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!!
GATES BELTS, HOSES, AND APPLICATIONS
Tuesday, February 28, 2012
Tuesday, February 7, 2012
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:
- Be careful when handling the belt, especially when installing the belt in a tight area.
- 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.
- 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.
- 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.
Tuesday, January 24, 2012
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.
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.
Monday, January 16, 2012
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.
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.
Tuesday, January 3, 2012
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.
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.
Thursday, December 15, 2011
Interchanging Competitive Belts
Interchanging competitive belts can can be a simplified process. This site provides various interchange tools grouped by market and product type.
If a belt replacement is not listed in the interchange, Gates Application Engineers may be able to assist using measured belt dimensions. The number of teeth (synchronous belts only), length, width, and thickness can help the engineers identify the closest standard replacement.
It should be noted that replacing belts based solely on measurements is not ideal. In these cases, Gates cannot guarantee that the materials would be the same or that the belt will provide the same performance level as the original belt.
If a belt replacement is not listed in the interchange, Gates Application Engineers may be able to assist using measured belt dimensions. The number of teeth (synchronous belts only), length, width, and thickness can help the engineers identify the closest standard replacement.
It should be noted that replacing belts based solely on measurements is not ideal. In these cases, Gates cannot guarantee that the materials would be the same or that the belt will provide the same performance level as the original belt.
Wednesday, December 14, 2011
Belt Drives and Oil Contamination
Belt drive contamination with oil is never beneficial, but sometimes cannot be avoided. While occasional contact does not generally have adverse effects, prolonged contact with oil type lubricants, either directly or airborne, causes rubber compounds to soften and swell. Adhesion systems internal to belts are also weakened and broken down. This ultimately results in significantly reduced belt service life.
V-belt drives rely exclusively on friction to transmit power, so any contaminants that reduce friction also reduce the ability of the belt drive to transmit power. Banded type V-belts might have slightly improved resistance, compared to "raw edge" or "cut edge" type V-belts, with the outside cover temporarily shielding internal components. Also, neoprene based V-belts will have greater resistance to oil than EPDM based V-belts.
Synchronous belt drives rely less on friction to transmit power than V-belt drives. They also tend to perform better in oil contaminated environments. Rubber based synchronous belts, however, are still susceptible to swelling and adhesion system breakdown over time. While alternate rubber compounds may provide some marginal improvement in durability, it is best to prevent oil from contacting rubber synchronous belts if possible.
Gates Poly Chain type belts use a urethane based construction that is quite resistant to oil contamination. This prevents material swelling and breakdown that cannot be avoided with rubber materials. Note that synchronous belts still rely on friction to transmit power, so lubrications will interfere with power transmission. Poly Chain GT Carbon belts are used successfully in environments with heavy misting of oil based lubricants and cutting fluids, and have even been submerged in oil. Poly Chain GT Carbon belts are the best bet for applications that cannot avoid oil contamination.
V-belt drives rely exclusively on friction to transmit power, so any contaminants that reduce friction also reduce the ability of the belt drive to transmit power. Banded type V-belts might have slightly improved resistance, compared to "raw edge" or "cut edge" type V-belts, with the outside cover temporarily shielding internal components. Also, neoprene based V-belts will have greater resistance to oil than EPDM based V-belts.
Synchronous belt drives rely less on friction to transmit power than V-belt drives. They also tend to perform better in oil contaminated environments. Rubber based synchronous belts, however, are still susceptible to swelling and adhesion system breakdown over time. While alternate rubber compounds may provide some marginal improvement in durability, it is best to prevent oil from contacting rubber synchronous belts if possible.
Gates Poly Chain type belts use a urethane based construction that is quite resistant to oil contamination. This prevents material swelling and breakdown that cannot be avoided with rubber materials. Note that synchronous belts still rely on friction to transmit power, so lubrications will interfere with power transmission. Poly Chain GT Carbon belts are used successfully in environments with heavy misting of oil based lubricants and cutting fluids, and have even been submerged in oil. Poly Chain GT Carbon belts are the best bet for applications that cannot avoid oil contamination.
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