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Old Dec 08, 2012, 12:46 AM
chuck
santa barbara, CA
Joined May 2009
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Quote:
Originally Posted by anlucas View Post
Chuck,

In the airframe, the amps will go up.

Testing on the bench should be done with the lip because this approximates how the fan will perform in the airframe.

Your kv decicions should be made with either the fan in the airframe or on the bench with the lip on.
thanks!
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Old Dec 08, 2012, 01:49 AM
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USA, CA, Aromas
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Part of the problem could be my 5s batteries. I only have 3000mah 20c Zippys
Bingo!
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Old Dec 08, 2012, 09:15 AM
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NEW JERSEY U.S.A.
Joined Mar 2010
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Originally Posted by Jetnfast View Post
Your jet flies great on that motor, thanks for providing the data. Seems like you had a stiff headwind that day too.
Thanks! Yes, I think about 10-13mph that day if I remember correctly.
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Old Dec 08, 2012, 03:09 PM
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Australia, QLD, Woody Point
Joined Aug 2011
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Originally Posted by jcdfrd View Post
Bingo!
Bingo? What does "Bingo" mean in the context of my enquiry? I'm trying to learn here. A bit more information would have been helpful without the sarcasm. I know that high discharge rate lipos are preferable in EDF applications but because of budgetary constraints I often use Zippy 5s 3000 20c lipos on my jets with 5 blade fans & get 1.3 kgs of thrust in those airframes. I wouldn't have thought that the lower C batteries would be so crucial just because I switch to a 10 blade fan
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Old Dec 08, 2012, 04:03 PM
Extreme CNC Alloy EDF
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Australia
Joined Mar 2006
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Until we know your amp draw and watts, its not easy to say your batteries are the total cause of low output. Ok it would be easy to surmise that a 3Ah pack with a 20c rating will sag out when put under the load the CS10 will give, but there are other things to consider.

What is the physical size of the motor? Weight? The motor may not be very efficient in the CS10, and might be wasting a lot of power as heat. The batteries could be sagging out under the load, thats why we need to know amps and watts under load, not peaks, let it run 10-15 seconds then take the readings.

Pull the canopy off and see if it changes the static thrust, mine certainly does.
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Old Dec 08, 2012, 04:37 PM
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USA, CA, Aromas
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Quote:
Originally Posted by warbirdzfan View Post
Bingo? What does "Bingo" mean in the context of my enquiry? I'm trying to learn here. A bit more information would have been helpful without the sarcasm. I use Zippy 5s 3000 20c lipos on my other jets with 5 blade fans & get 1.3 kgs of thrust in those airframes so I wouldn't have thought that the lower C batteries would be so crucial just because I switch to a 10 blade fan
there was no sarcasm I was only confirming YOUR suspicion that the batteries could be the issue.
yes different rotor will have different loads. the 10 blade is a lot higher loaded rotor so it will turn less rpm at a higher amp draw, if your motor is up to the task of the increased load then you will need the right battery to feed it

batteries need to be matched to your total amp draw of your power system (once the proper motor, kv, and voltage for the rotor has been selected)......so if your setup draws 60amps at wot you would need a batt with a rating of around 150% or more of the 60amps. so the zippy 3000 20c works out like this
20c = 20 x capacity or "c"
3000mah = 3ah
3ah x 20c = 60amps continous rating
so this would not be a good battery for a total system draw of 60amps as the voltage would drop quickly. "c" ratings are just that ratings and not very reliable so because of this I use my 150% rule. so for a 60amp total system draw you should use a batt rated to at least 90amp rating or 60amps x 150% = 90amps. so a 3000 30c batt would be rated at 90amps continous and be a lot better. the battery would be able to hold voltage under a 60amp load and thus you will have a lot more power or rpm......remember voltage = rpm, rpm = power. holding a higher voltage means you will be turning more rpm which = power. this is done after a proper selection of motor, kv, voltage and rotor of coarse.

your zippy 3000 20c pack is good for system draws of 40amps or less
I would bet your system with the 10 blade on it is drawing way more than that and so your battery voltage under load is dropping to below 3.5vdc per cell. this would be no good

John
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Old Dec 08, 2012, 04:39 PM
Don't Move I've Dropped My Nut
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United States, AL, Huntsville
Joined Feb 2009
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Quote:
Originally Posted by warbirdzfan View Post
I often use Zippy 5s 3000 20c lipos on my jets with 5 blade fans & get 1.3 kgs of thrust in those airframes. I wouldn't have thought that the lower C batteries would be so crucial just because I switch to a 10 blade fan
Mark is correct. The 10 blade fan demands much more work out of a given motor than the work needed to turn a 5 or 6 blade fan. Current draw will be up quite a bit. If the motor driving a 5 blade fan shows, say 40amp load, same motor driving the CS10 will show 58+amps. Batteries gotta be up to the task!
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Old Dec 08, 2012, 04:46 PM
chuck
santa barbara, CA
Joined May 2009
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and the motor!!!
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Old Dec 08, 2012, 11:32 PM
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Australia, QLD, Woody Point
Joined Aug 2011
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Quote:
Originally Posted by jcdfrd View Post
there was no sarcasm I was only confirming YOUR suspicion that the batteries could be the issue.
yes different rotor will have different loads. the 10 blade is a lot higher loaded rotor so it will turn less rpm at a higher amp draw, if your motor is up to the task of the increased load then you will need the right battery to feed it

batteries need to be matched to your total amp draw of your power system (once the proper motor, kv, and voltage for the rotor has been selected)......so if your setup draws 60amps at wot you would need a batt with a rating of around 150% or more of the 60amps. so the zippy 3000 20c works out like this
20c = 20 x capacity or "c"
3000mah = 3ah
3ah x 20c = 60amps continous rating
so this would not be a good battery for a total system draw of 60amps as the voltage would drop quickly. "c" ratings are just that ratings and not very reliable so because of this I use my 150% rule. so for a 60amp total system draw you should use a batt rated to at least 90amp rating or 60amps x 150% = 90amps. so a 3000 30c batt would be rated at 90amps continous and be a lot better. the battery would be able to hold voltage under a 60amp load and thus you will have a lot more power or rpm......remember voltage = rpm, rpm = power. holding a higher voltage means you will be turning more rpm which = power. this is done after a proper selection of motor, kv, voltage and rotor of coarse.

your zippy 3000 20c pack is good for system draws of 40amps or less
I would bet your system with the 10 blade on it is drawing way more than that and so your battery voltage under load is dropping to below 3.5vdc per cell. this would be no good

John
Thanks very much for that well informed answer John & please accept my apologies for my previous outburst
The motor I was using was a 2200kv NTM Prop Drive. It peaked at around 850 watts @ 43 amps but dropped to around 750 watts @ 40 amps after 15 seconds. Probably a bit light on for the CS-10 unit & maybe a better combo for 6s. I did subsequently manage to get a much better result by using a Turnigy L2855 2800kv motor on 5s. It pulled over 1300 watts @ 78 amps & gave me 1.3kg (46oz) of thrust mounted in the plane. Hopefully that motor will handle the 5s without burning out. I'll need to install a bigger speedie before I can test fly it though & following your advice I will also order a couple of 40-45c lipos.
Thanks again for your help.
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Old Dec 09, 2012, 12:12 AM
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Greece, Attica, Athens
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Quote:
Originally Posted by warbirdzfan View Post
The motor I was using was a 2200kv NTM Prop Drive. It peaked at around 850 watts @ 43 amps but dropped to around 750 watts @ 40 amps after 15 seconds. Probably a bit light on for the CS-10 unit & maybe a better combo for 6s. I did subsequently manage to get a much better result by using a Turnigy L2855 2800kv motor on 5s. It pulled over 1300 watts @ 78 amps & gave me 1.3kg (46oz) of thrust mounted in the plane. Hopefully that motor will handle the 5s without burning out. I'll need to install a bigger speedie before I can test fly it though & following your advice I will also order a couple of 40-45c lipos.
Thanks again for your help.
The NTM 2200kv is for 6S but will not take the beating in this fan anyway.

The L2855-2800kv will not last at 78amps.... Is this with the same battery BTW?
I suspect it is and it must be stressing a lot to deliver 78amps albeit at a much lower voltage.
I 've only used it to 67-68amps max and that's on 4S.

The appropriate kv for 5S is 2300-2500kv. 2800kv on 5S is only possible with motors that can take the 80amps+. Such a motor is the Cyclone Power 480-2800kv
You will find(measusing motor temp) that a part of the 1300watts is generated heat.
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Old Dec 09, 2012, 12:17 AM
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USA, CA, Aromas
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your welcome warbirdz
and as others have correctly stated their are many factors to consider, the motor choice for the voltage and rotor your going to run being the most critical.
I am not familiar with your particular motor but 40amps on 5s with the 10blade seems awful low.

there ya go better info above
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Old Dec 09, 2012, 01:38 AM
chuck
santa barbara, CA
Joined May 2009
4,320 Posts
agreed, drawing 1300 watts and making 1300 watts of power at the shaft are 2 totally different things. imo it is not reasonable to expect a ~100 gram motor make 1300 watts of power, it just will not dissipate the heat .

chuck.
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Old Dec 09, 2012, 02:13 AM
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manuel v's Avatar
Mexico, BC, Mexicali
Joined Aug 2004
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Quote:
Originally Posted by anlucas View Post
2800kv on 5S is only possible with motors that can take the 80amps+. Such a motor is the Cyclone Power 480-2800kv
You will find(measusing motor temp) that a part of the 1300watts is generated heat.
A 2800 Kv motor to 5s requires weighing at least 185 grams and the battery should support near 100A., to be efficient in this fan.

Regularly a high Kv motor, does not develop its full potential, because it is powered with a very small battery.

In many cases this battery serves as a fuse to prevent motor burn out.

It is best choice to choose both the motor and the battery for the development of the maximum power and better efficiency.

At the end of the day this ends up being something heavier than one would like.

Possibly for the 70 mm EDF needed to start having models more large regular to put the new power levels that are now used.
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Old Dec 09, 2012, 04:26 AM
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United States, TX, Grand Prairie
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Originally Posted by bamaguy View Post
Mark is correct. The 10 blade fan demands much more work out of a given motor than the work needed to turn a 5 or 6 blade fan. Current draw will be up quite a bit. If the motor driving a 5 blade fan shows, say 40amp load, same motor driving the CS10 will show 58+amps. Batteries gotta be up to the task!
The thrust to watts are commensurate

I put 1800 watts into a twin 70 10 blade or a 5 blade (sapac, eflight) etc I get very similar thrust (around 7lbs)
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Old Dec 09, 2012, 07:33 AM
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Australia, QLD, Woody Point
Joined Aug 2011
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Quote:
Originally Posted by anlucas View Post
The NTM 2200kv is for 6S but will not take the beating in this fan anyway.

The L2855-2800kv will not last at 78amps.... Is this with the same battery BTW?
I suspect it is and it must be stressing a lot to deliver 78amps albeit at a much lower voltage.
I 've only used it to 67-68amps max and that's on 4S.

The appropriate kv for 5S is 2300-2500kv. 2800kv on 5S is only possible with motors that can take the 80amps+. Such a motor is the Cyclone Power 480-2800kv
You will find(measusing motor temp) that a part of the 1300watts is generated heat.
Thanks for that info. I changed my ESC timing from low to high & got more respectable figures out of the 2200kv NTM Prop Drive. 1022 watts @ 58 amps on a 3000mah 5s. I'll test this in my Vampire tomorrow & suspect it will give a satisfactory result until my ordered L2855 2300kv motor arrives.
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