force acting axially along the shaft.
D-80
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