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.

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.

Micro-V Belts

Gates has a line of belts that we call Micro-V. They are called this because the belt is made up of a band of small V-belts put together. They are also called Poly-V belts by others in the industry. These belts are actually very common, in fact, you may have worked on one, and not even known it! Micro-V belts come in different sizes, or sections. One of these sections is called K-section, this is the type of belt that runs the accessory drives (alternator, water pump, etc…) under the hood of your car. While they are commonly called serpentine because of the way that they move around the pulleys, these are in fact K-section Micro-V belts. K-section belts are mainly used on automobiles and industrial gasoline and diesel motors. The less known sections of Micro-V’s include H, J, L, and M sections. H section is very small, and is typically not used for design except by large OE’s. J , L, and M section belts are the standard industrial line that we can help you design with. These belts push a lot of power for their size, are quiet, and can handle higher speeds well. One thing to keep in mind, however, is that we don’t have any off the shelf pulleys for them. This means that you would either need to have something made to order, or you could contact us for the groove information to create your own pulleys. You can find more information about these belts in our Light Power and Precision Drive Design Manual or as always by contacting us directly.

Water & Synchronous Belt Resistance

Light and occasional contact with water, such as occasional wash downs, should not generally affect synchronous belts seriously. Prolonged contact such as spray or submersion, however, can have detrimental effects.Rubber synchronous belts are considerably more vulnerable than Poly Chain GT Carbon belts.


With rubber synchronous belts, water soaking reduces the tensile strength of fiberglass tensile cords in addition to breaking down adhesion systems between the cord and the rubber compound. While aramid type tensile cords are more resistant to water than fiberglass, they are dimensionally unstable in the presence of water or humidity, so can result in belt length stability problems. Soaking also causes the rubber body to swell, lesser than but similar to oil contamination. This can negatively impact belt pitch fit with pulleys and sprockets in addition to material weakening. Additives to water such as lubricants, chlorine, anti-corrosives, etc. can intensify detrimental affects of water soaking.


Poly Chain GT Carbon belts are quite resistant to water soaking, and have even been used successfully in submerged applications. While urethane can exhibit a small amount of swelling, overall belt performance and the ability to transmit power remains relatively stable.


When considering the use of synchronous belt drive systems in moist or wet environments, the resistance of the hardware to corrosion is also very important. Coatings or treatments used on standard iron based hardware may not have adequate corrosion resistance. Special corrosion resistant coatings such as zinc or nickel plating are available on a made-to-order basis.


Contact our Made-To-Order Metals Group at (800) 709-6001 for further information about hardware corrosion protection options. Contact our Product Application Engineering Group at (303) 744-5800 for further information about applying belt drive systems in adverse environments.

Motorcycle Belts

Customers often contact Gates regarding belts for motorcycle applications. Unfortunately, Gates does not sell motorcycle replacement belts directly to aftermarket users. The best method to obtain a proper replacement belt is to go through the dealer network for the particular brand of motorcycle.

Various aftermarket distributors also service the market, and they serve as an alternate source for replacement belts. However, some motorcycle belts sold through the original dealer network may be manufactured with proprietary constructions not available through aftermarket distributors.

The standard Poly Chain® GT® Carbon™ belts sold by Gates general market distributors have the GT tooth style. These belt are not recommended for use with motorcycle sprockets, which are typically designed with the HTD® tooth style.

Aftermarket distributor can typically assist with custom motorcycle applications. However, belts in lengths other than those available from aftermarket distributors may require new tooling at costs in excess of $25K per mold.

Synchronous Belt Drive - Test for Structural Integrity

Since synchronous belts are a positive drive and do not slip, they will attempt to transmit all the load that is applied. V-belts will slip at peak loads, almost acting as a clutch and as such not passing that peak loading on to the system's structure.

Since synchronous belts will not act as a clutch, it is important to make sure that the drive structure is adequate. This is more of a concern for HVAC type applications, given their structural considerations.

To check for structural rigidy, first make sure that the system is powered off, locked down and tagged out. Never touch or work with any belt system without taking appropriate safety measures.

Then, grab the opposing belt spans and push or squeeze them towards each other. While doing this, keep an eye on the shafts in the system. If you see significant movement or deflection, the system is not an ideal candidate for synchronous belt conversion without further structural strengthening. If you do not see any movement, or minimal movement, the system's structure is adequate and a good candidate for converting to synchronous belts.

Rust Inhibitor - Krown KL 73

Krown KL 73 is a solvent free rust inhibitor and lubricant that is used with metal products to help protect against rust and also to lubricate moving parts. As with any belt drive, it is not recommended to use any lubrication or belt dressing on the drive. Furthermore, KL 73 can be detrimental to the integrity of the rubber used in power transmission V and synchronous belts. Because of this, KL 73 is not recommended to be used as a rust inhibitor on any power transmission sheave or sprocket containing V or synchronous belts. Find more information on Krown KL 73

Belt Installation and Maintenance Toolbox

Gates recently introduced a new toolbox product to contain some of the most useful Gates tools used for belt installation and maintenance operations. As user sophistication increases, it is becoming more common for technicians to have the EZ Align and Sonic Tension Meter tools in their possession. This new case keeps these tools and accessories together and well protected.

The case includes sheave gauges and the Pocket Preventative Maintenance Guide. Users that have already purchased one or both tools can simply place them in the new case. The high density foam has been pre-cut perfectly to hold them securely. Additional tools and accessories can be purchased separately. The Gates product number for this toolbox is 7420-2000.

V-belt Matching

V-belt drives often use multiple belts to transmit power. In these applications, matched belts should be used to ensure even load distribution. The allowable length deviations for a "matched" set of belts (per RMA Standards IP-20 and IP-22) are:
Many Gates V-belts are manufactured within the above match tolerances, allowing stocked belts to run as matched sets. However, there are some exceptions to the match tolerances listed above. V-belts with aramid tensile cords stretch very little, requiring a match tolerance that is tighter than the RMA standard. V-belts with aramid cords (such are Predator®) should be matched by selecting belts with a single punch code.

Gates belts manufactured within the RMA match tolerances are identified in the Gates Industrial Power Transmission Systems catalog by the designation "V80". Belt sizes not included in the V80 match system with standard polyester tensile cords should be special ordered as matched sets.

Bushings and Keys

An often asked question is "will there be key stock provided with that bushing?" The answer is actually pretty simple; only if the bushing uses a shallow key. This means that for any drive that uses standard key stock, you will need to purchase the key stock separately. If your bushing uses a shallow key, the key stock will be provided with the bushing. The charts below can be found on page 80 of our Poly Chain GT Carbon Drive Design Manual. These charts will show you which shafts will use standard keys, and which will use shallow keys.

Sonic Tension Meter Accessories

The Sonic Tension Meter model 507C (7420-0507) is supplied with:

• a cord sensor (7420-0206)
• a storage case
• batteries
• a manual
• a mass constant quick reference card

Two additional sensors are also available for purchase separately. The flat flexible sensor (7420-0205) can be bent, making it easier to measure tension in tight spaces. The flexible sensor also allows for measurements with one hand. The inductive sensor (7420-0212) measures a magnetic field instead of sound. The inductive sensor is useful for very noisy or windy environments. Find out more at Gates.com.

Considerations for Synchronous Belt Drives on HVAC Applications

Some HVAC drives will experience high starting loads if the motor has an across the line start.  The fan will be forced to ramp up to speed nearly instantaneously, and the start up loads can be as much as 150% to 200% of the normal operating loads.

Designers that are considering using synchronous belts on HVAC drives need to be aware of this potentially high start up load.

If a soft start or variable frequency drive (VFD) is used on the drive, there is no need to take any special design precautions as the load is ramped up gradually.

If an across the line start up happens infrequently, simply applying a bit more installation tension will help prevent any ratcheting or start up issues.  

If start ups occur regularly and/or frequently, it is good practice to add .2 to the service factor when designing the synchronous belt drive.  This will provide a slightly more conservative drive design that will avoid any issues at start up. Learn more about HVAC drives and synchronous belts at Gates.com.

Taper Lock Bushings

I’ve been talking to people about Taper Lock bushings for quite a while now. However, the other day, I learned something new that I thought was pretty useful. Taper Lock callouts have always seemed a bit out of left field to me, but I figured there had to be a reason behind it. Turns out there is! A Taper Lock part number is called out by four numbers followed by the shaft bore that it will attach to. The first two numbers represent the maximum bore size, and the last two represent the total length. For example, a 2012 has a maximum bore of 2.0 inches, and a length through bore of 1.25. To properly call out a 2012 bushing to fit a shaft (let’s use 1.5” for example), you call out the whole inch followed by the fraction. This means our 1.5” 2012 bushing would be called out like this: 2012 1.1/2. Metric is pretty simple, you call out the bushing followed by the shaft diameter and include MM behind it; let’s use 20mm as an example size. The Metric convention would look like this: 2012 20MM I know this will certainly speed up my answers, hopefully it will help you too!

Synchronous Belts & Exposure To Water

Light and occasional contact with water (occasional wash downs) should not seriously affect synchronous belts in general. Prolonged contact (consistent spray or submersion) can result in significantly reduced tensile strength in fiberglass belts, and potential length variation in aramid belts.

Prolonged contact with water also causes rubber compounds to swell, although less than with oil contact. Internal belt adhesion systems are also gradually broken down with the presence of water. Additives to water such as lubricants, chlorine, anti-corrosives, etc. can have a greater detrimental effect on belts than pure water.

Poly Chain GT Carbon belts use polyurethane compound and carbon fiber tensile materials that are both very resistant to water. Poly Chain GT Carbon belts can withstand prolonged contact with water without detrimental effect.

Sprockets operating in the presence of water may be vulnerable to rust and corrosion unless resistant materials or coatings are used. Sprocket corrosion can result in accelerated belt wear and tension loss. These can both shorten belt life significantly. For assistance in the design and acquisition of rust and corrosion resistant sprockets and bushings, contact Gates Made-To-Order Metal team.

Gates Drive Design Manuals

Customers often ask where they can find technical information about Gates belt drives. The Gates Drive Design Manuals are a great resource for this type of information.

There are several manuals available at www.gates.com/drivedesign/:

• Poly Chain® GT® Carbon
• PowerGrip® GT2®
• Heavy Duty V-Belt
• HVAC
• Light Power and Precision
• Air-Cooled Heat Exchanger

Below is a sampling of the topics included in the manuals:

• Drive selection procedures (including power rating tables)
• Gates hardware specifications (for standard sheaves, sprockets, bushings, etc).
• Discussion of design considerations such as installation tension, conductivity, alignment, noise, flywheel effect, NEMA motors, tolerances, idlers, etc.
• Standard calculations
• General troubleshooting guidelines

Splicing and Clamping Synchronous Belts

The question is often raised if it's possible to cut a synchronous (timing) belt into a custom length and splice the belt back together when a standard length does not fit the application. To answer this question: yes it can be done, but not very easily. Splicing two ends of a synchronous belt can be done when the belt is made with a particular type of polyurethane construction and additional polyurethane is used as "glue" to attach the ends of the belt. After this splicing process you can expect about 40% of the initial strength of the belt. This is because once you cut the tensile cord you've eliminated the strongest part of the belt. The spliced section is now the weak link of the belt, and like your co-ed softball team, you're only as strong as the weakest link. There are currently no processes to splice together a rubber synchronous belt.

Clamps are often used to attach two ends of a synchronous belt together. If this is done, the clamp must be contained on the belt span between the two pulleys. If a clamp ever attempts to ride over a pulley, catastrophic results will surely follow. If a clamp is used to attach two ends of a synchronous belt, a minimum of 6 teeth in mesh on each side of the belt is recommended. Anything below 6 teeth will lower the belts available working strength (6 teeth = tensile strength of belt), and premature belt failure from tooth shear is more likely to occur.

Synchronous Belt Storage

Did you know that something as simple as storing your belts properly can make a huge difference in your belts life and performance? Here are a few storage recommendations that will keep your belts out of trouble, and performing the way they were designed to.

Whenever possible, store your belts in the original packaging until the moment it is ready for installation. This is the best way to keep from damaging the tensile cords of the belt.

Keep the belts away from direct sunlight and moisture. One way to avoid this is by keeping your belts away from windows.

Keep the belts out of the heat. Do not store your belts near heaters or radiators. Make sure that they are not in the airflow of a heating device.

Don’t store belts on the floor. This may seem a little over the top, but floors are high traffic areas, and a belt could easily be stepped on or rolled over, causing tensile cord damage.

Keep the belts away from chemical exposure. Any place that has solvents in the air could damage your belts. This includes chemicals such as ozone, which could be present near transformers or electric motors.

Belts should ideally be stored in a cool dry environment at a temperature of 85 degrees F or less with lower than 70% relative humidity. If done properly, a belt can be stored for up to 6 years.

Synchronous Drives Operating in Environments with Dust and Debris

Dusty environments do not generally present serious problems to synchronous drives as long as the particulates are fine and dry. Note, though, that particulate matter can act as an abrasive resulting in more rapid belt and sprocket wear. Damp or sticky particulate matter deposited and packed into sprocket grooves can cause belt tension to increase significantly. This increased tension can impact shafting, bearings and framework and can even result in belt tensile failure. Static electrical charges within drive systems can sometimes attract particulate matter, so may need to be dissipated to ground.

Debris should be prevented from falling into any synchronous belt drives by using screens or guards. Debris caught in belt drives is generally either forced through the belt or may result in a stalling of the system. In either case, serious damage will occur to the belt and related drive hardware.

Gates Flat Idler Pulleys

Idlers are included in belt drives for a variety of reasons (e.g. to apply the proper pre-tension or increase the belt wrap angle on a pulley). In the past, the Gates idler product line consisted of idler sprockets, brackets, and idler bushings. However, Gates recently introduced flat idler pulleys to give designers additional flexibility.

The flat idler pulleys can be used with the existing idler brackets and they are available in a range of sizes for use on both synchronous and V-belt drives. Available sizes and technical details regarding Gates idler product line are available at www.gates.com/idlers/.

Custom Synchronous Belt Sizes

There are two types of custom synchronous sizes, a different width and a different length.

Making stock belts in custom widths is usually easy to do. Synchronous belts are made on a mold that makes a single wide belt which is then cut down into the individual belt widths. If you need something other than a standard width, we require that you purchase the slabs worth of the custom width because we must set the tooling up to cut the whole slab. The number of belts will depend on the mold size and the width you are requesting.

Making custom lengths is much more difficult. Each size length is made on its own individual mold. In order to do a custom length not listed in our catalog, we have to machine a new mold for that size. This means that you will be charged for tooling fees and minimum order quantities, which is usually not feasible except for equipment manufacturers that will be placing large orders.

Polyflex Belts Unique Characteristics

Gates Polyflex belts have some unique characteristics. Therefore, special considerations may be needed in designing drive systems and in assessing operating environments:

Liquids act as lubricants – Because of the broad 60° groove angle, belt wedging forces are reduced making the coefficient of friction between belts and sheave grooves critical in transmitting load. Liquid contaminants such as water, chemicals or oils can decrease the coefficient of friction, allowing belt slip. Belt slip can result in belts turning over in the sheave grooves. Heat from belt slippage may also cause belt softening or melting, resulting in catastrophic failure. Adequate shielding should be used when liquid contaminants (either airborne or splashed) are present near Polyflex drive systems.

Damage from debris – The 60° belt sidewall angle and thin cross section both make these belts susceptible to debris. Debris can cause belt instability resulting in belt turn-over, which will result in catastrophic failure. Adequate shielding should be used when debris is present near Polyflex drive systems.

Backside idlers – Polyflex belts running on flat backside idlers can create objectionable noise due to the molded ribs on the back of the belts. Perceived sound level is inversely proportional to the sheave diameter, so using larger idlers can reduce generated noise.

Static conductivity - Polyflex V-belts do not meet the RMA requirements for belt conductivity. Polyflex V-belts should not be used in potentially explosive or flammable environments without the use of adequate static dissipating devices such as grounding brushes.

Measuring A Synchronous Belt

We get a lot of questions from people trying to find a suitable replacement belt. There seems to be a lot of confusion as to what information they need to provide for us to try to ID the particular belt. It’s not as difficult as it seems. The first question that we are going to ask you is to get us any print on the back of the belt. Industry callouts are pretty similar, and if you can find a part number, a lot of times we can ID it from that alone. Now if it comes down to measurements, there are only a couple that we need: length, width, and pitch. We also need to know the shape of the teeth. This is pretty simple, as there are only about 3 different types that we can interchange for power transmission belts; square/trapezoidal, half circle, and curvilinear with a flat spot on the top of the tooth. These shapes help us ID the type of belt, from here, all we need are the other three measurements to really get going.

Length: measure the outer circumference of the belt. If the belt is broken in half, just measure the total length.

Width: measure the width across the back of the belt. This could be in metric or imperial units; it doesn’t matter which one you give us, we just need the best measurement you can get.

Pitch: measure from the center of one tooth to the center of the next tooth. Simple, but sometimes the teeth are small. Getting as close as possible on this really helps – see above about the metric/imperial units issue.

We will also ask you to count the teeth, it’s not that we don’t trust your measurements, but this is verification of the correct length and pitch measurements. I know, I know… There may seem to be a lot of them, but even a belt with 200 teeth will only take a minute or two to count.

That’s it, from here, all it takes is knowledge of our product line to ID the type of belt, and a catalog to see if it’s a stock size. Sometimes we can’t cross a belt because it was made special for someone. In these cases you will have to go back to the manufacturer of the machine that your belt came on – even if we made the belt in the first place.

Fan Drives: High Start Up Loads and Synchronous Belt Drives

Start up loads can be a significant concern when evaluating potential drives for conversion to PowerGrip® GT®2 or Poly Chain® GT® Carbon belt drives.  PowerGrip^® GT^®2 and Poly Chain^® GT^®Carbon belt drives will transmit all of the start up torque, where V-belts may slip if the load is excessive.  Due to the inertia of the fan, start up loads can potentially be 150% to 200% of the normal operating load.  This is obviously much more of a concern when the drive will be operating on a system that frequently cycles on and off.  Drives that run continuously will only see the start up load intermittently, so are not as sensitive to the combination of high start up loads and weak structures.  It is important that the start up load be considered when evaluating a drive.  If the structure is weak, a high start up load will further adversely effect the PowerGrip^® GT^®2 or Poly Chain^® GT^® Carbon belt drive's performance by allowing center distance collapse.  This reduction in center distance results in an under tensioned belt which may wear prematurely from being undertensioned, or even worse, premature failure from ratcheting.  If an electrician or properly trained technician is available, an ammeter can be used to compare the start up amperage to the steady operation amperage.  If the amperage is 1 1/2 to 2 times the steady state amperage, the structure should be carefully inspected to insure that it is robust enough to prevent center distance collapse upon start up.  With the drive shut off and safely locked out, the structural rigidity can be checked by pushing the two belt spans inward toward each other and looking for any relative movement in the structure.

Belt Drive Inspection and Replacement

We sometimes get questions about how often belt drives should be inspected or replaced. This does not have a simple answer because belt wear and life depends on a variety of factors. Belt life depends on the original drive design, the actual loads experienced vs. the design loads, the pulley alignment, the installation tension and maintenance, and environmental conditions such as heat and chemical exposure. As you can see, many of these factors are out of our control, so therefore it is nearly impossible for any manufacturer to give an accurate estimate of the belt life without testing the actual drive. There are also many things to consider when deciding how often to inspect the drive including: Critical nature of the equipment Drive operating cycle Accessibility of equipment Drive operating speed Environmental factors Temperature extremes in the environment Probably the most important factor is the critical nature of the equipment. A belt powering an integral process to a manufacturing line should be inspected much more frequently than a small, seldom used HVAC unit should be. If the belt were to fail and shut down the assembly line, it could cost the operator a lot of money in downtime. Our general recommendations are to do a quick visual and noise inspection every one to two weeks for critical drives and once a month for normal drives. A complete shutdown inspection should be completed every three to six months. These can be adjusted depending on the factors above. For more information about drive inspection, see our Belt Drive Preventive Maintenance Manual available here: www.Gates.com/Catalogs

Selecting the Right Synchronous Replacement Belt

When replacing a synchronous belt on an existing drive, it is important to select a belt that is compatible with the sprockets. Selecting the right belt will optimize the performance and longevity of the drive.

However, the variety of styles available from numerous manufactures increases the difficulty of identifying a replacement belt. To help users select the proper replacement belt, Gates has created the Gates Belt/Sprocket Interchange (http://www.gates.com/index.cfm?location_id=3881). At this site, users can select their sprocket type and determine the best Gates replacement belt.

Rim Speeds and Maximum Diameters

Occasionally I have people asking me what the speed rating in on a specific belt. Here at Gates, we don’t give our belts a maximum speed rating like some of our competitors do. How fast is too fast then? It depends on the metal that you want or need to run. All of our sprockets and sheaves are statically balanced. We rate them to be able to run comfortably up to 6500 feet per minute (feet per minute is based on rpm AND diameter). If you plan to run them faster, you will need to have them dynamically balanced for the maximum speed you are going to reach. So what does this mean for a maximum belt speed? There are unfortunately a lot of things to consider if you’re going to be running at high speeds. If you are looking to run past 6500 ft/min, we recommend that you contact Product Applications so that we can discuss what you might expect when trying to design for high speeds.

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

Minimum Diameters

Different belts have different dimensions. They also use different materials; for instance, the cord inside an A section V-belt is smaller than the cord inside a B section V-belt. While this larger cord gives a B section belt more power capacity, it also means that your sheaves have to be above a larger minimum size than an A section belt’s sheaves. This applies to all of our belt lines. The smaller section belts can use smaller diameter sheaves and sprockets. The same concept applies to backside idlers as well. Going below these minimums on either the inside, or the backside of the belts can have a significant affect on belt life. To find out what minimum diameter sheave, sprocket, or idler your belt needs, check out our Belt Preventive Maintenance Manual available for free at www.gates.com/catalogs Click on the hyperlink for Power Transmission Catalog Collection to get to the page where you can download it.

Belt Drives and Dissipating Static Charge Buildup

All types of belts can generate electrical charges while operating in belt drive systems. Factors such as humidity and operating speed influence the charge potential. With static charges present there is potential for arcing or sparking in flammable environments. Other possible issues may be found with material handling processes or sensitive electronics.

In order to minimize possible issues with static charge build up, V-belts are generally manufactured in conductive constructions (Predator and PowerRated belts are not static conductive), and rubber synchronous belts can be produced in conductive constructions on a made-to-order basis. Note that Poly Chain GT Carbon belts cannot be produced in a conductive construction. The Association for Rubber Products Manufacturers (ARPM; formerly Rubber Manufacturers Association) defines standards for static conductive belts in their bulletin IP-3-3.

Static conductive belts meeting the ARPM Standard IP-3-3 should have sufficient conductivity to prevent measurable static charge buildup, thus preventing static discharges. Belt drive systems operating in potentially hazardous environments, though, must be properly grounded. A continuous conductive path from belt to ground is necessary to bleed off static charges. This path includes a static conductive belt, a conductive sprocket, a conductive bushing, a conductive shaft, and conductive bearings, all along the path to ground.

In hazardous environments, additional protection should be employed to assure that there are no accidental static spark discharges. Unusual or excessive debris or contaminant on belt contact surfaces or sprocket grooves, for example, can reduce the ability of belts to conduct static charges into hardware. In addition, belt conductivity properties are known to decline over time from normal use. Static conductive brushes or similar devices should be employed to bleed off any residual static buildup that might remain around belts.

Power and Fan Speed for Belt Drive Conversions

The power required to drive a fan relates to the fan shaft speed as follows:

Initial_Horsepower/New_Horsepower = (Initial_Fan_RPM/New_Fan_RPM)^3

A small speed change can result in a substantial increase in power consumption. Therefore, this relationship should be considered when replacing a V-belt drive with a synchronous belt drive for energy savings.

To ensure that the fan speed does not increase, the design speed ratio should be based on a measured fan shaft RPM of the existing V-belt drive. This measurement can be made with a contact or a strobe tachometer.