3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

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--Oz--   1 mW

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3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by --Oz-- » Sep 04 2019 9:17am

I am trying to spin a object as fast as I can for cheap (under $30).

Videos and details here:
https://www.rcgroups.com/forums/showthr ... RPM-motors

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by markz » Sep 05 2019 9:16pm

Magnetism is the best method, no friction from surfaces touching each other, would benefit greatly!

Also how would you even measure that kind of RPM?

--Oz-- wrote:
Sep 04 2019 9:17am
I am trying to spin a object as fast as I can for cheap (under $30).

Videos and details here:
https://www.rcgroups.com/forums/showthr ... RPM-motors

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--Oz--   1 mW

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by --Oz-- » Sep 05 2019 10:03pm

markz wrote:
Sep 05 2019 9:16pm
Magnetism is the best method, no friction from surfaces touching each other, would benefit greatly!

Also how would you even measure that kind of RPM?
Electronics are fast, mechanical things = very slow.

20,000rpm is only 333 rev per sec, my best 3.8 million is only 63,000 rev per sec (63KHz), in electronics that's child's play. FM band is 100,000,000 cycles per sec (100MHz). RC control is 2,400,000,000 cycles per sec (2.4GHz).

The hall sensor detects the south pole of the magnet ball, it turns on the fet, that turns on the coil that pulls the ball around, when the north pole comes around, the hall turns off (and so does the coil current), very simple circuit.

Your correct about the friction, I have got mag levitation working, but not really to my satisfaction and its currently not whats holding my speed at 3.8Mrpm. Its the magnet balls self exploding from centripetal forces (24M G's at the equator at 3.8Mrpm). Maglev in a vacuum would be the best.

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by Punx0r » Sep 06 2019 2:39am

Is there any way of driving a solid steel ball bearing with reluctance torque? If not you could spin it with a jet of compressed air

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by --Oz-- » Sep 06 2019 9:28am

Punx0r wrote:
Sep 06 2019 2:39am
Is there any way of driving a solid steel ball bearing with reluctance torque? If not you could spin it with a jet of compressed air
Yes there is, but the complexity and difficulty factor is much higher than the simple magnetic ball circuit. With the magnetic ball, there is one simple feedback circuit that solves a few problems with the KISS simplicity, getting rid of the magnet/hall then requires several optical feedback circuits to control it. And currently when I tried it without levitation to reduce friction, the friction to get it started was too much (not much torque compared to the magnet), so maglev or air bearing needs to be done.

The compressed air would work, but the speed would be slow, why, because with my current personal record with 3mm ball, the equator speed is ~1300mph, so the air stream would need to be higher for more rpm. :lol:

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by markz » Sep 06 2019 2:36pm

I thought I remembered something on YT about high rpm, but checking now it was only 11M : 1 reduction.

https://www.livescience.com/3075-spin-r ... n-rpm.html
November 14, 2008
Industrial motors can spin at a head-spinning 250,000 revolutions per minute. But a new matchbook-sized motor runs circles around the competition.

Researchers from ETH Zurich's Department of Power Electronics created a drive system in cooperation with its industrial partners that exceeded 1,000,000 rpm in tests.

https://www.cnet.com/news/fastest-man-m ... -600m-rpm/
Fastest man-made spinning object clocks in at 600M rpm
August 28, 2013
how fast 600 million revolutions per minute is.

Because that's exactly the rotational speed scientists at Scotland's University of St. Andrews achieved with a man-made microscopic sphere of calcium carbonate basically for the sole purpose of observing what would happen at such a speed. The results were published in Nature Communications on Wednesday.

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by --Oz-- » Sep 06 2019 11:09pm

60 billion rpm
https://www.purdue.edu/newsroom/release ... anics.html

I did mention low cost :D I play with this on my lunch time and have spent ~$30 to get to 3.8Mrpm.

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by Punx0r » Sep 07 2019 4:42am

You're banging up against the limit of the material strength of the magnet ball so you either need a stronger material or a smaller ball :D

The compressed air would have to be high pressure with a sonic nozzle. An argon welding gas cylinder would probably be the easist and cheapest source of a few thousand psi.

I do like the ease and cleanliness of your magnetic drive though.

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by --Oz-- » Sep 07 2019 10:25am

I bought 216 5mm neo magnet balls for $7 on banggood.com, but the rpm limit is ~1.1M, then I got 216 3mm balls for $6 on banggood, took a while to find 2mm balls, but they want $50 for 10! Not going to happen, lol.

I got my maglev working ok (not great, its not as stable as I want it, I think I know why), but it suspending a magnet(s) using the same simple circuit I use to drive the ball and hall sensor for the height. I need to build a better coil to lift a steel ball or bar and use optical height control. I noticed the higher the freq the maglev is, the more stable it seemed, but I am just starting playing in this area, its fun testing and tuning.

@Punx0r Would that airstream be over mach2?

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by Punx0r » Sep 08 2019 3:53am

Not sure to be honest. I recall a small defunct wind tunnel where I used to work that was mach 3 or 4 powered by compressed air in the thousands of psi range.

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by --Oz-- » Sep 10 2019 4:23pm

Punx0r wrote:
Sep 08 2019 3:53am
Not sure to be honest. I recall a small defunct wind tunnel where I used to work that was mach 3 or 4 powered by compressed air in the thousands of psi range.
It would be interesting to try this method. Have to figure out a way to hold it, then use optical tach to get the rpm. I am curious how much "slip" there would be from nozzle air speed to ball circumference speed, especially on a smooth and small ball.

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by Punx0r » Sep 10 2019 6:35pm

Not sure. To be honest, the more I think it's going to be difficult to keep the ball aloft and stable and spinning in an air jet. It's like the floating Malteser trick times a million...

It's a done trick to remove the seals from a caged ball cartridge bearing, wash out the grease and then spin them up to very high with a compressed air blow gun (100psi). The speed on the individual balls could be inferred from the speed of the inner or outer race if you assume no slip/skidding. Friction might be too high to get anywhere close to the speed of your electromagentic drive - that is near ideal for this challenge, the magentic ball is just too weak mechanically.

Hold on, any chance you could sufficiently magnetise a solid steel ball to use? I'm guessing it doesn't have to be a strong magnet to work?

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Re: 3,808,800 RPM, 63,480 RPS, 1338mph, 2153kph, 24.3M G's

Post by --Oz-- » Sep 11 2019 11:56pm

Punx0r wrote:
Sep 10 2019 6:35pm
Hold on, any chance you could sufficiently magnetise a solid steel ball to use? I'm guessing it doesn't have to be a strong magnet to work?
I tried it using the most powerful new magnets I have (cheata 15,000rpm HDD drives, and while it does magnetize the ball bearing, it is nothing like a new ball magnet, less than 500 times powerful if I were to guess. So in my similar setup, it would not start to spin. I could make adjustments to holding apparatus and stronger more focused coils to see if it would work. I think maglev is the next major step in my endeavor.

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