From the four basic capacity ranges available in FDA TSK HI-LEX push-pull controls it will be possible to select a cable suitable for almost any requirement. The following basic elements should be established when specifying the correct HI-LEX control cable for each application.

• The output load;
  
• The required stroke;
  
• The total number of degrees of bend angle assumed in the routing of the cable;
  
• The operating environment;
  
• The method of actuation;
  
• Mounting detail.
  

The operating loads within the system, together with the total bend angle and stroke largely determine the size of cable that will be required, and influence the frictional characteristics of the assembly. It is the frictional factor which dictates the resultant input load in relation to the working load, and forms the basis of selecting the size of control cable required.

Determine the maximum force that will be required to both push and pull the load at the work end of the control cable (output end). Care should be taken to anticipate any abnormal or intermittent loads to which the control may be subjected. If there is a likelihood that this situation may arise then an allowance should be made for these forces when selecting the cable size.

Estimate the total number of degrees of bend the control cable will be subjected to in the course of installation routing. It is usually wise to prepare a sketch of the proposed installation in order to calculate the number of degrees of bend involved. The bend radius nominated in the technical section is that at which the cable will perform most efficiently, but care should be taken not to decrease the bend radius specified. Refer example illustrated.

Determine the maximum travel through which the load is to be moved.

NOTE: All push pull cable designs have some lost motion referred to as “backlash” and is a product of the inner core member to casing clearance. The Hi-LEX design of control keeps this to an absolute minimum. The total amount of lost motion is dependent upon several factors including the cable design clearances, the degrees of bend in the cable installation, and to a lesser extent travel and load. The following formula provides a means of calculating the lost travel as a result of the total bend angle in the system and this is normally adequate for calculating the stroke loss from compression to tension conditions.

BACKLASH = 0.005mm × TOTAL BEND ANGLE

Applications which demand that a cable be operated near the extreme upper limit of the design load capacity or installations which require ultra sensitivity may be affected by the small additional losses of load and travel. These should be referred to Flexible Drive Agencies Pty. Ltd. Engineering Department.

After establishing the details of items 1-3 inclusive, turn to the formulae shown on the page 43, and determine the approximate input force required to move the work load. By plotting across the chart, determine the recommended cable size relative to the required stroke, for the input load previously determined from Table 1 shown on the page 43.

F.D.A. Hi-Lex controls using normal materials will operate satisfactorily in ambient temperature environments of - 40ºC to + 95ºC. Installations where local short term “Hot Spots” are likely, require the application of a heat shield. F.D.A. can assist with heat sleeves. For long term exposure to high temperature contact F.D.A. for recommendation on alternative materials.

From the installation mounting requirements, determine the type of end fittings required for each end. Details of these are shown on Page 46.

Establish the required length of the control from the previously prepared sketch or by assuming the installation conditions, following as accurately as possible the path which the cable will take. The length is to be established as an overall length, that is, over the extreme ends of the inner core end fittings. For knob controls, measure from the upper securing nut or cap.