Lego axle variable velocity.

[system]

Here are couple videos shows how to make velocity that varies, but remains constant over longer time. Very simple setup.

Rotation with intervals. There is small chance that gears stuck.

A-axle connected to motor and rotated with constant speed. B-axle connected through chain. Part time of cycle rotates faster, part time - slower. Both axles do full cycle in same amount of time.

In both cases i attached axle to a gear in non-standard way. Attaching axle by different angle (but same place) will move center of rotation closer to gear side by 1 mm.

You could place axle-pin to that place to fixate another axle in one of 4 holes of that gear. This gives another alternative for speed and position

The only problem - I haw no idea where to use this approach :D

So let me know if you used it anywhere.

[Saberwing40k]

I've used an approach similar to this, but with larger 40z gears, as a substitution for a Geneva mechanism.

[Jeroen Ottens]

The first one I knew of, the second one is new to me...

Now to think of an application for it...

Hmmm... robotics? automatons (like the 18/19th century ones)?...

Thx for the idea

[Lipko]

Oval gears are sometimes used in bicycles too.

[arik]

Thanks so much for this!

I've actually been trying to figure out something like this. I think I did experiment with 24t gear like that but didn't get the effect I wanted. (I guess the speed variation was not right for me.)

What I've been looking for is setup where there's (roughly) half of the rotation with speed X and then half of the rotation with speed 3X. Why? Because I'd like to create a four legged walker with realistic walking gait. And for that I need to have 3 legs at ground at a time and one leg making the step forward.

I didn't get it working nicely only with gears. I also tried with linear actuators, but it didn't turn out well either. At the moment I'm setting up this with pneumatic cylinders (don't know yet wheter it will actually work).

Back to the setup in videos, I think it might not work for me in the scale I'm building, but maybe with larger gears. Thanks anyway!