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Old Mar 19, 2012, 10:29 AM
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Originally Posted by Glacier Girl View Post
Andrew/ Peter, with the HK motors there is almost always a variance in specs, even from what they list on the site, so in their case the specs listed are worthless.

And I think just like using a calc program, you should only use listed specs of this fan and that motor as guide. It's never going to be gospel. Too many things, like Andrew said can skew em. Off wind, draggy bearings, poor balance, funky pack, weird esc and so on.

10 of us could order the exact same items, and I'd be willing to bet we get 10 different readings.
True. also...I think when it comes to proving systems TRUE apple to apple testing has to be done.

We cant compare a test were the volts are 21 to a test were the volts are 23 with same KV motor.

We also cant compare a motor with 50% more winding mass than a similar KV'd motor with less winding mass.
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Old Mar 19, 2012, 10:30 AM
Kamikaze Ace
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Something I noticed through trial and error, and verified against both my WeMo's and E-flite's. The mount flanges on the CS are offset to one side. And the others are not.

Drove me up a wall fitting em to my nacelles. Drop the shroud into the nacelle half with the stick mount and sometimes the other nacelle wouldn't fit for diddly, other times it would pop right on.

Took a straight edge and lined up the flanges and sure enough they sit off to one side slightly from the center hole.

I guess it makes sense in a way, if you are using a stick mount the offset lets the fan stay centered (if installed correctly) But on the other hand, when the airplane manufacturer offsets the stick mount for a centered flange shroud you'll go batty trying to make these fit.


p.s. I'm not going to say how I notched the lower shroud on one half of the nacelle to clear the flange, then reassembled the whole thing to find I notched on the wrong side. Notched again, reassembled again, and find the new notch wasn't needed. Or that I did it on both nacelles before I found the problem.
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Old Mar 19, 2012, 10:41 AM
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Originally Posted by erh7771 View Post
The 2w25 is a bigger motor than the L2855 series outrunners, there is no comparison here.

The 2w25 has around 45mm of windings while the the L2855 has around 30 - 32mm of stator at best.
Well the comparison has been done but it's not a fair one.

I would expect that people realise, without anyone pointing it out, that these inexpensive motors cannot be expected to provide the same performance as the HET motors.

The L2855 approx 20% of the price of the 2w25.

I will be using the L2855-2800kv in smaller 70mm foamies, up to 1-1.3Kg max for single EDF systems.

The 2100 and 2300kv versions give good thrust on 5S for heavier airframes but have to be proven over time. For twin systems up to 2.5-3Kg, they are also a good low-cost solution on 4S.

I have recently installed a CP480-3300kv in my heavy(1.8Kg) Starmax Mig15 and it handles the 85Amps without any problems. I get much better performance and sound from the CP-3300kv + 10 Blade fan compared to the 4S RC Lander combo which is a similar priced item.

I don't have any HET inrunners to test against but I suspect that at $44 shipped it's a solid choice.
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Old Mar 19, 2012, 11:34 AM
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Quote:
Well the comparison has been done but it's not a fair one.
better stated

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Originally Posted by anlucas View Post
...The 2100 and 2300kv versions give good thrust on 5S for heavier airframes but have to be proven over time. For twin systems up to 2.5-3Kg, they are also a good low-cost solution on 4S...
I think this is the sweet point of these motors, I wish HK had them in stock as they are only 12usd

for 3.5lbs of thrust on 5s for the 2300kv or 4lbs of thrust for the 2100 on 6s the price is hard to beat
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Old Mar 19, 2012, 12:54 PM
RAVI KOTHARI
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would be a great idea to run the L2855 series on less critical (Read Cheap) applications and go for the more expensive HET's for more expensive edf.

I have had great experience with the HET motors, and they do seem to last forever.

Now i have a bunch of leftover edf motors from hobby King and they have cost me more in the trial & error process, i plan to only buy the tried & tested, Probably my bad luck since there are more than a few people enjoying the EDF out runners from HK. And they are so cheap..................
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Old Mar 19, 2012, 01:15 PM
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Originally Posted by anlucas View Post
...

I don't have any HET inrunners to test against but I suspect that at $44 shipped it's a solid choice.
44$ shipped is a good price - I'd buy one; where?
thx
Clemens
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Old Mar 19, 2012, 01:41 PM
EDF rules... :)
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Originally Posted by PeterVRC View Post
I was thinking about thrust....
If anyone bench tests the unit, with a lip, for a given RPM everyone should get the same thrust. So the real aim is to find out what RPM any given motor can drive the fan to, with the next aim to achieve that for the least Amps possible.
A motor's KV is not really important to know - but of course you have to write something as the motors name or description.... all that matters is the final RPM it can drive the fan to (thus its thrust on a bench), for what amps.

After changing to a 70A ESC not much changed over the 50A ESC anyway.
But I have done more tests, on the L2855-2800 and 2300. All on 4S only.

Both I can run at around 30,000 RPM which is 0.9Kg thrust.
The 2300 at 43A, the 2800 at 56A
So I may as well just use the Amp efficient 2300, seeing they are the same final thrust result.
The 2800 is obviously struggling with the RPM/load and thus being over-worked - which is why its higher KV is not being converted into RPM gain.
I ran two 4S in parallel and it didn't help at all. So the battery(ies) were not a limit in the earlier tests (or in these). Nor was the ESC, seeing changing to a 70A ESC didn't change anything either.

The best I got from the 2800 was on fresh battery, thus it was the short lived Peak only, which was 1.1Kg at 31,000 RPM and still the same 56A. Just the battery volts were higher while they lasted that short period (20secs or so?).
I didn't specifically check and record the 2300 at 'battery fresh peak', but I don't think I saw over 1.0kg thrust at best from it. So that suggest the 2300 is running happily in its comfort zone the wole way.

So anyway, a curve could be plotted for RPM to thrust. eg 30,000 will be 0.9Kg and 31.000 will be 1.1Kg. I only know a few points between those two, though I could have recorded down the scale with less throttle setting applied.
The curve is unlikely to be linear... or maybe it would be, at least to say 35,000 RPM, or whatever... or I guess really it would probably taper off a bit as it goes upwards (and get less and less gain as it goes).
This is RPM, not Watts..... Watts required would probably rise more than linearly. (some form of exponential?)

In my region of operation (30K) every 500 RPM is 0.1Kg of thrust.

But all in all, somehow it doesn't seem to add up. If other people are testing the L2855-2800, and 2300, and getting Current X and thrust Y, why is my thrust lower? The main remaining common item is that both my ESC's are 'cheapies' So maybe a 'great' ESC can drive the motor more efficiently. ??

People need to list their RPM also really. That gives an extra cross check figure of use and will show if things add up or not... or can also be of use to try to pinpoint a shortfall, or a great (or overly great) result.
I am guess 1.3Kg would need 32,000 rpm.
And now that I think about it..... my RPM meter might have the wrong total poles set(???) as 30,000 seems too low for 1.0Kg area? LOL Surely 1.6Kg needs up towards 40,000rpm.
So if my pole setting is wrong and I need to change that, then it will of course move the RPM scales up (I was really getting more RPM than thought/recorded). DOH.
I am thinking I will need to go back over the tests.... again.... to get the true RPM numbers. sigh.
Here ya go.

http://www.rcgroups.com/forums/showp...4&postcount=16

Eric B.

I would think that good batteries would have little problem holding 3.7 volts/cell (14.8volts for a 4cell) this is 93% of the available cell voltage. Thinking you can get 15volts and higher is only valid for a few seconds not over long runs, just look at a discharge graph.
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Old Mar 19, 2012, 01:55 PM
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Good quality does not mean high price, I've paid for an 84,000 dollar car back when I thought nice rides correlated with success and it was a THOROUGH pain in the a** relative to the price I paid for it. Quality control was NOT done on it and it was nationwide so it wasn't my copy of the vehicle that got bit and this was AFTER I bought some really high dollar speakers and thought they were really high dollar quality....the correlation is not there for the price paid.

I then learned to look at specs of devices or ways to delineate one device from the other. Later on in my career I learned about "White Boxing" of devices and how much was charged for them, I've never looked back at notion that somethings can be found less expensive somewhere else.
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Old Mar 19, 2012, 01:56 PM
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Originally Posted by mopetista View Post
44$ shipped is a good price - I'd buy one; where?
thx
Clemens
I would also like to know
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Old Mar 19, 2012, 01:57 PM
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Quote:
Originally Posted by mopetista View Post
44$ shipped is a good price - I'd buy one; where?
thx
Clemens
I was referring to the Cyclone Power motors.

Many places sell them, EDFHobbies, RC-Castle, PW-RC....
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Old Mar 19, 2012, 02:00 PM
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I was referring to the Cyclone Power motors.

Many places sell them, EDFHobbies, RC-Castle, PW-RC....
Oh, I was thinking you were referring to the HET motors.

I don't know why more people haven't been flying the CP motors, they have some real potential for the money.

They go on my list of standard motors for the price
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Old Mar 19, 2012, 02:07 PM
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Originally Posted by erh7771 View Post
I would also like to know
Prime example of going back to read everything before posting something....

Sorry for getting your hopes up guys....
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Old Mar 19, 2012, 02:37 PM
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Originally Posted by ravikoth View Post
would be a great idea to run the L2855 series on less critical (Read Cheap) applications and go for the more expensive HET's for more expensive edf.

I have had great experience with the HET motors, and they do seem to last forever.

Now i have a bunch of leftover edf motors from hobby King and they have cost me more in the trial & error process, i plan to only buy the tried & tested, Probably my bad luck since there are more than a few people enjoying the EDF out runners from HK. And they are so cheap..................

I am with you.
thx for sharing your experience with the HET
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Old Mar 19, 2012, 02:55 PM
EDF Jet Jam 2015 , May 28-31
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Agree that the 2100kV -2500kV motor is the best bet for this fan. The HK motor that I'm using works well.
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Old Mar 19, 2012, 04:04 PM
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Originally Posted by anlucas View Post
I have recently installed a CP480-3300kv in my heavy(1.8Kg) Starmax Mig15 and it handles the 85Amps without any problems. I get much better performance and sound from the CP-3300kv + 10 Blade fan compared to the 4S RC Lander combo which is a similar priced item.
Here's a short video from Saturday's maiden with the new motor...

Most of the time I was on 60-70% throttle monitoring amps and volts....
On Sunday I had a few more adventurous flights but the camera man wasnt there...

HK Mig-15 70mm CS 10 Blade CS480-3300KV (1 min 47 sec)


About 12-15mph headwind. Temperature 18C.

The sound is not the best but some bits sound good.....
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