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Old Oct 08, 2012, 05:41 PM
Registered Crasher
United States, TX, Coppell
Joined Feb 2011
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That's the correct motor, but you may need to adjust the pitch down on that to pull less amps. Some of this depends on whether you're running 4s or 3s. I suggest going over things on eCalc first.

You don't need the metal motor mount for any reason I can see. I still can't even figure out why that thing exists...

The power 25 bolts right up, perfect spacing. Heat is not an issue in melting the stock mount. If it was, the metal mount would just melt the firewall.
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Old Oct 08, 2012, 05:53 PM
Shut up and fly
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United States, CO, Firestone
Joined Jun 2008
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metal motor mount only for a very aggressive and hot set up
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Old Oct 08, 2012, 06:12 PM
Parkzone junkie
kalmon's Avatar
United States, MI, Grand Traverse
Joined Oct 2008
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Quote:
Originally Posted by jtaylor996 View Post
That's the correct motor, but you may need to adjust the pitch down on that to pull less amps. Some of this depends on whether you're running 4s or 3s. I suggest going over things on eCalc first.

You don't need the metal motor mount for any reason I can see. I still can't even figure out why that thing exists...

The power 25 bolts right up, perfect spacing. Heat is not an issue in melting the stock mount. If it was, the metal mount would just melt the firewall.
The other option would be the Power32 770kv, this motor is only about 10g heavier than the 25 and should allow you to run that 4 blade prop at the stock 10 pitch.

+1 on checking out eCalc first through.
-Brian
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Old Oct 08, 2012, 06:19 PM
ronht
Joined Sep 2009
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Hope this isn't a stupid question, but I'd like to know.

I put a Power 25 and a 60 amp ESC on my P-47 with a 4 blade prop and used the throttle curve in my transmitter to limit the top end Amp draw to 54 Amps. It seems to work great, I'm just wondering, why this isn't also an acceptable solution to running a 4 blade prop instead of all the CG issues that come with a heavier motor?

I understand it's the same as limiting my throttle to 3/4 travel, but I get plenty of speed with this setup without burning anything up while keeping the scale look of the 4 blade prop.
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Old Oct 08, 2012, 06:27 PM
Some.. call him Tim...
Ducati Mechanic's Avatar
United States, TX, Austin
Joined Oct 2008
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Quote:
Originally Posted by papabatman View Post
metal motor mount only for a very aggressive and hot set up
And.... It's really cool....
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Old Oct 08, 2012, 06:48 PM
Parkzone junkie
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United States, MI, Grand Traverse
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Quote:
Originally Posted by ronht View Post
Hope this isn't a stupid question, but I'd like to know.

I put a Power 25 and a 60 amp ESC on my P-47 with a 4 blade prop and used the throttle curve in my transmitter to limit the top end Amp draw to 54 Amps. It seems to work great, I'm just wondering, why this isn't also an acceptable solution to running a 4 blade prop instead of all the CG issues that come with a heavier motor?

I understand it's the same as limiting my throttle to 3/4 travel, but I get plenty of speed with this setup without burning anything up while keeping the scale look of the 4 blade prop.
You are pushing the limits. It might work for ever or it might blow up tomorrow. Throttle limiting is not an effective way of reducing the power the ESC sees. An esc is a switch. It varies power by turning off and on at different speeds. When it is on it is full on. Meaning that it is seeing the full power the setup is capable of producing.

Also, Eflite motors are usually overrated so you probably will be safe. Just know you are riding the top edge of the limits of the components.

-Brian
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Old Oct 08, 2012, 07:06 PM
You can't take the sky from me
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United States, OH, Cincinnati
Joined Aug 2011
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I don't think that's correct, as long as the max draw is limited to 54 amps, it won't go above. i don't see how the esc could be handling more amps than the ammeter is seeing. By that logic, flying around at full throttle should yield equal flight times to flying around at half throttle.
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Old Oct 08, 2012, 07:15 PM
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Northern IL
Joined Sep 2006
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I was thinking of the CC ICE LIte 75 esc and going 4S with CC BEC inline, 6 HS 65HB's.

With the Ice Lite 75 do you think I could go either the Power 25 or the Power 32 and still run the HL 4-Blade at a 10" pitch?

I wonder if this will be able to handle the weight of all of this? I know it will not be a floater and Have to be flown but that is ok, just dont know if all this is to much for it.

I am a Mac guy trying to get e-calc to work on it is not working any suggestions?
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Old Oct 08, 2012, 07:39 PM
Has Sloped Off
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Uk South Wales
Joined Aug 2009
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Ther is also the question of ESC calibration, it reads the signal it gets from the RX at max and min and sets it internal max and min to match. So limiting the travel will only work until it recalibrates itself. This may happen inadvertantly by powering up at the ESC at WOT etc.

Its not the Amps per se that kills things its the heat, our ESC units work by constantly flicking an on/off switch to limit the speed...longer off than on makes slower, but its done tens or hundreds or thousands of times a second. that produces heat...lots of heat this is were the excess energy goes to slow the motor down so running at low throttle still produces heat in the ESC sometimes this is almost as much or more than running WOT its a simplistic view but isnt too deep..... not like the full on electronic theory version....lol

Whats important is to know that running 1/2 throttle can put nearly as much or more heat strain on an ESC as running WOT.

I run the HL prop with a G25, the Turnigy version of the power 25, I had to pitch it back to hit the Amp limit of the motor but it still takes off in 6 feet and pulls verticle to a dot if you want it to, I can launch it straight up as well although it will torque roll unless I give it a good shove........lol well I had try didnt I ......all in the name of research.........

Dave
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Old Oct 08, 2012, 08:08 PM
Parkzone junkie
kalmon's Avatar
United States, MI, Grand Traverse
Joined Oct 2008
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Quote:
Originally Posted by copperbricks View Post
I don't think that's correct, as long as the max draw is limited to 54 amps, it won't go above. i don't see how the esc could be handling more amps than the ammeter is seeing. By that logic, flying around at full throttle should yield equal flight times to flying around at half throttle.
Quote from Castle Creations' website: http://www.castlecreations.com/suppo...eral.html#gen6
6. Can I control how much current passes through my speed controller by limiting full throttle travel on my transmitter with endpoint adjustments/trim? In other words can I use a 25 amp speed controller with a motor that will pull 45 amps but lower my top throttle endpoint on my transmitter so my watt meter only shows 25 amps at full throttle? Will this be OK?

NO!!! A speed controller controls power to the motor by turning full throttle current on and off really fast, 11 to 13 thousand times per second (Pulse Width Modulation or PWM). The percentage of each on/off pulse that is off compared to the part that is on determines how much power the motor sees. I.E. With a pulse that is 50% off and 50% on the motor will see 50% power*. Because each on pulse is 100% of full throttle current, a system set to pull 20 amps at full throttle through a Phoenix 10 will not last if you are throttled back to the point where you only see 10 amps on a wattmeter. The ESC in this case is still switching 20 amps, which it can’t do for long. Actually it is worse than the simple example above. Because an electric motor will always to try to pull as much power as is available to get to its rpm (volts times Kv), when you are running the motor below its Kv speed by switching power on an off, each on pulse will actually be way over the full throttle amp draw. That is why ESCs work harder at partial throttle than full throttle and why we underrate our ESCs. We underrate not so they can handle more current than their rating at full throttle, but so they can handle extended partial throttle operation with no problems.

* Actually, electric power is not linear as in this example, but you get the idea.

Remember this is the ESC not the motor.

-Brian
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Old Oct 08, 2012, 08:35 PM
You can't take the sky from me
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United States, OH, Cincinnati
Joined Aug 2011
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Oh, okay. funny...
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Old Oct 08, 2012, 10:29 PM
2 Fast 2 Low & 2 Loud
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United States, CA, Winchester
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That's a good explanation, one everybody can understand. Thanks for bringing that kalmon.
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Old Oct 08, 2012, 11:42 PM
Registered Crasher
United States, TX, Coppell
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Quote:
Originally Posted by Ducati Mechanic View Post
And.... It's really cool....
Well, tell me where to buy a clear cowl so you can actually see it...
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Old Oct 09, 2012, 12:19 AM
Some.. call him Tim...
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United States, TX, Austin
Joined Oct 2008
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Quote:
Originally Posted by jtaylor996 View Post
Well, tell me where to buy a clear cowl so you can actually see it...
Or mill Half A dozen cooling slits in the cowl.. Between that and the shinny red motor.. There should be some Bling peaking out..

I"m going Red tail with my Kit.
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Old Oct 09, 2012, 07:14 AM
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United States, MI, Grand Traverse
Joined Oct 2008
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Quote:
Originally Posted by copperbricks View Post
Oh, okay. funny...
Quote:
Originally Posted by scootrb4 View Post
That's a good explanation, one everybody can understand. Thanks for bringing that kalmon.
The hardest part to understand is "How can this be true when my Amp meter is telling me otherwise?"

Even the most expensive Fluke Meter wont have the refresh rate to show you the pulses. They probably update about 10-12 times a second. Watch the meter as you throttle up you'll see 0 70 150 230 etc(or similar) in relatively quick succession.
How they work is they measure how much current has gone through between each time it updates.
example:
So on a millisecond scale, just to make it easy say the meter refreshes every 100ms (10 times a second). Now lets say the esc it switching 10,000 a second at 75% throttle to get 50Amps on the meter. here is whats happening.
for .0025ms the esc off sending 0 to the motor, then for .0075ms it is 100% on sending full power to the motor which in this example is 66Amps. Assuming this is a static test, and you don't touch the throttle for the .1 seconds between meter updates it will accurately show 50amps because that how much current passed though between updates. (3/4 of the time was at 66amps and 1/4 was at 0)

Now this is a VERY simplistic example and know that electric power doesn't scale linearly like this but the idea is the same. At least this is how I understand whats happening.

-Brian
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