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Old Sep 09, 2012, 09:38 AM
Why the dirt on the wings?
moparmyway's Avatar
New York
Joined Jan 2009
4,999 Posts
Our temps are cooling off, maybe want to extend WOT bursts and feel motor temp after a little 5-6 second run.
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Old Sep 09, 2012, 12:18 PM
Why the dirt on the wings?
moparmyway's Avatar
New York
Joined Jan 2009
4,999 Posts
Quote:
Originally Posted by brolley View Post
Here's a graph of my last flight.
Mega 16/40/1.5sc
6S 4500 nano tech 45-90C
CC Ice 100
APC 6.5 x 6 pylon prop
I was thinking of running my 16-45-F5Dec on 8 cells in my 40" Demon, then realized that the motor would be better in a very high cell count for an EDF application !!

If you ever decide to purchase another Mighty MEGA, please remember to pm me with some details. Getting a F5D or a 1 turn really makes it sweet and Rite !!
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Last edited by moparmyway; Sep 09, 2012 at 12:30 PM.
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Old Sep 09, 2012, 01:42 PM
Team Higher Than The Clouds
United States, NY, New York
Joined May 2012
168 Posts
Hey all,
I have a power question.
I have a ZII with the O.S. 1200kv motor and castle ice 75amp. I am planning to get two 3300mah 25c - 40c Turnigy Nanotechs. Can my ESC handle the amps that the batteries output?
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Old Sep 09, 2012, 02:21 PM
Crash Test Dummy
e2346437's Avatar
United States, ME, Mapleton
Joined May 2005
902 Posts
Quote:
Originally Posted by Techmeister View Post
Hey all,
I have a power question.
I have a ZII with the O.S. 1200kv motor and castle ice 75amp. I am planning to get two 3300mah 25c - 40c Turnigy Nanotechs. Can my ESC handle the amps that the batteries output?
You don't mention how many cells you intend to use, but there is a chart here that indicates that motor only draws 50 amps maximum.

Eric
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Old Sep 09, 2012, 04:28 PM
Registered User
brolley's Avatar
United States, PA, Center Valley
Joined Dec 2008
393 Posts
What kills a motor? The number of amps going through it or the heat produced by those amps.
Reason is with my new scoop, the motor seems to be staying pretty cool and I am wondering if it could handle a few more amps?
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Old Sep 09, 2012, 11:02 PM
never mind the boll⁣⁣⁣ocks
brosius85's Avatar
Australia, NSW
Joined Dec 2010
1,256 Posts
im gonna say its the watts that kill it not the amps

with a wire cutter for foam you set the heat by watts per inch of wire not amps or volts...

anyone else wanna chime in?
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Old Sep 09, 2012, 11:22 PM
Kiwi in Australia
steveobhave's Avatar
Australia, NSW, Carlingford
Joined Mar 2012
245 Posts
Watts = Volts x Amps

You're technically correct as it's the 'work' that the electrical system is doing but it's thanks to large voltage and high current.
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Old Sep 09, 2012, 11:27 PM
Mum is the word!
Joined Jun 2003
6,791 Posts
Watt's and amps are both a measure of current flow , so saying it is 1 of the other doesn't make sense
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Old Sep 09, 2012, 11:42 PM
Kiwi in Australia
steveobhave's Avatar
Australia, NSW, Carlingford
Joined Mar 2012
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Well Watts are a measure of the total 'work' that the system is doing - amps are a component of that 'work' as are volts.

1 Watt is the amount of work done when 1Amp of current flows through wire to equalise 1Volt of Potential Difference.
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Old Sep 10, 2012, 12:38 AM
Mum is the word!
Joined Jun 2003
6,791 Posts
Yes and it al boils down to current flow wich is amps , and watts,lol
Run 200 amps through somthing rated for 50 and it will burn, run 3000 watts through a 300 watt motor and it will burn , now if you want me to convert that 3000 watts to amps for you than we can,lol.
It all goes hand in hand.
My Last job FYI of 24 year was being an electrical contractor and electrician.
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Old Sep 10, 2012, 01:00 AM
Kiwi in Australia
steveobhave's Avatar
Australia, NSW, Carlingford
Joined Mar 2012
245 Posts
Good'O - I did electrical engineering at varsity and also my B level electrician certification so I guess we both know what we're on about
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Old Sep 10, 2012, 06:52 AM
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Peter M's Avatar
Newcastle, New South Wales, Australia
Joined Sep 2007
2,365 Posts
Can I have a go at trying to answer Brad's question a little more specifically?

Brad,
As you increase the load on your motor by increasing the size of your prop, the current draw of your motor increases.

Since the current draw increases at a greater rate than the voltage of your batteries drop due to this extra load, the power draw or wattage also increases too.

Since the motor's resistance remains largely static, the extra current draw creates extra heat. (The resistance actually increases but the rate of increase is relatively small but let's not make this too complicated!)

Also once you start to heavily load the motor you are also likely to be running it in a zone were it isn't as efficient in converting electrical energy into motion and this causes extra heat too. (This can be significant if you imagine a really efficient motor is only about 85-90% effective in converting its electrical input into motion. ie for a 1000 watt motor this could be at least 100 watts that is wasted in heat that we somehow have to get rid off otherwise it causes the motor temperature to rise rapidly.)

So anyway as you increase the load, the current draw would get to a point where the heat generated can't be dissipated fast enough into the surround air and the motor temperature rises dangerously to a point where it starts to cause the insulation on the windings to break down and eventually causes the windings to melt and oxidise.

So you are correct that extra cooling will allow you to run larger props, draw more current (and consequently more power) and allow your motor to survive by allowing it to dissipate more heat into the surrounding air and threfore moderate the increase in the motor's temperature


So good idea with installing the scoop to help prolong the life of the motor.


Oh, BTW, I'm a road worker if that makes any difference!
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Old Sep 10, 2012, 09:34 AM
never mind the boll⁣⁣⁣ocks
brosius85's Avatar
Australia, NSW
Joined Dec 2010
1,256 Posts
finally got my D40 dialed in nicely and a video recorder for the FPV link.

there were a few horses in the adjoining paddocks so i was a bit reluctant to fly too low... horse owners can be aggressive people i have found :P

the poor old turnigy packs are dropping to 14.3 at what should be the 50% capacity mark and power goes from 1000w to 800w... im gonna need some better batts soon.

Ritewing D40 fpv (4 min 34 sec)
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Old Sep 10, 2012, 09:41 AM
Why the dirt on the wings?
moparmyway's Avatar
New York
Joined Jan 2009
4,999 Posts
Quote:
Originally Posted by brolley View Post
1. What kills a motor?
2. Reason is with my new scoop, the motor seems to be staying pretty cool and I am wondering if it could handle a few more amps?
1. Too much throttle !

Especially after Peter M's very informative post,

2. I would start to extend the WOT duration some ......... before going up to 6.5x6.5.
Shoot for 5-7 seconds of WOT, then land and get the temps !!
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Old Sep 10, 2012, 07:02 PM
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brolley's Avatar
United States, PA, Center Valley
Joined Dec 2008
393 Posts
Thankyou Peter
My question was pretty vague but your answer nailed it.

So as long as my motor stays cool I can lengthen my WOT runs and possibly increase prop size if the temps stay in check? I'm sure I will start loosing motor efficiency as prop size increases. The batteries will probably sag more too equaling slower RPM.

Now I know why Mopar asked me "are you sure you only want to go 150", this speed thing is addicting!

I think I see another motor in my future.


Oh, almost forgot. Did some tree pruning today. I really wish I had a good video camera and someone willing to use it. Made an approach this morning right into the top of a big oak. When I realized I was behind it I tried to goose it and pull up.... too late, Prop shredded some branches and it fell about 30 feet.
Good news... plane is in good shape. Brought it home to look it over real good but looks like only the prop is broken and lost a winglet. Nose is a little crushed but not bad at all, still very flyable. Need to pull the motor and check the shaft, hopefully the combat shaft beats the oak.

Pics below after the crash and the scoop keepin my Mega alive!
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