Algodoo

For me,there is no difference.Both of them were the same!

I concur.

I prefer true circles over circular polygons because you can easily change the size by adjusting the radius.

Grab the gears with the drag tool and try moving them. I got the polygon gear to skip 5 teeth. The circle gear, nothing. The collisions on circles are better because circles can be determined based on the radius. I made a circle collision code in Java. It ended up being only like 10 lines. But I made one for complex polygons with 4 vertices and that was like 50 lines. So just use circles.

You're making oversized gears. I don't think that a wankel can be bigger than half a meter, and those gears are huge (I guess that a practical use in a wankel needs 20 cm gears...?) so they work better. And what I meant in the rotary engine scene is that in those rotary engine types, if yours has much density on the spawned balls, the rotor suffers from sudden kicks from the balls, and that makes the gears unsync sometimes, even if they are heavy and with the least number of circles possible (8 and 12, for example).

Still testing but it is a well done test setup Thanks

I suspect that we would all agree that, when it comes to using circles vs. circular shaped polygons, circles are the better choice, because they are exact, easy to use, and have a simpler mathematical model. As far as circles being substantially stronger than polygons, I just don't see it.

Jimmyfisherman,
Regarding "Grab the gears with the drag tool and try moving them", that is an uncontrolled test. That is why I used a brake to control the resistance. I can break either set of gears with the drag tool.

Regarding "The collisions on circles are better". What is a "better collision"? Is it stronger, faster, or does it use less resources? Please show me. The circle gears and the polygon gears each have equal amounts of bodies, geometries, narrow collision tests, contacts, and constraints.


The Linkage,
Regarding "You're making oversized gears", I think you are right, but it was unintentional. I scaled them to 1/10th the original size and still don't see any big difference between circles and polygons.

Regarding "the rotor suffers from sudden kicks", it may be that circles tolerate impact better than polygons. I had done some tests with colliding balls but couldn't see any significant difference.

Both,

Regarding tooth strength, I suspect that tooth strength has more to do with object density and area than it has to do with whether it is a circle or polygon.

Regarding gear stability, I suspect gear stability has a lot to do with contact geometry and the number of contacts required to move the gear. In this regard, circles excel because there is only one contact when two circles collide. Polygons can be designed for minimum contacts, but this is not automatically guaranteed like it is for circles.

after some testing, not extensive, with side by side angular velocity plots on the driven gears it appears that, Drum Roll Please....

Both SUCK at smooth power transmission with no quantifiable difference between the circles and the polygons in this example
In my tests at one point I had the plot set at 1 second time span and it was bouncing all over the place even with the rpm set low, no load, sim speed at .1
and frequency at 1200
What I think this is telling us is: Algodoo really struggles with multiple overlapped colliding objects especially at speed
This illustrates to me why some of my older projects never made any speed
Bottom line, use the fewest possible number of teeth
Thanks for the test set up S Noonan

Regarding "bouncing all over the place" it looks like 7% regulation at 15 RPM and 20% at 300 RPM at 200 Hz and 100 Nm load.

Regarding "use the fewest possible number of teeth", I don't think that matters since fewer teeth don't necessarily reduce the number of collisions. Each gear set her has one or two collisions at any one time; one if a tooth is handling the full load, 2 if it is passing the load off to another tooth.

Circle gears are better off having 6 teeth... they can be used to do so many things. In a wankel engine, mesh a 6 with a 8 and you have a reliable eccetric gearing set. 8 tooth circle gears are still reliable. And you could attach a 6 gear to a 12 gear to make the camshaft for a 4 stroke engine, also still very reliable.

Regarding the collision codes for circles and polygons,

To determine the collision box for a circle, all the code needs to do is check if a part of an object is within a radius distance of the center, and then move it back a bit.

To determine the collision of a polygon, the code must be able to find the lines in between the vertices, get the points that fall on the line, determine which side of the line faces inwards into the polygon, and then calculate the angle to push the object back outwards. Alot more code for polygons.

I am going to make a test scene for this