Herringbone Gear and Rack don't mesh

[BonyJordan]

In particular line 120 inside module rack():
mx = modul/cos(helix_angle); // Module Shift by Helix Angle in the X-Direction

causes the rack version to increase the tooth size whereas the gear version doesn't have the equivalent line. Which is correct?

[david-venancio]

Hi !
what do you mean by "Gear and Rack don't mesh" ?

[david-venancio]

Hmm ok I understand.
Here's how I reproduced the problem :
translate([0, -20, -10 ])
herringbone_rack(modul=1, length=60, height=5, width=20, pressure_angle=20, helix_angle=30);
translate([0, 0, -20/2 ])
herringbone_gear (modul=1, tooth_number=30, width=20, bore=4, pressure_angle=20, helix_angle=30, optimized=true);

Not a simple problem indeed.

[david-venancio]

I forgot a 180 degrees rotation on one of them.
But we can see that the gear has rounded teeths and the rack doesn't...
I bet that setup wouldn't function IRL obviously.
Maybe it deserves a special case for this pairing ?

[david-venancio]

Here's how to look at the problem:

rotate([0,180,0])
    translate([0, -20, -10 ])
        herringbone_rack(modul=1, length=60, height=5, width=20, pressure_angle=20, helix_angle=30);
translate([0, 0, -20/2 ])
    herringbone_gear (modul=1, tooth_number=30, width=20, bore=4, pressure_angle=20, helix_angle=30, optimized=true);

[david-venancio]

(I use those gears on my reprap. Thanks again!)