We often get questions from customers about the force/deflection tensioning recommendations on a Design Flex printout. The report lists the "Rib/Strand Deflection Distance" and the "Rib/Strand Deflection Force" for both a new and used belt. If you have never used this method of measuring tension, our Belt Drive Preventive Maintenance and Safety Manual has thorough instructions.
Some people think that you can measure the tension by only measuring deflection. However, in order to properly tension a belt, you must measure both the force and deflection distance. Measuring one inch of deflection with 5lbs of force is a very different tension than one inch of deflection that requires 100lbs of force.
Some confusion arises from the "Rib/Strand" portion of the title. For a synchronous drive, there is almost always only one belt, so you can use the listed force/deflection values. V-belts however, often have more than one belt on the same drive. In order to properly tension the drive you must multiply the deflection force by the number of strands that you will be deflecting. Even though your PowerBand belt looks like a single belt, you must multiply the force by the number of ribs. The deflection distance is not multiplied by the number of ribs and is calculated as 1/64 of an inch per inch of span length.
People also wonder what is considered to be a used belt. Any belt that has not been run more than about 24 hours is considered a new belt. If you are reassembling a drive with the same belt that was used previously, it is recommended that you measure the tension before dis-assembly and reinstall it at the same tension. If you did not measure the tension, you can reinstall with the used belt values.
GATES BELTS, HOSES, AND APPLICATIONS
Monday, November 29, 2010
Tuesday, November 16, 2010
Minimizing Noise In Synchronous Belt Drive Systems
Drive noise evaluation in any belt drive system should be approached with care. There are many potential sources of noise in systems including vibration from related components, bearings, and resonance and amplification through framework and panels. Belt drives sometimes receive blame from noise generation that they don't actually produce.
Noise from synchronous belt drive systems generally results from the process of belt tooth meshing and physical contact with sprockets. The sound pressure level generally increases as operating speed and belt width increases, and as sprocket diameter decreases. Drives designed with moderate sprocket sizes and without excessive capacity (over-design) are generally the quietest.
Proper belt installation tension is very important in minimizing drive noise. Belts should be tensioned at a level that allows them to run with as little meshing interference as possible.
Drive alignment also has a significant effect on drive noise. Special attention should be given to minimizing angular misalignment (shaft parallelism). This assures that belt teeth are loaded uniformly and minimizes side tracking forces against the flanges. Parallel misalignment (sprocket offset) is not as critical of a concern so long as belts are not trapped or pinched between opposite flanges.
Noise from synchronous belt drive systems generally results from the process of belt tooth meshing and physical contact with sprockets. The sound pressure level generally increases as operating speed and belt width increases, and as sprocket diameter decreases. Drives designed with moderate sprocket sizes and without excessive capacity (over-design) are generally the quietest.
Proper belt installation tension is very important in minimizing drive noise. Belts should be tensioned at a level that allows them to run with as little meshing interference as possible.
Drive alignment also has a significant effect on drive noise. Special attention should be given to minimizing angular misalignment (shaft parallelism). This assures that belt teeth are loaded uniformly and minimizes side tracking forces against the flanges. Parallel misalignment (sprocket offset) is not as critical of a concern so long as belts are not trapped or pinched between opposite flanges.
Gates Supports FIRST Robotics 2011 Preseason
Gates is offering free 2011 preseason belt drive components to all interested FIRST Robotics teams. To help teams determine what parts may be needed, Gates has free drive design manuals and design software available at www.gates.com/drivedesign/.
To order parts, first fill out the form at http://www.usfirst.org/roboticsprograms/frc/content.aspx?id=18398 then email the completed form to ptpasupport@gates.com. Please include the team name, number, and the word FIRST in the email subject.
Parts will be ground shipped to the address provided on the form free of charge. The deadline for submitting orders is December 15, 2010.
If you have any questions, please contact Gates Product Application Engineering at 303-744-5800 (Option 2) or email ptpasupport@gates.com. Gates reserves the right to limit the style and quantity of parts provided to each team.
To order parts, first fill out the form at http://www.usfirst.org/roboticsprograms/frc/content.aspx?id=18398 then email the completed form to ptpasupport@gates.com. Please include the team name, number, and the word FIRST in the email subject.
Parts will be ground shipped to the address provided on the form free of charge. The deadline for submitting orders is December 15, 2010.
If you have any questions, please contact Gates Product Application Engineering at 303-744-5800 (Option 2) or email ptpasupport@gates.com. Gates reserves the right to limit the style and quantity of parts provided to each team.
Tuesday, November 9, 2010
Measuring Efficiency - An Average Value in an Instantaneous World
We publish that converting from V-belts to synchronous belts will save an average of 5% of the drive's energy consumption. Sometimes this can be confused with measurements taken to confirm energy savings by end users.
Note that the 5% is an average estimate.
Both highlighted words at the end of that sentence need further explanation.
The savings is an average value because the savings comes over time. Newly installed and properly tensioned V-belts running in good sheaves are going to be very efficient. Comparing a newly installed synchronous belt drive with an instantaneous measurement to a newly installed and properly tensioned V-belt drive, or a newly re-tensioned V-belt drive will most likely only show a couple of % difference in energy savings for the synchronous belt drive.
Average is just that - an average over time that demonstrates not only the reduced bending stresses and cooler operation of synchronous belts, but also the natural trend of increased slip and creep of V-belt drives...over time. An average value isn't a guarantee of a minimum 5% performance increase, but is an average over time.
If an attempt is made to measure efficiency gains, that measurement is only a small slice of the average total result. Its an instant out of the entire operating period, and not representative of the overall efficiency gain.
The savings are also quoted as an estimate. This is done because every drive and circumstance is different. The savings gain from a conversion of poorly maintained systems will most likely exceed 5%. The savings from converting a well maintained system may not achieve 5% savings. Systems that are redesigned to use the consistent speed of a synchronous belt drive can more accurately run at speeds that are actually needed to do the work required may have dramatically higher savings. Extensive field tests, confirmed by laboratory testing, has confirmed that the estimate, of average savings, is reasonable to use at 5%.
So - keep the above in mind when discussing or handling the energy efficiency issue. Don't use an estimated average value to guarantee a minimum instantaneous expectation.
Note that the 5% is an average estimate.
Both highlighted words at the end of that sentence need further explanation.
The savings is an average value because the savings comes over time. Newly installed and properly tensioned V-belts running in good sheaves are going to be very efficient. Comparing a newly installed synchronous belt drive with an instantaneous measurement to a newly installed and properly tensioned V-belt drive, or a newly re-tensioned V-belt drive will most likely only show a couple of % difference in energy savings for the synchronous belt drive.
Average is just that - an average over time that demonstrates not only the reduced bending stresses and cooler operation of synchronous belts, but also the natural trend of increased slip and creep of V-belt drives...over time. An average value isn't a guarantee of a minimum 5% performance increase, but is an average over time.
If an attempt is made to measure efficiency gains, that measurement is only a small slice of the average total result. Its an instant out of the entire operating period, and not representative of the overall efficiency gain.
The savings are also quoted as an estimate. This is done because every drive and circumstance is different. The savings gain from a conversion of poorly maintained systems will most likely exceed 5%. The savings from converting a well maintained system may not achieve 5% savings. Systems that are redesigned to use the consistent speed of a synchronous belt drive can more accurately run at speeds that are actually needed to do the work required may have dramatically higher savings. Extensive field tests, confirmed by laboratory testing, has confirmed that the estimate, of average savings, is reasonable to use at 5%.
So - keep the above in mind when discussing or handling the energy efficiency issue. Don't use an estimated average value to guarantee a minimum instantaneous expectation.
Monday, November 1, 2010
HTD Does Not Stand for Synchronous
A lot of people associate the acronym HTD with synchronous belts. While there is good reason for this, most take it a little too far, and believe that HTD refers to all synchronous belts. This is not the case. HTD stands for High Torque Drive, and calls out a specific tooth profile. This type of profile is called a curvilinear profile. An HTD tooth form looks like a half circle. Other curvilinear profiles are available today as well, including our GT profile. Here at Gates, we replaced our main 8mm and 14mm HTD belt lines with our GT tooth form quite a number of years back. HTD is still offered stock in 3mm, 5mm, and 20mm pitch belts, but not in our 8mm and 14mm lines.
Some of our competitors still offer off the shelf 8mm and 14mm pitch belts and sprockets. This causes questions about interchangeability. When we designed our GT tooth form for 8mm and 14mm pitch, we designed the belts to be able to drop into the old HTD sprockets. This is a one way replacement; you cannot drop an HTD belt into our GT sprockets. The HTD tooth is wider than that of our GT belts. Also, this drop in ability is only for the 8 and 14mm pitch belts, not for the smaller 3 and 5mm pitch.
There are reasons why one would still want to use HTD in 8mm and 14mm belts today, and it's possible with special order belts. Keep in mind though, special order means lead times and minimum order quantities. If you have a standard industrial application, it's likely it will be alright to switch to GT. If you have a specialty drive such as a supercharger on a car, you may want to call us to be sure.
For more interchange information, check out our Belt/Sprocket Interchange Guide. You can download your free copy at www.gates.com/drivedesign Click the link to Drive Design Manuals, and scroll down until you find it (you will have to register if you haven't previously done so).
Some of our competitors still offer off the shelf 8mm and 14mm pitch belts and sprockets. This causes questions about interchangeability. When we designed our GT tooth form for 8mm and 14mm pitch, we designed the belts to be able to drop into the old HTD sprockets. This is a one way replacement; you cannot drop an HTD belt into our GT sprockets. The HTD tooth is wider than that of our GT belts. Also, this drop in ability is only for the 8 and 14mm pitch belts, not for the smaller 3 and 5mm pitch.
There are reasons why one would still want to use HTD in 8mm and 14mm belts today, and it's possible with special order belts. Keep in mind though, special order means lead times and minimum order quantities. If you have a standard industrial application, it's likely it will be alright to switch to GT. If you have a specialty drive such as a supercharger on a car, you may want to call us to be sure.
For more interchange information, check out our Belt/Sprocket Interchange Guide. You can download your free copy at www.gates.com/drivedesign Click the link to Drive Design Manuals, and scroll down until you find it (you will have to register if you haven't previously done so).