Gear creator calculation - Something is Not right!

[Beyondforce]

Hi Guys,

It seems there is something wrong with the Gear creator calculation. I'm assuming that the default input is in Metric measurement (Diametral Pitch=Mod)!

The Input:

Diametral Pitch - 3 cm (= 0.3 MOD)

Pressure Angle - 20 deg (default) 

Number of Teeth - 84

Gear Thickness - 2 cm (default)

Expected Output:

Overall Diameter: 258 mm 

Actual Output:

Overall Diameter: 286.667 mm

The formula for the Overall Diameter (Outside Diameter) is:

This is a screenshot of the Actual results:

This is a screenshot from a Gear Size Calculator web site: 

I look forward to hear from you guys.

Cheers / Ben

[HughesTooling · Accepted solution]

No the script is using DP but it's in cm, who ever created it did not understand metric (Mod) or Imperial (DP)!

To get metric gears from the gear script you need to divide the module by 25.4 then divide by 2.54. So if you want a 3.0 module gear with 84 teeth it's (25.4/3)/2.54 = 3.3333333. The gear generated will have an OD of 258mm and the pitch diameter will be 3.0 x 84 = 252.

Mark

[HughesTooling]

Just in case you wanted to work with imperial gears in inches. Make sure your document is set to inches, run the script and enter 8.467/2.54 for the diametrical pitch.

Mark.

[Beyondforce]

Hi Mark,

Thanks for the help. It's working now and this is what I changed and how, so others can do it as well 🙂

It will be best if you could change the script in next release of F360. I wondered how many people didn't noticed that mistake and use it as it is!

Maybe there should be 2 scripts one for metric (Mod) and one for Imperial (DP)!

Cheers / Ben

[TheCADWhisperer]

---

---

Never mind.

 Response deleted.

[ekinsb]

I have a new version of the gear add-in and would like a few people to use it and get some feedback before I update the existing sample.  It should have the previous issue fixed, but it also has several enhancements over the previous version.

• Handles units correctly
• Groups all of the resulting nodes in the timeline.
• Supports English and Metric definition.
• Displays the pitch diameter value based on the current input.
• Draws a circle in the model representing the pitch diameter.
• Draws a fillet at the root of the tooth.
• Draws a center hole in the gear.
• Remembers the last values used within a particular design.

I would prefer not to make this publicly available because there are likely some issues that still need to be addressed so I would rather keep the distribution of this version controlled.  If you would be interested in using it and providing some feedback, please contact me at brian.ekins@autodesk.com and I'll send it to you.  Thank you.