I came across this myself where the mechanical integrity of the conductors is to be considered for life expectancy. Usually, one is mostly concerned with the corkscrew effect if the cable is constantly moving. This is usually based upon the cable manufacturer where they use a type of "filler" that may be able to easily slide within the outer jacket material. Some will use stranded nylon filler, but the expensive guys will actually encase all wires with a resin with low friction which highly prevents the corkscrew effect. The wire is not very likely to fatigue and break before the corkscrew is seen. Some people use plastic guides that keep all wires tied in a ribbon cable fashion to prevent cork screw, as well. Either way, unless the cable is load bearing (including its own weight) there is no real specification or chart that one can refer to in this case (I have not seen this). This job is primarily that of the mechanical engineer with proper fatigue analysis. Making the wire thicker might actually hinder life expectancy, as well. This is due to the weight of the cable and the minimum bend radius (the thicker the cable, the less flexible it becomes regardless of the number of strands). The best way to do the job right is to make one, see how it performs, continue from there. Iteration is key in this case. Check it out http://images.google.com/imgres?im...8%26um%3D1