Subsystems

Elbow room ... Hinge or snap-out bars allow easy access for installing cables and hoses with fittings that cannot be fed through carriers.

Several accessories can be added to carriers to boost performance and simplify designs. For example, halfshear lockout systems reduce the need for pins and snap rings: These inserted molded elastomer torsion bearings at link-pivot points significantly reduce noise for equipment used in laboratories, medical and semiconductor equipment, and other applications where quiet operation is required. Other subsystems:

... and headroom ... Polymer rollers reduce the wear incurred by cables and hoses due to their relative motion. Window extenders add vertical space.

• Hinge or snap-out bars allow easy access and allow installation of cables and hoses with fittings that cannot be fed through carriers.
• Polymer rollers can reduce wear incurred by rubbing cables and hoses, as are window extenders that add more vertical room. Similarly, low-friction sliders added to nonmetallic carriers reduce wear and load on extremely long travels.
• Carriage support systems for plastic link carrier applications support heavier hose and cable loads and speeds. They incorporate major rollers and intermediate supports, which together bear the carrier for the complete length of travel. So, the entire system rolls on channels mounted to the floor or crane bridge for speed to 450 ft. per min. — suitable for overhead crane applications.
• Long-travel support systems with retractable roller systems ride on a simple rail. The carrier doesn't glide on itself; instead, as motion is created as links pass through the radius, rollers are lifted from the guide rail and pulled inwards. On the return travel, roller sets are pushed back out and sit down on the rail for rolling support through the complete travel. This makes for speeds to 5 m/sec, reduction of tow force up to 90%, and friction elimination on carrier links.

Steel vs. plastic

Low-friction sliders reduce wear and load on very long travels subject to fast travel speeds.

Most carrier manufacturers have concentrated recent development efforts on plastic carriers, but steel remains a useful design option. In fact, some newer steel versions are lighter than previous designs — with the added ability to support longer spans than plastic. Some tips when deciding between metal and nylon carriers:

Carriage support systems for plastic link carrier applications carrying heavy hose and cable incorporate major rollers and intermediate carrier supports, which together bear the carrier for the complete length of travel. Note the range of motion.

• Use metal if loads exceed 15 lb per ft.
• Use nylon with speeds over 100 ft per min.
• Metal carriers are most practical for travels up to 50 ft. Beyond that, nylon is more economical and functional.
• Nylon carriers perform best between 0° and 250° F.
• For corrosive environments, plastic carriers might be the logical choice; that said, carriers in stainless or zinc dichromate-plated steel are sometimes better, particularly for longer unsupported spans.
• Appearance should also be considered when choosing carrier material.

The Gortrac Division of A & A Manufacturing Co. Inc. provides CAD drawings at gortrac.com. Also visit motionsystemdesign.com/issue for the latest articles online.