If you spring mount the rail – you could use an electromagnet to compress one of the springs. Totally silent – no motors.

Hardly perpetual tho, requires batteries!?

If you use electromagnetics to manipulate the rail, you’ll have to watch out for influence on the movement of the (presumably) iron ball, or just use a ball of a magnetically inert material of course.

OK, one more thing … pulse BOTH the rail current AND the drive inductors, to improve efficiency.

I do like jdn’s solution but what I first thought this used was an electromagnet to gently push the ball around the track. A few capacitors and a coil would silently propel the ball, if not in noticeable spurts.

at the moment this looks like a “dumb” device… set the oscillation rate and make the marble keep up. how about making it “smart” by isolating a few sections of track and connecting it to an arduino or something, so the device knows where the ball is and can manipulate the oscillation rate to keep the ball spinning at whatever speed you want

“The term perpetual motion, taken literally, refers to movement that goes on forever. However, the term more commonly refers to any device or system that perpetually (indefinitely) produces more energy than it consumes, resulting in a net output of energy for indefinite time”

A microcontroller seems to be kind of an overkill for this… why not just hook up a geared down motor?

Wait, where is the arduino?

it sounds like robots having sex

Why not use muscle wires in stead of a servo.

But of course he can use couple of Miga Nano-muscles and be done with it: http://www.sparkfun.com/commerce/product_info.php?products_id=8782

Yeah, it would be cool to use coils and sensors to treat it like a railgun almost, constantly pulling the ball along. You could embed that all slightly below the surface of a piece of wood and it would be silent, and very cool looking. :)
-Taylor

Same as everyone else, use nichrome/memory wire/ etc.

It would be cool to do this with no electricity, just heated wire, possibly with a candle or something for power (large magnifying glass and the sun?)

I like the idea, keep hacking!

Hi

I am the person who made it.

Someone on the Picaxe forum told me I was on Hack-A-Day and sure enough! :D I do subscribe to the RSS feed but it’s buried at the bottom of the page so I nearly missed it.

While designing it noise of the servo was not on my mind at all, I knew it would be there but I wasn’t fussed about it. I have actually coded a mode now that uses loops to make very small changes. It is practically silent. I will upload a video of it since it seems to be an area that people first think about.

To people bothered about “perpetual” in the title should note two definitions:

2. lasting an indefinitely long time: perpetual snow.
3.
continuing or continued without intermission or interruption; ceaseless: a perpetual stream of visitors all day.

Which I think suits this piece quite well as it captures the fact it does go round and round and round.

To the comment “sounds like robot sex” that made me laugh.

A stepper motor may also work, not sure having never really used one before. Electromagnetics would take this piece away from being a very simple project which means I personally wouldn’t use them. They would give nice silent operation though.

As for making it “smart”, that was the original plan. The track wire is insulated so it would be pretty easy and there are plenty more inputs. The thing is it’s not needed at all. The ball just gets into the motion on it’s own. It may take a few seconds but it falls into place. I could use the potentiometer to vary speed but the Picaxe I am using doesn’t have the memory for all the code and I like the “random” motion. I could use a bigger Picaxe but its costs less than £2 which is cool.

As for the Arduino, I am aware of them but have never used them. I believe, living in the UK, Picaxe are quite a bit cheaper. I may be wrong so if anyone wishes to correct me, please feel free to do so.

This is most certainly not perpetual. It does not last an indefinite amount of time as the length of time the batteries would last could be calculated probably down to the minute given the electrical draw and whatnot. And as such it would not continue without intermission since the power source would eventually wear out. Still pretty neat though.

ridefst: craigs idea would work.

Start with an inner and outer ring, with the ball on it. Make the inner ring move eccentrically in a circular motion (keeping inner ring in same horizontal plane as the outer ring, and not actually rotating the inner ring).

It is easy to ensure it is *impossible* for the ball to “fall through” if the maximum gap is smaller than the ball diameter.

The “gap” moves around/forward at rate x, and so long as the ball moves around/forward at rate x then all is good. Easiest to imaging ball placed half way between minimum gap and maximum gap.

Alternatives could be:

a) tilt the inner ring in a rotational manner i.e. connect center of inner ring to a ball joint, make front of inner ring go up/down in sine wave, and the left of the inner right go up and down in cosine wave.

b) rotate either the inner or outer ring (keeping the other ring static), and the ball will move at approx half the rate of the tangential velocity of the ring.

ridefst: I suggest you should always assume someone has a clue, think about why you could be wrong in your first assumptions, and try not to jump to conclusions so quickly.

This is probably the best string of comments posted about such a simple project in a long time, I hope we see someone take on some of these ideas in a follow up post.

Nice project mate. The suggestions of the electromagnet 1 sound like a very nice idea, I would use the magnets to pull though (turn on 2 magnets to the left/ right of current ball postition). When I get some free time to get back into these projects I might make one myself :)

Servo needs a better mount

maybe using the same kind of electromagnet system used in hard drives?

I agree with Paul. Some of the noise is coming from the entire track rocking back and forth on the table from the servo.

So happy to have you on board. Can’t wait to go to Bigstuf with you. Welcome abord