spur gears & fishers ...newbie question...

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Posted by Anton Abaya at 1/20/2001 12:41 AM EST


Coach on team #419, Rambots, from UMass Boston / BC High and NONE AT THE MOMENT! :(.



can someone tell me what the "pitch 20" means in relation to spur gears? in the small parts catalog, they came in 20, 32, and 48 pitch series...

given that, can someone tell me the specs of the spur gear on that fisher price motor?

that or if you can tell me how to mount a shaft to the gear box, that should help even more....

-anton

[archiver]

Posted by Ed Sparks at 1/20/2001 9:02 PM EST


Coach on team #34, The Rockets, from Bob Jones High / New Century High and DaimlerChrysler.


In Reply to: spur gears & fishers ...newbie question...
Posted by Anton Abaya on 1/20/2001 12:41 AM EST:



: can someone tell me what the "pitch 20" means in relation to spur gears? in the small parts catalog, they came in 20, 32, and 48 pitch series...

In a nutshell, for all practicle reasons, it's the size of the tooth which relates to the strength of the gear. A 20 pitch sprocket has larger teeth than say a 32 pitch gear and is capable of a greater load.

: given that, can someone tell me the specs of the spur gear on that fisher price motor?

32 pitch, 20 degree pressure angle, 16 tooth

: that or if you can tell me how to mount a shaft to the gear box, that should help even more....

Use keyways or transtorques (small parts catalog) or weld (only if you have a VERY good welder)

: -anton

I haven't been able to respond to your email because my email server is down (I'm not having much luck this week). Try to download my spreadsheet again. I think all is fixed now.

[archiver]

Posted by ChrisH at 1/22/2001 2:01 PM EST


Engineer on team #330, Beach 'Bots, from Hope Chapel Academy and NASA JPL, J & F Machine, Raytheon, et al.


In Reply to: spur gears & fishers ...newbie question...
Posted by Anton Abaya on 1/20/2001 12:41 AM EST:



: can someone tell me what the "pitch 20" means in relation to spur gears? in the small parts catalog, they came in 20, 32, and 48 pitch series...


Pitch is short for diametral pitch. The short answer is the diametral pitch is the number of teeth per inch of diameter. So a 1" gear with 20 pitch would have 20 teeth. The same gear with 8 pitch would have 8 teeth. In the later case they would be pretty big teeth at that.

Another important gear number is the pressure angle. That's a little harder to explain without pictures. The important thing to remember is that for two gears to mesh properly the pitch and pressure angles must BOTH match. The standard pressure angles are 14 1/2, 20 and 25 degrees.

I'm not sure about any of the numbers for the FP motors.

Chris Husmann, PE
Team 330 th Beach 'Bots

[archiver]

Posted by Joe Johnson at 1/22/2001 8:31 PM EST


Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.


In Reply to: Re: spur gears & fishers ...newbie question...
Posted by ChrisH on 1/22/2001 2:01 PM EST:



All the gears in the F-P are pretty much standard gears
(they use a slightly modified tooth profile from
typical metal gears, one more suitable for molded
plastics, but for our purposes they mate just fine with
off the shelf metal gears). For gear heads in the
audience, they are note "enlarged" or otherwise
modified for strength or manufacturing purposes.

They are also all 20 deg. pressure angle gears.

Finally, they are all English pitch gears (not metric
module, but integer "Diametral Pitches").

I cannot recall all the pitches but I am pretty sure
they start at 32 DP at the motor and grow down to
something like 16 DP at the final stage.

Here is a trick to estimate the DP a standard gear:

DP = (Nteeth +2) / Outside Diameter

This works because the addendum of a standard gear is
1/DP. The Pitch Diameter is 1/Nteeth. So the OD =
Nteeth/DP + 1/DP + 1/DP Solve for DP and Viola!

Good Luck,

Joe J.