Helical gears are cylindrical gears whose teeth are angled and appear as a segment of a helix. They can transmit power between parallel or perpendicular axes. Key terms used in helical gears include helix angle, axial pitch, and normal pitch. The face width of single and double helical gears is determined based on the pitch, module, and helix angle. Helical gears are stronger than spur gears and can transmit higher loads while running more smoothly due to their angled teeth. They are commonly used in heavy load applications in industries such as steel, textiles, food processing, and construction equipment.

2. DESIGN OF HELICAL GEAR
ON PRO ENGINEER

3. GEAR
A Gear is a rotating machine part having cut teeth which
mesh with another toothed part to transmit torque.
Geared devices can change the speed, torque, and
direction of a power source.

4. HELICAL GEAR
Helical gears are cylindrical gears whose teeth are not
parallel to the axis of rotation. The teeth are angled and
appear as a segment of a helix. Helical gears can
transmit power between parallel or right angle axes.

5. HELICAL GEARS TRANSMIT POWER
BETWEEN PARALLELAXES

6. HELICAL GEARS TRANSMIT POWER
BETWEEN PERPENDICULAR-AXIS

7. TYPES OF HELICAL GEAR

8. TERMS USED IN HELICAL GEAR
1. Helix angle
It is a constant angle made by the helices with the axis of rotation.
2. Axial pitch
It is the distance, parallel to the axis, between similar faces of adjacent
teeth. It is denoted by pc.
3. Normal pitch
It is the distance between similar faces of adjacent teeth along a helix on
the pitch cylinders normal to the teeth. It is denoted by pN.
Mathematically.
Normal pitch, pN = pc cos B

9. FACE WIDTH OF HELICAL GEARS
 In case of single Helical Gear
b =1.15 Pc/ tanβ= 1.15*m ×π/tanβ , ( pc = π m)
Where
b = Minimum face width, and
m = Module
 In case of double helical or herringbone gears, the minimum
face width is given by
b =2.3 Pc/tanβ= 2.3*m *π/tanβ
The maximum face width ranges from 20 m to 30 m.
 In single helical gears, the helix angle ranges from 20° to
35°, while for double helical gears, it may be made upto 45°.

10. STRENGTH OF HELICAL GEAR
 WT =( σo × Cv) b.π m.y‘ where WT = Tangential tooth load
 σo = Allowable static stress
 Cv = Velocity factor
 b = Face width
 m = Module
 y' = Tooth form factor or Lewis factor corresponding to the formative
or virtual or equivalent number of teeth
 The value of velocity factor (Cv) may be taken as follows
Cv = 6 /6 +v for peripheral velocities from 5 m / s to 10 m / s.
=15/15+v for peripheral velocities from 10 m / s to 20 m / s.=
=0.75/0.75+√v for peripheral velocities greater than 20 m / s.

11.  The dynamic tooth load on the helical gears is given by
WD =
WT +21v ( b cos^2β +WT) cos β/(21v √b.C cos ^2 β+WT)
 The static tooth load or endurance strength of the tooth is
given by
WS = σe.b.π m.y'

12. NUMERICAL
A pair of helical gears are to transmit 15 kW. The teeth
are 20° stub in diametral. Plane and have a helix angle
of 45°. The pinion runs at 10 000 r.p.m. and has 80 mm
pitch diameter and having shape factor 0.16575 for 20°
stub teeth. If the gears are made of cast steel having
allowable static strength of 100 Mpa
Determine
A Suitable Module
Face width

13. ADVANTAGES OF HELICAL GEAR
 The angled teeth engage more gradually than do spur gear
teeth causing them to run more smoothly and quietly
 Helical gears are highly durable and are ideal for high load
applications.
 Helical gears can be used on non parallel and even
perpendicular shafts, and can carry higher loads than can
spur gears.
 At any given time their load is distributed over several
teeth, resulting in less wear.
 Can transmit motion and power between either parallel or
right angle shafts.

14. APPLICATIONS OF HELICAL GEAR
Helical gears are normally preferred to work under heavy
load efficiently.
 Helical gears are used in fertilizer industries, Printing
industries and earth moving industries.
 Helical gears are also used in steel, Rolling mills, section
rolling mills, power and port industries.
 Helical gears are also used in textile industries, plastic
industries, food industries, conveyors, elevators,
blowers, compressors, oil industries & cutters.

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