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Old Dec 25, 2011, 10:09 AM
we can take off without that
green_flyer's Avatar
London, UK
Joined Nov 2008
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Out of curiosity I tested the C05M 3-blade set up outside of the airframe. Performance was pretty good. After around 30 seconds 69g thrust at 5.4A, 7V, 38W.
I now think the F86 airframe is too restrictive and the little C05M struggles to suck air through it when static. When in motion thrust may be better and may potentially match the stock JPower fan.

C05M 35mm 3 blade (0 min 50 sec)
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Old Dec 25, 2011, 10:09 AM
It's a spiderweb of knit lines
Souderton Pa. USA
Joined Mar 2002
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GF,
I don't have a C05 to test so it's difficult to predict what it will do. It is possible that you are loaded way beyond max power and a lower kv will bring you closer but it isn't likely that you will match the J Power with a motor significantly smaller and lighter. Try rewinding it, see what you get.
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Old Dec 25, 2011, 10:27 AM
we can take off without that
green_flyer's Avatar
London, UK
Joined Nov 2008
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Thanks Mike, I wish I had confidence & skills to rewind these, I think I may try it later and fly with this one as is. The motor doesnt get hot even after 30s on static full throttle so that gives me some confidence that I wont fry it. Is the other way to bring kv down to stick more magnets in the bell?
I think you are right about this being over loaded, as a rough estimate if the Jpower motor gets 61g at 7.2V x 7000kv x 0.75(estimated load) = 37800kv, the C05M gets only 44g thrust (with same 5-blade), so its roughly spinning that rotro at 44/61 x 37800 = 27265. Its load free rpm at 7v should be 77000kv, so its only spinning at 27265/77000 = 35% of its no-load rpm.
3-blade fan changes things, I'm not sure how to estimate the difference in thrust & rpm vs the 5-blade. I need to get myself a cheap rpm meter.

I was just thinking this set up would be really good in a A-10 with its short ducts. It would keep the full 69g thust x2 and save 10g weight over 2 stock units, should easily give over 1:1 thrust to weight. (stock unit 13g, this unit 8g)
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Last edited by green_flyer; Dec 25, 2011 at 10:34 AM.
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Old Dec 25, 2011, 10:36 AM
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Hampton, VA
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Green_Flyer,

Would like to verify the bat you used for your test.

Ksqm
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Old Dec 25, 2011, 12:04 PM
will fly for food
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United States, CA, Ben Lomond
Joined Mar 2011
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Merry Christmas Pilots! I hope everyone has a GREAT New Year, and Happy Flying!

Wavekatcher and family
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Old Dec 25, 2011, 04:15 PM
Team30 Micro EDF
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Adelaide, Australia
Joined Apr 2004
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GF - go three cell on that motor.

Guiseppi - the kV is pretty low. A cut down 8 blader won't give you the thrust.

Mike, I am tinkering with micro retracts also. Shapeways has opened a door full of possibilities for our micro scene.
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Old Dec 26, 2011, 08:30 AM
we can take off without that
green_flyer's Avatar
London, UK
Joined Nov 2008
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Nitro, I desperately want to get 2-cell to work to see just how low the AUW can get. If I was to re-wind this motor for lower kv is it better to use more winds or more magnets?

Ksqm, I used a Thunderpower 2s 325mah 65c.

I managed to mod the Jpower housing to fit the C05m, set up is very light must be around 7g. Here are a few photos for comparison also the weights of some rotors.

I ran a static test using the modded housing, sorry about the bad angle of the watt meter screen, its illegible I'm afraid. After 30s the thrust was 44g, 5.3A around 7.0v (37W).
The motor got too hot. Just too hot to touch and there was a smell of hot varnish (from the wires). Its a bit of a mystery as to why the AEO housing kept the motor cool even after a 30s test with same Amps. I think its those big slots in the motor mounting section on the AEO housing that help push air through the motor core. I may have to accept the 1.1g weight gain and go back to the AEO housing.

Also, I removed one of the magnets from the canopy, they are not as big/heavy as I thought. They are 5mm dia x 4mm long weighing 0.5g. I replaced one with a 6mm dia x 2mm long 0.4 g magnet I had.
I'm now thinking its not worth replacing them with lighter magnets, althoug I'll still get rid of them from the fan hatch and glue it instead.

C05M in Jpower 35mm fan (1 min 0 sec)
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Old Dec 26, 2011, 01:26 PM
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United Kingdom, England, Cobham
Joined Oct 2007
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Quote:
Originally Posted by ksqm View Post
Jacques.Eloff,

You left out one very important data point. The amp draw. High amp draw means heavier bats and ESCs. Something that needs to be considered for a micro build. I'm with you on a new thread. I'd say make it a sticky thread to serve as a reference.

My bad. Ther is already a sticky thread for this. I would have to see if it's up to date. A lot has happened in the past year.

Ksqm
Current is already baked into the power record. P=V x I, as I’m sure you already know. Agreed, current has a bearing on battery capacity, but voltage required for any power level is as important. That's the reason for using power in these “efficiency” tests, as it considers both. I could add an extra column to show Amps, but don’t really see the point.

Jacques
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Old Dec 26, 2011, 03:27 PM
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Jacques.Eloff,

My point is in regards to current. The size (i.e. weight) of the bat that can satisfy current requirements can get heavy . The weight of a power system can be 1/3 to 1/2 (or more) of the AUW. When you start looking at 12a-15a on 2S, it's not to bad. But 15a-20a on 3S, your talking some weight for a micro. That's not to mention the ESC. I just think, knowing the size bat to power your plane is important to know also. And this is driven by your current requirements. The information you're providing is invaluable, but it would be more complete with current measurements. That's all.

Ksqm
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Old Dec 26, 2011, 04:04 PM
Life begins at transition
Australia, VIC, Sale
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I think Jacques' point is it doesn't matter about the current draw, it's the total power you're concerned about.

To use your case of 15-20A on 3s, that's roughtly 160-210 watts. I can do that with 7.5-10A on 6s if I wanted, or 45-60A on 1s. It's up to the builder. Either way, the batteries will weigh the same, but the current is hugely different...

Rather than worrying about A, I think w^3/g^2 (I think?) is more useful. It'll make the graphs a straight line
As it is, the graphs are hugely useful, as they allow at a glance a comparison between setups. In a perfect world, it'd be shaft power, but I know no-one likes to do that.
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Old Dec 26, 2011, 05:39 PM
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Okay Gents,

I give. But give due thought to running 6S or a 45a-60a ESC, in a 14"-15" plane.

Ksqm
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Old Dec 26, 2011, 05:40 PM
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United States, FL, Sebring
Joined Feb 2006
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Quote:
Originally Posted by Odysis View Post
I think Jacques' point is it doesn't matter about the current draw, it's the total power you're concerned about.

To use your case of 15-20A on 3s, that's roughtly 160-210 watts. I can do that with 7.5-10A on 6s if I wanted, or 45-60A on 1s. It's up to the builder. Either way, the batteries will weigh the same, but the current is hugely different...

Rather than worrying about A, I think w^3/g^2 (I think?) is more useful. It'll make the graphs a straight line
As it is, the graphs are hugely useful, as they allow at a glance a comparison between setups. In a perfect world, it'd be shaft power, but I know no-one likes to do that.
True to a point, but Watts with a volt bias instead of amps is considerably easier on the batteries. I don't know anyone who would prefer to do it the other way around. No matter what, we all want the lowest amp draw with the highest motor output for any given airframe.
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Old Dec 26, 2011, 06:18 PM
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Ksqm
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Old Dec 26, 2011, 07:50 PM
Life begins at transition
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Joined May 2007
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Many people run 2s in preference to 4s in these micro scale. That's a preferance for high amps?

As for being easier on batteries, I've never understood that point...
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Old Dec 26, 2011, 08:00 PM
Team30 Micro EDF
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Adelaide, Australia
Joined Apr 2004
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Quote:
Originally Posted by green_flyer View Post
Nitro, I desperately want to get 2-cell to work to see just how low the AUW can get. If I was to re-wind this motor for lower kv is it better to use more winds or more magnets?
Why would you want lower rpm's?
Wire will weigh less than magnets so put more turns on the motor.
You'd have to take all the magnets off and redo them if you went to 6 pole pairs.
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