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Old Mar 07, 2012, 05:36 AM
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United States, TX, Grand Prairie
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Originally Posted by manuel v View Post
I think:

3600kv * 12.6Volts= 45360/16.8=2700....
12.6 is no load voltage, load voltage is nominal at 3.5 a cell below that represents a cell that's not holding voltage in a pack.

Yeah, I wish per cell load voltage was 4.2....

So you do the math at [desired RPM / (3.5nominal cell voltage x cell count) ] and if you have higher c rated batteries you can go up around .1 for 30c or .2 for 40c on the voltage which makes a notable difference in RPM.

For Sherlocks case 37000 calculated RPMs is around 3lbs with this rotor so he should be cool if he has 3s packs that keep voltage...amps will go up of course
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Old Mar 07, 2012, 07:22 AM
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Originally Posted by manuel v View Post
The most efficient motors.

Manuel V.
Remember, these are settled numbers when comparing. Great numbers from that motor none the less. I wish that MB1 lower kv look alike would show up. Should be any day now.
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Old Mar 07, 2012, 09:49 AM
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I see the 2855/2100 and 2300kv's are showing late March now.
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Old Mar 07, 2012, 10:12 AM
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Originally Posted by Glacier Girl View Post
I see the 2855/2100 and 2300kv's are showing late March now.
How can you tell?

Thx
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Old Mar 07, 2012, 10:48 AM
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Originally Posted by erh7771 View Post
How can you tell?

Thx
On the product page in the "Stock Arrival Alert" box. It says "End Mar".
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Old Mar 07, 2012, 12:43 PM
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Quote:
Originally Posted by erh7771 View Post
12.6 is no load voltage, load voltage is nominal at 3.5 a cell below that represents a cell that's not holding voltage in a pack.

Yeah, I wish per cell load voltage was 4.2....

So you do the math at [desired RPM / (3.5nominal cell voltage x cell count) ] and if you have higher c rated batteries you can go up around .1 for 30c or .2 for 40c on the voltage which makes a notable difference in RPM.

For Sherlocks case 37000 calculated RPMs is around 3lbs with this rotor so he should be cool if he has 3s packs that keep voltage...amps will go up of course
The calculation is only to determine the resulting Kv of a motor.
in this case a 3600kv motor on 3s would work in the same range of power an engine of (X) Kv to 4s.
3600 * (3.5 * 3) = 37.800 / (3.5 * 4) = 2700.
this has nothing to do with rpm.

To calculate your fan rpm’s:


3 cell lipo, have a voltage of approximately 12.6Volts.
The new batteries 30 and 20 C 40C sustain discharge voltage 11V average. (Use the voltage rating is very rough and correct)

A very important factor that is missing from this equation is the NLS% (percentage of No Load Speed.)
In EDF is very important that the engine is not charged too much for this factor does not drop below 80%. Possibly in some applications where the motor is much torture can be used up to 75%. But it is highly not recommended.

Also consider the actual motor Kv can vary the die post for the manufacturer.


Take the voltaje of the battery and multiply the Kv of the motor and multiply for %NLS factor = fan RPM.
11.1V x 3600 x 80%= 31,968 RPM.

Manuel V.
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Old Mar 07, 2012, 12:55 PM
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Originally Posted by manuel v View Post
... Take the voltaje of the battery and multiply the Kv of the motor and multiply for %NLS factor = fan RPM.
11.1V x 3600 x 80%= 31,968 RPM.

Manuel V.
I used to take the 10-15% loss out of both calculations but later found it was moot because the RPMs would be proportional and that's why I put calculated RPM to thrust.
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Old Mar 07, 2012, 01:32 PM
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so at 32k rpm will it produce about 3lbs of thrust?

if so I will have about 6lbs for twin operation. That is plenty it would be more than 1 to 1 weight ratio on 3s light set up.
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Old Mar 07, 2012, 01:50 PM
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Sherlock.

I think that 86A for you motor is high.

Manuel V.
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Old Mar 07, 2012, 02:00 PM
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I guess you guys know both fans are availible here in the states now so no waiting on a HK order to get 1...
I'm planning to do a little experimenting as well....will post results here..
Take care............Chris
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Old Mar 07, 2012, 03:29 PM
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I think you are right

Quote:
Originally Posted by manuel v View Post
Sherlock.

I think that 86A for you motor is high.

Manuel V.
I will go another route, i cant find anyone that wants to buy the fan and motor< i got two sets of them LOL
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Old Mar 07, 2012, 07:46 PM
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Sherlock

You have few options.

1.- put to motors in 70mm EDF clone 6 blades. with 3s, around 600 watts.
for 4s is around 1000-1100 watts.with 5 blades starmax clone./ detrum.
in Het / wemo fan around 800 -900 watts.


2.- buy new motor L2855-2800Kv.

Manuel v.
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Old Mar 07, 2012, 09:00 PM
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Quote:
Originally Posted by Glacier Girl View Post
If you check back in the thread quite a few are using the fan with the Delta shroud, in the Habu and they are missiles! I would think the Hawk and Sabre would both be great ones for this unit. As for kv it would depend how big of a pack you want to run. Something in the range of 2100/2300 for 4 or 5S, even 6.
If you have a big amp esc and pack you could look at a 2800 to 3000 kv motor.


sherlockshah, Yeah I think you have too high of a kv motor for even 3S on this fan. You aren't going to be happy.
It seems this fan likes a low kv motor on high voltage to really make it shine.
Thanks for the advice!
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Old Mar 07, 2012, 10:18 PM
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Beat up on the CP 480 motor with another full charge 6s pack.

The pack kept voltage more and I did 6s\ 88amps \23v \5lbs 8oz....

Ambient air in room was 78f and motor temps were around 140 during the run which is a little high but doable.

The kick was when I stopped the motor after 20-30 second runs, the outside of the can wouldn't get more than 200f and the motor shaft stay the same!

Couldn't get temps over 200f with no cool down run so that's really pushing it IMHO, took pack down to 80% this time

I would think it's good for burst for year round use cause temps will go up during summer. In Nor Texas it's around 158f outside during the heat of the day so I wouldn't chance running WOT the whole flight.

If you're heavy on the go stick with most high power EDF setups make sure not to cut the motor off and let the heat soak into your ESC and motor windings...run the motor at the lowest power you can get it to cool things down for a minute or two after landing.

Very nice power out of that motor
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Old Mar 07, 2012, 10:49 PM
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Quote:
Originally Posted by erh7771 View Post
Beat up on the CP 480 motor with another full charge 6s pack.

The pack kept voltage more and I did 6s\ 88amps \23v \8lbs 8oz....

Ambient air in room was 78f and motor temps were around 140 during the run which is a little high but doable.

The kick was when I stopped the motor after 20-30 second runs, the outside of the can wouldn't get more than 200f and the motor shaft stay the same!

Couldn't get temps over 200f with no cool down run so that's really pushing it IMHO, took pack down to 80% this time

I would think it's good for burst for year round use cause temps will go up during summer. In Nor Texas it's around 158f outside during the heat of the day so I wouldn't chance running WOT the whole flight.

If you're heavy on the go stick with most high power EDF setups make sure not to cut the motor off and let the heat soak into your ESC and motor windings...run the motor at the lowest power you can get it to cool things down for a minute or two after landing.

Very nice power out of that motor
sweet ... a pair of them will be some serious 70mm fun.
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