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looooo / freecad.gears

a gear module for freecad
GNU General Public License v3.0
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Update features.py to support HTD Timing Gear Profiles #134

Closed BearTM closed 1 year ago

BearTM commented 1 year ago

I was frustrated that the GT3 gear generation in Freecad, while looking incredibly similar, did not work with the HTD gears and belts I require. The GT3 profile was slipping when trying to use a HTD3 belt. This led me down a Google rabbit hole with an utter lack of documentation. I eventually found a reasonably detailed HTD specification from a manufacturer in Singapore.

Reference Documentation: http://misbelt.com/wp-content/uploads/2018/01/htd.pdf

Using this information, I then added the 3M, 5M, 8M HTD Timing Gear Profiles. Additionally I corrected the GT8 Profile naming from "htd8" to "gt8".

Sample Profile Difference: GT3 HTD3 Gear Profile Difference

NOTE: I've noticed that the GT# gear diameters are different from the HTD# diameters for different number of teeth, but I have not had the need/opportunity to look into why the GT# profile configurations have a difference in diameters. Depending on time/availability I could look into additional timing gear profiles, but that won't be for a while.

looooo commented 1 year ago

thanks, I will have a look at this today.

looooo commented 1 year ago

thanks, looks good to me. Actually I do not have experience with these kind of gears and as you say, there are not a lot of good references for it. So there is the possibility I did something wrong with my implementation. But I guess over time people will optimise this feature (like you did). So thanks for the contribution!