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Old Feb 09, 2013, 08:26 PM
Lee Liddle
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Bench test with a 7.5oz outrunner, 1650kv on 8s

I got the 12 blade fan today just as I was doing some testing of a 7.5oz Turnigy Heli motor in a 70mm. So I decided to put the 12 blade rotor on it and get some results.
This is the T-500 Heli Drive 42xx . It`s listed as 1600kv, but I measured the unloaded kv to be 1650.

This is not a stock CS 12-70. I had to take a little off the dia, maybe a mm off each blade (2mm off the dia). It`s also running in a 4 stator shroud instead of the stock CS shroud. So with that said, I still think you`ll be interested in the results.

8s...........28.4v under load
Amps......94a
Watts......2.7kw
RPM........42k

Unloaded KV.................1650
Loaded KV at 2.7kw......1480
Running at 90% of unloaded kv

I`m not setup to measure thrust or efflux speed right now, but I`d say it`s probably on the high side. I`ll be pushing it harder next week when my new YEP 120HV gets here. I`m thinking 10s might get real interesting.
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Last edited by Knife Liddle; Feb 09, 2013 at 08:38 PM.
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Old Feb 09, 2013, 09:19 PM
Life begins at transition
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Lee, any chance you could measure no-load current of that motor? I'd like to check out it's efficiency. That looks like a nice setup for a light-weight 70mm
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Old Feb 09, 2013, 09:32 PM
Lee Liddle
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Sure, does the voltage matter? BTW, the weight of the motor/fan, with the aluminum spinner is 12oz (340g).

Here are a couple of shots of the fan. This motor can be fitted to the stock shroud, it just takes some time so I just did a quick test of the rotor in this shroud.
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Old Feb 09, 2013, 10:37 PM
Life begins at transition
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It makes a tiny difference, not worth thinking about. If it's near what you're running (8-10s), it'll be more than good enough!

That's a massive block of steel hangin' out the back! I wonder if the motor itself squeezes the exhaust to 85% FSA?
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Old Feb 10, 2013, 02:54 AM
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Hey knife, is that the shroud the freewing shroud?
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Old Feb 10, 2013, 05:36 AM
Extreme CNC Alloy EDF
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You may want to recheck the readings on that setup Knife, as I got 41,300rpm on the CS12 rotor in 4 stator housing at 1625 watts on 6s.
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Old Feb 10, 2013, 05:53 AM
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Quote:
Originally Posted by Maxthrottle View Post
On that note Mark, have you looked into or considered 8S with a CS70/12?
There's been talk in one of the other threads about using one of the leopard 2860 motors with a 1690, 1840 or 2040KV versions of the motor. All are rated for 29V and above with a max amp of 38, 40 and 47 respectfully. The 2040kv I've only considered for a Wemo.
Do you have any setups/motors that would fit this kind of demand? Still just looking to turn the fan at the 53K range.
No I never really had any inkling to go more than 6s with 70mm fans, and I still think there is room to push the CS12 to 3kg thrust, but until I test out the combos in my head I wont say anything, would rather have some successful numbers than just theory!
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Old Feb 10, 2013, 07:43 AM
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Is there any practical purpose to running such a large motor? Maybe a Chevy 454 could be fitted, but Why?
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Old Feb 10, 2013, 08:39 AM
Lee Liddle
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Quote:
Originally Posted by Extreme_RC View Post
You may want to recheck the readings on that setup Knife, as I got 41,300rpm on the CS12 rotor in 4 stator housing at 1625 watts on 6s.
Really? What motor were you running?

I can recheck, but I`m pretty certain that all of the numbers are correct. The loaded and unloaded kv readings are in line and unless my clamp-meter and voltmeter are defective the V and A are correct also.

The motor I`m using would have to be very ineffeciant to require 60% more power to hit the same rpms. If there was that much wasted power, the motor would overheat and burn up in a mater of seconds. My motor temps are good, so I doubt that is the case.
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Old Feb 10, 2013, 08:48 AM
Lee Liddle
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Quote:
Originally Posted by 4stripes View Post
Is there any practical purpose to running such a large motor? Maybe a Chevy 454 could be fitted, but Why?
The larger the motor, the less it is stressed at a given power level. Less stress equals better efficiency.

Just think, if you did hook up this fan to a 454 that could turn 40k, the 454 wouldn`t even know it had a fan attached. It would get the same gas mileage with or without the fan hooked up. Loaded and unloaded mileage being the same would indicate close to 100% efficiency.

That`s why larger motors are better, within reason of course. Just because manufacturers make 70mm fan housings with 30mm motor mount areas doesn`t mean that is the best size motor to achieve everything that the fan rotor is capable of doing. I`m looking for performance at the upper end of the curve. Namely, high efflux speed.
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Old Feb 10, 2013, 09:44 AM
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If the motor fills 1/3 more of the exit area a great amount of the efflux speed will be spent trying to get around the motor. The fan will self destruct at some point as well.
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Old Feb 10, 2013, 11:10 AM
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KL,

Your numbers are very different from mine. Thou i m running the CS10 not 12.

What is the thrust you get @ 94a 2.7kw? My 8s run on CS10 only at half of yours number.

CS70108s (0 min 57 sec)


Sorry for the poor quality, plus no pictures of the CS and motor.
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Old Feb 10, 2013, 11:47 AM
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The problem with fast running fans...

I'm sure these little fans will take 40K rpm plus, but is it really a viable thing to do? The problem is that at such high powers/rotational speeds your theoretical g/w will be 'pants' ... and your (actual) g/w (ie taking in the electrical losses) will be even more horrible Most of the energy will be used to 'warm-up-the-atmosphere'... by the way of (very) high velocity efflux

For anyone seeking much larger thrusts, you'd surely be better off considering a bigger diameter fan?
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Old Feb 10, 2013, 11:57 AM
Lee Liddle
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Quote:
Originally Posted by genghiskt View Post
KL,

Your numbers are very different from mine. Thou i m running the CS10 not 12.

What is the thrust you get @ 94a 2.7kw? My 8s run on CS10 only at half of yours number.

http://youtu.be/R6Z1sGiIk1I

Sorry for the poor quality, plus no pictures of the CS and motor.
What motor were you running? Without knowing the kv, it`s impossible to compare the two systems. Knowing the rpms would be better.
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Old Feb 10, 2013, 01:14 PM
Lee Liddle
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Carrollton, Tx
Joined Dec 2006
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Sorry.....Bad Data

Well, the bad numbers were a result of my esc. I need to send it in and see what CC says.

I`ve changed the earlier post with numbers on 7s With a Suppo 200a esc.

A...........57A
V (7s)....27.3V
W...........1550W
RPM.......39k

87% of unloaded KV

I`ll be testing the motor on higher voltage when my new ESCs come in.
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