Adjustable Center Drives
Series 21 Standard V-Belt Drives: 4M
 
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4M - 2:1 Speed Ratio
H.P.: 1/2Motor Speed: 1800 RPM
H.P.: 1/3Motor Speed: 1200 RPM
series 21 dimensional drawing
A
1-7/16
B
1-9/32
C
1-11/16
D
4
E
2-3/16
L
2-1/4
Std. bore
1/2 | 5/8 | 3/4
keyway
1/8 | 3/16 | 3/16
bore depth
Through
max bore
3/4
belt size
A
max. p.d.
3.7
min p.d.
1.85
weight
2.5 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.
1665
832
1110
555
4.0
7.6
10.1
12.1
13.6
17.6
22.1
28.6
34.6
37.1
42.6
47.1
1332
666
888
444
5.0
6.8
9.3
11.3
12.8
16.8
21.3
27.8
33.8
36.3
41.8
46.3
1110
555
760
370
6.0
5.9
8.5
10.5
12.0
16.0
20.5
27.0
33.0
35.5
41.0
45.5
951
475
634
317
7.0
7.6
9.6
11.1
15.2
19.7
26.2
32.2
34.7
40.2
44.7
832
416
554
277
8.0
6.6
8.7
10.2
14.3
18.8
25.4
31.4
33.9
39.4
43.9
740
370
493
266
9.0
7.7
9.3
13.4
18.0
24.5
30.6
33.1
38.6
43.1
666
333
444
222
10.0
8.3
12.5
17.1
23.7
29.7
32.2
37.8
42.3
605
302
403
201
11.0
11.5
16.2
22.8
28.9
37.4
36.9
41.4
555
277
370
185
12.0
10.5
15.3
21.9
28.0
30.5
36.1
40.6

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