Gear Advice Needed

[Simonboyle08]

Hi All,

I am working on project that requires a gear to be modelled, I am looking for advice on the best way to go about this



Thanks

Simon

 

[DavidJ]

Simplest - if it is any kind of standard item, download from manufacturer web site.

Next option - model 26mm dia blank, cut out one gap using dimensions from detail A, then circular pattern that gap 25 for 25 instances around the blank. Add the boss on one side side and the raised portion on the other. Finally make the tapped hole in the boss. I'll add a file if things stay quiet.

 

[simonb65]

Start by creating yourself some reference geometry to draw a single tooth ...



Create a tooth ...



Extrude it ..



Feature pattern around the origin ...



Then add the end bossses and cut a hole through ..

 

[simonb65]

Add the threaded hole ...

 

[Simonboyle08]

Start by creating yourself some reference geometry to draw a single tooth ...

View attachment 32682

Create a tooth ...

View attachment 32683

Extrude it ..

View attachment 32684

Feature pattern around the origin ...

View attachment 32685

Then add the end bossses and cut a hole through ..

View attachment 32686

Hi Simon,

thank you for the detail, I will give it a try

Simon

 

[simonb65]

thank you for the detail, I will give it a try

Your welcome! As @DavidJ said, you can do this many ways. Some like to model as if they are machining the part, i.e. like create a solid cylinder then revolve cut, then pattern cut, etc. Some build upwards by adding material. Either way, do whatever is easiest and most logical for you, but the important part is being able to analyse and breakdown the part into it's constituent features and then how to generate those in the tool. Which ever way you do it, just try to keep things simple and small logical steps. It's easier to manage that way!

 

[DavidJ]

Modelling it will force you to look critically at things like - 'where is the centre of the flank radius ?'

I placed it on the base 24mm base circle, looking at Simon's sketch he took a different approach (matching the original detail better). It's very easy to make assumptions that aren't quite correct from other's drawings!

Moral - always double check the result against the source information.

 

[Simonboyle08]

Thank you for all your assistance,

Here is my results following the example from Simon

 

[albie0803]

Remember that unless you are using your model to manufacture from, the teeth do not need to be accurate. The OD is important and the correct centre distance when assembling is also necessary.
Your drawing actually looks like a spline, not a gear and should be to an existing standard, which would not be dimensioned like that.

 

[JST]

Does look like a spline, or a timing pulley, or a type of stub tooth gear that I am not familiar with.

Most gears are either hobbed, in which case the tooth form is "generated" in the process, or else cut with form tools on a milling machine, in which case the form tool cuts the correct form. All that really needs to be shown is the module (or diametral pitch) and tooth count.

Many times for a gearbox I will design using the OD and the pitch diameter, using the pitch diameter to set clearance for the gear center distance. The OD is useful to avoid interferences between gears or gear to housing, etc. I never bother with the tooth form etc.

Of course, for 3D printing, you may need to exactly model what you want. There are programs for generating gears and tooth forms, such as "Gearotic CAD", which can output importable templates. https://www.gear2motion.com/

 

[HaroldL]

To me, it almost looks like it will drive a toothed timing belt.