topic Re: Helical Gear using sweep twist angle for a planetary gear in Fusion Design, Validate & Document Forum

Helical Gear using sweep twist angle for a planetary gear

chrisvargsch — Thu, 23 Apr 2020 01:23:49 GMT

Like you can see i design a ring and planet gear. But when i use sweep and twist angle to create the helical type of gear. The inclination does not match even though it has the same angle And i need that to make it works.

I use the same angle in the ring and in the planet 20 degrees but its to different, i try to change that divide but it's still not exact. Somebody can explain me what happen?

Re: Helical Gear using sweep twist angle for a planetary gear

etfrench — Thu, 23 Apr 2020 07:27:03 GMT

Adding a guide rail to the sweep may help it maintain the correct shape.

This thread shows how I made a herringbone (helix) gear a few years ago. It was 3d printed and worked quite well.

Re: Helical Gear using sweep twist angle for a planetary gear

wmhazzard — Thu, 23 Apr 2020 13:48:32 GMT

The problem is that using the twist angle is the wrong tool for the job. That is rotating your profile 20 degrees in rotation so depending on the diameter of the gear, the helix angle will change. The larger the diameter the greater the helix angle for the same amount of rotation. You will need to project a 20 degree line to the face of the gear and sweep the profile along the line.

Re: Helical Gear using sweep twist angle for a planetary gear

chrisvargsch — Thu, 23 Apr 2020 17:30:26 GMT

Thanks for your answer makes to much sense. But can tell me the specific detail of of the position of the angle that i need to make, I create a copy in another plane with 20 degrees of rotation. im trying but without sucsees.

Re: Helical Gear using sweep twist angle for a planetary gear

chrisvargsch — Thu, 23 Apr 2020 19:08:44 GMT

I just tried again and its work, you can see. I had to use extrude too like you see

Re: Helical Gear using sweep twist angle for a planetary gear

chrisvargsch — Sun, 26 Apr 2020 02:04:54 GMT

Hi man, i found another problem like i did i get a straight angle gear but the originals have like a curve. How can i do it, my friend? You dont have a video?

Re: Helical Gear using sweep twist angle for a planetary gear

wmhazzard — Sun, 26 Apr 2020 02:19:35 GMT

I don't know what you mean when you say the gear has a curve. Can you show a photo of what you are trying to reproduce.

Re: Helical Gear using sweep twist angle for a planetary gear

chrisvargsch — Sun, 26 Apr 2020 02:35:53 GMT

The original like i want and the other that its straight

Re: Helical Gear using sweep twist angle for a planetary gear

etfrench — Sun, 26 Apr 2020 07:06:00 GMT

Did you look at the link in my post #2?

Re: Helical Gear using sweep twist angle for a planetary gear

chrisvargsch — Sun, 26 Apr 2020 16:19:52 GMT

hi, yes but not have the solution, in this link you have a free store autodesk program https://apps.autodesk.com/FUSION/en/Detail/Index?id=9029586664984391977&appLang=en&os=Win64&autostart=true.

but i want to do it myself i have another video but dint find the answer https://www.youtube.com/watch?v=NDDiYzLuacQ

Re: Helical Gear using sweep twist angle for a planetary gear

laughingcreek — Sun, 26 Apr 2020 16:54:41 GMT

I think the original idea of using a sweep with twist for the smaller gear was on the right track. when cutting the teeth on the planetary gear you would need to sweep using an edge created from the first gear as a guide path.

Re: Helical Gear using sweep twist angle for a planetary gear

chrisvargsch — Sun, 26 Apr 2020 17:08:08 GMT

I think this its the solution modify the distance of the path like the small gear.

Re: Helical Gear using sweep twist angle for a planetary gear

chrisvargsch — Sun, 26 Apr 2020 17:55:51 GMT

But i found another problem, nobody know how to do it. One side its ok but the other wrong. Lol

Re: Helical Gear using sweep twist angle for a planetary gear

wmhazzard — Sun, 26 Apr 2020 18:10:11 GMT

There is a helical gear generator available from the app store.

https://apps.autodesk.com/FUSION/en/Detail/Index?id=9029586664984391977&appLang=en&os=Win64

Re: Helical Gear using sweep twist angle for a planetary gear

chrisvargsch — Sun, 26 Apr 2020 18:38:44 GMT

The solution my friends after alot of work, create 3 sketch with 15 degrees of differents and use loft. Using this video https://www.youtube.com/watch?v=NDDiYzLuacQ&t=6s

Re: Helical Gear using sweep twist angle for a planetary gear

manticoretango — Sat, 27 Feb 2021 01:34:17 GMT

First up, I found a great video explaining the proper way to work out the sweep angle: https://www.youtube.com/watch?v=re8-kYZjjyY - it uses the actual mathematics and explains it carefully. Secondly, if you just want to do this quickly and don't need the gears to be a specific angle, just to mesh together correctly, you can skip some of the equations. Say you have a 11 tooth gear, a 30 degree sweep angle looks right for it, and you want to make a 19 tooth gear to mesh. 30/ (1/11) = 330. Now all you need to do is (1/19) * 330 = 17.368 sweep angle for your 19 tooth gear.

Re: Helical Gear using sweep twist angle for a planetary gear

manticoretango — Mon, 01 Mar 2021 11:46:16 GMT

after posting this I realised I'm being dumb and didn't simplify the equation enough. It's just: 30*11/19 to get 17.3684

Re: Helical Gear using sweep twist angle for a planetary gear

anthonyma24 — Tue, 16 Sep 2025 16:12:24 GMT

The sweep feature can still be used in this situation, but the twist angle must be calculated from the specified helical angle (α), pitch circle diameter (D), and gear height (H). This is because the definitions of helical angle and twist angle (θ) differ.

Formula:

θ=2⋅arcsin⁡(H⋅tan⁡(θ)/D)

This relationship is derived from the geometric construction shown in the diagram below.

For example:

With α = 20°, H = 6 mm, and D = 8 mm (planet gear), the twist angle θ is 31.7°.
For the ring gear, using the same height (H = 6 mm) but a larger pitch circle diameter (D = 24 mm, to accommodate four planet gears and one sun gear), the twist angle θ is 10.4°.

Of course, all gears must share the same module to mesh properly.

Below is proof of the assembled result and its cross-section view:

As others have mentioned, you can use the GF Gear Generator add-on to automatically generate gears of this type. However, it does not support on-the-fly parameter editing. This means that if you want to try a different gear size, you’ll need to start over—re-doing the alignment, joints, etc.—since nothing is linked. For this reason, I usually prefer to build a simple custom gear component myself. It makes iteration and development much easier later on.