Application Considerations
Bends
The only limitation on the number of bends is the effect on efficiency and backlash. The total degree of bends is proportional to backlash and inversely proportional to efficiency. As bend radius is reduced, the force needed to move the core will increase. The point where the radius is minimized such that a large amount of force is required to either stroke the core or hold the conduit in the configuration is considered the minimum bend radius for the core/conduit assembly.
Stretch
Stretch is made up of cable strain and mechanical clearances between the core/conduit assembly. Factors of 0.5% to 2% per pound force per foot can be used as a guide. Cables should be tested if a precise value is desired.
Temperature Effect
Temperature increases will adversely affect the backlash and load capacity. Most plastics' strength diminishes rapidly as the temperature approaches their operational limit. This causes the conduit to radically stretch as a load is applied. The liner or cover may also rupture or take a permanent set.
At low temperatures, the plastic liners and jacket may become stiff and more difficult to configure, but will not affect the performance. Where applicable, the greases used to lubricate the core/liner will become thicker and add more resistance to the no load friction and efficiency values. AeroControlex selects appropriate materials to meet the environmental requirements of each specific application.
Endurance
The fatigue life of the wires used to make the core are usually in the range of 1 X 106 for the bend radii recommended. The failure point of most sliding cables during endurance is galling of the end rods and fittings or wear of the conduit liner or core jacket.
Backlash
Backlash, which is apparent as lost motion under light push-pull input forces, is caused by the core member of the cable assembly moving from the inside to the outside of the bends in the cable with the change in direction of movement. It is a function of the clearance between the core and liner and the total number of degrees of bend in the cable. Cable length is not a factor. (See figure to right.)
Lost motion, the sum of backlash plus core and conduit elongation, will increase as cable length, degrees of bend, and loads are increased. The use of larger cable sizes for a given load will decrease the elongation portion of lost motion.
Weights
The weights for the core/conduit combination are listed in the application tables. Additional weights must be added to account for the end configuration type, accessories, and other hardware specified. Contact AeroControlex engineering for detailed weight analysis of your specific application.
Routing
The performance of the control cable will depend greatly on the path of the control cable. Critical variables include: applied axial load, number of bends (total degrees), minimum bend radii, seal nut pressure, and external side loads.
Environment
Typical applications are capable of sustaining the requirements of MIL-STD-810 for high / low temperature, humidity, salt fog, dust, and vibration.
Systems in which Teflon is used may be limited to environments below 350ƒF.
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