How To Choose The Right Telescopic Bearing
Materials. To minimize deflection, carefully consider all possible materials for your telescopic bearing. Some common materials, along with their pros and cons, include:
- Aluminum: Even though it’s a good choice for lightweight and low duty applications, aluminum has more deflection than other materials.
- Stamped Steel: Easily the most economical choice, stamped steel doesn’t handle vibration and shock loads as well as other materials.
- Cold Rolled Steel: Cold rolled steel is another low cost option that doesn’t undergo heat-treatment. However, pitting and denting occurs in raceways since the ball hardness is greater than the rail and slider.
- Hardened Cold Rolled Steel: For the most robust designs, hardened cold rolled sliders and raceways are your best bet. Even though they’re most expensive to manufacture and assemble, this material lets you preload for better rigidity and less deflection.
Stroke Options. When picking a telescopic bearing, there are three stroke options to choose from: partial, full and over-extension. Partial extension stroke refers to an extension length that’s 50 to 65 percent less than the closed length. In a full extension stroke, the extended length is equal to the closed length. With over-extension, the extended length is up to 150 percent greater than the closed length.
Telescopic rails also come with dual or double stroke configurations, allowing loads to move in both directions while maintaining the same closed length.
Load Placement. Another important factor to consider is load placement. Your load’s center of gravity should be placed as close as possible to the mounted rail, and centered about the moving element for even load distribution among the balls. Load calculations are usually made with the assumption that the load is properly distributed.
Life Calculation. When sizing a telescoping bearing for continuous operation, make sure you use the right life calculation and dynamic load capacity. Some manufacturers express load and deflection specifications based on the slides being used in pairs, while others think of load capacity using a single rail. You should take the time to understand how the slides are rated and what specifications the manufacturer provides.