Pulleys and Belts – Poly-V
There are so many belt types available. The prefix offers dimensional standards, and somewhat defines the purpose of the belt. This knowledge allows you to understand which belts can be substituted, and which cannot.
Meaning less than 1 HP. Especially in cases where one or more of the pulleys are small in diameter. I run this warning because common sense would lead you to believe a 3V belt is a comparable substitute for a 3L, or that an AVX belt is a suitable substitute for an AX belt.
Common sense would be wrong. Never substitute or mix these belts. They do not fit properly into pulleys designed for 3L and AX belts. They do not make full contact against the bottom and walls, and therefore will fail to perform. For example, most applications up to 7.
Also, when multiple belts are used in industrial applications, the V and VX belts are narrower at the top to allow for a better fit.
And since industrial applications are typically higher horsepower running at higher RPM, the belts need to be tightened more than non-industrial applications, which make the V and VX belts better. The V and VX belts are not as flexible as the A, B, C belts; therefore they are typically used with larger sheaves, and cannot be used with Backside Tensioning Pulleys.
That stiffer characteristic also makes them better for the long center distance span. According to the website BeltsForAnything. Be careful when measuring a worn belt, they can and do stretch as they wear. Therefore the measurements between the old and new may not be exact. If you are unable to read the belt part number, you will need to measure. I could take the time to better explain, but instead will defer to a brief instructional video embedded below.
Using a permanent marker, overlap the ends and mark any point between where the two overlapping end pieces. Lay the marked string on a flat surface, and measure the distance between the two markings with a tape measure. This is the Inside Circumference IC for your replacement belt. Interpreting Belt Part Numbers Too often the belt you need to replace is either gone, the part number information is worn off, or the belt disintegrated when it broke.
Therefore, once you have obtained the part number, it will be easy to interpret and understand how to discover the replacement for an equal, or better quality belt. The information below will not return an exact measurement as implied by the belt part number. Example: A 4L Belt 0. To convert the measurement to an Outside Circumference OC , use the following information.
To convert the measurement to an Inside Circumference IC , use the following information. Proper tension and pulley to pulley alignment is critical, and necessary for long, satisfactory operation. However, there is still a wide range of tension which a belt will operate satisfactorily. The intent is to find this proper range for any V-Belt drive.
Always consult an owners guide for the proper tension range. For example, if the span length is 50 inches, the desired belt deflection is 0. The more you tension a belt, the faster it will wear out. Your belt should spring back when you press down on the backside. Proper Pulley Alignment Two misaligned pulleys will quickly wear out belts and bearings as well as cause belts to fall off.
Alignment should be performed with the use of lasers. Stop The Squeak Everyone hates this noise. If your fan system has developed a squeak the root cause could be due to the belt wearing out, dirty pulleys, belt is too loose, incorrect belt type, poor belt quality, oil on the belts, a bad bearing in a pulley, worn idler pulley, motor going bad, or belt misalignment.
The belt should always be seating and aligned to the center of each pulley. It is from Browning and is available for free. I recommend you follow this link and print as a reference guide.
Types of V-Belts
Belt drive disadvantages Power transmission belting has been used for more than years. The first belts were flat and ran on flat pulleys. Later, cotton or hemp rope was used with V-groove pulleys to reduce belt tension. This led to the development of the vulcanized rubber V-belt in The need to eliminate speed variations led to the development of synchronous or toothed belts about and the later development of fabric-reinforced elastomer materials.
Today, flat, V, and synchronous belting is still being used in power transmission. When compared to other forms of power transmission, belts provide a good combination of flexibility, low cost, simple installation and maintenance, and minimal space requirements. Belt-driven equipment uses readily available components.
Replacement parts can be easily obtained from local distributors. This availability reduces downtime and inventory. Sheaves and pulleys are usually less expensive than chain drive sprockets and have little wear over long periods of operation.
Belt types All power transmission belts are either friction drive or positive drive. Friction drive belts rely on the friction between the belt and pulley to transmit power. They require tension to maintain the right amount of friction. Flat belts are the purest form of friction drive while V-belts have a friction multiplying effect because of wedging action on the pulley.
Positive drive or synchronous belts rely on the engagement of teeth on the belt with grooves on the pulley. There is no slip with this belt except for ratcheting or tooth jumping. Flat belts Modern flat belts are made with reinforced, rubberized fabric that provides strength and high friction levels with the pulley Fig.
This eliminates the need for high tension, lowering shaft and bearing loads. Good efficiency is due to lower bending losses from a thin cross-section, low creep because of friction covers and high modulus of elasticity traction layers, and no wedging action into pulleys. Pulley alignment is important to flat belts. Belt tracking is improved by crowning at least one pulley, usually the larger one.
Flat belts are forgiving of misalignment; however, proper alignment improves belt life. Different flat belt surface patterns serve various transmission requirements. In high-horsepower applications and outdoor installations, longitudinal grooves in the belt surface reduce the air cushion flat belts generate. The air cushion reduces friction between the pulley and belt. The grooves nearly eliminate the effects of dirt, dust, oil, and grease and help reduce the noise level.
Flat belts operate most efficiently on drives with speeds above fpm. Continuous, smooth-running applications are preferred. Speed ratios usually should not exceed At higher ratios, longer center distances or idlers placed on the slack side of the belt create more wrap around the smaller pulley to transmit the required load.
V-belts Fig. V-belts come in V-belts are commonly used in industrial applications because of their relative low cost, ease of installation, and wide range of sizes Fig. The V-shape makes it easier to keep fast-moving belts in sheave grooves than it is to keep a flat belt on a pulley. The biggest operational advantage of a V-belt is the wedging action into the sheave groove. This geometry multiplies the low tensioning force to increase friction force on the pulley sidewalls Fig.
Classical V-belts are frequently used individually, particularly in A and B sizes. The larger C, D, and E sizes generally are not used in single-belt drives because of cost penalties and inefficiencies. Narrow V-belts, for a given width, offer higher power ratings than conventional V-belts. They have a greater depth-to-width ratio, placing more of the sheave under the reinforcing cord. These belts are suited for severe duty applications, including shock and high starting loads. Banded V-belts solve problems conventional multiple V-belt drives have with pulsating loads.
The intermittent forces can induce a whipping action in multiple-belt systems, sometimes causing belts to turn over. The joined configuration avoids the need to order multiple belts as matched sets. Banded V-belts should not be mounted on deep-groove sheaves, which are used to avoid turnover in standard V-belts. Such sheaves have the potential for cutting the band of joined belts. Extremely worn sheaves produce the same result.
V-ribbed belts combine some of the best features of flat belts and V-belts. The thin belt operates efficiently and can run at high speeds. The ribs ensure the belt tracks properly, making alignment less critical than it is for flat belts. Synchronous belts Synchronous belts have a toothed profile that mates with corresponding grooves in the pulleys, providing the same positive engagement as gears or chains.
They are used in applications where indexing, positioning, or a constant speed ratio is required. The first tooth profile used on synchronous belts was the trapezoidal shape Fig. It is still recognized as standard.
Recent modifications to tooth profiles have improved on the original shape. The full-rounded profile distributes tooth loads better to the belt tension members. It also provides greater tooth shear strength for improved load capacity. Synchronous belts can wear rapidly if pulleys are not aligned properly, especially in long-center-distance drives, where belts tend to rub against pulley flanges.
To prevent the belt from riding off the pulleys, one of them is usually flanged. A recent development has produced a belt and pulley that use a V-shaped, instead of straight, tooth shape. Undertensioning causes performance problems. The drive may be noisy because belt teeth do not mate properly with pulley grooves or the belt may prematurely wear from ratcheting. High forces generated during belt ratcheting are transmitted directly to shafts and bearings and can cause damage.
Link belts Link-type V-belts consist of removable links that are joined to adjacent links by shaped ends twisted through the next link Fig. With this design, belts can be made up of any length, reducing inventory. Link-type belts are used to make instant V-belt replacements These belts can transmit the same horsepower as classic V-belts. The links are made of plies of polyester fabric and polyurethane that resist heat, oil, water, and many chemicals. Disadvantages include cost and the possible generation of static charges.
The belt should be grounded when used in high-dust applications. Alignment Misalignment is one of the most common causes of premature belt failure Fig. The problem gradually reduces belt performance by increasing wear and fatigue. Depending on severity, misalignment can destroy a belt in a matter of hours. Improper drive maintenance is the biggest source of belt drive problems Angular misalignment Fig.
A related problem, uneven belt and cord loading, results in unequal load sharing with multiple belt drives and leads to premature failure. Angular misalignment has a severe effect on synchronous belt drives.
Wide belts are more sensitive to angular misalignment than narrow belts. Uneven belt and cord loading is not as significant a concern as with angular misalignment. Parallel misalignment is typically more of a concern with V-belts. They run in fixed grooves and cannot free float between flanges to a limited degree as synchronous belts can. Parallel misalignment is generally not a critical concern with synchronous belts as long as the belt is not trapped or pinched between opposite sprocket flanges and tracks completely on both sprockets.
Tension Total tension required in a belt drive depends on the type of belt, the design horsepower, and the drive rpm. Since running tensions cannot be measured, it is necessary to tension a drive statically.
Once a calculated force is applied to the center of a belt span to obtain a known deflection, the recommended static tension is established. Most design catalogs provide force and deflection formulas. With too little tension in a V-belt drive, slippage can occur and lead to spin burns, cover wear, overheating of the belt, and possibly overheating of bearings. Not enough tension in a synchronous belt causes premature tooth wear or possible ratcheting that will destroy the belt and could break a shaft.
When installing a new belt, installation tension should be set higher. Generally 1. This is necessary because drive tension drops rapidly during the seating-in process. This extra initial tension does not affect bearings because it decays rapidly.
Belt application matrix.
The difference between a flat and V-belt drive
Some of the most common types of v-belts include ribbed ones, notched ones, cogged ones, banded ones, wedged ones and smooth ones, each of which is specifically designed to help serve a different purpose. The guides for the v-belts can also come in several types, mostly based on shapes and surface with the most common shapes being a triangle profile, a rectangle profile, a special rectangular profile with rounded corners and a special v-profile a trapezoidal shape. Normal Uses V-belts are widely used because of their versatility as well as ability to handle directional changes that might prove challenging with other types of conveyor belts.
They can be used for basic tasks such as product alignment, offsetting connections, diverting, merging and directional changes. The different types available are what make v-belts so versatile. Features No matter which type of v-belt you select or what surface you opt for, there are several features that are common for all of these belts.
Depending on the width of the pulley, this hump usually ranges between 0.
Types of belts for belt drives
This achieves self-centering of the belt and prevents it from running off and the belt keeps track. Figure: Pulley for flat belts Flat belts generally generate very little noise. This also has positive effects on the service life and the efficiency approx.
Due to the relatively small belt thickness, the belt can be very strongly bent and thus allows the use with relatively small pulleys. A disadvantage of flat belts, however, is the relatively high bearing load caused by the high pretensioning forces.
Flat belts have high efficiency and flexibility as well as low wear and low noise levels; however, they require relatively high pretensioning forces! V-belts The high bearing load when using flat belts can be significantly reduced by using V-belts.
Therefore, only relatively low preload forces are necessary to generate the required frictional forces for power transmission. Accordingly, the bearing load is also significantly reduced. Figure: Standard V-belt wrapped Conversely, with the same pretensioning forces, much higher torques can be transmitted when using V-belts instead of flat belts. To further increase the power transmission, two or more V-belts can also be arranged parallel to each other.
Figure: V-belts V-belts can transmit significantly higher torques with the same bearing load than flat belts; however, the efficiency is lower! The V-belt must therefore not touch the groove bottom, as the contact force must only come about by the flanks. Otherwise there would be no wedge effect! For the same radial force bearing loadthe total friction force is significantly higher for V-belts. Expressed in figures, a factor of 3.
Since the V-belts only rest on the flanks, they are specially designed for a certain range of pulley diameters as well as for certain wrap angles. Otherwise, for example, belts designed for larger pulleys would bend too much and the flanks would buckle and then no longer rest flat.
Gates V Belts
Animation: V-belt cross section Due to the greater belt thickness of V-belts compared to flat belts, the energy required to bend the belt around the pulleys is higher. Therefore, V-belts have a slightly lower efficiency than flat belts approx. While the transmission ratio for flat belts is determined by the outer diameter of the pulleys, in the cas of V-belts the so-called pulley pitch diameter must be taken as a basis for calculating the transmission ratio due to the special geometry.
The nominal width corresponds to the belt width at the level of the neutral axis. Thus, according to the definition of the neutral axis, the nominal width always remains constant even when the belt is bent i. It must be noted that V-belts must run in after initial assembly before they can be put into operation.
HVAC – The Basics of V-Belts
This requires a correspondingly increased preload of approx. Over the course of time, different types of V-belts have developed, depending on the application. The most important ones are described in more detail in the following sections. Tension cords made of steel, aramid, polyester or glass are embedded in an elastomer core covered by a top layer.
Contamination by black rubber dust is a consequence of this. This cannot be done by estimation, but must be calculated. The sign of a correctly installed flat belt is when it moves towards the center on both belt pulleys and tension has been reached.
Thus a correctly installed flat belt does not need readjustment and is maintenance free. V-belts are often installed by estimation and do have a certain error margin, however this affects the service life.
Basics of belt drives
V-belts must be tensed from time to time since their grooves wear down. Design At Habasit we manufacture flat belts customized to your needs. You do not need to stick to standard lengths or widths. We make it possible to design optimized operations from a technical, economical, and energy efficient perspective. I hope this blog has been helpful in understanding the differences between belt types.
Would you like to hear other examples or learn more about how our flat belts compare to our V-belts? Do not hesitate to contact us! He has worked at Habasit for over 35 years and has extensive experience in drive belts, as well as webbing in most industries and applications.