Belt Drives and Environmental Temperature

Both high and low environmental temperatures can present problems with belt drive systems.

In general, the maximum recommended temperature for belt drive systems for standard belts is 185 deg. F (85 deg. C). For rubber belts, temperatures exceeding this can result in gradual compound hardening and eventual cracking as belts stiffen. For urethane belts such as Poly Chain GT Carbon, the urethane will may begin to soften and will eventually melt at temperatures exceeding 200 deg. F (93 deg. C). There are a few options for belt drives operating in high temperature applications, but belts made from materials with higher temperature resistance are still limited to a maximum temperature of about 230 deg. F (110 deg. C).

Belts can "overheat" from slippage even when environmental temperatures are not excessively hot. If belts are hard and appear glazed from heat, always check to make sure the tension is at the recommended level, and that sheave grooves are not worn excessively. In most normal environments, belt surface temperatures do not typically exceed 120 deg. F (49 deg. C) or so.

Belts are generally limited to a minimum temperature of about -30 deg. F (-34 deg. C). Rubber belts operating in temperatures lower than this can harden and crack. Cold soaked belt drive starts are especially vulnerable to belt cracking. Poly Chain GT Carbon belts are capable of operating at temperatures down to -65 deg. F (-54 deg. C).

Gates Launches New Metals Technical Guide

Earlier this month, Gates published a new Metals Technical Guide. The guide provides general background information on hardware topics such as:

• Material considerations
• Manufacturing and process capability
• Bushing capability
• Sheave specifications
• Sprocket specifications
• Gates Made-to-Order Metals team

The guide is available for download at www.gates.com/catalogs/ under the Power Transmission Catalog Collection link.

Designing Replacements for Existing Drives

When customers come to us looking for a replacement for a current belt or chain drive, sometimes they do not know the horsepower/torque and rpm of the motor. This is very important for us to know because we try not to design belt drives based on only the old drives ratings.

While we can calculate the power ratings for the old drive, if we design the new drive based on the old drives ratings we are trusting that it was designed properly in the first place. However, it is entirely possible that the old drive was improperly sized because the customer is replacing it for a reason! By knowing the horsepower and rpm of the motor, as well as the components of the old drive we can follow our proven design procedure to give the best results to the customer.

To design a belt drive we need to know:
-Horsepower and rpm of the motor
-Ratio of any gearbox in between the motor and belt drive if applicable
-Desired speed ratio for the belt drive (The old pulley sizes can tell us this)
-Center distance (The pulleys and belt length can tell us this)
-Shaft diameters
-A description of the operating conditions (24/7/365 or high shock loads?)

Synchronous Belt Meshing Frequency

Meshing frequency is defined as the number of belt teeth that enter and exit the sprocket grooves per unit of time. Meshing frequency is assumed to be the primary frequency of noise generated by synchronous drives since the noise is generated from meshing interference and land impact during operation. The most common unit of meshing frequency is # teeth/sec. This is equivalent to cycles/sec. Each sprocket may have its own meshing frequency, but the major noise generator tends to be the driveR with the belt entering at its highest tension.

Meshing frequency can be calculated as follows:

(# Sprocket Grooves x rpm) / 60 = cycles/sec