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High RPM Slip Ring Recommendation

Night Watcher

Nov 6, 2017
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Hi,

I bought an EMAX RS 2205 2600KV Motor, and I want to attach a slip ring to it that has 6 cables.

The slip ring will be turning at a minimum of 1440-1800 RPM, ideally it would be running at 3600 RPM, and at max it might be running at 72000 RPM. However depending on the price of such a slip ring I might settle for the minimum RPM.
The slip ring will be running for a few minutes on occasions, and therefor there's no need to look for something too durable, but I don't want something of terrible quality either.
I would appreciate your recommendation for a high speed slip ring that fits the criteria and can be installed on this motor, preferably from a company that ships worldwide.
Note that I never used a slip ring before, therefor I am unsure how to install one on this motor, and I would appreciate some pointers as well.

This is the motor I bought:
https://www.aliexpress.com/item/EMA...CW-Black-Prop-Nut-RS2205-for/32694139341.html

Thank you :)
 

Harald Kapp

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Nov 17, 2011
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sliprings will probably not be very reliable. How about a wireless solution?
 

Harald Kapp

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Whatever it is that you put on the rotor: at 72000rpm it will fly off at high speed unless very, very, very carefully balanced. Even at a comparatively small 3600 rpm you need careful balancing.

A typical car tire rotates ~ 500 rotations per km. If a car runs at 200 km/h, that is equivalent to 100000 rotations / 60 minutes = 1666 rpm which is much less than what you expect. And you know that a car tire needs to be balanced to get a decent operating lifetime.
 

duke37

Jan 9, 2011
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o_O Isn't the rotor a permanent magnet type?
Please tell us where the slip rings will be connected on the rotor and what signals they will be passing.

I was involved with getting strain gauge signals from a railway wheelset which could go to 1000rpm. The slip ring unit cost the earth and was unreliable due to vibration. When I left the organisation, they were developing a radio system but the rotating batteries would not work properly due to the centrifugal force pushing the electrolyte to one end.
 

Minder

Apr 24, 2015
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The motor is an out runner where the outer shell of the motor is the rotor.
So anything would need to be attached to/around it.
M.
 

Night Watcher

Nov 6, 2017
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Hello everyone, thank you for the prompt reply, here are more info:
The engine will be rotating a 50 cm rectangular piece, which holds some electrical components that I want to control using the signal transmitted by the microcontroller.
That is why I want to use a slip ring, if you think there is a better way to approach this please let me know.

Also if I can't in any way send the signal from the micro controller to the spinning piece, let's assume that I can attach the microcontroller to spinning piece, how can I send power? The battery is pretty heavy and large to attach to the spinning part.
 

Night Watcher

Nov 6, 2017
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o_O Isn't the rotor a permanent magnet type?
That was my point also.....

I don't want to charge the rotor, I want to send an electrical signal to the components attached to the rotor

Whatever it is that you put on the rotor: at 72000rpm it will fly off at high speed unless very, very, very carefully balanced. Even at a comparatively small 3600 rpm you need careful balancing.

A typical car tire rotates ~ 500 rotations per km. If a car runs at 200 km/h, that is equivalent to 100000 rotations / 60 minutes = 1666 rpm which is much less than what you expect. And you know that a car tire needs to be balanced to get a decent operating lifetime.

The piece attached to the rotor is fairly large (50cm) and therefor a little easier to balance, I've worked on something before, and you are right pieces do fly off, but with the right gluing method I managed to keep my components attached

Please tell us where the slip rings will be connected on the rotor and what signals they will be passing.

I was involved with getting strain gauge signals from a railway wheelset which could go to 1000rpm. The slip ring unit cost the earth and was unreliable due to vibration. When I left the organisation, they were developing a radio system but the rotating batteries would not work properly due to the centrifugal force pushing the electrolyte to one end.

The device I am building is more of a toy grade, maybe it might be cheaper and more reliable...I hope? I can find an equivalent solution for the wireless approach, though how do I send power, because I can't attach the battery


 

Bluejets

Oct 5, 2014
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I think you need to outline exactly what it is you are trying to do to get any relative help. Personally I cannot see your getting anywhere near your rev range with a 500mm disc not to mention any additional load.
 

Night Watcher

Nov 6, 2017
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I think you need to outline exactly what it is you are trying to do to get any relative help. Personally I cannot see your getting anywhere near your rev range with a 500mm disc not to mention any additional load.

I made a quick diagram of what I am trying to build
The rotor has a PCB on it containing identical components which should be perfect for balancing. I do not know how much the rotor weights yet since not all components are built yet, but it should not exceed 50 grams.

The RPM I mentioned is the maximum limit I want to reach, though the device can still operate at a lower RPMs
 

Bluejets

Oct 5, 2014
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To begin with, I do not think those little motors would have any chance of spinning a 500 mm disc at even the low range of 1800 rpm. Secondly, I don't think you are aware of the centrifugal forces that would be exerted again at the minimum quoted speed. Time to do a re-think maybe.
 

Night Watcher

Nov 6, 2017
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To begin with, I do not think those little motors would have any chance of spinning a 500 mm disc at even the low range of 1800 rpm. Secondly, I don't think you are aware of the centrifugal forces that would be exerted again at the minimum quoted speed. Time to do a re-think maybe.

I have built a similar device with heavier unbalanced components and a slower engine before, therefor I am positive this will work. Yes you are right there is a lot of heavy balancing work that needs to be done but it is doable.
The question is not how can I reach those speeds, the questions is where can I find component that would work even if I reached that speed.

For this iteration I need to send 5 cables to to the rotor. With some trade-overs I can reduce that number to 2 cables for power source transfer.

P.S.: I did some adjustments to the design, and just needs to run at half the specified RPMs, Also let's reduce the length of the rotor to 30 cm diameter
 
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