Page 179 - C:\Users\trainee\AppData\Local\Temp\msoEAA3.tmp

Fundamentals of Stress and Vibration
[A Practical guide for aspiring Designers / Analysts] 1. Mathematics for Structural mechanics

ˆ –Š‡ –‘‘–Š •‹œ‡ ‰‘‡• †‘™ǡ –Š‡”‡ ƒ”‡ –™‘ ‘•‡“—‡ ‡•ǣ
· Š‡ „ƒ Žƒ•Š ‹ ”‡ƒ•‡•Ǥ ˆ –Š‡ –‘‘–Š •‹œ‡ ‹• Š‹‰Š‡”ǡ –Š‡ǡ –Š‡ „ƒ Žƒ•Š †‡ ”‡ƒ•‡•Ǥ 
‡š–”‡‡ ƒ•‡•ǡ •ƒ›ǡ ƒ Š‹‹‰ –Š‡ ™”‘‰ —„‡” ‘ˆ –‡‡–Šǡ –Š‡ ‰‡ƒ”• †‘ ‘– ”‘–ƒ–‡Ǥ
· Š‡ ƒ”„—”‹œƒ–‹‘ †‡’–Š ƒŽ•‘ †‡ ”‡ƒ•‡•Ǥ

Solution: the over pin dimension goes down by 0.5mm, meaning, for a symmetric gear about the
diameter, the dimension lost, radially, is:

0.5
= 0.25mm
2
Since, it is also known that the pin is tangential to the gear tooth (approximately at the pitch circle
radius), the radius of the pin, makes an angle Φ , which is equal to the pressure angle, with respect
to the horizontal, as shown in [Fig 1.80].

It can be observed that, the material lost on the profile is measured along the radius of the pin.

[Fig 1.80: pressure angle subtended at the center of the pin]

QP No. SSC/Q4401, Version 1.0, NSQF Level 7, Compliant with Aero and Auto Industries,
Page 82