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Old Jul 22, 2008, 08:03 AM
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5G6 Brushless Motor development

Since the demise of the 5g6 MODS thread, I decided to start another one where anyone interested in brushless motor modification or development for the 5G6 can post, to keep the momentum developed in David's thread moving. Let's learn from that experience; just keep it polite and keep the content to information and questions. Remember, you can not win an argument with:

1) your wife
2) a policeman
3) someone on an internet forum

A lot of good was happening on the MODs thread, let's keep it going.

Whilrybird, I'll look at those formulae, but I don't think that we need to get too deep into the overall performance. We're stuck with the rotors and the gear ratios, shaft sizes, motor size, etc., so the choices are relatively simple. We know the battery capacity, how much power is needed with the rotor system to keep the heli airborne, and the rpm of the rotors at hover. From that, with all the other constraints, I think we can come up with a spec for the motor pretty easily. I could take a guess right now of 9000kV, efficiency of >60% at 1.5W out and 17000rpm, weight 2-4gms, rotor diameter<12mm, shaft size 1mm extending out the bearing tube by 6mm, and bearing tube diameter <5mm. Probably a few more to firm it up, but those are the most important.

Mark
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Old Jul 22, 2008, 08:29 AM
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Dave, can you give us details on the little brushless inrunner that you found? If you have any info like kV, rpm and current under load, dimensions, availability, that would be very interesting.

Thanks!

Mark
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Old Jul 22, 2008, 03:21 PM
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Haha, I was starting a new thread since the other one was closed. I closed my thread after I saw yours.

So that graph you did was at hover. What kinda amps do you think we will be pulling at full throttle?
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Old Jul 22, 2008, 03:51 PM
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I measured 3A at full throttle on the stock motors. A brushless probably will pull more, as I think it will have less effective series resistance, thus the larger surge thrust.

Mark
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Old Jul 22, 2008, 06:27 PM
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Mark,
what voltage and wattage were you reading with the 3A load?
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Old Jul 23, 2008, 07:25 AM
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Quote:
Originally Posted by whilrybird
Mark,
what voltage and wattage were you reading with the 3A load?
I don't remember exactly, but I would predict that it would be somewhere around 3.3V from the battery, due to the additional voltage drop due to the increased current, putting the power at 3.3*3=9.9W.

Mark
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Old Jul 23, 2008, 09:15 AM
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Quote:
Originally Posted by scrat111
Dave, can you give us details on the little brushless inrunner that you found? If you have any info like kV, rpm and current under load, dimensions, availability, that would be very interesting.

Thanks!

Mark
Useless as a popup aparently.

Dave
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Old Jul 23, 2008, 10:11 AM
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Fair enough.

I'm sorry.

Let's talk motors. . . .
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Old Jul 23, 2008, 12:36 PM
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Hey you guys

I started this thread because a number of people couldn't play nice, and now it is happening here as well! Dave, what did I ever do to you to piss you off? I tried to not respond to all the mudslinging, and to keep my posts on topic and neutral. Now I try to get a simple answer on a possibly very useful piece of information that you might have, and I get a completely useless response. That really is not very nice. And Butters, I have a lot of respect for what you have done, but please refrain from responding with any kind of post other than informational and informative? Jeez, I feel like I'm back on the Subaru forum reading rants about blowoff valves. I expected it from those guys, but not here!

Mark
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Old Jul 23, 2008, 12:43 PM
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Turnigy 5g with the magnets redistributed

As a test of my fine motor control skills, I demounted the magnets in one of my Turnigy 5g motors and redistributed them to NNSSNNSSNNSS. It worked; the kV went from 4700 to 7300, not quite the factor of two I was expecting, but the magnet spacing was pretty large, so that might be the difference. Surprisingly, the I0 dropped from .31 to .17A; I was expecting it to rise. I plugged the data into PeakEFF, and the efficiency was still crap, only like 30% at the 1.5W motor output we need. The Rm was 1.7!!! No wonder the efficiency was terrible. The Dualsky ESC that I had modified for 1S operation had a bit of a hard time starting the motors until I put on the masking tape loads; apparently I need a bit more rotational inertia for reliable startup. Don't know if the gear train and the rotors will serve that purpose, or make it worse.

Now it those D1000's would show up.

Mark
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Old Jul 23, 2008, 12:53 PM
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Quote:
Originally Posted by scrat111
As a test of my fine motor control skills, I demounted the magnets in one of my Turnigy 5g motors and redistributed them to NNSSNNSSNNSS. It worked; the kV went from 4700 to 7300, not quite the factor of two I was expecting, but the magnet spacing was pretty large, so that might be the difference. Surprisingly, the I0 dropped from .31 to .17A; I was expecting it to rise. I plugged the data into PeakEFF, and the efficiency was still crap, only like 30% at the 1.5W motor output we need. The Rm was 1.7!!! No wonder the efficiency was terrible. The Dualsky ESC that I had modified for 1S operation had a bit of a hard time starting the motors until I put on the masking tape loads; apparently I need a bit more rotational inertia for reliable startup. Don't know if the gear train and the rotors will serve that purpose, or make it worse.

Now it those D1000's would show up.

Mark
Even if it doesn't work its great to see the kind of numbers we get when changing the magnets around. I would like to try the same mod on a 3.5 gram outrunner but am scared to try removing the magnets, they are tiny, packed in tightly and breaking one means ruining a nicely working motor.

I really want my 2 gram outrunners to arrive as well!
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Old Jul 23, 2008, 04:43 PM
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Quote:
Originally Posted by TheSteve
Even if it doesn't work its great to see the kind of numbers we get when changing the magnets around. I would like to try the same mod on a 3.5 gram outrunner but am scared to try removing the magnets, they are tiny, packed in tightly and breaking one means ruining a nicely working motor.

I really want my 2 gram outrunners to arrive as well!
Yeah, it took me a while to screw up my courage to start messing with the magnets, but the potential benefits and the fact that I didn't care much about the Turnigy motors cuz of their lousy efficiency helped. Also, the magnets were pretty far apart(probably one of the causes of inefficiency), so it was a good first try. There was a coating of epoxy around the magnets which I had to scrape off, but after that was gone it was pretty easy to remove the magnets by carefully prying with an Exacto knife right on the edge of the magnet. There did appear to be CA under the magnets, not epoxy. I'm hoping that the D1000's will have enough room between the magnets to scrape out any coating, or that there won't be any coating and I can just pop them out. I think that after you get the first one out, the rest will be easier. I'm going to get some CA solvent and try soaking the D1000 rotors in that if there's no epoxy; that should make them trivial to remove, and the solvent shouldn't hurt the rotor.

Once I got all the magnets out, reinstalling them was easy. The six ventilation holes gave me a nice pattern to match, and the magnets were relatively cooperative in staying in place once I placed them on the rotor, even with two similar poles right next to each other. I mounted six magnets equally spaced first, bonded them with a drop of Loctite 406 low viscosity CA, and then placed the magnets with the same polarity next to the bonded magnets. Once they were stable in place just by friction and the magnetic attraction, I put a drop of CA on them and I was done.

If that all works on the D1000s, there rest of the job will be easy. The stock pinion should slip right on the inverted shaft, and I can fab up two motor mounts with tapped holes in the correct location for mounting in the standard location pretty quickly. That will get me to the point where I can spin some rotors and test the thrust and current drains, and see if we have a 2g solution. If that's a go, I'll build up a bird with your dual converter and two FEIGAO escs. Then I'll get back to doing the dual FLEA layout. It's too bad I have a real job; I could just about do this full time and still have things to do, haha.

Mark
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Old Jul 24, 2008, 07:49 AM
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D1000 sould be the next step for 5G6 BL conversion.....

with 0.42g new ESC from HU and original gear....300mah lipo...

of course need some rewinding/remagnet

I still waiting a credit code(I win few $ with posting some DIY on there blog:myhobbycity.com) to order 2x D1000 to hobbycity


******
stock motor=6.5gx2=13g
D1000=2x2g +1g carbon frame fixing=5g
=>7g less

400mah lipo=11g
300mah=7g
=>4g less

about 1g for 2xtiny ESC and CMS converter

carbon tail,(servo+motor+quartz) plastic plug+plastic 4in1=>3g less


45g coax 4CH BL is coming out!!!!!

*******

Jay
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Old Jul 25, 2008, 02:13 PM
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Hi guys,

update since my other meeting was rescheduled and the current guy I'm dealing with went on leave for thurs and friday. I found another company that seems even more eager to help find a solution.

I need the numbers off the side of the 5g6 motor if anyone has them. Thanks
I can read all but maybe the last 2 numbers due to solder on the motor for the ground filter.
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Old Jul 25, 2008, 02:31 PM
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Bah this sucks, I want to fire off the email, but being held back by one number.
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