# Math help - radial change, circular movement

I am attempting to build a face powered by a “perpetual motion machine”.
Something like this GIF from the internet (but moving clockwise based on #DWFSS#):

I could use a sequence, but was hoping to build it in Facer directly with each ball as individual object.

The motion of a ball can be broken down to circular rotation with large and small radius and transitions between these, plus a phase change at 6 o’clock.

I am stuck on how to implement the radius transitions. The problem is that the change is not straight to the centre. Thus a simple interpAccel for radius does not work and adding a phase change concurrent with radius change does not result in straight line movement.

Anybody up for a challenge or just a hint to get my mind working in the right direction?

What a great idea @mountain_lion. There are probably a few ways to do this, but if I were to do it, I’d break it out into say 12 different balls moving 1/12 of an orbit around the circle, that when combined simulate a complete orbit around the circle. To get an idea of what I mean take a look at the seconds in this face.

Each marble moves down just a little bit smoothly, then back up to it’s original position instantly. When combined, they all look like they are smoothly sliding down all the way. A sleight of hand so to speak. Inspection is open.

In your perpetual motion scenario, the balls between 10:00 and 2:00, and 4:00 and 8:00 are simply orbital motion expressions moving a total of 1/12 the orbit of a circle, before jumping back to their original position. The balls at 3:00 & 9:00 are simply linear expressions in the line you want them to take from the inside orbit to the outside orbit location, or vice versa. The ball at 6:00 is simply another transition from the stable orbit between 4:00 & 5:00 to the orbits between 7:00 & 8:00. Each balls motion has to complete their sequence over say 1 second from (#Ds#-#Dsm#). Combined together individual each jumping ball will look like a smooth motion where you can follow one ball around the whole loop of the circle.

I hope this makes sense?

3 Likes

That’s a good way to break it down @bradtc!
I was trying to make 1 ball make the actual movement all the way around, which is a lot harder to do, lol.

I’m not sure if this link will work, as it isn’t published, but here is an idea of what I was thinking of. With Balls at 1:00 and 7:00 active. They aren’t quite synced well with the wheel, but you should get the idea.

Edit:
I can’t figure out how to get inspection turned on for an unpublished face. But in a nutshell,
1:00
X:` (160 - cos(((#Ds#-#Dsm#)*25 - 90) * ((pi)/180)) * 50)`
Y: `(160 + sin(((#Ds#-#Dsm#)*25 - 90) * ((pi)/180)) * 50)`
7:00
X: `(160 - cos(((#Ds#-#Dsm#)*25 + 90) * ((pi)/180)) * 140)`
Y: `(160 + sin(((#Ds#-#Dsm#)*25 +90) * ((pi)/180)) * 140)`

Now you just need to populate 2-6:00, and 8-12:00.

Edit#2: Inspection is now on. Thanks @ThaMattie

1 Like

Until now I was also trying to get one ball to go one revolution. I got close but not good enough to my liking

Will try your suggested approach next (will need to re-read when my mind is fresh) .

It says “enable inspection” if not yet enabled

1 Like

Those ideas are amazing, you guys really know your stuff

I never saw anything become of this thread, so I decided to finish off the demo I made. I think I took a page out of @icrltd4 's handbook and made it quite flashy, but it seems to work. I was a little worried it would automatically be removed upon publishing since I used the word “perpetual” int he name, but it’s still there. Inspection is open.

5 Likes

Nice one. It could use an interpAccel on the drops, to make it extra realistic

2 Likes

Very good idea @ThaMattie . I was thinking that the sliding balls were too linear and weren’t reflective of “g”, but couldn’t figure out how to incorporate it. That might be just the idea to make it more realistic. I’ll look into it. I like the challenge.

2 Likes