Anybody here using brushless RC motors?

I've been looking at the brushless motors used for RC planes and the like. They are amazingly powerful for their size. And they really spin
up fast! One web site has kits you can buy to wind your own armatures. Anyway, I have been wanting a rotary tool that is a cross between a Dremel and an air powered tool I have. Something with an OD of about 1 inch. Like a Foredom handpiece. Faster than any of my Dremels but slower than my small air powered hanpiece that spins at 80,000 rpm. So I'm thinking one of the "inrunner" type motors might work. At 80,000 rpm the surface speed is about 2600 SFPM. Even though the speed drops quickly as soon as the rotary tool contacts the work the speed is still too high for carbide on steel and the burrs and rotary files dull quickly, which makes them cut slower. On the other hand, the Dremel and Foredom rotary tools are too slow and this ends up costing time too. Something that spins about 40,000 rpm and maintains that speed along with the smaller diameter would be great. In fact, a tool that was .75 or even .625 diameter would be even better. I have a dental handpiece that I use for some delicate work and it is just under .5 diameter and is very easy to hold because of the small diameter. If I could build an electric rotary tool with the torque of a Dremel, 40,000 rpm, and 1/2 inch in diameter I would be very happy. Even one that matched the Dremel torque and speed specs but was 5/8 or 1/2 inch diameter would please me greatly. So, anyone here play with brushless RC motors? Thanks, Eric,
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On Mon, 25 Nov 2013 18:20:47 -0800, etpm wrote:

Not for what you're contemplating -- but I do have a couple of RC planes that I fly with them.
It may work. I'd use an ESC with a helicopter "governor" mode for steady speed. Make sure you have lots of fan cooling -- those motors get light in part by being designed for steady airflow (they're AIRPLANE motors!! ). I wouldn't count on the motor bearings to hold up to much side-force, so you'll have to provide support against that.
--
Tim Wescott
Control system and signal processing consulting
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On Tue, 26 Nov 2013 00:15:06 -0600, Tim Wescott

I of course would only be subjecting the motor to torque forces. Robust ball bearings are needed to support the cutting tool. I didn't know about the ESC "governor mode". Thanks for that. Eric
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On Tue, 26 Nov 2013 09:06:18 -0800, etpm wrote:

I never know what someone knows...

Please submit a full report when you're done -- I think it's a cool idea.
--

Tim Wescott
Wescott Design Services
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On Monday, November 25, 2013 9:20:47 PM UTC-5, snipped-for-privacy@whidbey.com wrote:

A real 'caution' is that most ESCs are sensitive to the lead length to the battery/power-source, long wire length tends to lead to damaged ESCs. The fix is added capacitance at the ESC. Not sure how much is required.
Lead length from ESC to motor is not normally an issue.
I run a few brushless outrunner powered planes, the power is amazing.
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snipped-for-privacy@whidbey.com wrote:

you may have problems unless them motor has internal position sensors/ more than three fat power leads. They're mean to run fans or a gearbox and a fan with no sudden load changes. Brushless fan controllers don't tend to like loads other than air, or they get confused and lock up and do other nutty stuff.
The RC controllers may be more tolerant of this, but again, if the motor lacks position sensors, it's probably not meant for dealing with abrupt load changes or putting out lots of torque at low speeds.
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On Tue, 26 Nov 2013 18:20:54 +0000 (UTC), Cydrome Leader

A friend was using a super-duper RD brushless motor on a speed-record attempt bicycle. Something like 45 HP out of a motor the size of a baseball - WITH position sensors I believe. Last I heard was he was going over 60mph working the bugs out. Then his (brain) cancer came back, so I don't know if he's been able to go any farther
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On Tuesday, November 26, 2013 1:20:54 PM UTC-5, Cydrome Leader wrote:

o

Outrunners are pretty tolerant of what you describe (lotsa spinning mass), inrunners might be more sensitive, but as long as it's spinning fairly quic kly it should work. With no prop I've put loads on my motors with my hand- at small throttle settings, heh.
This application would work best with 'low timing', that is, not a lot of a dvance. There are also settings for PWM frequency.
Neither outrunner nor inrunner will like starting with a large load (which shouldn't be an issue with this app).
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On Tue, 26 Nov 2013 18:20:54 +0000 (UTC), Cydrome Leader

I don't know how well the RC controllers will work either. My feeling is that since they can spool up the motors pretty fast they will tolerate some speed fluctuations from loads. I'm hoping the torque will be high enough to keepthe speed fairly constant. Eric
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On Tue, 26 Nov 2013 12:56:10 -0800, etpm wrote:

If not, the motors for RC cars have sensors. An RC car motor and ESC combo should work down to zero speed, and not show the "nuttiness".
--
Tim Wescott
Control system and signal processing consulting
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On Tue, 26 Nov 2013 18:20:54 +0000 (UTC), Cydrome Leader

Big and quick load changes is no problem at all. Have a look at this electric helicopter:

http://www.youtube.com/watch?v=p8t41avFuCc

Position sensors are only needed when you need torque at zero speed, such as in a car.
--
RoRo

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On Tue, 26 Nov 2013 18:20:54 +0000, Cydrome Leader wrote:

Damn. I should have thought of that when I made my response. RC airplane propellers are pretty much fans, as are (well, duh) ducted fans.
RC car motors have sensors, and come in a variety of sizes.
--
Tim Wescott
Control system and signal processing consulting
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quote: wrote in message
I've been looking at the brushless motors used for RC planes and the like. They are amazingly powerful for their size. And they really spin up fast! One web site has kits you can buy to wind your own armatures. Anyway, I have been wanting a rotary tool that is a cross between a Dremel and an air powered tool I have. Something with an OD of about 1 inch. Like a Foredom handpiece. Faster than any of my Dremels but slower than my small air powered hanpiece that spins at 80,000 rpm. So I'm thinking one of the "inrunner" type motors might work. At 80,000 rpm the surface speed is about 2600 SFPM. Even though the speed drops quickly as soon as the rotary tool contacts the work the speed is still too high for carbide on steel and the burrs and rotary files dull quickly, which makes them cut slower. On the other hand, the Dremel and Foredom rotary tools are too slow and this ends up costing time too. Something that spins about 40,000 rpm and maintains that speed along with the smaller diameter would be great. In fact, a tool that was .75 or even .625 diameter would be even better. I have a dental handpiece that I use for some delicate work and it is just under .5 diameter and is very easy to hold because of the small diameter. If I could build an electric rotary tool with the torque of a Dremel, 40,000 rpm, and 1/2 inch in diameter I would be very happy. Even one that matched the Dremel torque and speed specs but was 5/8 or 1/2 inch diameter would please me greatly. So, anyone here play with brushless RC motors? Thanks, Eric, /quote
I wanted to try one of these as a cheap alternative to a conventional brushless dc motor in a mechanism we were prototyping at work, so I grabbed a couple with controllers off ebay to explore. Then I learned that the control input needed to be a variable duty cycle digital signal, something like (from old memory so I'm sure it's a little off) 10 or 15 ms period and 0-5 msec on time for 0-100% of motor speed, sigh. I used a signal generator to fake it for the initial tests but it would have been a pain to drive it with our controller if it had worked out (we were set up to output 0-5V for 0-100% motor speed). After getting the parts it was clear that the ESC and the motor winding could handle some pretty hefty currents to make the hp they claimed, but there was no way they could dissipate even 10% of the resultant heat steady state. These were airplane motors and ESC's so they were engineered to run for 1-2 minutes max, and then have many, many minutes of cool down time while the battery pack was recharged or swapped out. The motor bearings were pretty wimpy, too, so I was afraid that putting a pulley on the motor shaft and having the lateral load from a belt would kill things pretty quickly, but I never got that far since it was obvious that the package wasn't what we needed. Hey, it was a fun experiment, anyway :-). I'll dig one out Monday or Tuesday and see what rpm it's rated for, maybe you could play with one.
----- Regards, Carl Ijames
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On 12/1/2013 10:42 PM, Carl Ijames wrote:

I don't know anything about your controller, Carl, but pulse width modulation is really fairly trivial (these days!).
<http://www.instructables.com/id/QuickStart-one-transistor-DC-motor-controller/
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"Richard" wrote in message

The signal that a R/C brushless motor controller takes is a pulse approximately every 20 milliseconds. The width of the pulse is what determines the output, a 1 ms pulse would, or could be 0%, a 2 ms pulse is 100%, or, if it's reversible, a 1.5 ms pulse is 0%, 1 ms is 100% in one direction, 2 ms is 100% in the opposite direction. Some of the speed controls learn the settings as they power up, for example, on my planes, you power up with the stick at low throttle, it learns whatever that pulse width is as the low throttle setting, then you take it to full throttle, it pulses the motor 2 times, once you go back to low throttle, it's ready to go. Some R/C car setups use 70% travel forward throttle and 30% reverse, so the 0% would be more around 1.3 ms. Microcontrollers like the Basic Stamp and Arduino have commands to send a pulse to R/C servos.
The reason for the odd control is because old school transmitters transmitted a 4.5 ms sync pulse, then a pulse for each channel ranging between 1 - 2 ms, then it would start the frame over. The receiver syncronized with the 4.5 ms pulse and then sent the first pulse to channel 1, 2nd pulse to channel 2, ...
RogerN
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On 12/2/2013 5:48 AM, RogerN wrote:

All true, of course. But I can't let the Arduino and Basic Stamp reference slide by so easily. That example is my offering for a Propeller P32x8 microcontroller. :)
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"Richard" wrote in message <snip>

I'm going to have to get a propeller microcontroller sometime! If I understand correctly, they are like multiple microcontrollers that have shared memory area. That would be awesome for processing sensor data, control programming, and servo output all at the same time. I would like to use a controller for R/C flight, using gyro & accelerometers + GPS to make it capable of following programmed flight paths. I got a 6 axis gyro plus accelerometer module for under $10, looking for bargain GPS.
RogerN
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On 12/2/2013 1:03 PM, RogerN wrote:

Yeah. Eight independent processors (with independent RAM in each) around a central hub (with more RAM - and ROM), PLUS some really interesting counters (that can do many things, like produce VGA or TV video). The individual processors are referred to as COGS.
There are no dedicated I/O circuits on board. Those are loaded as software driven devices as desired. Any COG can access any I/O pin (OR-ed writes)
The Parallax Object Exchange (OBEX) has hundreds of pre-written drivers and aps.
And no interrupts! Perfectly determinate timing!
I'm not a big fan of (forced) indented structures the way SPIN (the native programming language) uses, but it works fine - once you wrap your mind around it.
And you will probably find drivers for the stuff you already have.
Pick up a QuickStart board at Radio Shack. You'll have a ball with it, Roger.
Intro to model airplane autopilots: http://www.instructables.com/id/Intro-to-Model-Airplane-Autopilot/
http://electronicdesign.com/boards/how-multicore-chip-flies-quadcopter http://diydrones.com/profiles/blogs/705844:BlogPost:6607
Or maybe the Hoverfly board??? It already has everthing you'd need! <http://www.parallaxsemiconductor.com/customer-success/hoverfly-technologies
Or Octopilot? (the eight thing again in corny names) https://code.google.com/p/octopilot/
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On 02/12/13 05:00, Richard wrote:

Probably a bit over the top for controlling a hand piece. I bought a servo tester from Conrad while I was in Munich about 20 years ago and they still do them, see http://www.conrad.com/ce/en/product/234915/ . That'll give manual control on the PWM that can then be supplied to the ESC. I don't know if Conrad have a US branch but some digging might reveal the circuit diagram which from memory was quite simple and used a common 4000 series CMOS chip. Looking in the downloadable documents section and the first file shows the circuit diagram and it uses a 4001 and a few discrete components, simples!.
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On Mon, 02 Dec 2013 19:27:33 +0000, David Billington

It looks like Hobby King has a motor or two that will work. Along with an ESC and a servo tester. I also found a circuit for building my own servo tester. I could hook up my Basic Stamp too. But for 5 bucks I'll get the one that comes in a box. Thanks everyone so far for the replies. I know the inrunner motors will overheat if run at high currents for too long. I will need to come up with some type of cooling scheme. I am amazed by the power of these little motors. A 20mm diameter motor thats rated at 330 watts! Of course the motor would melt if not kept cool. Maybe I should connect a coolant hose and run LN2 from a thermos through the thing. Eric
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