What is fastest motor RPM? a quick internet search showed it as 104,000.
Is there one that spins faster? what is the theoretical limit?

How well would a beam attached perpendicular to this hold up? (motor spindle attached to the center of the beam)

Let's say the beam was strong and well ballanced, and the contraption operated in a vacuum.
I would imagine the speed at the outer edges of the beam would travel very fast along the circular path.

If a motor could only be built to be so fast, cound multiple motors be attached end to end, multiplying the speed of the last motor?

any uses for such a device? what do you think the maximum speed could be?

maybe I am just sleepy, so I am thinking about this wierd idea.

What is this 104,000 RPM car?
Is it the Veyron?

I feel stupid for asking this but, what does RPM stand for?
I know what it is but what does it stand for?

Revs per Mile or Revs per minute

Revolutions per minute, and it certainly isn't a car. Being on my phone and too lazy to Google it, what is that motor in?

A vacuum, apparently.

Yeah, this motor is in a vacuum cleaner I guess.
But my use of the term vacuum means that a different device could be made, kept in a space without an atmosphere in order to reduce friction.

So a problem would be centrifugal force.

What about going super fast (maybe near light speed) but in a circle, instead of a straight line. what are the limits to this?

Could there be a sphere of high density at the center of the beam, that can be controlled to spin seperately to counter the centrifugal force?
Maybe the people with knowledge on gravity can chime in here. Obviously I am not a physicist.

I had this dream last night of a giant cylindrical building in the middle of a desert that housed a time machine. :hehe:

I am under the impression that in a car, the limit is somewhere between 12,000 and 15,000 RPM, but I'm not really sure. My car redlines at 7,000. (And that's because of the intake/exhaust valves remaining inside the cylinder when the piston comes back up). I don't know anything about other kinds of RPM (except HDDs, lol).

What kind of motor are we talking? An electric motor? AC or DC? There are limits everywhere. Salient pole rotors cap out at 1800 rpm, because any faster and the forces would snap the poles and break the rotor. Turbo rotors can operate much faster, but then you get into issues with heat buildup...and I suppose those "don't count" since they're turbine.

And what in the devil is a digital motor? Looks like they have some magic stuff there. No windings? Is it a straight iron core? How does it spin? It doesn't have carbon brushes or commutators, so it's definitely not DC.

I wonder how it works. Digital pulse technology. Even with digital control of the AC voltage I don't get how they can create torque without two interacting magnetic fields...so they have to create a magnetic field sans armature windings.

Oh never-mind. They have a neodymium magnet in the rotor. That's it. So they pulse the stator field with digital control and that causes the spinning. I see now. That's also how it can spin much faster than the limitations of 60Hz 120VAC can provide, and it allows control of the rotor with DC voltage instead of AC, since you rely on the digital circuit to switch polarity instead of the sine wave...

My guess is that it CAN spin faster, and the limitations are in the "impeller" they have to cause air flow and generate suction in the vacuum. That must have enough friction to pose a serious barrier.

And the speed of the digital controller is probably a limit. It takes finite time to switch the magnetic field, and I think if it got too high in frequency you'd melt the windings from hysteresis losses...

Also:



No I don't think it works that way.

so motor A, with a plate spinning at 10,000 rpm. then mount motor B to that plate, so motor B is spinning. then turn on motor B, so it has a plate now spinning at 20,000 rpm relative to the operator's position, just keep adding to this.
would that work?

I wonder if anyone has tried it using those little hobby-kit electric motors.

Nope. Not at all. How would you even attach motor B to motor A and have it spin at the same speed, while also being independent of motor A such that you can increase motor B's speed on it's own?

Either it's fixed solid, in which case you can't increase B's speed without also increasing motor A's speed at the same time, or it's not fixed, in which case motor A would not cause motor B to spin at 10,000 rpm to begin with.

motor B would be fixed solid on a plate, so the whole thing is spinning on motor A. then turn on motor B by a remote. No?

Don't know if there's a theoretical limit. I guess it depends on what constitutes and engine. Obviously the speed of light is a hard limit on everything. But before you reach that you'll have stress limits on the materials involved. I think if you strap a couple of antimatter engines to a rotor you'll reach that limit pretty easily for most materials. That's when components start breaking off and your super fast motor becomes a Gunstar pulling a Death Blossom.

Agreed.
So there would have to be something (I don't know what) in the center that pulls things back in, countering the centrifugal force.

http://i137.photobucket.com/albums/q235/Lomoru/Untitled-1.png

Rotor A cannot cause rotor B to rotate unless they are physically attached to eachother, yes?

The stator can't be connected to the rotor, because that defeats the purpose of relative motion between the two magnetic fields and won't produce torque. If rotor A spins up to 10,000 rpm, and causes rotor B to spin at 10,000 rpm, you cannot apply the exact same power to rotor B's stator and expect it to suddenly go 20,000 rpm.

Infact this configuration exists in the real world everywhere, called a motor generator set, where A starts out as a motor and B a generator, and A spins B up to synchronous speed (because of it's configuration you can't just start a synchronous motor from 0, but that's the whole relative motion thing and I'd have to explain how synchronous motors work), and then you switch A to a generator and B to a motor. There is no advantage to having both of them be motors at the same time, because it's basically supplying twice the power to get the same result.

http://i137.photobucket.com/albums/q235/Lomoru/Untitled-2.png

Also on the note of theoretical limits, there is a limit to how much power you can actually apply before the counter electromotive force, the voltage generated by a spinning motor in the opposite direction of the voltage that caused it, may become so large that it straight up stalls out the motor, since you can't apply any more voltage (and therefore current) beyond what the copper wires in the stator can carry before they melt.

Attaching any additional mass to the rotor will reduce the maximum RPM of the motor. It doesn't just depend on the mass, but on the additional http://en.wikipedia.org/wiki/Angular_momentum as well. So a stick weighing e.g. 1 kg won't reduce the maximum RPM of the motor by the same amount if it is attached to the rotor perpendicularly and if it is attached to it at a smaller angle.