Planetary Gear Inner Gear

[ajacobspilot]

OS: Windows 7
Word size: 32-bit
Version: 0.14.3700 (Git)
Branch: releases/FreeCAD-0-14
Hash: 32f5aae0a64333ec8d5d160dbc46e690510c8fe1
Python version: 2.6.2
Qt version: 4.5.2
Coin version: 3.1.0
SoQt version: 1.4.1
OCC version: 6.5.1

Hi. Building a planetary gear and I've got the carrier, planet gear, sun gear done, but I cannot figure out how to do the internal gear. Some people call it the ring gear. Does someone have an easy way to do an inner gear? I tried using an involute gear and padding it. I then created a sketch and made a circle that was a larger diameter than the gear hoping I could pocket the involute gear, but that doesn't work. Curious how folks do this.

[DeepSOIC]

You can cut the inverse of it (the one you padded) from a cylinder using Part Cut

[ajacobspilot]

Thank you. After several attempts I was able to get it to make a pocket with part cut, but I've yet to be able to remove the involute gear completely from the cylinder. I'll play with it again tomorrow. Thanks for pointing me in the right direction.

[OakLD]

I know this is an old thread.

But I want to emphasize, that if you substract involute gear from a cylinder you DON'T get valid involute inner teeth.
I did it yesterday, but it was too quick thinkging. The result could be acceptable for some info graphics, but certainly not e.g. for 3D printing a real gear.

I think, that at this moment, the only way is to take an engineering handbook and draw a precise sketch to base the gear with inner teeth on...

[meme2704]

know this is an old thread.

But I want to emphasize, that if you substract involute gear from a cylinder you DON'T get valid involute inner teeth.
I did it yesterday, but it was too quick thinkging. The result could be acceptable for some info graphics, but certainly not e.g. for 3D printing a real gear.

I think, that at this moment, the only way is to take an engineering handbook and draw a precise sketch to base the gear with inner teeth on...

Complete Fake news, you do not know anything about machining pinion, look at my answer 2 post above

[ppemawm]

I think, that at this moment, the only way is to take an engineering handbook and draw a precise sketch to base the gear with inner teeth on...

Or, one could use the PartDesign>InvoluteGear feature:

internal_gear.JPG (59.73 KiB) Viewed 922 times

.
This creates a sketch which you can drag/drop in a body and use this to pocket a blank disc to create a ring gear.

[NormandC]

Complete Fake news, you do not know anything about machining pinion, look at my answer 2 post above

You have no other reply in this topic.

[OakLD]

know this is an old thread.

But I want to emphasize, that if you substract involute gear from a cylinder you DON'T get valid involute inner teeth.
I did it yesterday, but it was too quick thinkging. The result could be acceptable for some info graphics, but certainly not e.g. for 3D printing a real gear.

I think, that at this moment, the only way is to take an engineering handbook and draw a precise sketch to base the gear with inner teeth on...

Complete Fake news, you do not know anything about machining pinion, look at my answer 2 post above

Well, I'm not an expert on gears, true . Perhaps I made a mistake, but please provide a reference. It would be for benefit of all other visitors of this thread.

Just to make it clear, I undertand you're saying that if you make a gear of required teeth count, with given modulus and given angle of engagement (aka pressure line angle, let's say 20°) and create an inverse shape, you'll get a valid outer ring for any gear with the same given modulus and angle of engagement. Right?

[OakLD]

Or, one could use the PartDesign>InvoluteGear feature:


internal_gear.JPG
.
This creates a sketch which you can drag/drop in a body and use this to pocket a blank disc to create a ring gear.

Thank you, this tool has option for external and internal teeth. However, the "High precision" option doesn't do anything aparent to the gear, it looks like a simplified model with any value selected.

Gear.png (23.23 KiB) Viewed 903 times

Sides are formed by 3 lines. Do you get the same?

[ppemawm]

Sides are formed by 3 lines. Do you get the same?

No.
Using your same parameters:

tooth_profile.JPG (13.92 KiB) Viewed 897 times

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.14838 (Git)
Build type: Release
Branch: master
Hash: 0d228bce02f3a4aa39f2b0f2bfbd5ca5eb2a6d4b
Python version: 2.7.14
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
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