gears - general guidance

[BlueInGreen]

I've started working with gears. I do not see a tutorial on this - those I have seen, e.g. on YouTube, use FCGears which I think is old. I can make one gear alone, and two so far with different numbers of teeth, and translate them around. that's as far as I have gotten. I can tell there is a lot of documentation and web results out there but some guidance would be very helpful :

* for two gears to work together - in real life - I am getting the impression they must be designed in the same freecad session - that is, one cannot make a gear, get the svg file, and somehow make other software match them up. Or, maybe it will work with trial and error, for example with a wood cutting machine.

* it looks like I will need to understand the Test framework, to show that the design will work.

thanks.

[Willem]

FCgears is still update, on the githyb page you can see that last update is made 15 days ago https://github.com/looooo/freecad.gears

[vocx]

...
* for two gears to work together - in real life ...

There is a theory to gears, it isn't magic. It's like asking, "how does a compressor-evaporator system work?" Well, you have to study this, from the physical principles all the way to the actual operation of the machines. This is the reason there are people trained in mechanical engineering and machine design in charge of building these systems. They know what sorts of gears, number of teeth, diameter ratios, materials, etc., are necessary to produce a calculated displacement and torque. I think you have to study this up, it can't be treated like a newbie topic. Once you understand this, then FreeCAD can help you create whatever you want.

* it looks like I will need to understand the Test framework, to show that the design will work.

The Test Workbench or Test Framework does nothing of this sort. It basically just refers to the system that runs the unit tests defined in every other workbench. It tests that the basic tools work.

[BlueInGreen]

It's like asking, "how does a compressor-evaporator system work?"

My questions are focused on how a gear (or any part) designed in freecad, can possibly be modeled in freecad, to test e.g. if the teeth of a gear will fit. That is also to say, that taking output from freecad - e.g. flattened svg files, (which I have to stop being obsessed with)- and using other software to get things to work could just lead to confusion - and it would be best to learn how to do everything in freecad because it will compute if these parts will work together. I noticed the Test Framework - that looked interesting because it seemed it might model the gears rotating together.

[vocx]

...because it will compute if these parts will work together.

Nothing can compute if it's going to work for you. This needs engineering knowledge. FreeCAD gives you tools, and you, the user, are supposed to use these tools to create something that will work.

You can build a steel structure and run FEM simulations, but that won't tell you if the structure will fall or not. It will give you information that you have to interpret and decide if the design is good enough or not.

In order to know if gears will match or not, you'd need some sort of kinematic solver to test for collisions and things like that. But you still need to know how gears are supposed to work.

I noticed the Test Framework - that looked interesting because it seemed it might model the gears rotating together.

But why? The Test Workbench doesn't mention anything about simulation at all.

[drmacro]

Gear design is a pretty well known subject. The formulas have been honed by engineers for a long time and are published. Many web pages dedicated to the design as well.

Whether they'll work or not is why people like Matthias Wandel make his template generator: https://www.woodgears.ca/gear_cutting/index.html

and Abel Vincze make his simulator: https://geargenerator.com/#200,200,100, ... 0,0,3,-515

...so us mortals don't need to be gear design gurus.

You can use the numbers you settle on from those web sites to then use the FC gear generators to model the things for, say, 3D printing. If you're going to machine them, then you have a whole different set of things to consider...first, where you gonna get the gear cutters.

[BlueInGreen]

Matthias Wandel make his template generator: https://www.woodgears.ca/gear_cutting/index.html

and Abel Vincze make his simulator: https://geargenerator.com/#200,200,100, ... 0,0,3,-515

I didn't know about Vincze's site - I'll check it out [UPDATE : Oh yes, that site, I remember it now - that is an interesting site ]. I knew about Wandel - he has great stuff, amazing resource. Sadly, the nice gear software he has is essentially take-it-or-leave-it..?.. and has led me... well, here.

today's searching turned up a pretty good beginner site for gears :

https://makezine.com/2010/06/28/make-your-own-gears/

... I remain determined to learn more about freecad, if only with two gears in the program.

Thanks for the guidance.

[iplayfast]

It's like asking, "how does a compressor-evaporator system work?"

My questions are focused on how a gear (or any part) designed in freecad, can possibly be modeled in freecad, to test e.g. if the teeth of a gear will fit. That is also to say, that taking output from freecad - e.g. flattened svg files, (which I have to stop being obsessed with)- and using other software to get things to work could just lead to confusion - and it would be best to learn how to do everything in freecad because it will compute if these parts will work together. I noticed the Test Framework - that looked interesting because it seemed it might model the gears rotating together.

From my understanding is that you want the pressure angle to match in order for the gears to mesh. The module is part of the formula
diameter = module * number of teeth.

So you can do useful things like changing the diameter of the gear by setting the module to a formula that is dictated to by the size of your gearbox for instance.

Hope this helps