Design and Testing of Agricultural Machines: Belt, Pulley, Sprocket, Chain, Gear Drives Flashcards by greatlemae basbano

the most simple method of transmitting power in agricultural machines and widely adopted in driving various production and postproduction parts of agricultural machines.

Belt-and-pulley drive

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The cost of transmitting power is very much lower

compared with sprocket-and-chain and gear drives.

Belt-and-pulley drive

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a flexible material which is banded on two or more
pulleys where power is transmitted from the driver to the driven pulley. Power transmission primarily depends on the friction between the belt and the pulley surfaces.

Flat Belt

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is a transmission system that consists of an endless
flexible belt that transmits power by contacting and gripping the sheaves which are keyed to the shaft of the driving and the driven machine.

V Belt

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TRUE/FALSE
Flat Belt and Pulley Drives are suitable for high-speed drives, adaptable to the dusty and abrasive environment, and transmits power on a long-distance shaft.

TRUE

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TRUE/FALSE
Flat Belt and Pulley Drives have longer life span, high efficiency, low cost, and low maintenance. Also applicable for the short-distance drive using pivoted or spring-actuated motor bases. Requires tension to minimize slip below 2 percent. High bearing load due to high tension requirement for the belt.

TRUE

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TRUE/FALSE
V-Belt and Sheave Drives are suitable for short-center-distance driving and the ability to transfer heavy tensile load.
Usually used to transmit power between parallel shafts and used for non-parallel drives applicable for single or in multiple sheaves.

FALSE (long-centered)

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Prone to elongation because of wear and operation; hence,

there is a need of mechanism to maintain the proper tension to take up the belt slacks.

V-Belt and

Sheave Drive

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They rotate with slip and creep conditions’ therefore, the angular velocity between the two shafts is neither constant nor exactly equal to the ratio of the sheave pitch diameter. Power losses caused by slip and creep ranged from 3 to 5 % for most belt
drives.

V-Belt and

Sheave Drives

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– is used to transmit rotary motion and power
between two shafts which lie flat on the face of the
corresponding pulley.

Flat Belt

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– is a belt with trapezoidal cross-section to

transmit rotary motion to parallel shafts.

Narrow V-Belt

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– is a V-belt with inverted V on top making it

more suitable for multiple-sheaves drive arrangement.

Double V- Belt

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– is a V-belt with teeth design for a special kind
of sheave to provide more gripping action to obtain higher
efficiency hence minimizing belt slip.

Cogged Belt

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– combines the features of a flat belt and a
V-belt. It operates very efficiently and can run at a very high
speed.

V-Ribbed Belt

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– is most common where there is a
large center distance between shafts or where drive ratio
goes beyond the commonly supplied drive.

Variable-Speed Belt

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It can carry significant load of up to 500hp and
can provide long service life. However, it is costly and
requires to be cleaned and dressed at all times. It is also
prone to stretch and shrink. Also, it is normally limited to low
or moderate speed.

Leather

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This is a combination of both
fabric and cord reinforcement that provides the strength of
chord reinforcement and the abrasion resistance of the
fabric.

Rubberized fabric or cord

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This kind of belt material is the least
costly of all. For the same width and thickness, this type
transmits less power and has a shorter life than leather.

Rubberized Fabric

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This is only available as endless belt and
not designed to be spliced. It carries 50% more power that
fabric reinforced belt.

Rubberized Chord

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This has a nylon member
covered by rubber or plastic. Its capacities ranged from
fractional horsepower to 100hp per inch of width. It is capable
of operating at 40,000 fpm.

Reinforced Rubber or Plastic

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It is made either of plain or with chemical or

rubberized coatings. It has the ability to tract uniformly

Fabric

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ordered according to the material, width and
number of plies. Example, canvas-type flat belt 4in. wide, 4
plies.

Flat belts

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ordered according to brand, type, (A, B, C, D, E,
etc.) and length. Example, Mitsubishi B-52 belt means type B
with circumferential length of 52 inches.

V-belts

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are used to transmit the power from the belt to the shaft. Generally made of cast iron. However, there are steel pulleys that are also available and are made in various sizes
and combinations. And should be carefully selected to fit the need and requirement of the drive

Pulleys and sheaves

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are grooved sheaves or flat pulleys which do not serve to transmit power. Instead they are used to tighten belt when it is not possible to move either shaft for belt installation and take-up

Idlers

Pulley shafts are parallel with each other Pulleys have the same direction Shorter belt length Smaller arc of contact of belt on two pulleys Suitable for v-belt and flat belt drives

Open-Belt Drive

• Pulley shafts are perpendicular with each other • Requires longer belt than open-belt drive • Relatively higher arc of contact between belt and pulley • Suitable for flat belt or special type of v-belt

Quarter-Turn Drive

* Pulley shafts are parallel with each other * Pulleys direction are opposite * Requires longer belt length * Higher arc of contact of belt on pulleys * Suitable for flat belt drive or special type of v-belt

Cross-Belt Drive

Pulley Speed and Diameters Formula

N1 D1 = N2 D2

Speed Ratio Formula Speed Ratio – It is the ratio of the angular speed of two pulleys making no allowance for slip and creep.

Nr = N1 / N2

Belt Velocity Formula Belt Velocity – is the linear speed of the belt.

Vb = 0.262 x D x N

Belt Length (Open Drive) Formula Belt Length – is the stretched-out length of the belt.

L = 2C + 1.57 (D + d) + [D – d]^2 / 4C

Belt Length (Crossed Drive) Formula

L = 2C + 1.57 (D + d) + [D + d]^2 / 4C

Belt Length (Quarter Turn Drive Formula

L = 1.57 (D + d) + √(C^2 + D^2) + √(C^2 + d^2)

Length of Arc Formula Length of Arc – is the length of belt that is linked on pulley or pulleys.

La = D x A / 115

Arc of Contact of Smaller Pulley Arc of Contact – is the angle by which the belt is in contact with the pulley.

Arc = 180 - [ 57.3 ( D – d ) / C ]

Design Power for V-Belt Drive Formula

DP = NPR x SF

V-Belt Power Rating Formula

Power Rating = Table Rating + Additional power for Speed Ratio

V-Belt Corrected Power Rating Formula

Corrected Power Rating= Power Rating x Arc of Contact Factor x Belt Length Correction Factor

Number of V-Belts Formula

Number of Belts = Power Capacity / Corrected Power Rating

What formula is this? Wb = ( H x S ) / ( K x C )

Width of Flat Belt

What formula is this? Wp = Wb +Allowance

Width of Pulley

An engine is to be used to drive a hammer mill to run at 3,000rpm speed. How would you couple the hammer mill to the engine?

By connecting the engine to the mill using belt and pulley drive to reduce its speed while running the mill at 3000 rpm.

If two shafts are perpendicular with each other, what type of drive system would you recommend?

Flat belt

When one pulley is to be driven horizontally and the other pulley is to be driven vertically, what drive system would you recommend?

Quarter-turn drive

If two parallel flat pulleys are to be driven in opposite direction, what drive would you recommend?

Cross drive

Drive used to run perpendicular | shafts.

Machine element used to drive | flat belts.

Pulley

Pulley that is used to tighten | the belt of a drive system.

Idler pulley

Flat pulleys are usually | provided with crown to ____.

prevent the belt from slipping

Flat pulleys are crowned by making the center diameter larger than the edge diameter by ___.

1/8 in. per foot of the pulley | diameter

If the driver pulley diameter is increased, the speed of the driven pulley will ____.

Increase

Commonly used belt drive for | engine-driven multi-pass rice mills.

Flat belt

``` Type of flat belt that has the advantage of high-tensile strength to hold metal fasteners satisfactorily and has high resistance to deterioration due to moisture. ```

Reinforced-nylon chord belt

basically consists of an endless chain whose links | engage the teeth of sprocket keyed to the shaft of the driving and the driven mechanisms.

chain drive

used to transmit power and to synchronize motion or maintain a fixed-speed ratio between rotating shafts and commonly used in the construction of transmission boxes for power and puddling type floating tillers in the Philippines.

chain drive

TRUE/FALSE The chain drive shaft distances are unrestricted, i.e. the drive is well suited for long and short center distances. They do not creep or slip but maintain a positive speed ratio between the driver and the driven shafts.

TRUE

TRUE/FALSE They are physically not more compact than belt drives and require less accurate alignment of the shaft and the sprockets. Arc of contact is bigger for chains than for belts. They are more practical for mild speed.

FALLSE (more compact, more accurate, smaller for chains, low speed)

is one of the oldest styles chains that are still in use today

Detachable Chain

• They are used for slightly higher speed (up to about 450 fpm) and heavier loads. • They are made of individual cast links having full round barrel end with offset sidebars.

Pintle Chain

• They are high-speed chains used predominantly for prime | mover power take-off drive.

Inverted-Tooth or Silent Chain

• They are used for manually-controlled or slow-speed drives.

Bead or Slider Chain

a type of roller chain made of basic components called link plates, rollers, bushings and pins. The chain can be either single- or multi-strand and comes in various sizes with different tensile strengths.

Engineering Steel Chain

• This is the most important type for agricultural use. It is available either single- or multiple-strand type. • Roller chain composed of roller, links, and pin links, alternately spaced throughout the length of the chain. The roller link consists of two sets of rollers and bushing, and two link plates, and the pin links consists of two pins and two link plates.

Roller Chain

``` Types of Sprockets • A - • B - • C - • D - ```

* A - plain plate * B - with hub on one side only * C - with hub on both sides * D - detachable hub

Materials of Sprockets • Cast iron – for large sprockets • Steel - small sprockets • Stainless steel or bronze – for corrosion resistant application • Formica, nylon, and special purpose plastic – for special condition

• Cast iron – for large sprockets • Steel - small sprockets • Stainless steel or bronze – for corrosion resistant application • Formica, nylon, and special purpose plastic – for special condition

It is the distance between adjacent joint members.

Chain Pitch –

It is the diameter of the pitch circle that passes through the center of the link pins as the chain wrapped on the sprocket.

Pitch Diameter

TRUE/FALSE The size of chain-and-sprocket drive is designated as RC Number. The higher the chain number, the larger is the loading capacity of the drive.

TRUE

What is this formula? Nr Tr = Nn Tn

Sprocket Speed

What is this formula? R = Nr/Nn

Speed Ratio

What is this formula? V = [ p x T x N] / 376

Chain Velocity

What is this formula? L = 2 C + [(Tl – Ts)/2] + [(Tl-Ts)/ 4 π^2 C]

Length of Chain

Sprocket Pitch Diameter Formula

PD = P / [ sin (180/T)]

Chain Forces Formula

Cp = 1000 P / V

Design Power = Power to be transmitted x service factor / | Multiple strand factor

Power Rating

Power Rating Required = Design Power x Design Life / | 15,000

Power Rating Required

– Oil is supplied periodically with | brush or spout can once every 8 hours of operation.

Manual Lubrication

– Oil drops are directed between the link | plate edges from a drip lubricator.

Drip Lubrication

– The lower strand of chain runs | through a sump of oil in the drive housing

Bath or Disc Lubrication

– The lubricant is usually supplied by a circulating pump capable of supplying each chain drive with a continuous stream of oil.

Oil-Stream Lubrication

``` A drive system consisting of an endless chain whose links engage the teeth of sprocket keyed to the shaft of the driving and of the driven mechanism that is commonly used for power tiller transmission boxes. ```

By connecting the engine to the mill using belt and pulley drive to reduce its speed while running the mill at 3000 rpm

Roller chain drive

Chain size is usually specified | in terms of ____.

roller chain number

RC-50 chain is stronger than | ____.

RC-40

Minimum size of chain for the transmission box of a walking-type hand tractor.

ANSI chain number 50

Length of chains is usually | expressed in ____.

pitches

If roller chain number 40 is to be replaced with no. 60, the strength of the chain will ____.

increase

For slow-speed operation, the recommended number of teeth for driver sprocket is ____.

16 teeth

Recommended minimum number of sprocket teeth for highspeed operation.

18 - 24 teeth

The slack strand for chain with horizontal center should be located at the ____.

lower side

``` Which of the following is not a part of the roller chain construction? a. Rollers b. Pins c. Outside link plates d. Inside link plates e. None of the above ```

e. None of the above

``` Connecting link assembly for easy and rapid replacement of parts of chain drive. a. Pin link b. Link plate c. Retainer d. All of the above ```

All of the above

Profiled wheel with teeth that meshes with a chain, track or other perforated or indented material.

Sprocket

Drive in which shafts are operating on a counterclockwise direction.

Gears

Gears are used for agricultural | machinery because ____.

they transmit high power and | efficiency and with long service life

Most common type of gear used in agricultural machinery with straight and parallel teeth to the shaft axis.

Spur gear

The projecting part of a gear that comes in contact with the other gear resulting in an opposite direction rotation.

Gear tooth

Spacing of gear teeth which is | measured along the pitch circle.

Circular pitch

Type of gear commonly used for | gear reducers or gear motors.

Worm gear

Type of gear used for powertake- | off drive.

Spline shaft gear

Smallest gear that is meshing | together.

Pinion

``` Service factors used in calculating the design power for gears include ____. a. type of load b. type of lubrication c. All of the above ```

All of the above

A gear is rotating at 800 rpm and is driven by another gear at 400 rpm. What is the speed ratio of the gear drives?

AGMA stands for ____.

American Gear Manufacturers | Association

Type of gear used to transmit rotational motion and power between parallel shafts.

Helical gear

Type of gear used for intersecting shaft usually at right angles.

Bevel gear

Type of gear used to transmit rotational motion and power between intersecting shafts.

Bevel gear

Type of gear used to connect an implement shaft to the tractor PTO shaft.

Spline shaft gear

When buying gear box, which of the following important parameters need to be specified?

Speed ratio & power rating

The larger part of the | meshing gear is called

Gear

The larger part of the | meshing gear is called

pinion gear

``` Which of the following belongs to parallel shaft gears? a. Spur gears b. Helical gear c. Internal gear d. All of the above e. Two of the above ```

All of the above

Parallel shaft gears with | straight tooth line.

Spur gear

Parallel shaft gear with | winding tooth line.

Helical gear

Parallel shaft gear that can transmit high load and higher speed applications.

Helical gear

A straight rod that mesh with pinion used to convert rotational motion to linear motion

Gear Rack

``` Which of the following belongs to non-parallel shaft gears? a. Bevel gear b. Worm gear c. Miter gear d. All of the above e. None of the above ```

All of the above

are tooth wheels used to transmit power and motion at a constant ratio from one rotating shaft to another by means of a positive contact of successively engaging teeth.

Gears

TRUE/FALSE Compared with V-belts and chain drives, gear drives are more compact and can operate at a higher speed. Gear drive also provides precise timing of motion.

TRUE

TRUE/FALSE In agricultural machinery, gears are commonly used in loading drives for tractors, self-propelled combines, power tiller, and many others.

FALSE (transmission)

refers to the pitch circle or pitch diameter of the | gear.

Gear size

is the height of the gear tooth beyond the pitch | circle.

Addendum

is the depth of the tooth below the pitch circle.

Dedendum

is the spacing of the gear teeth measured | along the pitch circle.

Circular Pitch

is the ratio of the number of teeth to the | pitch diameter in inches.

Diametral Pitch

is the sum of addendum and dedendum

Gear Depth

is equal to the sum | of the addendum.

Work Depth or Depth of Engagement

is equal to the sum | of the addendum.

Work Depth or Depth of Engagement

is the line connecting the center of gear | rotation

Line of Centers

is a curve formed that unwrapped around a | cylinder.

Involute

is a curve generated from the involute

Base Circle

is a line through the point of tangency | and tangent to the base circle.

Pressure Angle

It is the most common type of gear identified as simple, low cost, and easy to maintain. The teeth are straight and parallel to the shaft axis.

Spur Gear

It can carry more load than the equivalent size spur gear. Operates more smoothly and quietly however it is more costly than spur gears.

Helical Gear

It is a quiet and smooth action that provides a maximum reduction ratio for a given center distance used only for speed reduction.

Worm Gear

Cannot back-drive at ratios greater than 20:1. | The contact area is large hence load capacity is high and shafts are almost always at right angles.

Worm gear

This is the simplest type of gear for intersecting shaft. It is commonly used for shaft intersecting at right angle but can also be used for shaft mating at any angle.

Straight Bevel Gear

Gears are designed in pairs thus are not always interchangeable. The supporting shaft and bearings must be rigid to maintain proper tooth contact.

Straight Bevel Gear

Similar to spiral-bevel gears except that the shafts do not intersect. Operates more smoothly and more quietly and is stronger for a given ratio also permits a very high drive ratios and shaft angles usually 90 deg, but other angles are possible.

Hypoid Gear

Module = Circular Pitch / π Module = Pitch Diameter / Number of Teeth Pitch Diameter = Number of Teeth x Module Number of Teeth = Pitch Diameter / Module Tooth thickness on the Pitch Line = 1.5708 x Module

Formula for Spur Gear

Outside Diameter = 2 Addendum plus pitch diameter Addendum = Module Dedendum = 1.25 x module Clearance = Whole depth – 2 dedendum Min Whole Depth = 2.35 x Module Center Distance = Module (t1 + t2) / 2

Formula for Spur Gear

It is the ratio between the number of teeth of the driver and the driven gear.

Gear Ratio

What is this formula? ``` Ft = T / [D/2] or = 19.1 x 10^6 kW / [ D x N ] where: Ft - transmitted load, N D - pitch diameter, mm kW - power, kW N - speed of shaft, rpm ```

Gear Tooth Load

This is a required power which is a function of the type of | load and of lubrication. Identified as Power to be Transmitted multiply with the Service Factor

Design Power