Adjustable Center Drives
Series 21 Standard V-Belt Drives: 3M
 
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3M - 2:1 Speed Ratio
H.P.: 1/4 Motor Speed: 1800 RPM
H.P.: 1/8 Motor Speed: 1200 RPM
series 21 dimensional drawing
A
1-21/32
B
1-1/2
C
1-1/4
D
3-1/8
E
1-7/8
L
2-7/16
Std. bore
1/2 | 5/8
keyway
1/8 | 3/16
bore depth
Through
max bore
3/4
belt size
A
max. p.d.
2.8
min p.d.
1.4
weight
1 lb.
Driven Speeds
Driven
Sheave
Pitch
Diameter
Belt vs Minimum Center Distance
1800 RPM Motor
1200 RPM Motor
A 26
A 31
A 35
A 38
A 46
A 55
A 68
A 80
A 85
A 96
A 105
Max.
Min.
Max.
Min.
1680
840
1120
560
3.0
9.1
11.6
13.6
15.5
19.1
23.6
30.1
36.1
38.6
44.1
48.6
1260
630
840
420
4.0
8.3
10.8
12.8
14.3
18.3
22.8
29.3
35.3
37.8
43.3
47.8
1008
504
672
336
5.0
7.4
10.0
12.0
13.5
17.5
22.0
28.5
34.5
37.0
42.5
47.0
840
420
560
280
6.0
6.5
9.1
11.1
12.6
16.7
21.2
27.7
33.7
36.2
41.7
46.2
720
360
480
240
7.0
8.2
10.2
11.8
15.8
20.3
26.9
32.9
35.4
40.9
45.4
630
315
420
210
8.0
7.2
9.3
10.9
14.9
19.5
26.0
32.1
34.6
40.1
44.6
560
280
373
186
9.0
6.1
8.3
9.9
14.0
18.6
25.2
31.2
33.7
39.3
43.8
504
252
336
168
10.0
7.2
8.9
13.1
17.7
24.3
30.4
32.9
38.4
43.0
458
229
305
152
11.0
12.1
16.8
23.5
29.5
32.1
37.6
42.1

WARNING: All open belt drives must be adequately guarded for personal safety during operation.