How to select cable under tension....

[CDUB]

I'm trying to help colleagues with an issue involving a cable under tension. The cable is approximately 12" long, .035" in diameter....The system consists of a trigger, that when depressed adds load to the cable and articulates the head of an arm. I guess you could compare it to an excavator arm...but instead of hydraulics, a cable and pulley system is working the 'bucket'. The problem we're facing is...under certain loads the cable is stretching too far, and the desired articulation isn't occurring. Instead of the 'bucket' (arm) flexing 30 degrees, it's only flexing 20 degrees. Does anyone know any good sources for cable selection and/or design? I understand I should thicken the cable, etc....but I want to understand the physics and material selection for certain systems.

Thanks!

[CDUB]

Here's a really generic sketch of the device. Again...I'm just looking for advice on cable selection or a link to some good references. The cable we're currently using is stretching to much when force is mechanically applied under certain loads. We need to be able to lift a certain weight and the cable is stretching at that point limiting the articulation (x degrees).

[jboggs]

You first step will be to calculate (or measure) the actual load on the cable. Depending on the geometry of your device a payload of 5 lb could actually result in a 50 lb load, or more, on the cable. Then calculate (or measure) how much the actual cable length is stretching under load. That will give you the strength parameters of your current cable. All cables will stretch some amount under load. You just need to determine how much stretch is acceptable for your loads. Then get in touch with a cable manufacturer or distributor.

[CDUB]

You first step will be to calculate (or measure) the actual load on the cable. Depending on the geometry of your device a payload of 5 lb could actually result in a 50 lb load, or more, on the cable. Then calculate (or measure) how much the actual cable length is stretching under load. That will give you the strength parameters of your current cable. All cables will stretch some amount under load. You just need to determine how much stretch is acceptable for your loads. Then get in touch with a cable manufacturer or distributor.

Thanks @Jboggs