# Highest RPM?

1. ### fedorfan

113
Does anyone know what the highest rpm in the universe is?

2. ### Ki Man

555
RPM? are you talking about tires or computers or what

if its speed related dont doubt the power of c

3. ### Crosson

No, but John Wheeler would jokingly discuss the maximum upper limit on horsepower (about 10^64), an engine with which would instantly rip itself into a black hole .

4. ### fedorfan

113
My best guess would be a turbocharger at like 180,000 rpm. I guess the universal speed limit would be the speed of light. Also, Im talking about whatever is rotating the fastest. Not pkanets or something though, I mean revolutions per minute, not year.

Last edited: Jan 22, 2007
5. ### Crosson

This illustrates the problem with the question, because RPM on its own has no limit (as the revolving system decreases in radius). Using a radius about one meter, the speed of light limits us to an RPM of about 18 billion, so that is a safe upper limit.

6. ### Danger

9,878
My semi-educated guess is that the fastest that anyone will ever likely run across in reality would be a black hole. Since the angular momentum of the remains of the original star is conserved, those suckers can spin.

7. ### fedorfan

113
Yeah danger, thats probably a very close guess, although I suspect a microscopic black would be even faster.

8. ### fedorfan

113
Noone else knows anything?

9. ### spartinf

1
flagellum

I'd say it is the flagellum at up to 17,000 rpm....if you look at a figure of it you'll be pretty amazed at it's complexity and sophistication

10. ### tehno

363
Electrons around nuclei in atoms good enough candidates?

11. ### Danger

9,878
To start with, that would be revolving, not rotating... but it doesn't count anyhow. As for the electron spin component, it isn't really spin. I think that you pretty much have to stick with macroscopic phenomena.

1

9,878
14. ### turin

2,326
How could one convince one's self that Dyson's little motor is running at such a high rpm? Even with an oscope, how would one know that the oscope isn't simply picking up "fake" electronic signals from the control circuit? I don't believe that I can hear such a high pitch. Maybe some angular momentum test?

15. ### Superstring

119
The maximum RPM in the universe is dependent on the radius of the spinning object.

The formula for calculating velocity of the outer edge of the "wheel" using RPM is:

$$\upsilon=C*RPM$$

Therefore:

$$RPM=\frac{\upsilon}{C}$$

Plugging the speed of light in for velocity (and making it an inequality to show that it has to be less than c):

$$RPM<\frac{c}{C}$$

So the maximum RPM of an object is the speed of light divided by the object's circumference. That means the smaller the object, the faster it can spin.

Last edited: Aug 11, 2009
16. ### Danger

9,878
Which brings us back to black holes...

17. ### diazona

2,156
Well, actually
$$\omega < \frac{c}{r}$$
and convert to revolutions per minute. (RPM is a unit, it sows confusion to try to use it as a variable)

I got
$$\omega < \frac{2.86\times 10^9\,\mathrm{m}}{r}\cdot\frac{\mathrm{rev}}{\mathrm{min}}$$
so... for something with radius equal to the Planck length, $1.77\times 10^{44}$ revolutions per minute? (If such a thing could exist, of course)

5
19. ### jasc15

156
:uhh:
You mean a brushless stepper motor?? What will he invent next??:uhh:

20. ### hobbez

1
Hi. I just signed up because i was google-ing for the highest recorded rpm for an electric motor and happen to find this forum.

That 1,000,000 rpm motor is pretty amazing.

I come from a hobby world where we use fa-130 size motors (about the radius of a nickle and about an inch in length) running on 2.4 to 3 volts. Most of the aftermarket motors for this hobby are made in china or the philippines and claim excessively high numbers anywhere from 68,000 to 500,000. One of them claimed 1,200,000 rpm. All these are supposedly tested at 3 volts and with no weight on the motor axle. I don't know what testing equipment they used on these motors for such numbers, but i'm more than positive that most of these are highly inaccurate.

I did a little math considering one of the faster cars going 60 mph and plugged in the wheel size and gear ratio to find out that some of these motors do about 60,000 rpm under load, so i can see the same motor, free of load, doing at least 100,000 rpm.

I'm not sure about this, but i think high end slot car drag motors can go even higher, especially given the voltage pushed into those things. Or maybe they just have severally intense gear ratios. I don't know.

To come to a conclusion, i just wanted to point out that 100,000 rpm is a very easily achievable number for a small electric motor, so i am not surprised to hear about that 1 million rpm motor, although i was kind of hoping someone had already pushed the limit higher...oh say to 1,500,000.