Since we were talking about gears, I wanted to look for any input on "Planetary/Inside ring gears.

When looking at images and online stuff, I cannot find anything referencing this.

My question is, shouldn't the tooth profile be "Inverted" also?

I see everybody do just a negative to get the outer ring. Maybe if the outer ring is STATIONARY and only provides a rotational constraint to all the inner gears.
There was an update made to the gear script for "Inner" where he mentions he just reverses the addendum and dedendum to get clearances...

But if the outer ring rotates, the teeth should also be inverted? (See image) To maintain the designed "Pressure Angles" and such.



As I type, I think maybe the outer ring is always meant to be "stationary" in its function? (Lack of understanding on my part)

Anyway, Any enlightenment is welcome..

Hi Burr,
Perhaps downloading a file from here may help.
https://geargenerator.com/#200,200,100,6,1,3,3444.8999999996604,4,1,8,2,4,27,-90,0,0,0,0,0,0,16,4,4,27,-60,0,0,0,0,1,1,12,1,12,20,-60,0,0,0,0,2,0,60,5,12,20,0,1,0,0,0,0,0,3,-468
Cheers
Barry

Hi Barry,
Thanks for the link, that's pretty cool looking stuff.

But it doesn't really answer my fundamental question of inverting the tooth design.

It appears to just swap out the addendum and dedendum like the MoI script does.


I also asked the question in another forum. Maybe I can get an engineer to let me know I've taken a wrong turn :o

It's just a curiosity and a play on how my thoughts work.

Something like this?

https://woodgears.ca/gear_cutting/template.html

Seems excellent!

Check out Gearotic.

Martin.

Hi Burr,
I found this https://en.m.wikipedia.org/wiki/Involute_gear which shows the constant velocity the involute shape produces.
So I think the answer is inverting the tooth shape without inverting it’s axis (origin of construction)will result in a inconstant velocity thro the tooth meshing.
Cheers
Barry

Hi Barry,
I agree. But this still misses my point.

If you search and look at all the models and such, they are just made with "negative" cutouts.

So, my point is the tooth profile should not be a negative, but inverted.

Inverted would include all the knowledge, math and calculations to create involute meshimg, just like on opposing module spurs... (obviously a recalculation. Not just simple coordinate inversion. So my image is simplified.

I was looking for the wiki or blog on how to calculate the inversion...

Have you tried using the image search option to look for pictures with calculations?

Just typed in "How is rack pitch calculated?" with image search results and found several images with calculations.

Like:

https://www.sdp-si.com/resources/elements-of-metric-gear-technology/index.php