INTRODUCTION TO design of spur GEARS GUIDE : D M KATEGERI BY MAHESH DESAI NARESH KURDEKAR OMKAR PODAJALE ASIF GOUNDI
May 24, 2015
INTRODUCTION TO design of spur
GEARSGUIDE : D M KATEGERI
BYMAHESH DESAINARESH KURDEKAROMKAR PODAJALEASIF GOUNDI
FIRST LET US KNOW
WHAT IS GEAR,
TYPES OF GEARS
AND
GEAR TERMINOLOGY
GEARS• Transmit motion between shafts
• Gear types– Spur gears – parallel shafts – most common
– Bevel gears – perpendicular shafts
– Worm gears - perpendicular overlapping shafts
– Rack and pinion gears – convert circular motion to linear motion
GEARS
SPUR GEAR
WORM GEAR BEVEL
GEAR
GEAR TERMINOLOGY
PITCH DIAMETER
ROOT DIAMETER
CENTER DISTANCE
OUTSIDE DIAMETER
DIAMETRAL PITCH= TOOTH SIZE
GEAR TERMINOLOGY• DIAMETRAL PITCH = “P” = Tooth size = teeth
per inch of pitch diameter
• PITCH DIAMETER = “D” = Design diameter of gear if it were a smooth wheel
• NUMBER OF TEETH = “N” = Total number of teeth on any given gear. Must be a whole number.
THE GEAR DESIGN FORMULA
D = NP
(or N = DP, or P = N/D)
EXAMPLE: Number of Teeth (N) = 24, Diametral Pitch (P)= 6Pressure Angle (PA) = 20 0
Pitch Diameter (DP) = N/P = 24/6
= 4” = 101.6 mm
Outside Diameter (DO) = (N+2)/P = (24+2)/6
= 4.33’’= 110.06 mm
Root Diameter (RD) = (N-2)/P = (24-2)/6 = 3.666’’ = 93.13 mm
Base Circle Diameter (BC) = DP * cos PA
= 101.6 * cos 20o
= 95.47 mm
DESIGN OF GEAR IN PRO-E
Open the pro e software and select the part drawing
Select the front plane and the extrude option
Click on placement and select define
Click on Placement
Then click on Define
First draw a circle with root diameter (93.13 mm).
Select Circle option to draw the circle
After drawing Click here
93.13
Then select thickness of the circle and click on right mark
Select the thickness of the circle
Then click here
This is the root circle of the gear
Now again select the front plane and extrude
Now draw circles with outside diameter, pitch circle and base circle.
Outside circle(110.06 mm)
Pitch circle(101.6 mm)
Base circle(95.47 mm)
Root circle(93.13 mm)
Steps to draw tooth profileClick on the Datum Curve and select From Equation, click on Done
Click on Datum Curve
Then select From equation
Click done
Click on PRT CSYS DEF
Select cartesian
After selecting cartesian a notepad will prompt where we have to write the formula for Datum Curve
Datum curve
Datum curve
Zoom into the Datum curve, using curve option draw a curve line from base circle to outer circle on the involute curve.
Curve line
Draw another curve from root circle to base circle which is tangent to the first curve.
Curve line
Then draw a small circle at the intersection of pitch circle and involute curve.
Small circle
The diameter of this curve is calculated using formula [ /(2*P)]. In this example we get the diameter as 6.649 mm..
6.649 mm
Then draw a center line passing through the center of the root circle and tangent to the small circle drawn.
Centre line tangent to the circle
Then make mirror image of the curve line drawn below to the other side of the center line.
Mirror profile
Then trim all the lines living behind the tooth profile as shown in figure.
Then select 20 mm as thickness and click right mark.
Then select the tooth profile and click on pattern tool.
Pattern tool
Select to pattern
Select dimension as Axis, enter number of teeth, and select 360 degree. Then click on right mark.
1) Select Axis
2) After selecting Axis click on this Axis
3) Number of teeth to be pattern
4) Select 360 degrees
This completes the spur gear design.