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Old Apr 22, 2012, 08:07 AM
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So, I rewound the little c05 motor. I cannot say the thickness of the wire cause I do not know. It is he same thickness as the wires leading to the tail motor. It is also about twice as thick as the original 34g wire in the stock c05 wind. The original wind was 8turns of 34awg wye dual strand. I wound it and could only fit 7 turns of this thicker wire. I had to epoxy the winds so the magnets wouldnt hit them on the sides of the stator.

I have been running the stock motor with a 9t pinion. I ran this rewound motor too with a 9t pinion and received the same power but less runtime and my batteries were warmer then usual. The stock motor kv is 11,000 and this rewound should be 12,572kv

The power seems the exact same. It seems though with the stock wind the blades fart on high G maneuvers. It doesnt do that with the new wind. Also the new wind seems to make the heli more stable. That might be because my stock motor shaft is 1mm and i might have bent it trying to take the pinion off it. Or is there another reason?

Anyone know if I put a smaller pinion, like a 8t or 7t if I would get more power and runtime with the new wind? Or is the magic in that last turn of wire to make it 8 turns of wire? I could only achieve 7 turns but the wire is thicker. The new wind is pulling more amps, so If I had better batteries would their be more power?

I just dont understand why there is less runtime and the batteries are warmer than usual
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Old Apr 22, 2012, 01:12 PM
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Ohm's Law and Wiring Resistance pertaining to Motors

I barely know anything about electric Motors; however, do know some about basic electricity, Ohm's Law, and wire resistance.

Ohm's Law applies to a normal wire as follows:

Voltage drop across device = Resistance of device * Current going through device

V = R * I

Resistance through device can be calculated as follows:

Resistance through wire = Resistivity of material * Length / Cross-sectional Area

R = k * L / A

Note: For most applications where wire temperatures are safe to touch with bare hands, the "resistivity" of the wire's material is considered a constant of the material.

So if you wind two identical Motors with copper wire, one Motor with thicker wire, and the other Motor with thinner wire, you'll get fewer turns of thicker wire than thinner wire in the same amount of space, and therefore also use shorter length of thicker wire than thinner wire. As described in the above Resistance equation, a wire having shorter length and thicker cross-sectional area will have less resistance than a wire having a longer length and thinner cross-sectional area. Also according to the above Ohm's Law equation, for a given Voltage across the wire: the longer, thinner wire with higher resistance will have less current going through it, than a shorter, thicker wire with less resistance.

For most electrical devices, the amount of heat produced in a second is related to the electrical Power consumed according to this equation:

Power = Voltage * Current

P = V * I

and that equation can be re-written using Ohm's Law (V = R * I, I = V / R)

P = V * V / R

which can be re-written once again using the Resistance Equation (R = k * L / A)

P = V * V * A / ( k * L)

The above equation predicts for a given Voltage across a wire, the thicker, shorter wire will produce more heat per sedond than the thinner, longer wire. It sounds like you've confirmed the validity of the above equations when you described the Motor and Battery used with the thicker, shorter wire get hotter than with the thinner, longer wire.

Also, the Resistance and Ohm's Law equations predict the thicker, shorter wire will produce more current than the thinner, longer wire. It sounds like you've confirmed the validity of those equations as well when you described the Battery used with the Motor having the thicker, shorter wire didn't last as long as it did with the Motor having the thinner, longer wire. The LiPo is only able to produce XX mAh of current, so the Motor with the smaller resistance will be able to allow more mA of current but for a shorter amount of time than a Motor with a larger resistance which will allow less mA but for a longer amount of time. Imagine two identical containers with each having a different size hole in it's bottom: the container having the larger hole (less resistance) will allow more current to flow through and will empty faster than the container having the smaller hole (more resistance). The LiPo is like the container, and because of its size can only store XX mAh of "juice", the less the resistance the LiPo "sees", the faster the current being drawn out of it, and therefore the less time before it becomes empty. You get the same amount of juice out of the LiPo either way; however, one way empties the usable Charge out of the LiPo faster than the other. Both ways still produce the exact same amount of work/heat (amount of energy being released), just the one with the lower resistance releases it faster and therefore is able to do more work quicker, and get hotter faster.

The above explains about the relationship between Voltage, Current, Resistance, and heat. Those are all important things to consider when dealing with electricity; however, Motors are more complicated because they operate by electromagnetism. I'm just now starting to learn about electric Motors and have learned that there are many design trade-offs to consider when choosing a Motor: weight, size, number of wire turns, thickness of wire, diameter of wire turns, length of wire, internal resistance, strength of magnets, amount of current, heat, torque, rpm, etc.

Many things/trade-offs to consider:

Power In = Voltage In * Current In

Power Out = Mechanical Power + Heat

Heat = Friction + Electrical Resistive Heat

Mechanical Power = Work / Time = Force * Distance / Time = Torque * RPM

Efficiency = Mechanical Power Out / Electrical Power In


NOTE: When I started this post, I didn't plan on it becoming a "rant", so I better stop now before it gets worse.
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Old Apr 22, 2012, 01:46 PM
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Originally Posted by nac View Post
... BTW the canopy is EPP!
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Wow!

That painted Canopy only weighs 1.32 g.

The stock Canopy weighs 2.25 g.

Compared to the stock Canopy, how crash worthy is the EPP Canopy?

AFAIK, I don't have experience with EPP foam. Did you have to do anything special like use heat or something to pre-form the EPP into that tight of a radius used for the Canopy?

One of these days, I'll probably try DIY Canopies using a few different materials: Egg cartons, plastic Milk jugs, and the clear un-tearable plastic many things come packaged in.
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Old Apr 22, 2012, 01:49 PM
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Quote:
Originally Posted by mescalinedream View Post
So, I rewound the little c05 motor. I cannot say the thickness of the wire cause I do not know. It is he same thickness as the wires leading to the tail motor. It is also about twice as thick as the original 34g wire in the stock c05 wind. The original wind was 8turns of 34awg wye dual strand. I wound it and could only fit 7 turns of this thicker wire. I had to epoxy the winds so the magnets wouldnt hit them on the sides of the stator.

I have been running the stock motor with a 9t pinion. I ran this rewound motor too with a 9t pinion and received the same power but less runtime and my batteries were warmer then usual. The stock motor kv is 11,000 and this rewound should be 12,572kv

The power seems the exact same. It seems though with the stock wind the blades fart on high G maneuvers. It doesnt do that with the new wind. Also the new wind seems to make the heli more stable. That might be because my stock motor shaft is 1mm and i might have bent it trying to take the pinion off it. Or is there another reason?

Anyone know if I put a smaller pinion, like a 8t or 7t if I would get more power and runtime with the new wind? Or is the magic in that last turn of wire to make it 8 turns of wire? I could only achieve 7 turns but the wire is thicker. The new wind is pulling more amps, so If I had better batteries would their be more power?

I just dont understand why there is less runtime and the batteries are warmer than usual
There are several things at work here:

Battery current capability, gear ratio and efficiency to name a few. When you increase the kv of the motor you need to be able to provide the power required and that can be limited by the wire size but there is also the back EMF of the motor that limits the current at speed. You are probably over geared (pinion too big) to get the new motor into it's sweet spot. There is also the capability of the motor core to handle the flux density which can also give poor efficiency if losses are excessive.

YMMV, Don
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Old Apr 22, 2012, 06:41 PM
nac
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Quote:
Originally Posted by i812 View Post
Attachment 4803687

Wow!

That painted Canopy only weighs 1.32 g.

The stock Canopy weighs 2.25 g.

Compared to the stock Canopy, how crash worthy is the EPP Canopy?

AFAIK, I don't have experience with EPP foam. Did you have to do anything special like use heat or something to pre-form the EPP into that tight of a radius used for the Canopy?

One of these days, I'll probably try DIY Canopies using a few different materials: Egg cartons, plastic Milk jugs, and the clear un-tearable plastic many things come packaged in.
Yep I was surprised too how light it is compared to the stock one.
I haven't crash tested it as yet, but from experience with EPP planes they do do sometimes break, but are very easy to glue back together. The trick is to use the right glue.
It is very flexible stuff so no heating required. I just bent into shape, used some tape to hold it together whilst the glue dried.
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Old Apr 22, 2012, 09:06 PM
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Im new to CP and was wanting an opinion from one of you experienced guys, how awesome is the mini cp? I have zero CP experience and was thhinking of getting either a mini cp, a v120d02s , or a V200d03. where do i start? what are the flight times on the mini cp? what about a brushless upgrade?
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Old Apr 22, 2012, 09:46 PM
<Marty>
United States, KY, Springfield
Joined Jul 2011
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Quote:
Originally Posted by Shark_fighter78 View Post
Im new to CP and was wanting an opinion from one of you experienced guys, how awesome is the mini cp? I have zero CP experience and was thhinking of getting either a mini cp, a v120d02s , or a V200d03. where do i start? what are the flight times on the mini cp? what about a brushless upgrade?
personally i would get the Genius cause it has the same flight characteristics and basically uses the same parts excluding a few...plus you wont have to worry about the coil falling off like a lot of peoples has...cause the canopy rams it in a crash...Genius has longer flight times in stock form then the Mini...
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Old Apr 23, 2012, 07:50 AM
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Gorilla glue stops the coil from coming off, A genius motor in a minicp will get the same amount of flight times as the genius I would think.

Sharkfighter, go here and it will tell you all about the mini http://www.rcgroups.com/forums/showthread.php?t=1616585
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Old Apr 23, 2012, 06:59 PM
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MiniCP with V100D03 main motor. It works well. Great power. 3 1/2 minutes flight time on a stock 240 battery. It will fly longer, but that's when the power starts to drop off. I had to pull the original pinion and installed a 10 tooth pinion that would mesh with a Genuis main gear. I also noticed that the motor is only warm after the flight, not hot. Seems like a good fit. I like it so far. I've got to figure out how to post a picture.
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Old Apr 23, 2012, 07:19 PM
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MiniCP V100D03 Motor Pics
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Old Apr 23, 2012, 08:40 PM
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Thats the motor that comes in the double brushless kit.I think its a battery hog. I cannot believe you are using a 10t pinion on it! If you want more runtime go much lower. The stock pinion is a 9t on the double brushless motor. Double rainbow, Double brushless.....isnt that motor just too heavy? I have one and only tried it once with the whole double brushless kit installed on the mini. I tried it cause i received the kit free from helircstore on my first order!

Walkera Mini CP with Genius Double Brushless Upgrade (1 min 9 sec)
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Old Apr 23, 2012, 09:32 PM
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On my double brushless kit, the pinion is a 10 tooth.
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Old Apr 23, 2012, 09:59 PM
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Your right, it is heavier. I haven't wieghed it yet. The outrunner part is heavier and it seems like it doesn't bog down as much as my C05. I even lowered my throttle curve down to 65% in the middle instead of 80%. It feels more like my V120D02s which is what I was looking for.
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Old Apr 24, 2012, 06:11 AM
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Quote:
Originally Posted by mescalinedream View Post
Thats the motor that comes in the double brushless kit.I think its a battery hog. I cannot believe you are using a 10t pinion on it! If you want more runtime go much lower. The stock pinion is a 9t on the double brushless motor. Double rainbow, Double brushless.....isnt that motor just too heavy? I have one and only tried it once with the whole double brushless kit installed on the mini. I tried it cause i received the kit free from helircstore on my first order!

http://www.youtube.com/watch?v=L--ccyaawmk
What about tail hold with double brushless kit ?
is it normal ?
Thanks
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Old Apr 24, 2012, 07:44 AM
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The tail held just fine with the double brushless kit. The kit is way too heavy though since a 7mm brushed tail will hold just fine.

When I first received my mini the tail held great. Now that I have a c05 9t the tail will blow out 30 degrees on the hardest pitch pumps.The tail will go right back though if I let off the throttle. There is just too much torque with my setup for the tail to hold.

I did just change the entire tail over to a entire genius tail with minicp tail fin. I bought the genius complete boom/tail motor complete new as a spare. And it does it with the new tail too. I am switching to an 8t pinion when it gets here. Maybe the tail will hold with that.

We should be looking at different tail fins, maybe thats all we need to change. The chinese sites are using plantraco sp? tail blades with success.
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