Formula Selection Method
1. Select Coupling Type
Refer to Page 5 and select the type of coupling to suit your application. If an application requires a special purpose
coupling, refer application details to the local Folk Representative.
2. Determine Service Factor or System Peak HP
A. For MOTOR, TURBINE or ENGINE driven applications, refer to Tables 1 and 2.
B. For BRAKE and HIGH PEAK LOAD applications, refer to Step 3 below.
3. Calculate Required Rating
The coupling hp per 100 rpm rating or torque rating must equal or exceed the application requirements. Determine
the required coupling rating using the formula in Step 3A and the applicable formula from Steps 3B and 3C. Use the
highest required rating to determine the coupling size in Step 4.
A. NORMAL SERVICE: HP per 100 RPM = (Transmitted HP x 100 x SF) / RPM
Transmitted hp equals the measured hp or if not available, the motor or turbine rated hp with the exceptions noted
below.
B. BRAKE APPLICATIONS: Use the brake hp in the above formula if it exceeds the prime mover hp rating.
C. REPETITIVE HIGH PEAK LOAD APPLICATIONS: Use one of the following applicable formulas for applications
using motors with torque characteristics that are higher than normal, applications with intermittent operation, shock
loading, inertia effects due to starting and stopping and/or system induced repetitive high peak torques. The "System
Peak Torque" is the maximum that can exist in the system.
a. For NON REVERSING SERVICE: Req'd Coupling Torque Rating = System Peak Torque
b. For REVERSING SERVICE: Req'd Coupling Torque Rating = 2.0 x System Peak Torque
4. Determine Coupling Size
A. Refer to Table 5 - Trace down the HP per 100 RPM column or the Torque Rating column to a figure equal to or in
excess of the highest calculated value in Step 3. Read coupling size at left.
B. Check shaft diameters against coupling maximum bores shown in Tables 9 thru 11 for the type of coupling selected.
If a larger bore is required, select a larger coupling.
C. Cheek the required speed against the allowable speed shown in Table 5 for the type of coupling selected. For Type
T50 Floating Shaft design, check the allowable speed from Table 8 on Page 17. If a higher speed is required, refer
application details to the local Folk Representative.
D. Cheek application dimension requirements against selected coupling type dimensions shown on Pages 10 thru 19.
Example:
Normal Load Method
Select a coupling to connect a 450 hp, 1170 rpm electric motor to the reducer high speed shaft of a manoeuvring
winch. Maximum shaft gap is .25" The motor shaft diameter is 3.500" with a keyway of .875" x .438". The reducer
high speed shaft diameter is 3.000" with a keyway of .750" x .375". The motor and reducer shaft extensions are each
6.00" long.
1. Select Coupling Type - To connect close coupled shafts (.25" maximum gap), the Type T10 or T20 coupling is the
proper selection. Type T20 is selected.
2. Determine Service Factor - From Table 1, the service factor is I.S.
3. Calculate Required Rating - Use the Normal Service Formula from Step 3A.
HP per 100 RPM = (Transmitted HP x 100 x SF) / RPM
HP per 100 RPM = (450 x 100 x 1.5) / 1170 = 58
4. Select Coupling Size - (A) From Table 5, the coupling size 1100T20 with a rating of 80 hp per 100 rpm. (B) From
Table the maximum bore with square key is 4.000". (C) From Table the allowable speed is 3250 rpm.(D)Dimensions
for the 1100T20 coupling shown on Page 11 satisfy the application requirements
Example:
Peak Load Method
Select a coupling for reversing service to connect a gear reducer low speed shaft to a runout mill table roll. The electric
motor rating is 50 hp at the base speed and the system peak torque at the coupling estimated to be 150,000 poundinches. Coupling speed is 77 rpm x the motor base speed. The reducer shaft diameter is 4.000" with keyway of 1.000"
x .500". The runout table roll diameter is 5.25 (with a keyway of 1.250" x .625". Maximum shaft gap is 7.00". The
motor and reducer shaft extensions are each 7.00" long.
1. Select Coupling Type - To connect a maximum shaft gap 7.00", the Type T35 is the proper selection.
2. Calculate Required Rating
a. NORMAL SERVICE FORMULA (Step 3A) - From Table 1, the service factor is 3.0
HP per 100 RPM = (Transmitted HP x 100 X SF) / RPM
HP per 100 RPM = (50 x 100 x 3.0) / 77 = 195
b. REVERSING SERVICE FORMULA (Step 3Cb)
Req'd Coupling Torque Rating = 2.0 x System Peak Torque or 2.0 x 150,000 lb-in. or 300,000 lb-in.
3. Determine Coupling Size - (A) From Table 5, coupling size 1130T with a rating of 254 hp per 100 rpm. For a torque
300,000 pound-inches, select the larger size coupling; 115( (B) The 1 ISOT35 shown on Page 15, has a maximum
"BE" dimension of 7.38". The shaft hub has a maximum bore 10.000" with one rectangular key (Table 10). The T hub
has maximum bore of 8.000" with one rectangular key (Table 9). (1 From Table 5, the allowable speed for the 1
150T35 is 1500 rpm (D) Dimensions for the 1150T35, shown on Page 15, satisfies the application requirements.
Table 5: Coupling Ratings & Allowable Speeds
Allowable Speeds # - rpm
Coupling
HP per
Torque Rating
T20 & T31, T35 &
Size
100 rpm *
(lb-in.) *
T10
T70
T50 @ T10/G82
1020T
.67
422
4500 6000
3600
--
1030T
1.90
1,200
4500 6000
3600
10000
1040T
3.17
2,000
4500 6000
3600
--
1050T
5.56
3,500
4500 6000
3600
9000
1060T
8.73
5,500
4350 6000
3600
--
1070T
12.7
8,000
4125 5500
3600
8200
1080T
26.2
16,500
3600 4750
3600
7100
1090T
47.6
30,000
3600 4000
3600
6000
1100T
80.0
50,500
2440 3250
2440
4900
1110T
119
75,000
2250 3000
2250
4500
1120T
175
110,000
2025 2700
2025
4000
1130T
254
160,000
1800 2400
1800
3600
1140T
365
230,000
1650 2200
1650
3300
1150T
508
320,000
1500 2000
1500
--
1160T
714
450,000
1350 1750
1350
--
1170T
952
600,000
1225 1600
1225
--
1180T
1,320
832,000
1100 1400
1100
--
1190T
1,750
1,100,000
1050
--
1200T
2,385
1,500,000
1050 1300
900
1200
900
--
1210T
3,175
2,000,000
820
--
--
--
1220T
4,290
2,700,000
730
--
--
--
1230T
5,555
3,500,000
680
--
--
--
1240T
7,140
4,500,000
630
--
--
--
1250T
9,520
6,000,000
580
--
--
--
1260T
11,900
7,500,000
540
--
--
--
* HP per 100 rpm and torque rating values for hubs with Taper Lock brushings differ from those shown above; refer to
table 13.
# Consult Factory for speeds higher than those shown.
@ Speeds shown above are for single Type T50 couplings; speeds for Type T50 Floating Shaft couplings are shown in
Table 8 on Page 17.
