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Why does the working load
limit of a Clutcher decrease when hanging on an angle?
This is a common question when it comes to wire rope hanging systems. At first glance, it would seem that as long as the load is the same weight, the angle it’s being hung from wouldn’t matter. That is not the case.
When we talk about the working load limit for a Clutcher, we’re talking about the actual load, or tension, that’s being applied to the wire rope. When hanging on an angle, the wire rope is simultaneously being pulled down and to the side. The combination of these forces increases the amount of tension in the wire rope and Clutcher.
Since gravity is always the same, the force pulling down is always the same. As the angle of the wire rope gets larger and closer to vertical, the force pulling to the side increases. Looking at the illustration below, the downward forces and sideward forces form the legs of a right triangle with the wire rope as the hypotenuse. If the weight of the load and the angle are known, the tension on the wire rope and Clutcher can be calculated.
The wire rope tension is calculated using the cosine of the angle to calculate the tension on the wire rope.
cos (Ø) = Load weight / wire rope tension
or
Wire rope tension = Load weight / cos (Ø) |
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For example, if we had a 200lb load that was evenly supported at two points, each point would be supporting 100lbs. This would be the load weight. Suppose the wire rope is hung at a 45° angle. To calculate the wire rope tension;
Wire rope tension = Load weight / cos (Ø)
Wire rope tension = 100lbs / cos (45°)
cos (45°) = 0.707
Wire rope tension = 100lbs / 0.707 = 141.4 lbs
If a CL10 Clutcher was being used for this and the two supports were vertical (at 0°), it wouldn’t be a problem. But, if it is hanging on a 45° angle, that would put it over its rated Working Load Limit.
As an aid on your next project, the following chart gives the reduced working load limits for at each angle. An angle of 0 is vertical; an angle of 90 is horizontal.
Angle from vertical |
Working Load Limits - lbs |
degrees |
Clutcher CL 10 |
Clutcher CL 20 |
Clutcher CL 30 |
Clutcher CL 40 |
0 |
125 |
250 |
650 |
1250 |
5 |
124.5 |
249.0 |
647.5 |
1245.2 |
10 |
123.1 |
246.2 |
640.1 |
1231.0 |
15 |
120.7 |
241.5 |
627.9 |
1207.4 |
20 |
117.5 |
234.9 |
610.8 |
1174.6 |
25 |
113.3 |
226.6 |
589.1 |
1132.9 |
30 |
108.3 |
216.5 |
562.9 |
1082.5 |
35 |
102.4 |
204.8 |
532.4 |
1023.9 |
40 |
95.8 |
191.5 |
497.9 |
957.6 |
45 |
88.4 |
176.8 |
459.6 |
883.9 |
50 |
80.3 |
160.7 |
417.8 |
803.5 |
55 |
71.7 |
143.4 |
372.8 |
717.0 |
60 |
62.5 |
125.0 |
325.0 |
625.0 |
65 |
52.8 |
105.7 |
274.7 |
528.3 |
70 |
42.8 |
85.5 |
222.3 |
427.5 |
75 |
32.4 |
64.7 |
168.2 |
323.5 |
80 |
21.7 |
43.4 |
112.9 |
217.1 |
85 |
10.9 |
21.8 |
56.7 |
108.9 |
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