Do Belt Drives Generate Dust?

Belt drive systems are reliable, require low maintenance and are clean running. It is normal, however, for belts to generate small quantities of dust and particulates during operation. Rubber V-belts, Micro-V, Polyflex JB, rubber synchronous, TruMotion, Poly Chain, etc. belts all have individual and unique dusting characteristics, so “normal” behaviors will vary.

The quantity of dust generated from all belt drives is influenced by many factors including belt type, sheave and sprocket surface finish, drive alignment, belt installation tension or slippage, whether belts are new or used, and others. And not surprisingly, smaller drives tend to generate less dust than larger drives.

New belt drives generate the most dust during the first 24 to 48 hours of operation, and then dusting should taper off significantly. If dusting seems unusually heavy or continues after the initial run in period, this is abnormal and users should look more closely for possible causes.

For small synchronous belt applications that are sensitive to dusting, the Gates TruMotion construction is available on a made-to-order basis. TruMotion belts utilize materials and treatments that minimize dusting, so are well suited for clean operations.

Design Flex Pro: US and UK Version Correction

If you use Design Flex Pro for US customers, you must check your installation – see below.

Many of the new computer images have the default language/culture set to English-UK. This makes the computer look OK to English-US users, but does not make Design Flex Pro (DF-Pro) work correctly for US users.

• Notes required by US legal do not show up correctly for people using English UK.
• Some fields used for NA but not used in Europe do not show when English UK is selected.

Once DF-Pro is installed, changing the computer culture will not change the selected language.

Design IQ is not affected as it does not have a separate language for English-UK.

To correct this for DF-Pro:

• Open DF-Pro – make sure it is the only copy open
• Go to Tools Languages and make sure the language selected is correct for your area. If in the US, this should be English, not English-UK.
• Close DF-Pro to make the selection stick.

Gates 2012 FIRST Robotics Scholarships

Gates is excited to offer six $2000 scholarships to seniors using a Gates belt drive on their 2012 FIRST Robotics competition robot. In addition to using a belt, students will also answer a challenge question involving creative problem solving with belt drives. Application instructions, detailed requirements, and the challenge question are now available at www.gates.com/FIRST. All entries must be submitted online by May 15,2012 to qualify.

Good luck FIRST Seniors!!

Belt Failures - Tensile Cord Crimp

A very common failure mode for a synchronous belt is when the tensile cord is "crimped", occurring when the tensile member is bent to a radius smaller than recommended by the belt manufacturer. Crimping the belt will damage the tensile members and reduce the structural integrity of the belt.

Belt Crimp

Tensile cord crimp can happen by mishandling the belt, hanging the belt on a nail (or similar object), or by running the belt on a smaller than recommended pulley diameter. Another common cause of a belt crimp is when the belt ratchets over a sprocket groove. The instantaneous motion of a belt tooth exiting one groove and entering the adjacent groove can crimp the tensile cord in the area where the tooth jumped the groove.

After the tensile cord is crimped it loses tensile strength which the belt relies on to transmit the load. If the crimp is bad, the belt will fail exactly in spot where the tensile cord was damaged by shearing straight across the width of the belt in a clean break.

Crimp Failure

Ways to avoid a crimp failure with a synchronous belt are as follows:

1. Be careful when handling the belt, especially when installing the belt in a tight area.
2. If storing the belt, do not hang it on a nail or similar object. Use a saddle or rack at least as large as the minimum diameter sheave or sprocket recommended for the belt cross section.
3. Follow the manufacturer's recommended tension for the belt drive to ensure proper tension. If you notice that the belt is about to ratchet teeth or already has done so, increase the tension in the drive until the tooth has a tight fit with the sprocket groove.
4. Follow the manufacturer's minimum recommended diameter specification for the belt cross section being used. Gates' recommendations for minimum pulley diameters can be found in the preventive maintenance manual at www.gates.com/catalogs.

Belt Drives and Ozone Exposure

Ozone is a naturally occuring gas that is found in the air that we breathe. It consists uniquely of three oxygen molucules bonded together rather than the two of normal oxygen. Ozone is produced during lightening storms and is responsible for the fresh smell of the air afterwards. Electrical arcs from arc-welding or from around the brushes of electrical motors or ultraviolet light all produce ozone gas. It can often be detected by it's very unique chlorine bleach like smell in more concentrated form. Ozone is a powerful oxidant, so is sometimes used in air and water purification systems. To much, though, can have detrimental effects on plants, lung tissues, and organic materials like latex, plastics, and rubber.

The potential for excessive ozone concentrations is low for most environments in which belt drive systems are found. There are industrial environments, though, with higher concentrations of ozone gas making belt performance and durability a concern.

While all belts are designed for resistance to ozone, excessive concentrations can still affect rubber belts in much the same way as high environmental temperatures. Ozone slowly errodes the chemical composition resulting in rubber hardening and cracking. The amount of degradation is a function of the ozone concentration and the time of exposure. To prevent excessive detrimental effects on rubber power transmission belts, the following concentration levels should not be exceeded: (pphm = parts per hundred million)

Non-Conductive Belt Constructions: 100 pphm
Conductive Belt Constructions: 75 pphm
Non Marking Constructions: 20 pphm
Low Temperature Constructions: 20 pphm

The polyurethane material used in Poly Chain GT Carbon belts is considerably more resistant to ozone degradation than conventional rubber materials. Poly Chain GT Carbon drives are an excellent choice for drive applications located in environments with ozone concentrations.

Overhung Load

To prevent premature failures, manufacturers typically publish overhung load values for the speed reducers they offer. When designing a belt drive for use on a reducer, it is important to review the maximum published overhung load value to prevent overload of the bearings and shaft.

Along with their overhung load ratings, each speed reducer manufacturer publishes unique overhung load equations and constants. Therefore, it is crucial to obtain the correct overhung load calculation procedure from the reducer manufacture and to use their corresponding ratings.

If the overhung load is too high, the designer may consider increasing the pulley diameters, reducing the belt width, and/or mounting the pulley closer to the bearing. Following design adjustments, the overhung load calculations should be re-run to ensure that the drive is acceptable.

Right from the Start - Belt Storage

To get the most from a belt drive, its important to properly store a belt -all the proper installation procedures and design practices can be for nothing if a belt is improperly stored or damaged in storage.

A few of the major belt storage guidelines:

1) Belts can be stored up to 6 years if properly stored at temperatures less than 85 degrees F, and less than 70% relative humidty.

2) Make sure the belts are not bent to diameters smaller than the minimum recommended diameter for that cross section.

3) V-belts can be stored by hanging on a wall rack if they are hung on a saddle or diameter at least as large as the minimum diameter recommended for the cross section. Don't hang from a pin or nail!

4) Don't store in direct sunlight.

5) Don't store near heating devices.

6) Don't store near ozone generating devices such as transformers or electric motors.

7) Don't store belts where they are or could be exposed to solvents or chemicals.

8) Don't store on the floor unless in a proctive container.

9) Don't crimp belts, either in storage or handling.

Complete guidelines can be found in the Gates Belt Drive Preventive Maintenance & Safety Manual.