this tutorial makes it easy to combine 2 rotary gears

https://www.youtube.com/watch?v=xeO9OH4msH4

is there an easy way to combine a rotary gear with a linear gear ? (also called Rack and Pinion)

I don't think there is an easy way...

It is a math calculation.

So search for gear module formula (add in rack and pinion)

"Module" is for metric. Diametral pitch is for imperial...

By J. R. Colbourne:
Page 52+, (of 538 pages), has math for pinions. The pinion teeth can have flat sides.

https://www.academia.edu/32161717/The_Geometry_of_Involute_Gears

There is already an involute Gear script for MoI.

An easy way to mesh a spur gear and a rack is to download the step files from:
https://www.mcmaster.com/gears/
The step files don’t include the pitch circle diameter, but it’s on the product detail page or you can download a 2d file that includes the pitch circle. Gears with the same pressure angle and pitch/module will mesh correctly when the pitch circle diameters are tangent.
I found an MOI script for involute gears, but it didn’t allow for specifying the pitch/module, so wasn’t useful.
There is a Rhino plugin for gears, Rhinogears, that works well, and, it’s built from some open source code that’s available from:
https://github.com/cesarvandevelde/rhino-gears
It might be possible for someone to modify the Rhino Python code to work in MOI.
Rick

Hey Rick,
""""""""I found an MOI script for involute gears, but it didn’t allow for specifying the pitch/module, so wasn’t useful.""""""""""""

There are 2 gear scripts. 1 allows you to choose Diametral pitch (SpurGearProfile) along with number of teeth.

There is also "Gear" which uses a "scale" function. It seems to relate to 10 = 1 pitch (So 20 equals .5 etc)

Both produce a pitch circle on commit...





I am a bit out of my element to discuss gears much further. I don't remember who created the scripts to ask about reference...

Maybe someone else can dissect the 2 and talk more about the difference...

Burrman-
I did run the gear script that I have again, and it does include the pitch, but not pressure angle- another important value.
I model lots of gears and would prefer to stay in MOI instead of jumping around to other programs, maybe someday...
Rick

Yes. Max made the Gear Script and mentioned he made it as "simplified".

My CAM package has all the pressure angles and root fillets and like 4 other radius values to input..

The SpurGear script was Petr's and is simplified with just diametral pitch also...

Just concept stuff.....

So like here you can see Michael explain to Brian how to make a rack for the pinion...

http://moi3d.com/forum/lmessages.php?webtag=MOI&msg=1420.8

But really though, if you are designing for precision and manufacturing of real gears, there are things that need to be considered beyond simple modeling. Especially when translating radial motion to linear motion... things have to be engineered....

Anyway....

Hi,
Is this any use it generates gear and rack.
https://evolventdesign.com/pages/spur-gear-generator
Barry
Ps.
More info here.
https://khkgears.net/new/gear_knowledge/gear_technical_reference/involute_gear_profile.html

Thanks Barry,
The reference is the best one i have found yet... bookmarked

As a side note, a few years back i engaged Michael in an "unwrqpping" discussion and he gave some precise info on converting radians (for unwrapping).

All that discussion ended when he made MoI's "UnwrapCurve" command! :o

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