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Old Mar 06, 2012, 12:42 PM
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USA, MO, Kansas City
Joined Mar 2010
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Quote:
Originally Posted by Whomprat View Post
If you plan on going full throttle I would. I ran a 25 on my earlier assassin with no problems (but I wouldn't do WOT until the battery voltage dropped some). I went with a 30 on my new build. Like I posted early, it pulls >350 watts on a fresh battery, and that's with little tiny 2mm bullets.
I would strongly recommend a god 40 amp esc.
This is what I am using in my hot rod assassin and it doesn't even get very warm.
As I understand it the rule is "give yourself at least %25 more headroom on your esc than you think you will need.
I use a e-max 40 amps esc which allows me to go vertical until my plane is totally out of site in eight seconds.
I fly like a demon tearing the sky up.
cf2812 eight turn 24guage 45-90c nano 1300mha batteries and everything works like a dream. Just don't run full throttle for your entire flight and the batteries hold up very well.
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Old Mar 06, 2012, 02:09 PM
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KC Flyer's Avatar
Lee's Summit, MO USA
Joined Jan 2001
371 Posts
Quote:
Originally Posted by erashby View Post
First, I don't have a Assassin yet, but use a 36" Hobby Lobby Wild Wing right now.

I finally set up a Test station.

I did some quick preliminary testing of the following motors:

1) emax CF-2812 stock
2) emax CF-2812 rewound with MD 24 ga 9 turns
3) rctimer CF-2812/14 stock

Observable differences
Shaft: RCTimer 3mm; emax 2.8mm
Magnets: RCTimer larger, but emax create more cogging (?stronger?)
Bell: RCTimer appears sturdier
Wire Turns: RCTimer packs more copper wire in(better efficiency), I don't know the number of winds. emax 12 winds

All testing done at room temp of 72 degrees with
Prop:7x6 HK prop (set up as pusher)
Battery: Nanotech 3S 1300 25-50C
ESC: CC Phoenix 25amp


Motor Amps Thrust
1) emax CF-2812 (stock) 13 (max) 21oz
2) emax CF-2812 (MD 24 ga 9 turns) 14.5 21oz
20 (max) 27oz
3) rctimer CF-2812/14 (stock) 13 18.5oz
16 21oz
20 (max) 24oz

Conclusions/Confusions
RCTimer appears better made/beefier, more copper, slightly larger diameter shaft, beefier bell, bigger magnets (not necessarily more powerful).

RCTimer less thrust at 13 amps, able to handle 50% more amps with 15% more thrust (This doesn't seem worth it.)

emax rewind (it might be 8.5 turns some times instead of 9 turns) takes 1.5 more amps to produce 21 oz of thrust. It produces 3 more oz of thrust at the same max amps as the RCTimer. This is a 6oz (~30%) increase in thrust with only a 7 amp (~50%) increase in amps.

After some flight testing and a little more thorough bench testing with RPMs (I only had fluorescent light at the time, which messes up RPM readings.) I plan on rewinding the RCTimer. (Note: The 3mm HK prop mounts have to be drilled out to fit the RCTimer shaft.)
Welcome erash -

Looks like we have the same sort of affliction!

In case you haven't seen my setup, see below. You need to turn off room lights and use sunlight or a flashlight, lantern, etc to get good rpm readings.

I look forward to the RCTimer data.

Amps/rpm/thrust will be higher than my graph/data shows with fully charged NanoTech 25-50c batts as I held voltage slightly below 11.7v to simulate mid flight performance.

I would recommend 45-90c NanoTechs (not 25-50c) as one of the lesser ones puffed up and died on me (the other one dissapeared after a bad crash into a tree in the woods). I've had no problems with the better NanoTechs although some others say they are overrated.

This data is for an 8.5/9 turn motor that is still going strong today.
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Last edited by KC Flyer; Mar 06, 2012 at 02:40 PM.
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Old Mar 06, 2012, 03:07 PM
Big Jim
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United States, ID, Mountain Home
Joined Jun 2011
2,958 Posts
Speed run with my Assassin and Canmore GPS logger

the logger weighs 15 grams
Assassin Speed Run (3 min 50 sec)
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Old Mar 07, 2012, 05:27 PM
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Lee's Summit, MO USA
Joined Jan 2001
371 Posts
Quote:
Originally Posted by RTF Thumper View Post
the logger weighs 15 grams
Looks like a cool addon! How much and where do you get?

An 8 turn motor is next for me (I've rewound them for a buddy). My 9 turn was in the 70's according to the iPhone app.
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Old Mar 07, 2012, 10:58 PM
Big Jim
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United States, ID, Mountain Home
Joined Jun 2011
2,958 Posts
Quote:
Originally Posted by KC Flyer View Post
Looks like a cool addon! How much and where do you get?

An 8 turn motor is next for me (I've rewound them for a buddy). My 9 turn was in the 70's according to the iPhone app.
$27.99
from
http://www.bedoxinc.com/cagtusbgpsst.html
You have to use googel earth to view the files or any program that will take a KMZ
here is one from my Radian Pro
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Old Mar 07, 2012, 11:01 PM
Big Jim
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United States, ID, Mountain Home
Joined Jun 2011
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Google Earth is a free way cool pice of software check it out and you will get a case of the gotta haves ...lol
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Old Mar 08, 2012, 08:53 AM
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Joined Jun 2009
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That is cool!

Quote:
Originally Posted by RTF Thumper View Post
$27.99
from
http://www.bedoxinc.com/cagtusbgpsst.html
You have to use googel earth to view the files or any program that will take a KMZ
here is one from my Radian Pro
I found and have "driven" around your flying site using Google Earth Street View. Very nice place to fly, there is nothing like that here.
The view can be moved right into the flight path, 36mph at one point.
Another toy to add to the Assassin.
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Old Mar 08, 2012, 12:50 PM
IWantToFly
United States, AK, Dillingham
Joined Jul 2011
141 Posts
hey guys,
i just rewound my cf2812 with the 24AWG wire i got from gobrushless.com. i did 9 turns per pole and followed the video i found a few pages back. i just got it all ready and mounted for testing. i have a watt meter i got from hobbypartz.com
before rewinding, the motor peaked at 168W and 16amps.

after rewinding, the motor peaked at 209W and 18amps.
i wasn't able to go full throttle, because as it got near full throttle, the motor sounded and felt like it was slipping on something, started cogging and made screeching noises and then stopped. i tried peaking the throttle several times and got the same result. the motor got pretty hot right away, too.
any idea what i did wrong? help me troubleshoot. any help is welcomed and thank you.

-speedy
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Old Mar 08, 2012, 12:57 PM
Planes in flames,,,
jetpackninja's Avatar
Gravity Sucks
Joined Aug 2010
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It may need to be set to a higher timing setting.
Most ESCs have 3 settings a low med and high.

I have two HobbyPartz motors that I have found that I have to use the high timing setting.
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Old Mar 08, 2012, 12:59 PM
IWantToFly
United States, AK, Dillingham
Joined Jul 2011
141 Posts
thanks jet!

i didn't think about that. i'll go mess around with the settings and see how i what i come up with.
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Old Mar 08, 2012, 01:02 PM
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Hope it works
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Old Mar 08, 2012, 01:20 PM
IWantToFly
United States, AK, Dillingham
Joined Jul 2011
141 Posts
it worked! thanks jet! on a used (maybe little more than half charged) 3s lipo battery, it went all the way to full throttle and peaked at about 250W but i didn't check the amp ratings. i'm using a dynam 30A ESC. the high timing setup worked! thanks again! i can't wait to go try it out now
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Old Mar 08, 2012, 01:21 PM
IWantToFly
United States, AK, Dillingham
Joined Jul 2011
141 Posts
and by try i mean fly it
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Old Mar 08, 2012, 01:28 PM
Planes in flames,,,
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Quote:
Originally Posted by speedyAK View Post
it worked! thanks jet! on a used (maybe little more than half charged) 3s lipo battery, it went all the way to full throttle and peaked at about 250W but i didn't check the amp ratings. i'm using a dynam 30A ESC. the high timing setup worked! thanks again! i can't wait to go try it out now
Awesome!
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Old Mar 08, 2012, 04:59 PM
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Utah
Joined Aug 2001
1,938 Posts
Another thing to check

Quote:
Originally Posted by speedyAK View Post
hey guys,
i just rewound my cf2812 with the 24AWG wire ...as it got near full throttle, the motor sounded and felt like it was slipping on something, started cogging and made screeching noises and then stopped. -speedy
Glad you got it fixed.
I am about to maiden my rewound motor today.

Another thing to check is that the prop adaptor is not slipping. I had the same thing happen and found that the prop adaptor was slipping a little. I tightened it up and it solved the problem.
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Last edited by erashby; Mar 08, 2012 at 05:23 PM.
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