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Old Jun 18, 2015, 09:05 AM
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Hmmm, I did more cross-checking over all my CS12 motor/cell combos.....
Firstly, I thought the Fandrive 1500kv did 2600W on 7S... but it is 2100W....
I also had worked out the Fandrive is not even 1500kv really, but maybe 1450kv to 1400kv.
So it gets grey overall...... 7S maybe 2400W region for 1500kv... or is that 1400kv region really?

Then maybe 7S 1700kv to get 3000W (with an adequate motor for that Power).
Thus again, 7S 850kv does a bit over HALF that, so 1500W as desired......
The "halving" system does not truly work because the 3025-850 would be doing its task EASY and thus with greater efficiency - holding higher RPM towards its KV then a higher loaded motor can.
So again, a fair amount of GREY in the guesstimations!! Sigh....

I guess as long as I get a bit MORE, rather than a bit less, I can then limit Throttle.
But I am thinking I might just HAVE to go to 8S and YEP's really...... thus more efficient at the lower Power levels, and also fine to Throttle Limit it to the Maximum I want it to be. At $150 more in total cost!! Sheesh....

Seeing I have CS12's.... RedBrick 90Amp ESC's (that can do 7S).... I better just do the 3025-850kv and find out.....
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Old Jun 18, 2015, 09:15 AM
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More thought... next idea.....

6S.....

I have enough room to run two individual, fairly large, 6S batteries.
1500W needs 67Amps region.
Two 6S 4000mAH batteries..... 40C or better...... one per fan - MAYBE even an "X" paralleling setup.
A pair of YEP 80Amp EC's.... to get the Active Freewheeling.
WAY cheaper than HV ESC's !!! Nicer than Red Bricks.....

1500W needs approx 1300kv or so on 6S....

Test results I already have - but they do seem lack lustre, with the VOLTS being dragged down a lot!

6S 4000mAH 30C x 1 64.6A 20.4V 1320W 2.28Kg 1.72t/w
6S 4000mAH 30C x 1 66.0A 21.0V 1403W 2.33Kg 1.66t/w
6S 4000mAH 30C x 2 69.9A 21.8V 1526W 2.49Kg 1.65t/w

Note the PAIR of 4000mAh 30C could drive it "properly" - not the single 30C battery tests.
So 40C might not cut it either.
The 69Amps as predicted up earlier......
1.65 Thrust to Weight ratio is GOOD and shows the motor is doing it within its true specs.
I also remember the 3126-1300kv motor did it easily and no real HEAT at all.

BUT... you can't get that motor anymore..... International or Australia.... (I have ONE......)

Anyway.... 6S 1300KV region could do it ok. For a much lower total cost... at the bit higher battery stress region though.

Time to look for a 1400kv motor....... it can be Throttle Limited.
Which I guess a 1500kv could be also.......
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Last edited by PeterVRC; Jun 18, 2015 at 09:39 AM.
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Old Jun 18, 2015, 10:13 AM
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Solution:

This motor:
http://x-flight.com.hk/index.php?sp=...&more=&lang=en
1450kv run on 6S with YEP 80A LV ESC's....Throttle limiting to 1500W

BUT, then I got LAZY.....
And bought a pair of:
http://x-flight.com.hk/index.php?sp=...&more=&lang=en
Because this fan does the same results as 1450kv in a CS12. And nice that it has a ONE PIECE Rotor suited for up to 3000W, so I can use that in other things in the future if need be.
Still run on 6S with YEP 80A LV ESC's Throttle Limited to 1500W.

My 'redundant' CS12's (3 of) will remain unused......
I probably should have just bought the 1450kv motors..... and used the CS12's....
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Old Jun 20, 2015, 10:09 AM
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Well, that was probably a bit of a stuff up....
After ferreting through stuff I found three CS12's (I knew I had) and 'remembered' two Wemo Midi EVo's there too....
A quick setup and test of an EVO showed the Lander/DrMad 3674-1600kv on 6s is 1400W for 2.51Kg Thrust. The aim is 5Kg bench total... to allow for the drop when you run two in parallel (battery load), plus aircraft ductings (which in this case are very good really). Thus at least 4.0Kg remaining I would hope....

Seeing I have the two EVO's and one motor.... I could have just bought one more motor.....

Then the CS12's..... on a 1450kv motor they will be similar, for 6S. I had initially picked to buy a pair of the Changesun 1450kv Outrunners - and that would have worked fine! But the 13blade sets I bought are with 1500kv motors.... and even 1450kv was a bit high really, 1400kv would be best. The 13bl need quite a Throttle Limit drop, and the 1450kv CS12 would have needed none almost.
Or.... CS12 1200kv on 7S..... which I have one DrMad 1200kv motor already too.....
sheesh

A bit impulsive on the 13bl 1500kv it seems....

The best choice is the Wemo EVO DrMad 1600kv on 6S !!!! Just the right Power/Thrust I want, high efficiency (1.83 t/w ratio), and a better fan too. Plus no exhaust side issues - though this jet has no exhaust side problem for a CS12 either really.

Getting "Rid" of two of the CS12s (using 6S 1450kv) would have been useful too, as there is little chance they will be used otherwise. (The 13bl 1500kv pair could always be used elsewhere, or stripped...)
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Old Jun 21, 2015, 01:22 AM
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PeterVrc
I'm trying to make a graph of the behavior of the EDF. but the data obtained throughout the forum is inconsistent and incomplete.
This is the maximum that achieves.

Still, if the graph is not wrong, to 1500 watts.
To 6slipo, Kv motor from 1340 to 1400 requires, depending on its efficiency and weight.
For a 26,000 rpm.
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Old Jun 22, 2015, 09:53 PM
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You will find that a lot of numbers vary according to the battery, BUT the POWER always has to be reasonably consistent guide. No one really uses motors THAT far away from adequate....

As long as you have the Volts, Amps, preferably THEIR listed power too (what their meter showed) then you can cross reference things well.
I always make VIDEOS because all these numbers are fluctuating real-time, so anyone listing one set of numbers probably READ from one display to the other etc, and thus slight real-time mis-alignment of what they ALL were at the EXACT same moment.

And if you can't get the result someone else could, from just a simple "I used a 6S 500mAH 45C" etc, then you need to know the Voltage you actually had. (Or Power number).

So all in all, a lot of the 'error' across information is from NOT having the true numbers - not because people lie, but just don't record things appropriately to assure they ARE all accurate in TIME relationships.
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Old Jun 22, 2015, 09:57 PM
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I should have just bought the Changesun 1450kv and run 7S in Wemo EVos, because then you don't need to Throttle Limit and then I could have used $15 Red Brick ESCs! LOL
Versus 6S 13bl 1500kv with $48 YEPS - even though you would gain SOME benefit(s) from the YEP's.
Or the 1450kv in the CS12's sitting being 'wasted' still......

I will never use those CS12's in singles..... as those three are the older 'weaker' hubs and really need to stay under 2500W, if even that! So this Twin case of 1500W was perfect for them... sheesh.
It was a bit of a stuff up in economics..... but the Wemo EVO/YEP setup will be technically better. At a LOT more total cost!
Maybe I should get another 90mm Twin..... LOL (possibly the SAME jet anyway!)
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