pressure angle question

Question

pressure angle question

guest0821 (visitor)

(OP)

20 Nov 01 06:56

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

diamondjim (Mechanical) · Answer 1 · 2001-11-20 17:41:52

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

julio (Automotive) · Answer 2 · 2002-08-13 09:19:37

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.

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pressure angle question