Belt (Mechanical): Difference between revisions
(Content added) |
No edit summary |
||
| (9 intermediate revisions by 2 users not shown) | |||
| Line 2: | Line 2: | ||
== Introduction == | == Introduction == | ||
Belts are used for transmitting power between two shafts. Belts will be of two kinds, flat and vee belts. Belts are running over the pulleys which are mounted on two shafts. Belts are used when the distance between the shafts is large. Gears are used when the distance between the shafts is small. | Belts are used for transmitting [[power]] between two shafts<ref>{{Cite book|last=Dr. R. K., Bansal|title=Theory of Machines|pages=284}}</ref>. Belts will be of two kinds, flat and vee belts. Belts are running over the pulleys which are mounted on two shafts. Belts are used when the distance between the shafts is large. Gears are used when the distance between the [[shafts]] is small. | ||
== Types of Belts == | == Types of Belts == | ||
[[File:Belt types.jpg|alt=Belt Types|thumb|Fig 1. Belt Types]] | [[File:Belt types.jpg|alt=Belt Types|thumb|Fig 1. Belt Types]] | ||
* Flat Belt - This belt has a rectangular cross section as shown in fig 1. (a) . These belts are capable of transmitting power over long distances between pulley centres. The efficiency of this drive is around 98% and produce little noise. | * Flat Belt - This belt has a rectangular cross section as shown in fig 1. (a) . These belts are capable of transmitting power over long distances between pulley centres.<ref>{{Cite web|title=Belt Drives|url=https://www.theengineerspost.com/types-of-belt-drives/#:~:text=Flat%20belt%3A%20This%20belt%20has,long%20distances%20between%20pulley%20centres.}}</ref> The efficiency of this drive is around 98% and produce little noise. | ||
* V Belt - This belt is used with grooved pulleys, V-belts are trapezoidal in cross-section as shown in fig 1. (b). This belt permit large speed ratio and can transmit higher power. | * V Belt - This belt is used with grooved pulleys, V-belts are trapezoidal in cross-section as shown in fig 1. (b). This belt permit large speed ratio and can transmit higher power. | ||
| Line 27: | Line 27: | ||
=== Velocity Ratio : === | === Velocity Ratio : === | ||
Velocity ratio is the ratio of the velocity of the driven to the velocity of the driver. | Velocity ratio is the ratio of the [[velocity]] of the driven to the velocity of the driver.<ref>{{Cite web|title=Velocity Ratio|url=https://www.engineersgallery.com/velocity-ratio-and-slip-of-a-belt-drive/}}</ref> | ||
Let N<sub>1</sub>= Speed of the driver ; d<sub>1</sub>= Diameter of the driver | Let N<sub>1</sub>= Speed of the driver in r.p.m ; d<sub>1</sub>= Diameter of the driver | ||
N<sub>2</sub>= Speed of the driven ; d<sub>2</sub>= Speed of the driven | N<sub>2</sub>= Speed of the driven in r.p.m ; d<sub>2</sub>= Speed of the driven | ||
Length of the belt passing over the driver in one minute = circumference of the driver X number of revolutions per minute | Length of the belt passing over the driver in one minute = circumference of the driver X number of revolutions per minute | ||
| Line 45: | Line 45: | ||
π d<sub>1</sub> X N<sub>1</sub> = π d2 X N2 | π d<sub>1</sub> X N<sub>1</sub> = π d2 X N2 | ||
Velocity ration is <math>\frac{N_2}{N_1} = \frac{d_1}{d_2}</math> | Velocity ration is <math>\frac{N_2}{N_1} = \frac{d_1}{d_2}</math> --------- equation (1) | ||
== Slip of the belt == | |||
When the driver pulley rotates , due to the firm grip between the pulley surface and the belt, the driver pulley carries the belt. The firm grip between the pulley and the belt is obtained by [[friction]] which is known as frictional grip. But sometimes the frictional grip is not sufficient which may cause some forward [[motion]] of the driver pulley without carrying the belt with it. This means that there is a relative motion between the driver pulley and the belt. The difference between the linear speeds of the pulley rim and the belt is a measure of slip. Generally slip is expressed as a percentage | |||
== Creep of the belt == | |||
In a belt drive the belt is passing over the driver and driven(follower) pulley. Belt is subjected to tension during the power transmission. The portion of the belt which leaves the follower and approaches the driver is known as the tight side of the belt and is subjected to tension T<sub>1</sub>. The portion of the belt which leaves the driver and approaches the follower is known as the slack side of the belt and is subjected to tension T<sub>2</sub>. T<sub>1</sub> > T<sub>2 .</sub> Stretch in the belt due to different tensions on the two sides of the pulley will be different. A certain portion of the belt when passes from slack side to tight side, extends and the same portion contracts again when it passes from tight side to slack side. Due to these changes in length , there will be a relative motion between the belt and the pulley surfaces which is known as Creep.<ref>{{Cite web|title=Creep|url=https://old.amu.ac.in/emp/studym/99996967.pdf}}</ref> The creep reduces slightly the speed of the follower (driven pulley). | |||
== Cross Belt drive == | == Cross Belt drive == | ||
| Line 51: | Line 57: | ||
In an open belt drive both the pulleys rotate in the same direction, where as in cross belt drive the pulleys rotate in the opposite direction. | In an open belt drive both the pulleys rotate in the same direction, where as in cross belt drive the pulleys rotate in the opposite direction. | ||
The driver pulley A pulls the belt from CD side and delivers it to FE side. Thus the tension in the belt CD will be more than that in the belt FE. CD side is known as tight side and FE side is known as slack side. | The driver pulley A in fig 3. pulls the belt from CD side and delivers it to FE side. Thus the tension in the belt CD will be more than that in the belt FE. CD side is known as tight side and FE side is known as slack side. | ||
== Compound Belt Drive == | |||
[[File:Compound Belt Drive.jpg|alt=Compound Belt Drive|thumb|Fig 4. Compound Belt Drive]] | |||
Compound Belt drive is used when the power is to be transmitted from one shaft to another through a number of pulleys. In fig 4. shows Compound belt drive where in pulley 1 drives the pulley 2 . Pulleys 2 and 3 are fixed to the same shaft, hence the pulley 1 drives pulley 3 also. Pulley 3 drives the pulley 4. | |||
=== Velocity Ratio of Compound Belt drive. === | |||
Velocity ratio is the ratio of the velocity of the driven to the velocity of the driver. | |||
Let N<sub>1</sub>= Speed of the pulley 1 in r.p.m ; d<sub>1</sub>= Diameter of the pulley 1 | |||
N<sub>2</sub>= Speed of the pulley 2 in r.p.m ; d<sub>2</sub>= Speed of the pulley 2 | |||
N<sub>3</sub>= Speed of the pulley 3 in r.p.m ; d<sub>3</sub>= Speed of the pulley 3 | |||
N<sub>4</sub>= Speed of the pulley 4 in r.p.m ; d<sub>4</sub>= Speed of the pulley 4 | |||
From equation (1) Velocity ratio of pulleys 1 and 2 is | |||
<math>\frac{N_2}{N_1} = \frac{d_1}{d_2}</math> ------- (''i'') | |||
Similarly Velocity ratio of pulleys 3 and 4 is | |||
<math>\frac{N_4}{N_3} = \frac{d_3}{d_4}</math> -------- (''ii'') | |||
Multiplying the equations (''i'') and (''ii'') | |||
<math>\frac{N_2}{N_1} X \frac{N_4}{N_3} = \frac{d_1}{d_2} X \frac{d_3}{d_4}</math> | |||
N<sub>2</sub> = N<sub>3</sub> as the pulleys 2 and 3 are fixed to the same shaft. | |||
<math>\frac{N_4}{N_1} = \frac{d_1}{d_2} X \frac{d_3}{d_4}</math> | |||
which is | |||
<math>\frac{Speed \ of \ last \ follower }{Speed \ of \ first \ driver} = \frac{Product \ of \ diameter \ of \ drivers}{Product \ of \ diameter \ of \ followers}</math> | |||
== See Also == | == See Also == | ||
[[पट्टा(बेल्ट)]] | [[पट्टा(बेल्ट)]] | ||
== External Links == | |||
* [http://mechanicsmap.psu.edu/websites/7_friction/7-7_belt_friction/beltfriction.html Belt Friction] | |||
*[https://www.heiyi-belt.com/Belt-Drives-Types-Slip-Creep-V-belts-Advantages-Disadvantages-HEIYI-id3678333.html Slip and Creep] | |||
* | |||
== References == | |||
<references /> | |||
[[Category:CS1 français-language sources (fr)]] | |||
[[Category:CS1 maint]] | |||
[[Category:CS1 Ελληνικά-language sources (el)]] | |||
[[Category:Citation Style 1 templates|W]] | |||
[[Category:Collapse templates]] | |||
[[Category:Mechanical engineering]] | [[Category:Mechanical engineering]] | ||
[[Category: | [[Category:Navigational boxes| ]] | ||
[[Category:Navigational boxes without horizontal lists]] | |||
[[Category:Organic Articles English]] | |||
[[Category:Pages with broken file links]] | |||
[[Category:Pages with script errors]] | |||
[[Category:Sidebars with styles needing conversion]] | |||
[[Category:Template documentation pages|Documentation/doc]] | |||
[[Category:Templates based on the Citation/CS1 Lua module]] | |||
[[Category:Templates generating COinS|Cite web]] | |||
[[Category:Templates generating microformats]] | |||
[[Category:Templates that are not mobile friendly]] | |||
[[Category:Templates used by AutoWikiBrowser|Cite web]] | |||
[[Category:Templates using TemplateData]] | |||
[[Category:Wikipedia fully protected templates|Cite web]] | |||
[[Category:Wikipedia metatemplates]] | |||
Latest revision as of 14:04, 9 January 2023
Introduction
Belts are used for transmitting power between two shafts[1]. Belts will be of two kinds, flat and vee belts. Belts are running over the pulleys which are mounted on two shafts. Belts are used when the distance between the shafts is large. Gears are used when the distance between the shafts is small.
Types of Belts
- Flat Belt - This belt has a rectangular cross section as shown in fig 1. (a) . These belts are capable of transmitting power over long distances between pulley centres.[2] The efficiency of this drive is around 98% and produce little noise.
- V Belt - This belt is used with grooved pulleys, V-belts are trapezoidal in cross-section as shown in fig 1. (b). This belt permit large speed ratio and can transmit higher power.
- Circular Belt - This type of belt has a circular cross-section as shown in fig 1.(c). and is used with the grooved pulleys.
Types of Belt Drive
Open Belt drive
Cross Belt drive
Compound Belt drive
Open Belt drive
Open Belt drive consists of two pulleys A and B in fig 2. Driver pulley is the pulley which is keyed to the rotating shaft. Driven pulley is the pulley which is keyed to the shaft and to be rotated. Here Driver pulley is pulley A and Driven pulley is pulley B.
The mechanical power or rotary motion is transmitted from the driving pulley to the driven pulley because of the frictional grip that exists between the belt and the pulley surface.
The driver pulley A pulls the belt from the lower side and delivers it to the upper side. Thus the tension in the lower side of the belt will be more than the tension in the upper side. Lower side is called as tight side and the upper side is called as the slack side.
Sometimes in a belt-drive, there is always a possibility of some slipping taking place between the belt and the pulleys which cause the driven pulley to rotate at a lesser speed, consequently reduces the power transmission. Hence belt drives are said to be not a Positive type of power transmission system
Velocity Ratio :
Velocity ratio is the ratio of the velocity of the driven to the velocity of the driver.[3]
Let N1= Speed of the driver in r.p.m ; d1= Diameter of the driver
N2= Speed of the driven in r.p.m ; d2= Speed of the driven
Length of the belt passing over the driver in one minute = circumference of the driver X number of revolutions per minute
= π d1 X N1
Length of the belt passing over the driven in one minute = circumference of the driven X number of revolutions per minute
= π d2 X N2
Length of the belt passing over the driver in one minute = Length of the belt passing over the driven in one minute
π d1 X N1 = π d2 X N2
Velocity ration is --------- equation (1)
Slip of the belt
When the driver pulley rotates , due to the firm grip between the pulley surface and the belt, the driver pulley carries the belt. The firm grip between the pulley and the belt is obtained by friction which is known as frictional grip. But sometimes the frictional grip is not sufficient which may cause some forward motion of the driver pulley without carrying the belt with it. This means that there is a relative motion between the driver pulley and the belt. The difference between the linear speeds of the pulley rim and the belt is a measure of slip. Generally slip is expressed as a percentage
Creep of the belt
In a belt drive the belt is passing over the driver and driven(follower) pulley. Belt is subjected to tension during the power transmission. The portion of the belt which leaves the follower and approaches the driver is known as the tight side of the belt and is subjected to tension T1. The portion of the belt which leaves the driver and approaches the follower is known as the slack side of the belt and is subjected to tension T2. T1 > T2 . Stretch in the belt due to different tensions on the two sides of the pulley will be different. A certain portion of the belt when passes from slack side to tight side, extends and the same portion contracts again when it passes from tight side to slack side. Due to these changes in length , there will be a relative motion between the belt and the pulley surfaces which is known as Creep.[4] The creep reduces slightly the speed of the follower (driven pulley).
Cross Belt drive
In an open belt drive both the pulleys rotate in the same direction, where as in cross belt drive the pulleys rotate in the opposite direction.
The driver pulley A in fig 3. pulls the belt from CD side and delivers it to FE side. Thus the tension in the belt CD will be more than that in the belt FE. CD side is known as tight side and FE side is known as slack side.
Compound Belt Drive
Compound Belt drive is used when the power is to be transmitted from one shaft to another through a number of pulleys. In fig 4. shows Compound belt drive where in pulley 1 drives the pulley 2 . Pulleys 2 and 3 are fixed to the same shaft, hence the pulley 1 drives pulley 3 also. Pulley 3 drives the pulley 4.
Velocity Ratio of Compound Belt drive.
Velocity ratio is the ratio of the velocity of the driven to the velocity of the driver.
Let N1= Speed of the pulley 1 in r.p.m ; d1= Diameter of the pulley 1
N2= Speed of the pulley 2 in r.p.m ; d2= Speed of the pulley 2
N3= Speed of the pulley 3 in r.p.m ; d3= Speed of the pulley 3
N4= Speed of the pulley 4 in r.p.m ; d4= Speed of the pulley 4
From equation (1) Velocity ratio of pulleys 1 and 2 is
------- (i)
Similarly Velocity ratio of pulleys 3 and 4 is
-------- (ii)
Multiplying the equations (i) and (ii)
N2 = N3 as the pulleys 2 and 3 are fixed to the same shaft.
which is
See Also
External Links
References
- ↑ Dr. R. K., Bansal. Theory of Machines. p. 284.
- ↑ "Belt Drives".
- ↑ "Velocity Ratio".
- ↑ "Creep" (PDF).
