V-Belts and Low Temperature Operation

In extremely low temperature operations, the rubber material in V-belts becomes stiff. At sufficiently low temperatures, the rubber will actually reach a glass point, where (as the name implies) the rubber is hard and will shatter like glass if it is bent.

This is an extreme condition but approaching this state the rubber will go through various degrees of stiffness. As long as a drive is in operation, the heat generated through drive friction and bending will increase the internal belt temperature and maintain belt flexibility in temperatures well below the normally accepted minimum operating temperature. Trying to immediately transmit a load through a belt which has taken a cold set can cause belt failure because the belt is too rigid to bend.

Options to Reduce Overhung Load on Gear Reducers and Gearboxes

If calculated overhung loads are larger than those recommended by a gearbox manufacturer, there are three possible options that can be used to reduce overhung load:

1) Increase the diameters of the sprockets or sheaves on the drive.
2) Move the sheave or sprocket inboard, thereby moving the overhung load closer to the reducer.
3) Use a belt type with a smaller overhung load connection factor (and, therefore, less total operating tension).

Synchronous Belts vs. Ball Screws

From the design, construction, and first-cost standpoint, a synchronous belt drive can have distinct advantages over a ball screw in certain applications:

 - Significantly lower first cost
 - No lubrication or maintenance required
 - Clean running drive
 - Drive length design flexibility

Idler Bushings

Some belt drives require the use of an idler sprocket whether it’d be for tensioning or achieving sufficient belt wrap.

Gates does offer a handful of idler sprockets assemblies, however depending on the pitch and the width of the belt, there can be few options.

Gates also offers a number of idler bushings (see below) to allow for more flexibility when choosing idler sprocket tooth counts and widths. We offer idler bushings in both QD and TaperLock styles. Both assemblies are compatible with our idler bracket options.

If you are in need for a larger idler sprocket or have an old sprocket you want to reuse as an idler, our idler bushings may be for you.

For additional information on this or any other topic please contact Gates Product Application Engineering by phone at 303-744-5800 or by email at ptpasupport@gates.com.

Misalignment

Maintenance technicians may not always find it practical or possible to accurately calculate the total misalignment in a system while determining if it is in acceptable alignment. It is also difficult to visualize small fractions of an angle such as 1/2 and 1/4 degrees.

These can be more clearly illustrated with the following rules of thumb:

For v-belt drives, 1/2-degree angle = approximately 1/10-inch per foot between the drive shafts.

For synchronous, 60-degree angle, and V-ribbed drives: 1/4-degree angle=approximately 1/16-inch per foot between the drive shafts.

These rules can be used to estimate the amount of angular and parallel misalignment visually rather than having to calculate actual numerical values.

Alignment, Tracking, and Flanges

If  one side on a belt wears faster than the other, a tracking problem where the belt is riding against a sprocket flange may exist. This condition is typically caused by misalignment. In the most severe cases with heavily loaded drives, side thrust forces can actually push off the pulley flanges. 

If this type of belt wear is seen, or wear varies across the belt width, check the drive alignment and adjust as necessary to achieve proper alignment.

Belt Drive Inspection and Symptom Analysis

Gates recommends the following steps when inspecting a synchronous belt drive system:

With the power shut off, locked and tagged, and the machine components in safe positions, remove the drive guard and inspect the belt and sprockets for signs of unusual wear or damage.

Symptoms such as excessive belt edge wear, tooth shear, belt cracking and tensile break may indicate the need to correct alignment or to adjust tension to the correct values.