Mechanical Drives Archives - difference.minaprem.com

Difference Between Straight Teeth and Spiral Teeth Bevel Gear

Pintu — Sat, 08 Jun 2019 12:12:08 +0000

Gear drive is one part and parcel of mechanical power transmission system that transmits power and motion by successive engagement and disengagement of teeth of driver and driven gears. There exist four basic types of gear, namely spur gear, helical gear, bevel gear and worm gear. The spur gear and helical gear are applicable for power transmission between two parallel shafts, whereas bevel gear is useful for two intersecting shafts (not necessarily perpendicular). For non-parallel non-intersecting shafts, worm gear can be employed. Teeth of the bevel gear can be cut either straight or helical. If the tooth profile is straight then teeth of two mating gears come in sudden contact that imposes impact load on tooth and also increases vibration, noise and wear rate. This sudden contact can be replaced with gradual contact by altering the teeth form. Teeth that are cut in the form of spiral curve of the bevel gear blank can offer gradual contact. Accordingly, bevel gears can be classified into two groups—straight teeth and spiral teeth bevel gears.

As the name suggests, in straight teeth bevel gear, teeth are cut in the form of a straight line that converges on a common apex; while in case of spiral teeth bevel gear, teeth are cut in the form of a spiral curve that also converges on a common apex. Teeth of the straight bevel gear can be compared with that for spur gear, while the same for spiral bevel gear can be compared with helical gear, except that the teeth are cut on a conical gear blank (instead of cylindrical as in case of spur or helical gear). Spiral teeth minimize detrimental effects of straight teeth and offer a longer gear life. However, cutting such teeth is difficult and time consuming. Thus cost of the gear unit increases. Various similarities and differences between straight teeth bevel gear and spiral teeth bevel gear are given below in the form of table.

Similarities between straight teeth and spiral teeth bevel gear

Both are engagement type power transmission elements (unlike belt drive which is a friction drive).
Both offer slip-free power transmission. Thus they are positive drives.
Since both of them are bevel gears so they can transmit power and motion between two intersecting shafts. For example, both can transmit power at an angle of 90º.
In both the cases teeth are cut on a conical gear blank and the locus of all teeth converges on a common apex point.

Differences between straight teeth and spiral teeth bevel gear

Straight teeth bevel gear	Spiral teeth bevel gear
In case of straight teeth bevel gear, elements of the teeth are in the form of a straight line, which converges on a common apex.	In case of spiral teeth bevel gear, elements of the teeth are in the form of a spiral curve, which also converges on a common apex.
Here contact between teeth of two meshing gears occurs suddenly.	Here contact between teeth of two meshing gears occurs gradually.
Due to sudden engagement, teeth are subjected to impact loading.	Due to gradual engagement, teeth are subjected to gradual loading.
Sudden engagement of teeth also causes vibration and noise.	Operation of spiral teeth bevel gear is smooth and quite.
Load carrying capacity of straight teeth bevel gear is comparatively low.	Load carrying capacity of spiral teeth bevel gear is comparatively high.
These are suitable for low to moderate speed applications.	These can be utilized at high speed applications also.
Life of the straight teeth bevel gear is shorter as it is subjected to impact loading and vibration.	Spiral teeth bevel gears have longer life.

References

Introduction to Machine Design by V. B. Bhandari (McGraw Hill Education India Private Limited).

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Difference Between Double Helical Gear and Herringbone Gear

Pintu — Sat, 08 Jun 2019 11:43:04 +0000

In helical gears, teeth are cut at an angle (called helix angle) with the gear axis in the form of helix on the cylindrical gear blank. It replaces sudden engagement and disengagement of teeth (as in spur gear) by gradual mating and thereby reduces wear, vibration and noise. However, a pair of mating helical gears induces axial thrust force that is ultimately transferred to the bearings, which necessitates bulky and costly bearings. In order to eliminate this thrust force on bearings, two identical helical gears having same module and number of teeth and are joined on same axis but having teeth in opposite directions (one has left hand helix and other one has right hand helix) can be employed. While joining two helical gears, a small gap is sometimes maintained in between them. Primarily based on the presence or absence of this intermediate gap, two varieties of the helical gear have evolved—double helical gear and herringbone gear.

Although both are frequently used interchangeably, they are not exactly same. However, they serve same purpose and offer similar benefits as compared to single helical gear. In case of double helical gear, sufficient relief gap is provided between two identical helical gears having opposite hand of helix. It is easy to fabricate and cheaper. In case of herringbone gear, no such gap is provided. Thus two identical helical gears with opposite hand of helix physically touch each other. Its fabrication is complicated due to chance of immersion into the other halve and requires special type cutter for cutting the gear teeth. In both the cases, axial thrust force developed in one helical gear is opposite in direction to the thrust force developed in another helical gear. Thus the resultant thrust force becomes zero. Various similarities and differences between double helical gear and herringbone gear are given below in table form.

Similarities between double helical gear and herringbone gear

In both the cases, two helical gears must have same module, same number of teeth and same helix angle but opposite hands of helix.
Both gears are capable of eliminating thrust force on bearings. So their purposes are same.

Differences between double helical gear and herringbone gear

Double Helical Gear	Herringbone Gear
In double helical gear, a small gap is maintained by cutting a groove between two identical helical gears with opposite hands of helix.	In herringbone gears, no such gap is provided between two identical helical gears with opposite hands of helix.
Hobbing, a high productive gear cutting process, can be advantageously used for cutting double helical gears.	Hobbing is not preferred process for cutting herringbone gears as the hob (cutter) can run over the other half in the same way because of no gap. It is usually cut by gear shaper, which is a slow process.
Due to intermediate gap in between two helical gears, it requires more axial space.	Less axial space is required for same power transmission requirement.

References

Introduction to Machine Design by V. B. Bhandari (McGraw Hill Education India Private Limited).

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Difference Between Single Helical Gear and Double Helical Gear

Pintu — Sat, 08 Jun 2019 11:16:25 +0000

Gear drive is most widely used mechanical power transmission system in small to large scale machineries. It is one engagement type positive drive (no slip) suitable for transmitting motion, torque and power over comparatively small distances (usually below 1 m) and also modifying them as per requirement. Power is transferred from driving shaft to driven shaft by means of successive engagement and disengagement of teeth cut on the cylindrical gear blank. Different type of gears have different teeth arrangement. For example, spur gear has straight teeth that are parallel to the gear axis. In case of helical gear, teeth are cut in the form of helix on the pitch cylinder of the gear blank. Although spur gear and helical gear both are used for transmitting power between parallel shafts only, helical teeth offers numerous benefits such as higher load carrying capacity, low vibration, low noise, less wear rate and prolonged life. However, a pair of mating helical gears impose axial load on the bearings along with radial force.

This detrimental axial force can, however, be eliminated by employing two identical helical gears having same module and number of teeth and are joined on same axis but having teeth in opposite directions (one has left hand helix and other one has right hand helix). Such a helical gear arrangement is termed as double helical gear. Here, thrust force developed by each of the helical gears is opposite in direction but same in magnitude, and thus resultant thrust load becomes zero. It is worth mentioning that double helical gear and herringbone gear are used interchangeably, they are not exactly same, at least from construction and manufacturing points of view. Various similarities and differences between single helical gear and double helical gear are given below in table form.

Similarities between single helical gear and double helical gear

Like every gear drive, these two are also engagement type mechanical drives. A chain drive is another example for the same. Though belt drive is one mechanical drive, it is one friction drive.
In both the cases teeth are cut in the form of helix on the pitch cylinder of the gear blank. Hand of helix is, however, different for two cases.
In both the cases teeth of two mating gears come in contact gradually. Thus vibration, noise and teeth wear rate reduce substantially as compared to spur gear.
Both are applicable for transmitting motion and power between parallel shafts only. A bevel gear can be used for transmitting power between intersecting shafts, while worm gear can be employed for non-intersecting non-parallel shafts.

Differences between single helical gear and double helical gear

Single Helical Gear	Double Helical Gear
A single helical gear has teeth inclined in any one direction (either left hand helix or right hand helix).	Double helical gear consists of two identical gears jointed on same axis, and having teeth in opposite directions (one has left hand helix and other one has right hand helix).
Single helical gears develop axial thrust force and exerts the same on corresponding bearings. It also develops radial force.	Resultant thrust force developed in double helical gear is zero. Thus it exerts no axial load on bearings. But radial force exists as usual.
Power transmission capacity of single helical gear is comparatively low.	For same size and module, double helical gears can transmit larger power.
Single helical gears are cheaper.	Double helical gears are costlier as design and fabrication are difficult and time consuming.
High precision is usually not desired during alignment of the gears.	Two helical gears must be aligned precisely otherwise thrust force will not balance properly and the consequence will be unfavorable vibration.
Because of thrust load, high helix angle cannot be used. Helix angle for single helical gear usually varies within 15º – 20º.	Due to canceled thrust load, high helix angle (20º – 45º) can be advantageously used in double helical gears.
Efficiency of single helical gear is comparatively low.	Double helical gears can provide higher efficiency.
Bearing span (distance between two bearings) is short.	Bearing span is longer due to presence of center relief groove in between two gears.
Single helical gears are suitable for mechanical drives or power transmission requirements where each application usually requires a unique design for powers, speeds, and configuration.	Double helical gears are suitable for high power transmission requirements such as in cranes, marine drives or turbines.

References

Introduction to Machine Design by V. B. Bhandari (McGraw Hill Education India Private Limited).
Single vs. double helical gears by J. B. Amendola (2 Artec Machine Systems, October 2006. Featured in the Turbomachinery Magazine). artec-machine.com

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Difference Between Spur Gear and Helical Gear

Pintu — Sat, 08 Jun 2019 10:55:18 +0000

Gear drive is one important mechanical power transmission element that can transmit power and motion from one shaft to another by means of toothed wheel rigidly mounted on the shafts. It is one engagement drive that indicates power transmission occurs by means of successive engagement and disengagement of teeth of two gears. Whereas the belt drive (one type of friction drive) is especially suitable for medium to long distance power transmission, gear drive is preferred when distance between two shafts (driver and driven) is small (usually below 0.5m). They offer positive drive (no slippage) and thus velocity ratio remains constant. Gear drives can transmit power and motion between two parallel shafts (spur and helical gears), two intersecting shafts (bevel gear) and also two non-parallel non-intersecting shafts (worm gear). Different types of gears are available to fulfill such requirements.

Based on the profile of the teeth and its orientation on the gear axis, gears can be classified into four basic groups—spur gear, helical gear, bevel gear and worm gear. When axes of driver and driven shafts are parallel and gear teeth are also cut parallel to the gear axis then it is called as spur gear. So it is suitable for transmitting power between two parallel shafts only. Another gear, called helical gear, can be used for transmitting power between two parallel shafts. In case of helical gear, the teeth are cut in the form of helix on the pitch cylinder of the gear blank. Thus teeth makes an angle (called helix angle) with the gear axis. As compared to spur gear, a pair of similar helical gears can transmit higher power and can also offer higher velocity reduction. It is also capable in reducing vibration and noise; however, at the higher fabrication cost. Various similarities and differences between spur gear and helical gear are tabulated below.

Similarities between spur gear and helical gear

Both the gears are suitable for transmission of power and motion between parallel driver and driven shafts only. They cannot be used for non-parallel shafts.
Both can provide positive drive (no slippage and thus constant velocity ratio). In contrast, belt drive cannot offer constant velocity ratio due to inherent slip and creep.
Both are suitable for small distance power transmission (typically not above 0.5m).
No flexible element exists between two gears. In both the cases, driver and driven gears remain in physical contact. This is unlike belt or chain drive where intermediate flexible element like chain or belt exists. Such flexible elements can absorb vibrations and thus can protect the driver unit from undesired vibrations induced in machines. Every gear drive fails to fulfill this task.

Differences between spur gear and helical gear

Spur Gear	Helical Gear
In case of spur gear, teeth are parallel to the axis of the gear.	In case of helical gear, teeth are inclined with the gear axis in the form of a helix. This angle of inclination is known as helix angle (15° – 25°).
In spur gear drive, contact between teeth of two meshing gears occurs suddenly.	In helical gear drive, contact between teeth of meshing gears occurs gradually.
Here the contact between two meshing teeth is always a line of same length.	Here contact starts with a point, gradually becomes a line and leaves as a point.
Sudden engagement of teeth results in impact loading. So teeth are subjected to impact loading.	Due to gradual teeth engagement, load on the tooth builds up gradually. So teeth are subjected to gradual loading.
Impact loading caused by sudden engagement of teeth results vibration and noise.	Gradual loading provides a smooth and quite operation.
Load carrying capacity of spur gear is comparatively low.	For same size and same number of teeth, load carrying capacity of helical gear is comparatively high as larger number of teeth remains in contact at any instance.
Life of the spur gears is usually shorter.	Helical gears have longer life.
Two mating spur gears must have same module only.	Two mating helical gears must have same module, and same but opposite hand helix angle.
Spur gears are suitable for low to moderate speed applications.	Helical gears can be utilized at high speed also.
Spur gear drive produces only radial force. As the teeth are parallel to axis, the thrust force is zero.	Due to presence of helix angle, helical gear drive produces radial as well as thrust force. So the bearing must be capable of sustaining such thrust force.
It is suitable for the velocity ratio of 1:1 to 1:3.	It is suitable for the velocity ratio of 1:1 to 1:5.

References

Design of Machine Elements by V. B. Bhandari (Tata McGraw Hill Education Private Limited.
A Textbook of Strength of Materials by R. K. Bansal (Laxmi Publications Private Limited).

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Difference Between Open Belt Drive and Cross Belt Drive

Pintu — Sat, 08 Jun 2019 06:32:17 +0000

Mechanical power transmission system takes help of several drives and elements in order to transmit power, torque and motion from one shaft to another shaft. Such drives can be either engagement type (gear drive and chain drive) or friction type (belt drive and rope drive). Belt drive is one reliable mechanical power transmission system that is commonly used to transmit power and motion over considerably larger distance (even up to 15m) between driving shaft (usually a prime mover such as an electric motor) to driven shaft. Being a friction drive, belt drive is inherently associated with slip. So it cannot provide constant velocity ratio, thus it is one non-positive drive. This slip, however, can protect the driver unit from overloading in the driven part. Presence of flexible belt between two shafts also enables this drive to absorb vibrations induced in machinery. This belt many have various configurations, such as flat belt, V-belt, ribbed belt, etc. A flat belt is one jointed belt that has a rectangular cross-section. Only one surface of the belt comes in contact with the outer surface of the cylindrical pulleys.

Pulleys of the driver and driven shafts can be connected using the flat belt in two distinct ways—open belt and crossed belt. Each of them has unique benefits over the other one. In open belt drive arrangement, belt proceeds from top of one pulley to the top of other pulley without crossing. So the driver shaft and driven shaft rotate in same direction. Contrary to this, in crossed belt drive, belt proceeds from the top of one pulley to the bottom of other pulley and thus crosses itself in between two pulleys. Here driving shaft and driven shaft rotate in opposite directions. It offers higher contact angle, so power or torque transmission capacity also increases. However, due to crossing, belt continuously rubs itself, which leads to reduced belt life. Various similarities and differences between open belt drive and crossed belt drive are given below in table format.

Similarities between open belt drive and crossed belt drive

In both the cases, flat belt is used. V-belt and ribbed belt cannot be utilized in crossed configuration (they are always open).
In both the cases, driving and driven shafts must be parallel. However, a small misalignment does not possess noticeable problem.
Both can transmit power and motion for substantially large distances (even up to 15m). In comparison, trapezoidal belt or V-belt is suitable for short distance (usually within 1m).
In both the cases power transmission occurs by means of friction between the pulley and belt.
Slip can occur in both the cases. So none of them can offer constant velocity ratio. Thus they are non-positive drive.

Differences between open belt drive and crossed belt drive

Open Belt Drive	Crossed Belt Drive
In open belt drive, belt proceeds from top of one pulley to the top of other pulley without crossing.	In crossed belt drive, belt proceeds from top of one pulley to the bottom of other pulley and thus crosses itself.
In open belt drive, driving shaft and driven shaft rotate in same direction.	In crossed belt drive, driving shaft and driven shaft rotate in opposite direction.
Contact angle (or wrap angle) between the belt and pulley is comparatively small (always below 180º in smaller pulley).	Contact angle between the belt and pulley is comparatively large (always above 180º in smaller pulley).
Length of the open belt is smaller as compared to cross belt.	For the same pulley diameter and same centre distance between driver and driven shafts, longer belt is required in cross belt drive.
Here belt remains in same plane in every rotation during its operation.	Here belt bends in two different planes in every rotation during its operation.
Here belt does not rub with itself. So belt life is considerably high.	Here belt rubs with itself and thus life of the belt reduces.
Open belt drive is suitable when driving and driven shafts are in horizontal or little bit inclined.	Cross belt drive can be advantageously applied for horizontal, inclined and vertical positions of driving and driven shafts.
Power transmission capacity is small due to smaller wrap angle.	It can transmit more power as wrap angle is more.

References

Introduction to Machine Design by V. B. Bhandari (McGraw Hill Education India Private Limited).
A Textbook of Machine Design by R. S. Khurmi and J. K. Gupta (S. Chand).
Theory of Machines by R. S. Khurmi and J. K. Gupta (S. Chand).

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Difference Between Flat Belt Drive and V-Belt Drive

Pintu — Sat, 08 Jun 2019 05:54:23 +0000

Majority of mechanical machine units are driven by a prime mover, which converts mainly electrical energy into mechanical energy (usually in the form of rotation of a shaft). Power generated by the prime mover is transferred to the intended location for driving various elements of the machinery. Several power transmitting elements are used for such transmission purposes; each of them has specific advantages and disadvantages. Gear drive, belt drive, chain drive, rope drive, clutch, etc. are notable elements of mechanical power transmission system. Belt drive is one flexible drive where an endless belt (jointed or jointless) is employed to transmit power from driver shaft and driven shaft by means of friction between the belt and pulleys. It is simpler and economic as compared to gear drive or chain drive and can be used for medium to long shaft distances. It is also capable protecting the driver unit by absorbing vibrations. By means of slip, it can also keep the system safe from overloading.

Commercial belts are available in different cross-sections; among them flat belts and V-belts are frequently used. A flat bet has rectangular cross-section where width is significantly larger than thickness. It usages a cylindrical pulley where bottom surface of the belt comes in contact with the outer surface of the pulley. On the other hand, V-belt has trapezoidal cross-section with width comparable to height. It employs a pulley having corresponding V-grove to accommodate the V-belt. Both the side surfaces of the belt remains in contact with the pulley. Whereas flat belt is a jointed belt, V-belt is jointless. Although power transmission capability of flat belt is comparatively low, it can transmit power and motion to a longer distance. V-belt tends to eliminate slip but is costly and cannot be used for very long center distances. Various similarities and differences between flat belt and V-belt are given below in table format.

Similarities between flat belt drive and V-belt drive

Both flat belt and V-belt drives can transmit power and motion to a longer distance as compared to gear drive.
Both are suitable for transmitting power between parallel shafts only. Although little parallelism error does not possess any palpable problem, they are primarily not suitable for intersection shafts.
Both of them are flexible drives due to the presence of flexible element (belt). A flexible drive can isolate the prime mover from machine unit and thus restricts transmission of undesired vibrations.
Both are friction drives, which indicates power and motion are transferred from driver to driven shaft by means of friction between the pulley and belt.
Although V-belt drive eliminates slippage, both of them are categorized under non-positive drive because of creep motion. In fact, V-belt can also slip when load on driven shaft exceeds a certain limit.
Pulleys are indispensably required on both the shafts in every belt drive. However, pulley geometry varies based on belt configuration.

Differences between flat belt drive and V-belt drive

Flat Belt Drive	V-Belt Drive
Flat belts have a rectangular cross-section, where width of belt is much larger than thickness.	V-belts have a trapezoidal cross-section, where maximum width is almost same with the thickness.
The pulleys for flat belt drive are simple in construction and thus cheaper.	Here pulleys must contain V-slot to accommodate V-belts. Slot angles must match with that of the belt, otherwise power transmission capability will reduce. Thus these pulleys are costlier.
In flat belt drive, only one surface of the belt remains in contact with the pulley.	In case of V-belt drive, two inclined surfaces continuously remain in contact with the pulley.
Wide range of velocity ratio can be obtained by utilizing stepped pulleys of different diameters and easily shifting belt from one pulley to another.	Such shifting provision does not exist in V-belt drive.
Flat belts can be used for transmitting power to a long center distance (even up to 15m).	V-belt drive is suitable for power transmission in short center distance (usually below 1m).
Flat belt drive can be used either in open configuration or in crossed configuration.	V-belt is always used in open configuration.
Efficiency of the flat belt drive is comparatively higher.	Efficiency of the V-belt drive is low.
Power transmitting capability of flat belt drive is low.	V-belt drive can transmit comparatively higher power because of the increased friction force due to wedge action.
Flat belt drive is suitable when velocity ratio is up to 4:1.	Higher velocity ratio (up to 7:1) can be obtained by V-belt drive.
Slip occurs frequently in flat belt drive. Thus is not a positive drive.	Due to higher friction force for wedge action, slip does not occur at low speed in V-belt drive. However, if load exceeds the rated capacity, then slip may occur.
Flat belts are jointed (hinged), so their operation is noisy.	V-belts are endless, so their operation is quite.
Flat belt drives are usually suitable for horizontal power transmission.	V-belt drives are preferred for transmitting power in any direction, even when belt is vertical.
Flat belts are also relatively cheaper.	V-belts are costlier.
Flat belts are commonly used in belt conveyer, saw mills, food industries, etc.	V-belts are commonly used in electric pumps, compressors, machine tools, etc.

References

Design of Machine Elements by V. B. Bhandari (Tata McGraw Hill Education Private Limited).
Theory of Machines by S. S. Rattan (McGraw Hill Education India Private Limited).

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Difference Between Belt Drive and Chain Drive

Pintu — Sat, 08 Jun 2019 05:13:57 +0000

Basic purpose of mechanical drive is to transmit torque, motion and power from driving shaft (usually a prime mover like an electric motor) to driven shaft, and also to alter the intensity, direction and speed as per the requirement. There exist several mechanical drives to fulfill varying industrial and machinery requirements. Such drives can be classified into two major categories—positive drive and non-positive drive. A positive drive is free from slippage and thus provides constant velocity ratio. Contrary to this, a non-positive drive cannot provide fixed velocity ratio due to slippage or other similar issues. Each drive has unique advantages over the other one and thus is used in various applications. Gear drive and coupling are examples of positive drive. Chain drive also offers constant velocity ratio if designed and maintained properly. On the other hand, belt drive and rope drive are considered as non-positive drive as they are prone to slip and creep.

Belt drive is one type of mechanical drive where motion and power are transferred from one shaft to another by means of friction between belt and pulleys mounted on each shaft. As friction plays the primary role in power transmission, so it is also called a friction drive. Slip can occur between belt and pulley when load exceeds the rated capacity. Such slippage is not always undesirable as it can inherently protect various machine elements from overloading. On the contrary, chain drive is one engagement type power transmission system that transmits motion and power by means of successive engagement and disengagement chain with sprocket. Being a positive drive, it offers a fixed velocity ratio; however, sometimes fails to protect the system from excessive loading. Various similarities and differences between belt drive and chain drive are given below in table format.

Similarities between belt drive and chain drive

Both belt drive and chain drive are mechanical drives. Thus they utilize various mechanical elements which must be in physical contact for transmitting power. Apart from mechanical drive, other drives that are frequently used in industries include hydraulic drive, pneumatic drive and electrical drive.
Both belt drive and chain drive are suitable for transmitting power and motion for medium to larger shaft distance. For shot distance, gear drive is preferred. However, V-belt can be applied for short to medium distance also.
They can be applied for parallel driver and driven shafts only. They are not suitable for transmitting power between non-parallel shafts. It is worth mentioning that quarter-turn belt can be used for non-parallel non-intersecting shafts.
Both require frequent adjustment in tension; otherwise slip percentage increases as the belt or chain stretch out with service time.

Differences between belt drive and chain drive

Belt Drive	Chain Drive
Belt drive is one friction type mechanical drive where friction force between belt and pulley is used to transmit power and motion.	Chain drive is one engagement type mechanical drive where power and motion are transmitted by successive engagement and disengagement of chain with sprocket.
Belt drive is preferred for medium to long center distance between driver and driven shafts.	Chain drive can be used for short to medium center distances.
Although belt drive is suitable for parallel shafts, slight parallel error is tolerable and does not create noticeable problem.	In chain drive, parallelism must be maintained precisely, otherwise chain may leave sprocket without any warning.
Slippage occurs in belt drive when load exceeds frictional force.	No such slippage occurs in chain drive.
Because of slip, velocity ratio does not remain constant in belt drive. Thus it is not a positive drive.	Here velocity ratio remains fixed. So chain drive is one positive drive. However, polygonal effect may lead to non-uniformity in speed.
Efficiency of belt drive is comparatively low because of frictional loss.	Efficiency of chain drive is high, usually above 95%.
Belt tension is affected by atmospheric conditions and temperature. Thus performance of belt drive also changes with external factors.	Chain drive is usually not affected by atmospheric conditions and temperature.
Belt drive requires minimum maintenance.	Chain drive requires regular maintenance including lubrication.

References

Introduction to Machine Design by V. B. Bhandari (McGraw Hill Education India Private Limited).
A Textbook of Machine Design by R. S. Khurmi and J. K. Gupta (S. Chand).
Theory of Machines by R. S. Khurmi and J. K. Gupta (S. Chand).

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Difference Between Gear Drive and Chain Drive

Pintu — Sat, 08 Jun 2019 04:36:17 +0000

In many engineering applications, power is required to transmit from one point to another. Various power transmission systems such as electrical, mechanical, hydraulic, pneumatic, etc. can fulfill different requirements. Mechanical power transmission systems are used to transmit power, motion and torque from driver shaft (a prime mover such as electrical motor) to the driven shaft. Changing direction, speed and intensity are also important tasks for such transmission systems. There exist several drives to transmit a wide range of torque or power in various distances and subsequently modify them as per requirement. Gear drive and belt drive are two prominent mechanical power transmission systems overwhelmingly used in machineries and industries. Apart from these two drives, chain drive, rope drive, coupling, etc. are also examples of mechanical power transmission system.

In case of gear drive, power and motion are transferred from one shaft to another shaft through successive engagement and disengagement of teeth of two mating gears. Teeth are cut on both the gears and one such gear is mounted on driving shaft while other gear is mounted on the driven shaft. There is no requirement of ancillary element other than two mating gears. Gear drive is especially suitable from small distance but heavy power transmission. Contrary to this, chain drive is suitable for comparatively long distance power transmission requirements; however, load carrying capacity of chain drive is comparatively small. In chain drive, sprocket is mounted on each of the driving and driven shafts while an endless chain connects the sprockets. It is also engagement type drive, but it can inherently absorb vibrations induced in machine unit. Various similarities and differences between gear drive and chain drive are given below in table format.

Similarities between gear drive and chain drive

Both gear drive and chain drive are engagement type mechanical drives. Mechanical drives can be either engagement type of friction type (like belt drive or rope drive). In engagement drives, two elements engage and disengage successively for power transmission; while in friction drives, power transmission occurs only due to frictional force acting between two elements.
Both are positive drives as no slip occurs during operation. So they offer constant velocity ratio. However, chain drive sometimes fails to provide constant velocity ratio, especially during prolonged usage of chain (chain may stretch).
Both are suitable for small to medium distance power transmission requirements. For long distance (>1m), belt drive is preferred.
Both the drives require proper lubrication for prolonged service.

Differences between gear drive and chain drive

Gear Drive	Chain Drive
Gear drive is one engagement type mechanical drive as power and motion are transferred by means of successive engagement and disengagement of teeth of mating gears.	Chain drive is also one engagement type mechanical drive but power and motion are transferred by means of successive engagement and disengagement of chain with sprocket.
No additional element is required in gear drive (only two gears are sufficient for power transmission).	In chain drive, apart from two sprockets, a chain is indispensably necessary for power transmission.
It is not one flexible drive. Thus, it cannot protect the driver unit from vibrations induced in driven unit.	Presence of flexible element like chain makes it one flexible drive. It can easily isolate vibrations, and thus can protect the driver.
Gear drive is suitable for small centre distance between driver and driven shafts.	Chain drive can be employed for short as well as medium centre distances between driver and driven shafts.
For the same centre distance, gear drive requires more space. The drive unit is also heavy.	Chain drive is compact and thus space efficient. Drive unit is light in weight.
Gear dive requires precise centre distance otherwise performance will degrade sharply.	Centre distance is not so critical for chain drive. A small error is tolerable without much effect.
Gear drive requires full lubrication. For best performance and longer life in heavy duty applications, gears must be partially immersed into lubricating oil.	Chain drive also requires lubrication to reduce noise and wear of joints; however, it does not require full lubrication (periodic lubrication is sufficient).
Gear drive can be utilized for parallel (spur and helical gears), intersecting (bevel gear), and non-intersecting non-coplanar (worm gear) shafts.	Chain drive is suitable for parallel shafts only.
Operation of gear drive is quiet.	Operation of chain drive is noisy.
A wide range of velocity reduction (1:1 to 1:40) is possible with gear drive.	Chain drive is not suitable for high velocity reduction. It can be used when reduction is up to 1:10.

References

Introduction to Machine Design by V. B. Bhandari (McGraw Hill Education India Private Limited).
A Textbook of Machine Design by R. S. Khurmi and J. K. Gupta (S. Chand).
Theory of Machines by R. S. Khurmi and J. K. Gupta (S. Chand).

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