"The centrifuge is a genuinely terrifying device. The lights dim when it is switched on. A strong wind is produced as the centrifuge induces a cyclone in the room. The smell of boiling insulation emanates from the overloaded 25 amp cables. If not perfectly adjusted and lubricated, it will shred the teeth off solid brass gears in under a second. Runs were conducted from the relative safety of the next room while peeking through a crack in the door."
Read the rest to learn if a lava lamp will work on Jupiter or during a space shuttle launch (2.3 or 3 Gs).
Back when I was in high school I did a bit of biology research one summer. My lab's ultracentrifuge had a lid which was solid 3/8 to 1/2 inch steel plate. Working the lever to slide it to the side was a good reminder to ask the question "Are you sure you've properly balanced these (nitrocellulose) test tubes?"
It loads through the side of the drum, rather than the end—this addresses two major mechanical sore-spots in traditional front-load washers (which are otherwise vastly superior to top loaders).
It's not an entirely new concept (cf. http://www.staber.com/), but our approach to the door and very ingenious and novel.
If you plan to make one, make the radius smaller, but the velocity higher.
The energy stored in this goes by the radius squared. But the centripetal force on the object at the end goes by the radius.
So a smaller faster one is less dangerous, and also requires a less powerful motor (or the motor you have can give you a higher force).
Although the bearings are probably a bit harder to handle when it's faster, the whole thing will weigh less.
On the con side, a smaller one will have a larger difference in force between the top and bottom of the lava lamp, making your experiment less accurate.
Energy may go by radius squared, but the rpms change to match.
For visualization: the ice-skater who spins slowly & pulls arms in. By spinning faster, no energy is lost, as can be seen by extending the arms. However, a slower-rotating device can more easily be predicted and avoided / hand-stopped if needed.
Totally agree. But a smaller, faster one is less predictable, so you can't bleed of small amounts of energy as easily / safely.
Which would you rather try to stop, with your bare hands, assuming identical energy? A 1-inch pipe spinning at 10,000 RPM, or a large tire spinning at 10?
One is more predictable than the other. In that video, I can point out when the arm will come around again with relative ease, and can very easily be accurate to below a tenth of a second.
Now picture it going several times faster in terms of RPM, and tell me when it'd be safe to stick your arm in its path.
Lets scale it up. Picture the earth. Near the equator, the linear velocity is almost 1000mph. Scale it down to the size of the centrifuge in the video, while keeping linear velocity the same. I can easily point out when half of the earth is facing the sun. Could you point out when the centrifuge is pointing north?
If you are planning to play chicken with a centrifuge, sure.
But I am more concerned with what happens if you do actually get hit. Or if it comes apart, or falls down.
And if you do get hit, or it breaks, a smaller faster one is MUCH (exponentially much) safer.
The force goes up by the RPM squared, but it goes down only linearly by radius. You don't need to speed it up very much to counteract the smaller size.
On the other hand the energy goes up by radius squared. Meaning the smaller size helps a LOT in terms of destructive power.
I've been too long out of physics, so I'll take your word on it. I wasn't sure how quickly size effected energy. Though I'll still take my chances with something I can predict if I have to interact with it.
One question though: is energy->radius^2 based on angular or linear velocity?
Faster RPM also increases velocity of would-be shrapnel. Either you prepare for the risk of a slowly-rotating, large rotor/axis assembly failing catastrophically, or a faster-rotating, smaller assembly shedding poorly-fastened bits from the ends of its rotor.
The velocity of the shrapnel is the same as the linear velocity of the part it detached from. If it detaches from a faster moving surface, it will fly faster.
Sorry for fudging may response with a term for angular velocity, instead of linear velocity. I was writing from the assumption that the primary point of a smaller centrifuge would be to safely get higher centrifugal forces at the ends of the rotor, which would require that the ends of the shorter rotor move at greater linear velocity.
Well, if anyone's interested, these links should work in a bit over an hour (or two... fluctuating speed), provided it all downloaded correctly (I'm headed to sleep). Don't try before then, they won't be complete, I'm just downloading to my Dropbox.
Please mirror / set up a torrent if you can, I'd prefer to not nail my Dropbox too hard. (payload is interesting, you can see the twisting caused by the spinning)
Dropbox will shut you off without warning. I had a 25mb training video up there for a 15-person startup and my public folder was turned off astonishingly quickly.
I wouldn't be concerned so much with glass shrapnel, as with almost molten wax spraying out.
Have you ever opened up a lava lamp? The bottle is capped with an old-fashioned pull-off bottle cap. I guarantee that if anything goes pearshaped, it'll be the integrity of that cap.
As well as "IT LIIIIIIIVES!!!!" when you get it spinning for the first time, and scaring / awesome-ing the neighbor kids.
What the heck is that thing made of, anyway? An erector set? Juice bottles? Over-powered wires and motors? That beast is worthy of a Frankenstein moment.
So, pretty much yeah, an erector set, though possibly a bit stronger. It's not old-school erector, though. Looks like Meccano has been making Erector sets since about 1990.
I agree, who's spirit can only be really captured by a large toggle switch mounted on the wall that you have to flip which dims the lights as it happens.
"The centrifuge is a genuinely terrifying device. The lights dim when it is switched on. A strong wind is produced as the centrifuge induces a cyclone in the room. The smell of boiling insulation emanates from the overloaded 25 amp cables. If not perfectly adjusted and lubricated, it will shred the teeth off solid brass gears in under a second. Runs were conducted from the relative safety of the next room while peeking through a crack in the door."
Read the rest to learn if a lava lamp will work on Jupiter or during a space shuttle launch (2.3 or 3 Gs).