Roller Chain Drives

Roller Chain. Table 3-18 gives the typical service factor for roller chain drives [5], Table 3-19 gives the basic roller chain design dimensions for ANSI standard roller chains by ANSI chain number [14]. 

The power is provided to the drawworks by the prime movers at the master clutch (see Figure 4-9) and is transmitted to the master clutch shaft via sprockets and roller chain drives. The speed and the torque from the prime movers are controlled through the compound. The compound is a series of sprockets, roller chain drives, and clutches that allow the driller to control the power to the... 

Because of the versatility of roller chain drives, certain standards have been established. With these standards, interchangeability of chains is possible between one manufacturer and another. As long as chains are identifiable, they can be cross-referenced easily without any serious operational problems arising. Table 58.7 shows the standard roller chain American Standards Association (ASA) number by pitch length for single, double, and triple strand chains. 

FIGURE 5.M A roller chain drive operates multiple rolls in a heat-tieating furnace. 

Roller chain drives are used in a wide range of power transmission applications for all basic industries such as food processing, materials handling, oil field equipment, construction, agricultural equipment, and machine tools. 

Select a roller chain drive for the following conditions Source of power Gearmotor... 

Sprockets are fabricated from a variety of materials this would depend upon the application of the drive. Large fabricated steel sprockets are manufactured with holes to reduce the weight of the sprocket on the equipment. Because roller chain drives sometimes have restricted spaces for their installation or mounting, the hubs are made in several different styles. See Figure 7.3. 

FIGURE 1-18 Typical roller chain drives in a machine. 

Roller chain drives are often simpler, less costly, and more practical than gear drives. 

Roller chain drives normally are more compact than belt drives, and they can be nearly... 

Roller chain drives permit easier and less costly changes in center distance or speed ratios. 

Roller chain elongation due to normal wear is a slow process when the chain is adequately lubricated, and does not affect satisfactory operation of the drive. Therefore, adjustments are needed less frequently in a roller chain drive than in a belt drive. 

Silent chain drives are quieto and smooths than roller chain drives, and in some cases arc quieter than gear drives. 

Eingineering steel chain has all of the advantages of roller chain listed above, except that engineering steel chain drives tend to be somewhat noisiCT than roller chain drives. That is because of the additional clearances built into engineering steel chains and the pitch-line clearance usually provided in sprockets for engineering steel chain drives. However,... 

A roller chain drive or conveyor may be subjected to all of the tensile loads that were listed eariiCT, thus the roller chain must have several tensile strength properties to withstand the wide range of tensile loads that may be imposed on it. The main strength properties that a roller chain must have... 

The force diagram in Figure 4-28 may also be used to compute the tension in each link and the ejection force imposed on each roller engaging the sprocket, but that is beyond the scope of this book. For more information, see the book. Mechanics of the Roller Chain Drive by R. C. Binder (Prentice Hall, 1956). 

The following guidelines and procedures are intended to help a drive designer manually select a suitable roller chain drive as quickly and efficiently as possible. Some manufacturers offer roller chain drive selection software. These programs eliminate much of the work in selecting a roller chain drive, but be sure to read and follow all of the cautions and restrictions that come... 

GENERAL ROLLER CHAIN DRIVE SELECTION GUIDELINES... 

The small sprocket in a roller chain drive should have at least 11 teeth. The chain and sprocket with fewer than 11 teeth has more power capacity than the cold rolled shafting that will fit into the sprocket. That combination can cause the more costiy shafting to fail before the chain. 

Roller chain drives with multiple driven sprockets are fairly common (Figure 5-11). The drive designer should consult an ACA roller chain manufacturer for advice on drives with multiple driven sprockets. This is because each manufacturer uses different service factors for multiple driven sprockets. 

Software is available to select roller chain drives with multiple driven sprockets. That software is very useful and convenient, but the methods and equations are proprietary to the particular developer. 

Obtain the following listed infonnation before selecting a roller chain drive. Make every effort to obtain all of the needed information. 

The designer shonld select the type of lubrication recommended in the power rating tables. More detailed information on roller chain drive lubrication can be found in chapter 13. 

Many roller chain drives have large cyclic loads or impulses. These cyclic loads may occur once, or a few times, per revolution and they may come from either the driven machine or input power source. The magnitude of the impulse depends on how much the peak load exceeds the mean load, how much the peak power pulse exceeds the mean input power, the inertia of the driving and driven machines, and the stiffness of the drive. The frequency of the impulses is the sprocket speed, in revolutions per second, divided by the number of impulses per revolution. 

Roller-tooth vibration, and the impacts that incite it, arc the source of most of the noise in a roller chain drive. The amplitude of roUCT-tooth vibration increases approximately with the square of sprocket speed, so it is very important in high-speed drives. This is one of the reasons why the power capacity of a roller chain decreases so rapidly at high speeds (see Equation 5.6). 

As stated above, roller-tooth impact, and its resulting vibrations, are the source of most of the noise in a roller chain drive. Noise is a serious considraation in many roller chain drives. The roller chain industry has done considerable research on roller chain drive noise and has learned a lot about the many factors that cause roller chain drive noise. Evrai so, they did not find a way to calculate or predict with reasonable accuracy the noise that will be made by a given drive. 

Certain noise factors are related to the basic mechanics of a roller chain drive. Some of the basic findings of research on roller chain drive noise include the sound level (in decibels) increases with chain pitch, increases with chain tension, increases with the logarithm of the sprocket speed, and peaks at a frequency of about 6 kHz. 

Fortunately, industry research also found that drive designers and uscts could do a number of things to reduce the noise from a roller chain drive. Some things that can be done to quiet a noisy drive, along with a short explanation, include... 

Parts of S. W. Nicol and J. N. Fawcett, Vibrational charactmstics of roller chain drives, Engineering, January 1977, pp. 30-32, were used in preparing the section on vibration. 

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