Involute question

[msimpson]

Here are som large gears I cut.  The large ones are about 20" in diameter and the small ones 3" While they work very well with a very loose mesh, I noticed that the smaller gears have a nice envolute shape and the larger ones are more tranglula r.  Why is this?


http://youtu.be/YwLD2u1oh7g

[Dan]

This is the math behind the involute shape. The larger the gear is the closer it gets to a rack which is essential ly a triangula r shaped tooth profile. The tooth sides are straight lines and the included angle between them is twice the pressure angle.

Dan

[ArtF]

Hi:

   exactly so.. the larger the gear, the more the tooth's circular nature becomes flat.. so too does the curve represent ing its tooth. A flat tooth is just two straight lines at Pressure angle, the curve gets more involuted as it gets circular. . Its just the math....

Art

[ArtF]

And yes.... that IS a damn big clock..

Art

[John S]

Do big clocks have more than 24 hours ?

John S.

[ArtF]

I suspect they have less..  takes one hell of a spring or weight to run those big ones..

 ( Mine has 16" main wheels.. runs about 4 hours on a wind. lol ..pretty though..)

Art

[ArtF]

test

[CNC-Joe]

Very nice work on the large clock gears - I was amazed at how well they turn.
Are they running on a skate board bearing ? 

Well done!

[Mooselake]

Pretty cool!

What kind of electric drive is it?  Is that a magnet in the top gear?  Is it to trigger something like chimes?

Those of us with size envy are going to have to figure out how to cut them in 6x8 inch pieces.  Offset sections and laminatio ns, like checkerbo ard plywood?

Kirk