Problem with Bevel Gears and Contact set Animation

[psylencer]

Hi folks, this is my first post here, and Im pretty new to inventor so please be tame if this is a stupid question.

 

Basically im trying to use the contact solver with bevel gears. I've created the gears which in the design accelerator indicates full compliance without any errors or warnings.

 

If I create small gears say 1:1 ratio, 16 teeth each, everything works fine. I zoom in on the tooth profile and notice the gears seem to mesh properly at both the back side and front side of the gears. However when i create gears of a larger ratio (again without any errors), I notice the larger gears tooth profile is rather squarish, preventing it from meshing and Im guessing is the reason the contact solver seems to lock up.

 

I should point out, im not a gear person. My inventor experience is limited.

 

Im using inventor Pro 2012.

 

Really hope someone here can help.

 

Thx

[JD Mather]

The gears created in Inventor are simplified approximations based on Welman's Involute method. They are not intended for manufacturing purposes as you normally purchase gears from a gear manufacturer. It is possible to extract the "correct" curves - but this is not your question or real problem.

 

You should not be using Contact Sets with gears, not needed and too complex a calculation.

There is already a gear Motion - Rotational assembly constraint built into Inventor.

 

There are other more advanced techniques as well, but I think that is beyond the scope of this discussion (Dynamic Simulation Environment).

[psylencer]

Thanks JD for your response, Its humbling to be communicating my idea with a guru such as yourself.

 

I should clarify, those screen shots were only meant to illustrate what I believed to be the problem, they do not illustrate the actual problem.

 

Im using the bevel gear as a rack and pinion. Or a Beveled rack and pinion if there is any such thing. I do not believe THIS "beveled rack" can be manufactured using traditional hobbing means.

 

My rack is a section of the bevel gear (approximately 35 degree section). To make the matter more complicated, there are 2 racks and one pinion. When the teeth of one "rack" run out, the opposite racks teeth grab and reverse the action of the pinion. Without submitting my invention to the world, I''ve attached a screen grab of the setup to illustrate the problem. Please bear in mind, I've hidden much of the geometry to show this grab. If there is a way to use contraints to animate and simulate the idea, I'd love to hear yours or anyone elses thoughts.

(yes the pinion shaft is held in place (before anyone asks, that part is hidden to show the mechanism)).

 

If it is possible to extract the real curves, please let me know how. At this stage I DO believe Inventors approximation IS the problem. Processing power is not an issue. If need be, in order to simulate accurately I will purchase whatever hardware necessary.

 

Without revealing too much, I should also point out that this is a hand held tool, the driving force is linear, caused by a closing human hand in much the same way as using a pair of pliers.

 

Why aren't I using I using a traditional "ice cream scoop" style rack and pinion? Efficiency. I really need to get the most out of the human hand. Although technically possible, I also believe an efficient Ice cream scoop style rack and pinion will require much more complex rack design than the "beveled rack" i intend on using. Put it this way, this tool is not for releasing ice cream from a scoop.

 

Do you think this may be a case of having to model the "Beveled Rack" manually?

 

Thanks again.

Edited August 23, 2012 by psylencer

[JD Mather]

Forget Contact Sets for this.

You will need to learn Dynamic Simulation.

You must have Inventor Professional or Inventor analysis with Dynamic Simulation Environment.

 

You could animate it in Inventor Studio without Dynamic Simulation, but it would be a bit of a fudge. If you are sure the real mechanism is going to work when built - this might be good enough. If you want to analyze to see how well it will work or to make improvements in operation - you need to learn Dynamic Simulation Environment.

[psylencer]

Fair enough, but will dynamic simulation work with bevel gears that are (poorly) generated with the design accelerator as per the initial question?

[JD Mather]

Dynamic Simulation works with the pitch cone - doesn't even need the solid geometry.

I should warn that this is an advanced topic.

Search Amazon for Wasim Younis book and also go through the DS Tutorials built into Inventor Professional.

[psylencer]

Dynamic Simulation works with the pitch cone - doesn't even need the solid geometry.

I should warn that this is an advanced topic.

Search Amazon for Wasim Younis book and also go through the DS Tutorials built into Inventor Professional.

 

 

Its all good, i already know how to use dynamic simulation. 3D contact joints would be the obvious solution, however I need Design Accelerator to model the larger gear properly for this to work. i guess I was hoping there was there was some way of testing the locking potential / stress analysis of the gears with it. the reason I wanted to use contact set was to test that the gears did not lock up, something I cant do if im using the pitch cone alone. I['d really like to *prove* the concept before manufacturing.

 

Equally important, I need to manufacture the parts specified in the O.P. Can I get your clarification on this : In order to get the bevel "rack" manufactured, I will have to manually create it in inventor? obviously its a highly customized part, not something typically produced with traditional methods.

 

Thanks for your consideration.... Beginning the painful manual method. At least I can use textual output from Design Accelerator to help.

[JD Mather]

Its all good, i already know how to use dynamic simulation. 3D contact joints would be the obvious solution,...

 

3D contact will most likely not work (too complicated profiles for the calculations - my guess is that it will hang up unless very simple mechanism (2-gears)).

DA will not create best profiles - you will have to model them.

 

If you know DS, I am kind of confused why you were trying to use Contact Sets.

[psylencer]

The real issue for me was making the bevel "rack". CS or DS, it doesnt really matter. none of the above will work for me unless I can model the part properly.

 

Really I *just* want to *see* this thing work.

 

You will notice in the picture I supplied in my second or third reply that I have infact created a beveled rack with curved edges (manually). Unfortunately my calculations must have been wrong as it appears to lock up. I then tried reverting to the DA which didnt help, hence my question.

 

Thanks heaps for all your attention on this one. At least now I know exactly how to move forward with this.