Types of Gears

Faculty of Engineering - Shoubra
Benha University
Research Article
in fulfillment of the requirements of
Department Surveying Engineering Department
Division Second Year Surveying
Academic Year 2019/2020
Course name Electromechanical Engineering
Course code EPE/260
Mechanical Part
“Topic (5): Types of Gears”
By:
Name Edu mail B. N
Ahmed Yasser Ahmed Mohamed Nassar ahmed170165@feng.bu.edu.eg 210018
Approved by:
Examiners committee Signature

Benha University
Academic year 2019-2020
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TABLE OF CONTENTS
LIST OF FIGURES...........................................................................................................2
1. INTRODUCTION .....................................................................................................3
2. TYPES OF GEARS ....................................................................................................3
(a) SPUR GEAR ......................................................................................................4
(b) SINGLE HELICAL GEAR......................................................................................4
(c) DOUBLE HELICAL GEAR (HERRINGBONE GEAR) ...............................................5
(d) INTERNAL GEAR...............................................................................................5
(e) RACK AND PINION GEAR..................................................................................6
(f) STRAIGHT BEVEL GEAR .......................................................................................6
(g) SPIRAL BEVEL GEARS........................................................................................7
(h) HYPOID BEVEL GEAR........................................................................................7
(i) WORM GEAR ......................................................................................................8
REFRENCES ..................................................................................................................9

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LIST OF FIGURES
Figure ID Description Page
1-1 Gears 3
2-1 Types of Gears 3
2-2 Spur Gear 4
2-3 Helical Gear 4
2-4 Hobbing Machine 4
2-5 Herringbone Gear 5
2-6 Double Helical Gear 5
2-7 Internal Gear 5
2-8 Pinion and Annular of Internal Gear 5
2-9 Pinion Cutter 5
2-10 Gear Shaper 5
2-11 Straight-teeth Pinion in Rack and Pinion Gear 6
2-12 Helical-teeth Pinion in Rack and Pinion Gear 6
2-13 Steering Mechanism 6
2-14 Slide Gate 6
2-15 Straight Bevel Gear 6
2-16 Spiral Bevel Gear 7
2-17 Hypoid Bevel Gear 7
2-18 Worm Gear 8
2-19 Various Types of Gears 8

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1. INTRODUCTION
Gears (Figure 1-1) are a type of mechanical element, the surface with
the same space. It is toothed members used for the turning and
transmitting of power and/or motion by meshing a pair of elements
with no-slip from the driving shaft to the driven shaft. Therefore, gear
drives are called positive drives. The smaller one is called pinion in
any pair of gears and the larger one is called the immaterial gear that
drives the other. The smaller gear is called pinion in any pair of gears
and the larger one is called the immaterial gear that drives the other. If
the pinion is the driver, the speed is decreased and the torque increases. If the pinion
(the smaller one) is the driver, the speed is decreased and the torque increases, vice
versa. The gears may be classified according to their shape into spiral, cycloid, and
trochoid gears. Depending on the direction of the shaft, it can be categorized as Parallel,
non-parallel, transverse, and non-transverse shaft gear.
2. TYPES OF GEARS
as shown in the (Figure 2-1):
(a) Spur gear
(b)Helical Gear
(c) Double Helical Gear (Herringbone Gear)
(d)Internal Gear
(e) Rack and Pinion Gear
(f) Straight Bevel Gear
(g)Spiral Bevel Gear
(h)Hypoid Bevel Gear (Figure 2-1)
(i) Worm Gear
(Figure 1-1)

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(a)SPUR GEAR
Spur gears (Figure 2-2) are the simplest gear type. teeth are
parallel to the axis of the shaft and are used for power and
motion transmission and motion between rotating two parallel
shafts. They are simple to construct easy to manufacture, and
less expensive. They are extremely efficient and have a high
level of precision. They are used in high speed and high load
applications in all types of trains with a wide range of speed
ratios. Therefore, it is commonly used in clocks, kitchen appliances, bicycles,
automobiles and railways for aircraft.
(b)SINGLE HELICAL GEAR
Helical gears (Figure 2-3) are cylindrical gears that have winding teeth inclined to an
axis and are used with parallel shaft drives like spur gears. compared to spur gears They
have a better teeth grip, operate smoother and quieter, and have higher load-carrying
capacity, and precision rating is good, which makes them suitable for very high-speed
and loads applications. thrust bearings must be used when using the helical gears
because they generate an axial thrust on the shaft. so, their efficiency is slightly lower
than spurs.
The Spur Gear hobbing machine
(Figure 2-4) and tool can be used to
manufacture helical gears. Because of
the turn of the teeth, their production
has the disadvantages of a very difficult
product.
(Figure 2-3) (Figure 2-4)
(Figure 2-2)

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(c) DOUBLE HELICAL GEAR (HERRINGBONE GEAR)
Double helical or Herringbone gears used for transmitting
power and motion through 2 parallel shafts. Double helical and
herringbone gears are not quite the same. They have opposing
helical teeth with a gap (double helical gear) (Figure 2-6) or
without a gap (herringbone gear) (Figure 2-5) depending on
the manufacturing method used. it overcomes the issue of
single helical gears axial thrust by having 2 sets of teeth that
are set in a V-shape. The shaft is free from axial force because
of Two axial thrusts oppose each other. the need for thrust
bearings can be eliminated -thrust load equal zero-.
(d)INTERNAL GEAR
Internal gears (Figure 2-7) are used for transmission of power between two parallel
shafts. it's teeth of an internal spur gear cut inside the surface of a cylinder towards the
center and meshed with spur gears. the internal gear (pinion) mesh rotation always goes
in the same direction with the external gear(annular) (Figure 2-9). the manufacturing of
internal gears cannot be done with the usual hobbing machine (Figure 2-4) used in spur
gears. so gear shaper (Figure 2-10) equipped with a pinion cutter (Figure 2-8) is used
to manufacture of internal gears. internal gears are useful for applications with high load
and high speed with a high reduction rate.
(Figure 2-5)
(Figure 2-6)
(Figure 2-7) (Figure 2-8) (Figure 2-9) (Figure 2-10)

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(e) RACK AND PINION GEAR
Rack and pinion gear have a strip of rectangular linear cross-section (the rack), the teeth
on one side mesh with the teeth on the smaller gear (pinion). The pinion straight (Figure
2-11) or helical teeth (Figure 2-12) meshed with teeth on the rack which are tilted to
the pinion shaft axis. racks are transforming rotating motion into linear motion so that
you can control the wheel. Rack and Pinions are used for lifting mechanisms, horizontal
movement, positioning mechanisms, stoppers and to allow the rotation of shafts. rack-
and-pinion drives used in steering mechanisms (Figure 2-13) to change the direction of
cars. Also, it used for several other purposes, such as slide gates (Figure 2-14). The rack
and pinion systems on the steering wheel have a simple structure, high stiffness,
lightweight, and excellent response.
(f) STRAIGHT BEVEL GEAR
Straight Bevel Gears (Figure 2-15) have a conical shape and are used to transmit forces
between non-parallel and intersecting shafts (intersection axis). They can run under high
speeds and loads. Bevel gears teeth are formed on conical
surfaces. they offer good service and easy to design and
manufacture. But at higher speeds, they are noisy. They are
recommended in those cases at speeds up to 1000 ft/min where
maximum quietness has no critical importance.
(Figure 2-11) (Figure 2-12)
(Figure 2-13)
(Figure 2-14)
1111
(Figure 2-15)

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(g)SPIRAL BEVEL GEARS
Spiral bevel gear (Figure 2-16) is a bevel gear with
curved, inclined teeth. It has higher contact rate, strength
and durability, better performance of transmitting, and
reduced gear noise, because of the higher contact ratio
of teeth to provide gradual engagement and larger
contact surface at a given time than straight bevel gear. also, they involve some technical
problems in manufacturing, so they are too complex to produce. In addition, as the tooth
is curved, thrust is formed in the axial direction. Zero cone gears with a turning angle
of zero in helical bevel gear are called zero bevel gears. It has many applications such
as automobiles, tractors, automobiles, an ultimate cutting tool for ships. Especially
suitable for high-speed, high-load drivers.
(h)HYPOID BEVEL GEAR
Hypoid bevel gears (Figure 2-17) are also used for
right angle drive where axes are not intersecting. This
allows the pinion axis to be reduced which is an added
advantage in automobiles in avoiding the cone within
the driveline power transmission. However, non–
intersection introduces a considerable amount of
flexibility and requires good greasing for the driver to reduce friction and wear. Their
performance is lower than the other two types of bevel gears. These gears are widely
used in the current automobile driveline power transmission.
(Figure 2-16)
(Figure 2-17)

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(i) WORM GEAR
Worm gears (Figure 2-18) are used to transmit movement
between two rods unparalleled and non-intersecting. It has
helical gear and power screw (worm). Worm gears can be used
to drive spur gears or helical gears.
(Figure 2-18)
(Figure 2-19)

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REFRENCES
Jelaska, D., 2012. Gears and Gear Drives. New York: Wiley.
Jones, F. and Ryffel, H., 1984. Gear Design Simplified. New York: Industrial Press.
KHK Gears. 2020. Characteristics of Gears. [online]
Lynwander, P., 2018. Gear Drive Systems. Boca Raton: Chapman and Hall/CRC.
Nptel.ac.in. 2009. NPTEL: Mechanical Engineering - Machine Design II. [online]
Oberg.E, Jones.D.J., Holbrook L.H, Ryffel H.H., (2012). Machinery's Handbook. 29th edition. Industrial
Press Inc.
Bodnar, Nisbett.K. (2008). Shigley's Mechanical Engineering Design. 8th edition. McGraw-Hill
Gear Nomenclature, Definitions of Terms with Symbols, American Gear Manufactures Association,
Alexandria, Va., 1990.
Darle W. Dudley, Handbook of Practical Gear Design, McGraw-Hill Inc., New York, 1984.
Robert O. Parmley, Mechanical Components Handbook, McGraw-Hill Inc., New York, 1985.
Raymond J. Drago, Fundamentals of Gear Design, Butterworths, Stoneham, Mass., 1988.
P. M. Dean, Jr., Gear Manufacturing and Performance, American Society for Metals, Metals Park,
Ohio, 1974
Jones, Franklin D, and Henry H Ryffel. Gear Design Simplified. Industrial Press, 1961.
Worm Gearing. Industrial Press, 1910.

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