×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# pressure angle question

## pressure angle question

(OP)
I have a ring gear with a pressure angle of 20 degrees and a starter motor of 14.5 degrees. They are both the same module etc, the only difference is the pressure angle. Is there a problem putting the two together in an engine?

Thanks

Tom
Replies continue below

### RE: pressure angle question

Be prepared to jump back.
The pressure angles must be the same on both.

### RE: pressure angle question

Working as gear expert in starters applications I confirm the answer of diamondjim :IF THE MODULE IS THE SAME, THE PRESSURE ANGLE MUST BE THE SAME

BUT :
the real indispensable and compulsory condition is to have THE SAME BASE PITCH pb= PI*m*cos(alfa)
SO:
you can have different modules AND pressure angle on your pinion and your gear if this condition is respected :
PI*m1*cos(alfa1) = PI*m2*cos(alfa2)
Example :
module 2.11666 (DP12) and pressure angle 12°
module 2.20328 and pressure angle 20°
module 2.1385 and pressure angle 14.5°
these three definitions are used to determine pinions and gears for starter applications and they mesh perfectly together.
The only issue is when you must calculate the gear set : you can only use one module and pressure angle so you must "convert"one of the items from one module to the other keeping the base tangent length constant to determine the profile addendum modification equivalent.

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!