Best shape to flip or spin in Water?

[society]

So I'm not sure if this is the right place - and its a crazy question - but I am trying to get something to spin and/or flip when I put it in a beaker of water, just by its own weight and gravity. I have tried a maple seed shape, propeller shapes, simple curls, sprials, Rocchetti pasta shapes, but they all don't spin or flip fast enough. Does anyone out here know what the ideal shape would be? I know that the density will be an issue relative to the mass? But aside from that I need to know were to start , before trying to dial in the variables. Any ideas? By the way, a propeller type shape worked well but only with 4 blades and above. I have not been able to get anything to flip end over end yet. Any ideas?

It has to be quite small , like say the size of a penny or a dime.

-Cheers.

 

[berkeman]

So I'm not sure if this is the right place - and its a crazy question - but I am trying to get something to spin and/or flip when I put it in a beaker of water, just by its own weight and gravity. I have tried a maple seed shape, propeller shapes, simple curls, sprials, Rocchetti pasta shapes, but they all don't spin or flip fast enough. Does anyone out here know what the ideal shape would be? I know that the density will be an issue relative to the mass? But aside from that I need to know were to start , before trying to dial in the variables. Any ideas? By the way, a propeller type shape worked well but only with 4 blades and above. I have not been able to get anything to flip end over end yet. Any ideas?

It has to be quite small , like say the size of a penny or a dime.

-Cheers.

Can you use an external field, like a magnetic field to flip it at some depth? Can you post more details about the overall problem? An inverted dart will flip at some depth...

 

[society]

I can't use any external forces. Only gravity and the shape. I can't get too specific about the project, but the basic premise is that I need to release a dye/ink in fluid , in such a way that it will give the best overall consistent color throughout. So I was going to apply a water soluble colored coating to a shape which spins or flips at a controlled rate and the act of spinning or flipping will allow the coating to be released throughout the whole body of water consistently before landing at the bottom. Make sense? In other words, if I just drop a tablet into a beeker of water, the dye will primarily collect/release at the bottom of the beaker, and not throughout the whole volume. Unfortunately, I don't have the luxury of changing the density or weight of the tablet too much, or even adding other compounds to make it disolve faster etc... so the shape is the only way I could think to control the fall.

-thanks

 

[berkeman]

I can't use any external forces. Only gravity and the shape. I can't get too specific about the project, but the basic premise is that I need to release a dye/ink in fluid , in such a way that it will give the best overall consistent color throughout. So I was going to apply a water soluble colored coating to a shape which spins or flips at a controlled rate and the act of spinning or flipping will allow the coating to be released throughout the whole body of water consistently before landing at the bottom. Make sense? In other words, if I just drop a tablet into a beeker of water, the dye will primarily collect/release at the bottom of the beaker, and not throughout the whole volume. Unfortunately, I don't have the luxury of changing the density or weight of the tablet too much, or even adding other compounds to make it disolve faster etc... so the shape is the only way I could think to control the fall.

-thanks

Can you use something that releases CO2 or some other gas mixed in with the dye tablet? The bubbling action should help the solid dye to dissolve more evenly. Maybe even something like a little rocket-shaped tablet, with the CO2 bubbling out of one end to make the tablet move around in the liquid...

Alternately, you could embed some spring shapes in the solid tablet, so that as it starts to dissolve, different parts of the spring are released, causing agitation of the liquid and better disolving of the dye.

 

[Danger]

I have an assumption, but I'd better check to be sure. This is something to be mass produced in huge quantities, right? That would mean that it has to be as simple and cheap as possible to manufacture.
There's an idea tickling around in the back left corner of my brain, but I don't think that it'll work. I'm going to throw it out there anyhow, just in case. If it does work, you could just use the dye without a carrier shape.
What I'm thinking of is forming the pellet with increasing density toward the centre, with the outer layer having enough buoyancy to float the thing. As the pellet dissolves, it would gradually sink as that buoyancy decreases. Any hope for that?

 

[society]

I have an assumption, but I'd better check to be sure. This is something to be mass produced in huge quantities, right? That would mean that it has to be as simple and cheap as possible to manufacture.
There's an idea tickling around in the back left corner of my brain, but I don't think that it'll work. I'm going to throw it out there anyhow, just in case. If it does work, you could just use the dye without a carrier shape.
What I'm thinking of is forming the pellet with increasing density toward the centre, with the outer layer having enough buoyancy to float the thing. As the pellet dissolves, it would gradually sink as that buoyancy decreases. Any hope for that?

Thats nice! But yes you are correct in the mass production assumption. It would be quite hard to control the density to achieve that level of accuracy, also because the liquid will change slightly between use cases. This is one reason that I was trying to use a carrier. My hope was that the carrier Shape could be controlled easier than the carrier material - relative to the liquid conditions.

But I like your thinking! That hadn't crossed my mind yet.

 

[Danger]

I see. Hmmm... I'm going to go think on this some more.

 

[Claws]

A ball with a shape like the blade of a skill saw?
http://3.bp.blogspot.com/_9FRR9e1i5D0/SKwlMeFfAPI/AAAAAAAAAGg/0ZrOWBy78jA/s320/TCT_Saw_Blade.jpg

With holes in the recess and holes at the top on a 90 degree angle. The holes in the recess would draw out the inside liquid as low pressure appears there, outside liquid would be sucked in at the 90 degree holes to replenish the liquid inside.

Will it work? dunno, just throwing out ideas on a lazy Saturday :)

 

[Danger]

That sounds like a pretty ingenious approach, Claws. Multiple outlet points would certainly increase the distribution. I never considered that.
My thought before seeing that was to suggest trying various pitches on the 'propeller' shapes to optimize sink rate vs. rotation, but I like yours better.

 

[Moonbear]

What about something like a pinwheel shape...like the toys kids play with? Like one of these:
http://pslc.ws/macrog/kidsmac/images/pinwheel.jpg It's a slight modification of a propeller shape.

 

[Danger]

Wow! Moonbear showing up here just gave me another idea, since she's a biologist. You could genetically engineer sea-monkeys to excrete dye...