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.