Belts and chains have unique benefits and limitations. Those differences become more apparent in applications that require fast motion as part of their operation.

To shed additional light on the topic, we talked to industry experts, asking them what designers need to know to keep their belts and chains happy at high speed. Here's what they had to say.

Can you think of an extreme case where excessive speed caused a chain or belt to fail or degrade power transmission?

Peter/Jason Industrial: A very common example is blower belts on dragster race cars. The blower is driven at 8,000 rpm or more and the load is several times the rated horsepower of the timing belts used for this application. Consequently, the belt sometimes lasts only a couple of races, and many racers use a new belt each time. It is not possible to drive this application with a chain due to the high speed of the drive, centrifugal losses, and lubricant needs.

Steve/U.S. Tsubaki: When selected and lubricated properly, roller chain is very capable of running at high speeds. The difference between success and failure often comes down to using the proper type of lubricating system. When following the selection procedure and referring to the horsepower tables in the manufacturer's catalog, generally there are three distinct types of lubrication requirements:

• Manual or drip system

• Oil bath, with the chain enclosed in contained bath

• Oil bath with pump applying lubricant directly to the chain

Trouble may occur if the application requires oil-bath lubrication, but only manual or drip is applied. There is a very common application referred to as a pin oven: Chain is used in excess of 1,000 ft/min. Its purpose is to convey beverage cans through a drying oven at high speed to cure their painted labels. The lubrication requirement is oil bath due to the speed involved, but unfortunately, only manual drip or spray lubrication can be used. Oil baths allow excess lubricant to contact the product being conveyed and create other problems.

As a result, chain life on this application is only a few months, compared to years for other applications. Problematic high-speed applications are usually avoided by following selection procedure references or consulting with knowledgeable application engineers. In less common cases, endusers may make a selection without utilizing the above resources and very quickly realize an alternative selection is required, at which time they usually refer to the catalog or contact the manufacturer.

Gerhard/Gates Mectrol: The traditional weakness of most urethane timing belts has been their relatively low maximum operating temperature of 70° C. We are seeing new belts coming onto the market with higher operating temperatures, but heat dissipation is still poor. These two factors limit their continuous operating speed.

Most urethane timing belts are employed in conveying and positioning applications where speed is generally not a limitation.

Steve/U.S. Tsubaki: In the case of the pin oven application mentioned, chain load is often around 1,000 lb, considering chain tension and working load to move the 600-ft strand. Speed is generally about 1,000 ft/min. Oftentimes, premature wear can occur: Several months service life is considered premature wear, while a service life of one year or more is often considered acceptable.

Gerhard/Gates Mectrol: Our conveyor application engineers always take a closer look at applications to run at linear speeds over 5 m/sec, and they never recommend conveying components for linear speeds over 10 m/sec. As far as conveying belts go, the speeds involved are no problem. To illustrate: The rotational speed for a 100-mm pulley to move a belt at 10 m/sec is only 1,909 rpm. This is not considered fast for most rubber timing belts.