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Old Jun 09, 2012, 10:31 PM
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Originally Posted by Neoneo View Post
You said geometry, that link is algebra, not my area of expertise to say the least lol.
Try this original german link:

http://www.icer.ch/cms/Unternehmen/f...erechnung.html

Good Luck, Don
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Old Jun 09, 2012, 10:41 PM
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Brushed motor is good for something...

... I'm thankful that the magnets in the stock brushed motor are fairly strong. After the maiden flights of my Mini Pro today I noticed a tiny screw stuck to the motor housing. After looking closely at the bird, I noticed a hole on the right side (when facing the back of the heli) immediately above the servo, near the swash. It happened to be the same size as the screw. I thought everything was fine, until I realized that the screw wouldn't thread into the hole. Either something inside shifted or wasn't drilled correctly. I have to think that the Walkera factory drone noticed the same problem and simply stuck the screw in there.

Question is if this is something to worry about. I suspect the screw helps hold the top mounting plate on the servos so they don't shift. The other two screws are tightly in place. Any ideas what this particular screw should attach to? For the time being, I threw it in a zip-lock bag and hovered for 3-4 batteries with no apparent problems.
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Old Jun 09, 2012, 11:07 PM
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If my memory is correct this is the screw count:

3 - RX
2 - Main Motor
1 - Main Shaft Collar
2 - Rotor Head
2 - Feathering Shaft
2 - Blade Grips
2 - Servo Holder (1 Hole empty)
3 - Servo Arms
6 - Servos
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Old Jun 10, 2012, 12:02 AM
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Quote:
Originally Posted by dbennettya View Post
Try this original german link:

http://www.icer.ch/cms/Unternehmen/f...erechnung.html

Good Luck, Don
using this link it says I'm at 6 degrees. and your saying i should be at around 11?
by the way, good find, thanks
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Old Jun 10, 2012, 12:03 AM
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Quote:
Originally Posted by i812 View Post
If my memory is correct this is the screw count:

3 - RX
2 - Main Motor
1 - Main Shaft Collar
2 - Rotor Head
2 - Feathering Shaft
2 - Blade Grips
2 - Servo Holder (1 Hole empty)
3 - Servo Arms
6 - Servos
So your's also has an empty hole on the right side immediately above the servo?
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Old Jun 10, 2012, 04:17 AM
asp
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Spain, CN, Villaverde
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Quote:
Originally Posted by itsmillertime View Post
Brushless tail is on but I can't solder it until Mon. Gah, I can't wait:
[.jpg[/IMG].jpg[/IMG]
hey itsmillertime,
Can you give details on that nice brushless tail setup?
Thanks a lot
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Last edited by asp; Jun 10, 2012 at 04:39 AM.
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Old Jun 10, 2012, 08:57 AM
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Quote:
Originally Posted by Marioinc View Post
I have done anything I could think of. Adjusted my setup and servos, lubed main shaft and bearings and even motor bearing. Resoldered most connections.
Then I took some measurements to check I wasn't loosing voltage somewhere.
Multimeter says same exact voltage on battery, esc, rx, and motor leads (-0.01v of battery, that's acceptable right?) on the rx (where the brushed motor should go) so it's getting the full throttle command.
I measured the three wires from the esc to the motor, multimeter set to DC it shows 0 (which i guess is normal since it's AC), but when set to AC it says 2.5v (range is 200v, so don't know the accuracy but I'm guessing pretty accurate since 3.82v battery is displayed as 7.7v, it doubles the v since it's DC and it's expecting AC, and if that's the case it's spot on)

So now the question is, is 2.5v normal since the back EMF of the motor running would bring down the voltage?

As soon as I hit 3.92 on the battery, within 2 and a half minutes, it will only hover thanks to ground effect.

But I've just thought of something big. I'm using an LTC instead of the LT esc, so could it be just a little off timing so it runs but not as efficiently hence the motor getting warm?? Or would it just not run?
Those first two minutes are great though, lots of power, and the motor spins (freely, without the blades) as low as 7% throttle... so I don't know...

I'd really appreciate anybody who can give their opinion...
Nobody know's what could be up?
I inspected everything and cleaned up and relubed everything, and the only thing wrong are the rubber washers of the feathering shaft a little used up, but not even that much, could that be it? Could that really put that much more stress on the motor? Shaft isn't bent.The blades spin very smoothly and easily when not connected to the motor...

For those who are just reading this, I'm having very short flight time (a bit over 2 min on 350mah, then it won't hover out of ground effect, but voltage is still 3.94v) but most important of all the brushless c05 motor is very warm after a short 2 min flight. (8t w/ both genius or mini cp gear) The first two minutes have plenty of power, then it abruptly gets low on power.

Thanks to anybody who has any ideas...
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Old Jun 10, 2012, 09:28 AM
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How did you measure the 3.94 V? Is it the Telemetry Voltage while it is in the air, or on the ground?
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Old Jun 10, 2012, 09:36 AM
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Unfortunately i have a devo 7, so no telemetry. On the ground with a multimeter...

The thing that confuses me most is that the motor gets really warm (can't really keep my finger for more than a few seconds), so i don't think it's not getting enough current, but then the batteries aren't warm at all after a flight... So i really don't know what to try and troubleshoot...

EDIT:
Quote:
Originally Posted by i812 View Post
How did you measure the 3.94 V? Is it the Telemetry Voltage while it is in the air, or on the ground?
I taped down the heli and measured the voltage with the multimeter. Here are the results:
Batteries are stock 240 mAh (the only charged one I had...)
Low battery
battery 3.82v. I added throttle and pitch, at about 50% pitch and 90% th, it reached 3.46v and more pitch would just bog the motor but no change in voltage. As soon as I stopped, voltage shooted back up to 3.78 and then within 3 seconds to 3.81.

Charged Battery
Charged to 4.18v
connected to rx -> 4.15v-4.14v (is that normal??)
Went to full th and pitch, and this time it went down gradually throughout the stick, until 3.49v and then keeping at full th and full pitch after two seconds it crawled up to 3.54v.

Hope these numbers help to understand whats going on...
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Old Jun 10, 2012, 11:00 AM
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IMO, the easiest way to troubleshoot weak Motor without appropriate test equipment and knowhow is by "blindly" swapping/exchanging suspect part(s) with known good part(s):

LiPo
RX
(Converter)
(ESC)
Motor

A Voltmeter will help identify DC problems if you know how to use it properly. In most cases the Voltage measurement at normal operating current is the most important meausrement. In the below post, I try to explain why:

Quote:
Originally Posted by i812 View Post
Unless you have a really good (expensive 4 point) Ohm meter, you may not be able to easily measure the difference between a good wire with 7? strands, and a bad wire with 1 strand.

With a "normal" Ohm meter, both the good wire with 7 good strands, and bad wire with only 1 good strand will both appear to measure the same: very low resistance much less than 1 Ohm - down in the "noise".

The reason is due to Ohm's Law:

V (Voltage drop) = I (current through) * R (resistance)

I haven't made current measurements on any Walkeras, but to give you a "ballpark" idea of how the Voltage drops across wires with broken strands, lets use Ohm's Law and see what happens "on paper":

A heli uses the MINimum amount of power and current from a Battery when the Blades aren't spinning. I haven't measured the MIN current, but it is probably less than than 1 Amp current draw, probably closer to 0.1A

A heli draws the MAXimum amount of power and current from a Battery when the Blades are spinning at MAX rpm and pitch. I haven't measured the MAX current, but it is probably approaching 10 Amp current draw. I'm guessing this because the micro helis use 10 Amp ESC's.

I don't know the resistance of a good wire going between the LiPo and RX, but it is very small, something like 0.01 Ohm. My "normal" Ohm Meter measures down to 0.0 Ohm.

I don't know how many strands the wire has, but it is about 7. If 6 of them are broken, the wire's resistance will increase by 7. This means if the good wire with 7 good strands has 0.01 Ohm resistance, then a bad wire with only 1 strand left will have a resistance of 0.07 Ohm. A "normal" Ohm meter isn't going to be able to measure this increased resistance.

But will the heli be able to tell the difference between a good wire with 7 good strands, and a bad wire with only 1 good strand?

Let's use Ohm's Law, to determine what should happen on paper:

The MIN load Voltage drop across a good wire = 1 A * 0.01 Ohm = 0.01V = too small of a Voltage drop to measure

The MIN load Voltage drop across a bad wire = 1 A * 0.07 Ohm = 0.07V = 7 times more than good wire, but still too small of a Voltage drop to measure.

The MAX load Voltage drop across a good wire = 10 A * 0.01 Ohm = 0.1 V = small but measurable

The MAX load Voltage drop across a bad wire = 10 A * 0.07 Ohm = 0.7 V = very measurable = 4.2 V fully charged LiPo appears at RX as if it is 3.5V = time to land!!!!!! (even though the LiPo is fully charged)

I don't know how good my guesses were about the wire resistance and current usage are, but that wasn't the main point of my post. The main point of this post is the Voltage drop going across a wire isn't very noticeable until after a lot of current is going through it, the greater the current going through it, the greater the Voltage drop! The higher the resistance, the greater the Voltage drop.

Bottom line:

Unless all the wire strands are broken, measuring wire resistance with a "normal" Ohm Meter, isn't going to help identify a "weak" wire with broken strands.

Measuring Voltage drop across a wire with a "normal" Volt Meter at MIN load current, isn't going to help identify a "weak" wire with broken strands.

Measuring Voltage drop across a wire with a "normal" Volt Meter at MAX load current, is the most effective way to identify a "weak" wire with broken strands.

(Sorry for the long post, but I hope it helps, because I think many micro Walkera electrical problems are probably caused by bad wires with broken strands, but the wire problem really doesn't show itself until after the Blades are spun up, and approaching MAX current usage - MAX Voltage drop across weak wire(s). IMO, if a person knew which wire, replacing a wire is probably one of the cheapest repairs a person could make. Since I can get scrap wire for free, replacing a wire is a cheaper repair than using CA to fix stuff. I'm guessing many "broken" expensive Motors, ESC's, and LiPo's are trashed because of broken wires!)
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Last edited by i812; Jun 10, 2012 at 11:12 AM.
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Old Jun 10, 2012, 11:40 AM
<Marty>
United States, KY, Springfield
Joined Jul 2011
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Quote:
Originally Posted by Marioinc View Post
Nobody know's what could be up?
I inspected everything and cleaned up and relubed everything, and the only thing wrong are the rubber washers of the feathering shaft a little used up, but not even that much, could that be it? Could that really put that much more stress on the motor? Shaft isn't bent.The blades spin very smoothly and easily when not connected to the motor...

For those who are just reading this, I'm having very short flight time (a bit over 2 min on 350mah, then it won't hover out of ground effect, but voltage is still 3.94v) but most important of all the brushless c05 motor is very warm after a short 2 min flight. (8t w/ both genius or mini cp gear) The first two minutes have plenty of power, then it abruptly gets low on power.

Thanks to anybody who has any ideas...
only thing i can think off is you mentioned that the blades spin very smooth and easy when not connected to the motor...so perhaps when you put the motor back on you are getting the gear mesh to tight...the pinion and main gear needs to have back lash in it and not pressed together tight at all. leave it loose between the gears....
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Old Jun 10, 2012, 01:12 PM
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United States, CA, Mt Shasta
Joined Jun 2010
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I take a small piece of paper towel and let it mesh between the gears as a gauge when setting up the motor pinion because Marty is very correct, there needs to be some space between the gears.
BTW...I miss all you guys, I went over to the fixed wing side, but still fly micro helis in my backyard. Fixed wing is so easy and way more relaxing. Flying for a month now and still haven't had to buy any parts. $$.
Mike
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Old Jun 10, 2012, 01:25 PM
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Originally Posted by Neoneo View Post
using this link it says I'm at 6 degrees. and your saying i should be at around 11?
by the way, good find, thanks
Yes, I fly with +/-12* collective and +/-11* cyclic on my mCP X and V120D02S hybrids and have pretty decent flip rates and good controlability. You can increase in steps to see how you can handle the increased sensitivity. Don't just crank it to +/-11* because it may be a little touchy until you get used to it compared to +/-6* which isn't enough for 3D. Make sure your swash doesn't bind at the extremes of collective and cyclic combined.

Good Luck, Don
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Old Jun 10, 2012, 01:39 PM
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Thanks for the replies guys.
I checked the meshing, even tried different gears thinking it was maybe deformed or something.
Unfortunately I don't have any spare parts that's why I was trying to diagnose it with a multimeter.

Just a couple of things I want to make sure.
I just tried with a known good 350mah battery and from 4.20 it went to 4.18 when connected, is that normal just binding, no motor spinning?
Also with this battery full th and full pos pitch i still have 3.82v, (instead of the 3.55 of before), but still not getting a lot of flight time with this battery.
Does this high voltage mean there is too much resistance and not enough current getting through? What do you guys get as a telemetry voltage when under full load? I resoldered and rechecked all my connections three times already, and was ruling out a bad connection or bad batteries since the MOTOR is getting warm, so i thought enough current was getting through. Do you guys think this is a wrong assumption?

I guess I'm going to have to buy a new esc and motor and go from there...

Thanks for the help guys
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Old Jun 10, 2012, 02:20 PM
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michigan
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Quote:
Originally Posted by Marioinc View Post
Nobody know's what could be up?
I inspected everything and cleaned up and relubed everything, and the only thing wrong are the rubber washers of the feathering shaft a little used up, but not even that much, could that be it? Could that really put that much more stress on the motor? Shaft isn't bent.The blades spin very smoothly and easily when not connected to the motor...

For those who are just reading this, I'm having very short flight time (a bit over 2 min on 350mah, then it won't hover out of ground effect, but voltage is still 3.94v) but most important of all the brushless c05 motor is very warm after a short 2 min flight. (8t w/ both genius or mini cp gear) The first two minutes have plenty of power, then it abruptly gets low on power.

Thanks to anybody who has any ideas...
It sure does sound like it could be your ESC, I think you need a LT for a 4g3.
George
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