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Author Topic: width of racks  (Read 57 times)
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RConrad
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« on: April 16, 2018, 10:57:55 AM »

When making non circular gears and choosing racks, i can set the length of the rack (through number of teeth), the thickness of the rack, through the thickness tab  but I can set the width of the rack.

I am using .25 thick acrylic sheets and laser cutting.  Therefore my thickness will always be .25.  My length is controlle d by the number of teeth but I can only change the height of the rack by changing the module.  I am using a module of 1, pressure angle of 20.  This gives me a rack with a width of .22 inches or so.  If I go to a modules of .5, pressure angle of 20 my width is .1 inch or so. 

I need more meat under my rack so it is less fragile.  I would like to be able to change it just like I can the diameter of the spur gear which I use as the pinion.  Is this possible, am I missing something, or is it a bug.  My uneducate d guess is that you would change the width. 

This is not a show stopper for me as I can modify the dxf in my cutting software to add some width.  It is somewhat of an inconveni ence however.

Thanks

Robert

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ArtF
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« Reply #1 on: April 17, 2018, 07:57:24 AM »

Hi Robert:

  The thickness is controlle d by the Rim Ratio on the spoke tab up top. You can make it thicker or thinner as you go up or down in modules. It generally a % of the tooth height to keep
is regular, but the rim ratio allows that to be overridde n.

Thx
Art


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RConrad
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« Reply #2 on: April 17, 2018, 12:14:59 PM »

Perfect, works great.  I would have never figured that out for a rack.  Thanks.

Robert
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ArtF
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« Reply #3 on: April 17, 2018, 12:57:47 PM »

Robert:

  Yeah, not very intutive, but when you think of it, that area under the rack is really
the rim of the gear.. were it round.. Smiley

Art
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