Wire rope measurements

The most common way to do it is with a dynamometer (Dillon is one of the major manufacturers of dynamometers). Same thing would work on any wire rope. However, they are direct reading. Guy wire is tensioned with an inline dynamometer and deadended (or otherwise clamped) between a fixed point and the dynamometer at the desired tension (typically less than 25% of the rated breaking strength of the wire).

Tension can also be estimated indirectly say, on a level horizontal span, by measuring or estimating the mid-span sag. An approximate parabola method can be used:

S = Wc x L^2/8T

Where S = sag at the center of the span in meters (feet); Wc = weight of the wire rope in kg per meter (lbs per foot); L = span length in meters (feet); T = horizontal tension in Newtons (lbs).

Thanks. We are incrementally improving a telescopic mast. The hoisting mechanism needs to be removed each time we want a direct measurement. This helps.

Thanks

I used to work at W.C.Dillon & Co. Wendell at wjdent1@aol.com

If you want indirect measurement , this may give some inspiration.

If there is a fixed length between rope spool and pulley passover , twang the thing and record frequency. Pitch to load could be calibrated (?) maybe.

This is not as goofy as you might think. If the spacing is indeed fixed and you are able to do some calibration, plunking the cable will indeed emit a tone. An inexpensive guitar tuner (I have a 20 year old Korg that handles 7 octaves) can give you frequency for cheap. I suspect my $100 Korg now sells for $35 or less. Calibration would require that you install some fixed loads and measure the resultant "twang" frequency for each. If the cable is moving, however, this won't work too well. A moving cable could be routed through two sheaves so it makes a long horizontal run. A proximity detector could probably tell you how much the cable has sagged, and you could use the formula from the previous post. Or, one could install an idler between two points that is tensioned with a fixed weight, then measure how far the weight is pulled out of line.

Hi Guest.

My proposal was entirely serious. I was waiting for more detail to see it's feasibility. It depends on load and dimensions etc whether this could be used , but I see no reason why such a method could not work (based on the little information given in the question). The type of rope was not specified (Lang's lay /etc ). A rotational measure could also be made in some situations. A bit hard to help fully without exact application and dimensions.

Kris