FC Gears: Feedback thread

[looo]

it's called "shift". Thank-you, that works.

"Shift" moves the whole profile (uses different section of involute, resulting in a different alpha).

[Zolko]

"Shift" moves the whole profile (uses different section of involute, resulting in a different alpha).

The comment I got from Thyssen-Krupp is:

Profilverschiebung / Addendum modification xm2 = 2.0

But I don't know what the 2.0 unit is. The module is 4: is 2 the half of 4 (thus shift 0.5) or is it an absolute value, or something entirely different ? The closest result I get to the actual design is with shift 0.75 ...

[looo]

The comment I got from Thyssen-Krupp is:

Profilverschiebung / Addendum modification xm2 = 2.0

But I don't know what the 2.0 unit is. The module is 4: is 2 the half of 4 (thus shift 0.5) or is it an absolute value, or something entirely different ? The closest result I get to the actual design is with shift 0.75 ...

Shifting is a simple way to fit a given axial distance for a given module. Shift * module (length) is the amount of the tool-(rack)-translation. But computing the axial distance of two gears is a bit more complicated. freecad.gears provides a function to compute this distance:
https://github.com/looooo/freecad.gears ... ion.py#L26

Code: Select all

from pygears.commputation import compute_shifted_gears
ax_diff, alpha_w = compute_shifted_gears(m, alpha, t1, t2, x1, x2)

exampe for a rack, gear combination is attached:

[jackfreecad]

Hi everyone
First thanks for all the work that has be done on this gear workbench and FreeCAD
I would like to add a head parameter to the cycloid gear in the gear workbench
Updated files here:
https://github.com/jacprog/FreeCADclok1 ... ycloidGear

Well caution, I found out that I cannot edit gears that I have made earlier...

The long story
More in this video about custom cycloid gear:
https://youtu.be/GCvQ9-lPX-w
With these gears I was able to design this 3D printed clock:
https://forum.freecadweb.org/viewtopic.php?f=24&t=55567

At first I could not get it to work, so I did a test and hard coded simplified modified code in cycloid-tooth.py at 0.39 sec, using the clearance parameter to modify size of theet both at head and root at the same time

diameter at head of teeth:
self.da = self.d + (2 + self.clearence)*self.m (was: self.da = self.d + 2*self.m)
diameter at root of teeth:
self.di = self.d - (2.6 + self.clearance)* self.m (was: self.di = self.d - 2*self.m. -self.clearance* self.m)

To implement the head parameter, two .py documents have to be worked on:
feature.py and cycloid-tooth.py. I got it to work locally on this:
OS: macOS Mojave (10.14)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.23964 (Git)
Build type: Release
Branch: master
Hash: db9525e7d78c956df96dd6db2c52f20a50a2aa5f
Python version: 3.8.6
Qt version: 5.12.5
Coin version: 4.0.0
OCC version: 7.4.0
Locale: C/Default (C)

Modify and added code (It is working now)

feature.py

Add the selectable parameter in the class CycloidGear(BaseGear)
(starting line 418 or so)
copy feature from involuteGear line 82: head line116…

added at line 438 in feature.py

obj.addProperty(
"App::PropertyFloat", "head", "gear_parameter", "head_value * modul_value = additional length of head")

initialize head:
added to line 455 same as line 116:

obj.head = 0.

and line 468 same as line 157:

fp.gear.head = fp.head

cycloid-tooth.py

line28 added head

def __init__(self, z1=5, z2=5, z=14, m=5, clearance=0.12, backlash=0.00, head=0.00):

line 34

self.head = head

line 44

self.da = self.d + 2*self.m + self.head*self.m

line106 …add head

def _update(self):
self.__init__(m=self.m, z=self.z, z1=self.z1, z2=self.z2,
clearance=self.clearance, backlash=self.backlash, head=self.head)


It looks like it is working fine, however for small number of teeth, one must first reduce the inner and outer diameter accordingly or an error will be generated

also have links about cycloid gears that could be added as a reference on this page:
https://github.com/looooo/freecad.gears#readme
https://www.tec-science.com/mechanical- ... dal-gears/
https://www.tec-science.com/mechanical- ... dal-gears/

Thanks for the gear workbench, I think it is great
Files are here:
https://github.com/jacprog/FreeCADclok1 ... ycloidGear

[drmacro]

Just a curiosity question.

I was having a fillet discussion with on another platform and the attached gear was brought up as something that would crash FC.

And, it does indeed crash FC if a .6mm fillet is applied. If a .1mm is applied it works.

But, what caught my eye was the shape of the gullets and it surprised me that any fillet size works...

Snip macro screenshot-0e25b1.png (14.56 KiB) Viewed 1742 times

Had to delete the fillet to get it to forum size...

Tis is about 8 days old PPA...the PPA has not built during that time.

OS: Ubuntu 20.04.2 LTS (XFCE/ubuntustudio)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24333
Build type: Release
Branch: master
Hash: e8566f22bbeb0b7204e3c45519d0963e8881100b
Python version: 3.8.5
Qt version: 5.12.8
Coin version: 4.0.0
OCC version: 7.5.1
Locale: English/United States (en_US)

[chrisb]

Can you please attach your FreeCAD infos? I thought that Chennes had fixed the fillet crashes, but perhaps not all of the Part fillets?

Where do you wanted to apply the fillet? At the edge of the internal foot of the gear, where the orange marker is seen?

[chrisb]

Do you have the same effect if you reduce the number of teeth? That should make the file small enough for uploading.

[drmacro]

Can you please attach your FreeCAD infos? I thought that Chennes had fixed the fillet crashes, but perhaps not all of the Part fillets?

Where do you wanted to apply the fillet? At the edge of the internal foot of the gear, where the orange marker is seen?

Oops actually said to myself to do that while writing...

Fixed in OP

[drmacro]

Just tested on 0.20 I built yesterday and it does not crash, just produces a fillet in the tree with the red thing that looks like a red dot...cuz it's so small.

[El_Coder]

Hi,
I think there is something bad with the diameter settings!?! As you can see the teeth are not fitting/aligning with the underlaying circle (I do not know the right word for this.)

Or are my crown gear settings bad?

Crown_Gear_Diameters.png (99.16 KiB) Viewed 1561 times

I am running this with/on:
FreeCAD_0.19-24276-Linux-Conda_glibc2.12-x86_64
MX Linux 19.4
Kernel 5.8