Transmission belt drives

IP-3-13 Mechanical Efficiency of Power Transmission Belt Drives (1999). 

More information about the specific belt dimensions can be found in the Goodyear Power Transmission Belt Drives manual. 

Rlemen, m. belt, band, strap, thong oar. -an-trieb, m. (Mach.) belt drive, -fett, n. belt dressing, -kitt, m. belt (or strap) cement, -leder, n. belt leather, belting strap leather, -scheibe, /. belt pulley, -setuniere, /., -schmiennittel, n. belt lubricant, -trieb, m. belt drive, belt transmission,... 

The difference between the brake horsepower and the water or liquid horsepower is the pump efficiency. The requirement in either case is the horsepower input to the shaft of the pump. For that reason, the brake horsepower represents the power required by the pump, which must be transmitted from the driver through the drive shaft through any coupling, gear-box, and/or belt drive mechanism to ultimately reach the driven shaft of the pump. Therefore, the losses in transmission from the driver to the pump itself must be added to the input requirement of the driven pump and are not included in the pump s brake horsepower requirement. 

There are two types of flexible intermediate drives used to transmit torsional power belt drives and chain drives. Flexible belts are used in industrial power transmission applications primarily when the speeds of the driver and driven shafts must be different or when the shafts must be widely separated. The trend toward higher speed primary drivers and the need to achieve a slower, useful driven speed are additional factors favoring the use of belts. In addition to V-belts, there are round belts and flat belts. Chain drives are typically used in applications where space is limited or obstructions prevent direct coupling of machine-train components. 

Few belt-drive systems use a single belt for power transmission. The number of belts is determined by the horsepower requirements of the machine train. Determination of these requirements must be based on the full operating range of the system. Rapid speed changes, direction reversal, and other operating practices have a direct impact on the requirements of the belt system. Therefore, the selection process should be based on the most demanding operating conditions. 

The motor power can be transferred to the gearbox in a number of different ways. This is usually done via a belt drive or directly via a clutch. With the extruder powers common today, direct transmission via a clutch is now the standard method. However, belt drives are still used on lower-power systems and in case of special requirements due to limited space. 

The rotation is passed to the drive shaft of the motor through a V-belt transmission. The drive shaft rotates crankshafts synchronously and transmits the motion to milling blocks. The productivity of the mill depends on the size of jars, the frequency of shaft rotation, rate of material admittance through the jars, etc. Centrifugal mills providing the productivity of 5- -50 kg per hour have been constructed. 

Figure 274(a) depicts the drive system which was already part of the earliest machines (see Figure 225). More recent machines, instead of powering shaft (3) by transmission belts, apply a motor (5) with a torque-limiting clutch, a gear reducer (4), and a flexible coupling to drive gear shaft (3) mounted in or on the roller press frame. The gear on shaft (3) transmits torque to the coupled gears (2) on the roll shafts between two roller bodies (1).

For belt-driven loads the margin factor should be a little larger than for direct in-line driven machines due to the lower transmission efficiency of belt drives. Let an additional multiplying factor be used to that given in Table 5.11. This factor should be approximately 1.2 for the smaller motors to 1.4 for the larger motors. It is also advisable to obtain advice from the manufacturers of both the driven machine and the motor. 

Uses of flat conveyor and (power) transmission belts and V-belts (for power transmission) are to be found in almost all major industries. V-belts for different types cover applications ranging from fan belts for automobiles, belts for low-power drives for domestic, laboratory, and light industrial applications, to high-power belts for large industrial applications. 

Power transmission is as a rule effected by belt drive, at first this was with fiat belts and later with V-belts. A drive version using a direct-coupled electric motor with intermediate reduction gear was offered as an option as far back as the 1920s. (Fig. 42). Mobile extrusion units with an independent power supply from a diesel generating set were developed from 1950 for use in the Third World. 

Belt drives use adjustable sheaves. The axial distance between the sheaves can be varied this changes the effective pitch at which the belt contacts the sheave. This, in turn, changes the transmission ratio. The speed is usually varied by a vernier screw mechanism, which is hand cranked or activated electrically. Belt drives are used up to 100 hp. The largest speed ratio is about 10 1, and a maximum speed is typically 4000 rpm. Belt drives have a reasonable efficiency, tolerate shock leads, and provide optimum smoothness in a mechanical drive. Disadvantages are heat generation, possibility of slippage, and relatively poor speed control. In addition, belt drives are subject to wear and, thus, are maintenance-intensive belts generally have to be replaced every 2000 hours. 

Non-operational - for use on transmission gears, belt drives, shafts and parts that usually do not require frequent adjustments or approach by the operator. 

Single-rotor and twin-rotor hammer crushers are usually driven by slip-ring motors via a V-belt transmission system. As a rule, slip resistors are provided in order to ensure flexible behaviour of the drive motor. In the event of a drop in rotation speed due to impact loading of the rotor, the motor will still develop a high torque and the V-belt drive will be less severely strained. The drive pulley, which serves as a flywheel, is overhung-mounted on the rotor shaft - even on the largest crushers hitherto built - and is fixed by means of locking sleeves or similar devices. 

Belt drives are the most widely used method of flexible power transmission. Improvements in materials and methods of manufacture have allowed the introduction of new belts with much broader application capabilities. 

Flat belts, one of the earliest forms of flexible power transmission, are generally more suited to high-speed, low-horsepower applications. At low speeds and high loads, flat-belt drives usually become too large to be cost-effective. 

Drives is the term given to power-transmission equipment. The simplest form of power transmission is a belt drive. A belt drive can have a flat, V-belt, ribbed belt, or toothed belt design. These drives are common in applications such as conveyors. Conveyor manufacturers should be consulted for their catalogues on power-transmission capability. 

Mechanical transmission (power-grip toothed-belt drive) (see Fig. P-72)... 

Similarly, for shorter centre distances between the drive and the driven pulleys, the arc of contact will decrease. To ensure a good arc of contact, the centre distance C (Figure 8.10), should be kept as much as possible, otherwise the provision of a jockey pulley, as noted above, will also be necessary. A higher arc of contact will ensure a better grip of the belt on the pulley and hence a smaller slip during transmission of the load. A smaller slip would mean a higher transmission of load and vice versa. 

V-belts are common intermediate drives for fans, blowers, and other types of machinery. Unlike some other power-transmission mechanisms, V-belts generate unique forcing functions that must be understood and evaluated as part of a vibration analysis. The key monitoring parameters for V-belt-driven machinery are fault frequency and mn-ning speed. 

Unlike V-belts, chain drives do not rely on friction to deliver power. As a result, transmission of power is positive (i.e., no slippage) and in many ways resembles the action of gears. A chain is constmcted in such a way that it provides a connection between the teeth of the drive pinion and driven sprockets. 

The transmission motor or fan is operated by drive belts and pulleys. The support frame of the motor must be designed to obtain the tension of the belts without modification of the alignment of the pulley and to adjust this alignment. The motor class must be calculated with an over capacity of 30% of the used power and must be connected through a safety switch placed on the air handling unit. 

The granulator comprises a rotary plate mounted on a shaft in a pivoted-frame bearing assembly. The plate is rotated by a drive roller which makes contact with its contact surface. The roller drive turns on the motor, V-belt transmission, and reduction gear. 

I turned the key. The car started instantly. I fastened my seat belt. Nothing but a click. Steve got in the passenger seat, and we went for a test drive. We floated down the road. I couldn t hear a sound, but I decided it must be time to shift gears. I stomped around on the floor and grabbed Steve s knee before I remembered the car had automatic transmission. 

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