Vibration control technology

Compiled by Walter Weart

There are several reasons railroads strive to control vibrations created by train movements. Excessive vibrations can cause components — such as brackets under freight-car running boards and trackside electronics — to fail. In addition, strong pulsations can damage cargo, worsen ride quality and impact truck hunting, which, in turn, can damage track and cause derailments.

To gauge the vibration-control options available to railroads, Progressive Railroading contacted several suppliers last month. Information provided by the two companies that responded — ITT Enidine Inc. and Miner Enterprises Inc. — follows.

ITT Enidine

Brackets under covered hoppers' running boards are vital rail-car components that need vibration protection. Vibrations transferred from the car to running board via the mounting brackets can cause bracket wear and failure at attachment points, as well as at other locations along the running board, according to ITT Enidine.

The vibrations "excite" a running board's natural frequencies, causing increased stress at attachment points.

In response to a customer's request, ITT Enidine in 2008 developed a way to isolate the brackets from vibration by placing Enidamp™ tubes on top of the bracket under the running board, says Jeff Weisbeck, director of engineering, elastomer and wire technologies.

The Enidamp is designed to reduce vibration levels on running boards and associated stress cracking, he says. A small, lightweight enclosure filled with a granulated visco-elastic material, Enidamp attaches directly to a running board.

Vibrations on the running boards cause the elastic material to interact and provide damping, enabling the Enidamp to help reduce vibration and stresses at bolted connections, and extend the running boards' life, according to ITT Enidine.

The company also provides wire rope and elastomeric isolators to control vibration. The isolators are designed to protect sensitive electronic equipment and reduce noise caused by vibration.

The devices often are used to provide isolation for electronic components and devices on locomotives and cars, says Weisbeck.

Wire rope isolators feature stainless-steel stranded cable, which is threaded through aluminum alloy retaining bars, and crimped and mounted. Elastomeric isolators can be produced from various materials, including natural rubber, silicone or butyl.

Isolators can help control vibration for wayside equipment, and elastomeric isolators can be used for vibration attenuation and noise reduction, says Weisbeck.

Miner Enterprises

Ride quality and vibration control also are critical when it comes to truck hunting, according to Miner Enterprises. Truck hunting can damage track, shorten truck components' life and cause derailments.

As railroads increasingly deploy more sophisticated wayside detectors, they're detecting more wheel impact loads, says Bob Pokorski, Miner Enterprises' director of engineering, adding that the rail industry has stepped up efforts to investigate the cause of high wheel impact loads.

Miner TecsPak® constant-contact side bearings can significantly improve freight cars' ride characteristics, says Pokorski. The side bearings feature Miner's TecsPak® elastomer pads, which are designed to reduce truck hunting, increase car stability and reduce component wear for various car types.

Cars equipped with the side bearings can operate at higher speeds, up to 70 mph, and with substantially reduced truck and wheel wear vs. non-equipped cars that can travel at 45 mph to 50 mph, says Pokorski.

Miner plans to improve the side bearing by eliminating the gap between the top cap and housing. The company expects to introduce the "next-generation" side bearing later this year, says Pokorski.

Walter Weart is a Denver-based free-lance writer.