Parametric involute curve bevel gear design


#1

I’m trying to design and 3D print bevel gears that mesh correctly. I tried this video:

It looks ok but on close examination identical gears don’t mesh correctly - they overlap.
So I’m looking for some very clever person who knows how to model gears correctly and can help me make it happen in Fusion360. Fusion doesn’t natively support parametric curves directly BUT it can process a script that runs the equations to build a curve. So as long as I have the right equations I can build a script to generate the gear(s).

Do you have the right equations? @Gear105? @Big_Mak? @JohnC?


#2

The trick in making proper bevel gears is how you project them from your pitch circle line on the back angle. Straight off the bat, there is no perfect method. There are several styles of doing this and all of them have their own draw backs. Klingelnberg’s is pretty good the face and root angles are parallel to the pitch line and do not intersect with the apex. Gleason goes the other way and the face and root angles actually cross the pitch line before the apex. Then there is standard where everything meets up. As far as making an equation that is a pretty expansive question. I think I can whip up a model for you, but don’t really have the time to go though and show you the whole deal. If you want to go the equation route and sort it out on your own the math you want to look into is involute https://www.mathcurve.com/courbes2d.gb/developpantedecercle/developpantedecercle.shtml . I think you could do the gear generation more easily with relations instead of equations but I haven’t tried to do it in Fusion yet. That all being said the real magic of bevel gears is in how you project them from the back angle and you can use any standard gear profile to do that and experiment with the projection and meshing from there.


#3

Best solution IMO is to just buy a license to Gearotic. :slight_smile: https://www.gear2motion.com/


#4

Personally I have found Gearotic to be inaccurate. But it is probably good enough for most applications.


#5

I prefer just popping on mcmaster and downloading the CAD file of the relevant gear, so much faster:


#6

Continuing on this topic, what would be a way to design bevel gears that mesh at angles which are not 90 degrees?


#7

Still by projecting from the back angle centred around the pitch line just now the angles are a little different… if you draw out the side view, you can see that the pitch line is still half way between the gear centre line, but now the face and root angles have changed.


#8

Since you seem more knowledgeable about this subject than me, would you mind giving your opinion on the following bevel gear generating resource?

http://www.otvinta.com/bevel.html


#9

Seems a little strange to be honest. It is missing some functionality while adding some that I don’t understand.


#10

I find McMaster-Carr’s cad files are pretty damn good, but I’d contact their customer service to find out how accurate the cad files for their gears are – I’ve downloaded models from them that weren’t exactly representative of the product (key dimensions were accurate of course, but some of the details were a bit off)


#11

Downloading a mcmaster-carr gear is great… when they apply to your solution.


#12

I found a great resource with information about drawing involute curves.

http://www.cartertools.com/involute.html


#13

Perhaps some inspiration can be found from this hackaday contest going on right now: