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Old Jul 23, 2012, 12:21 AM
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So here is a L2855 versus HET 2W30..... for 6S use.

"2855".... the 55 obviously does not truly (or honestly) mean "55mm". The magnets are only 28mm long. Windings the same.
The HET is a 50mm can, with about 46mm magnets/windings.

So how are they going to compare in abilities..... ummm, the L2855 cannot possibly be a true match in this fight.
Or can it....

On the bench the 2200kv HET gives fractionally better thrust in the CS10, than the 2100kv L2855. Pretty well the exact amount that the 100kv would cause it to have more.
Both draw close to the same currents... pretty well in line with their output differences too. (working in around 1200W areas)

So we have a $12 28mm motor... with a 28mm magnet length. Achieving the same output (and input approx) as a $75 28mm motor, that has a 46mm magnet length.
A very impressive result for a $12 motor......
But......

Of course a smaller motor can't be as good as a bigger motor, can it?
Well it can... for a short time....
The HET does its job CRUISING... it doesn't even know it was working. I bet it would last ongoing until the day the bearings reached their MTBF hours.
The L2855 runs overly hot, and I have fried two of them in very short times... one or two flights.....
And really, you could not be surprised by that.... 28mm magnets versus 46mm.... the L2855 is being over-worked big time!!

Keep the L2855 under 1000W and it can cope with that sort of load pretty well - though it is still over-stressed really. But at least it will last for a better ratio to its $ value. If run down at around 900W - surprisingly about what the wishy-washy specs listed say - and it becomes a much longer term capable motor.

This basically means it is no good for 6S in a CS10. Because the 2100kv means it will attempt to drive it to RPM that need 1200W area. To only run out to 900W area it would need to be 1900kv area rating. And there is no L2855 of those specs.
So the 2100kv and 2300kv are optimal for 5S use.
If you want the 900W ability of it, use the 2300kv on 5S. If you don't need the thrust and want a bit more flight time, use the 2100kv on 5S.

If you want to run 6S.... buy a decent motor! LOL
From 2000 KV to 2300 KV....
2200kv is already getting into fair power needs, and by 2300kv you really need very good batteries and will have low flight times.

I have only found ONE "great value" motor for 6S. The Turnigy XK2850-2060kv. $32. Which is for a very good quality and ability inrunner. (not a cheap 'junkie' motor). But they don't have them anymore! BAH
At 2060kv it is a bit down on power and more in the "good thrust and ecomomical for flight time" area. But you get no choice... that is all they ever had (2060kv).

To tailor the motor KV to exactly what you want, Leopard have a wide range covering all KV's needed. Otherwise with HET you are stuck at 2200kv - which is fine if that suits your needs too. Both brands are much the same price areas.
2200kv will give you very close to 2.0Kg thrust. 2100kv around 1.8Kg. 2060kv around 1.7Kg

...
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Old Jul 23, 2012, 12:23 AM
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What was the c rating on the packs again?

AnLucas, how many flights on your 6s do you have?

Do you run the 2100kv with the bell?

regards
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Old Jul 23, 2012, 01:07 AM
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Thanks for posting that comparison Pete.

Very interesting and informative.

I'm currently running L2855 2300Kvs x 2 on 5S in my J-11B.

I'm lucky if I fly it more than once a month (combination of too many planes and working FIFO).

Very happy with the setup for the $$$$ though.
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Old Jul 23, 2012, 01:22 AM
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Originally Posted by erh7771 View Post
AnLucas, how many flights on your 6s do you have?
I 've run one of them for 20-25 flights so far(can't remember exactly) but on 3300mah 25c 6S batteries that can't hold 22V for long and with a Plush ESC on low timing... I too was concerned about their longevity when I tested them in the winter. I avoided the HK SS ESCs cause they seem to drive the motors harder leading to higher temps.

I run all of mine with the bell on.

I have clocked many flights with summer temps in the high 90s and they seem to be holding so far....

One of my L2855-2300kv with more than 100 flights has developed noisy bearings at low rpms(20% throttle) but as smooth as silk on full throttle.
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Old Jul 23, 2012, 01:38 AM
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Here are two more fried - but still running - L2855-2100kv from 6S use.
The left one not running very well anymore....

Battery totals were not even able to run them at the full power they would have drawn if they had more.
eg I can run them a bit harder on the bench if batteries are paralleled to have 'unlimited' Amps available.
So if I had used 40C, or better, batteries they probably would have fried quick smart! (err, even quicker)

It really comes down to watts, fed into them. So as mentioned, you don't really want to be running more than 1000W. Or rather... how many watts (above 900w area) for how long.
So for example you might get away with 1100w in short bursts etc. But they really aren't technically up to the CS10 6S job.

...
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Old Jul 23, 2012, 01:48 AM
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I haven't pulled out and stripped down my L2855-2300kv on 5S motor. But that is a fantastic combo for the CS10. Best power output for the $ !!
At that power level (approx 1000w or just under) the L2855 is at its optimum, and close enough within its specs range to do it long term fine.

All for just $30, for motor and CS10 fan!
It has to be the number one ladder position of all combo's. And very useful for a very wide range of 70mm EDF aircraft uses too.
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Old Jul 23, 2012, 07:54 AM
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Why is everyone so hooked up on running 6s on these fans?
I've been experimenting with a Cyclone Power CS480-3300 on 4s and it seems to work very well. I don't think this fan works well with long intakes or exhausts for the most part it works well with stock ducting on light weight setups. As Tam said the limits are around 46k. When I try to get 45k it shakes like a dutch roll, weird gyro rotational shaking, not imbalance
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Old Jul 23, 2012, 08:07 AM
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Can anyone pm me the best motor setup with this CS10 blades for a twin 70mm HET-F-15 or Prodesign 70mm twin Rafale? ie HET motors. will be using 6S lipo.
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Old Jul 23, 2012, 08:11 AM
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Quote:
Originally Posted by ApexAero View Post
Why is everyone so hooked up on running 6s on these fans?
I've been experimenting with a Cyclone Power CS480-3300 on 4s and it seems to work very well. I don't think this fan works well with long intakes or exhausts for the most part it works well with stock ducting on light weight setups. As Tam said the limits are around 46k. When I try to get 45k it shakes like a dutch roll, weird gyro rotational shaking, not imbalance
Some are trying to run this fan on 8s. When will this madness end?!!?!?
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Old Jul 23, 2012, 08:41 AM
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Some are trying to run this fan on 8s. When will this madness end?!!?!?
I've ran the fan at 3000 watts over 7lbs of thrust on a 28mm motor.

The sound is wicket, I don't blame folk for beating on 16usd rotors...


Hey Pete, so the packs you ran the motor on were > 40c?

Did you test with a thrust tube?

Regards
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Old Jul 23, 2012, 08:48 AM
Aka: Tom Jenkins
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Quote:
Originally Posted by erh7771 View Post
I've ran the fan at 3000 watts over 7lbs of thrust on a 28mm motor.

The sound is wicket, I don't blame folk for beating on 16usd rotors...


Hey Pete, so the packs you ran the motor on were > 40c?

Did you test with a thrust tube?

Regards
I trust you didn't use the stock housing?
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Old Jul 23, 2012, 08:52 AM
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I trust you didn't use the stock housing?
Nope, only ran two minutes though, I didn't have the motor heat sunk correctly and it demagged ....yeah, no burnt windings just demagged cause it got freakin hot.

I ran this combo at a lower cell count yesterday...thing sounds like a really small turbin at that power level in the air very similar whistle and whine ....I know a cam would never capture what these things sound like in person
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Old Jul 23, 2012, 09:32 AM
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There is nothing 'wrong' with anyone wanting to run one on 6S. Cell count is not about power, that is about efficient power.... OR, also power if you wanted that.
The motor KV is the key point in a Cell count choice.
If you only want 1.4Kg, you can get that from 4S, 5S, 6S.... and the 6S way will be more efficient. The less Amps you can run for any given power level the better. More cells means you can run less Amps.
If you want 1.7Kg, you are pretty well locked in for 5S or 6S. And if you want 1.9Kg or more... 6S.
Though you might even be able to fry up some motor pushing a 4S combo to 2.0kg too.... hehe

You would have fun finding a motor of the right KV for 1.4Kg on 6S though! LOL. It would need about 1700kv to 1800kv... which they do exist, but hard to get. (tho Leopard do make plenty of suitable ones right through that area too. 2850 series, or 2860 series).

I consider up to about 2.0Kg is totally fine for the stock rotor and housing. They are not showing an inkling of issue to that level. Just balance them up well... like you should to any fan anyway.
I have no interest in power over that level... well, maybe to 2.1Kg area approx. - on the bench, which will be less once in-plane use anyway.
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Old Jul 23, 2012, 09:53 AM
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Not '40C'.... but 174 Amps capable. (5800mAH 30C)

C is not that useful a rating, mentioned on its own. I would prefer to see a number quoted as "Capable Amps", which then makes the actual battery capacity and C rating irrelevant.
In these tests all you really want to know is what did the motor WANT to draw, and that the tester had more than that capacity available, because if you know that then you can work out what issues you will have when you use it in any other battery combo.

eg A combo tested 'properly' used 70 Amps, running from "200Amps capable", giving 2.0Kg thrust, so that means the motor was unimpeded in attaining the best it could do (whether that means it was run way over specs or not is not important here). Any other person that runs that test, with adequate Amps available, will get the exact same result (within a tolerance range). Because that is what that motor's physical construction, and KV rating, will drive a CS10 in every case that it is given adequate source current (Amps).

And a person with a certain aircraft, and certain batteries they already own, might see they don't even want 2.0Kg... so their first best choice is not to use that motor combo at all. They really need less KV to lower the RPM and thus thrust. They can also do the maths on their battery... hmm, it is "90Amps capable", due to its small size and C rating, and thus they will know that the motor WANTS 70A and it is pretty assured their battery will never truly give that out (the stated battery ratings they put on them are dream numbers! LOL), so if they still chose to use that combo it would suffer from voltage sag, and it would run weaker than that 70A test case.... maybe even fluking the lower thrust they wanted to have, but it would be damaging their battery in that process. The only reason it runs lower output, lower RPM, is because the motor load dragged the battery down which means bad for it.

If someone tests a motor on inadequate current capability, then those figures are not a lot of use to anyone (almost). Because it is not what it can truly do. Just what it did on their inadequate battery, which would have sagged X amount, been bad for it, and just under-quoted that combos true ability.
Even more useful is to do TWO tests.... one with more than enough current capability, to show the true maximum. And then using a typical battery people would probably want to use in such an application - that is because in the majority of these cases people ARE using batteries not truly up to the job of what they are driving. Because to have the truly adequate battery is too heavy for any aircraft the combo is used in. (when we are talking in these high end number regions - not an issue for lower output combos)
But you need the 'capable current supply' test to show what the true MAXIMUM need would be. Then you can say "Well I am getting 60A, and X sag, and the battery is X temp... and I know it would run to 70A in an adequate system, so my battery is 'this' far off that ability. Using higher C, or larger capacity, to have 10A more capability would be more correct so as not to damage the battery.".

There are a few other factors that come into play in it all (ESC, wiring), but not really important, beyond that outline above.
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Old Jul 23, 2012, 10:01 AM
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Originally Posted by PeterVRC View Post
Not '40C'.... but 174 Amps capable. (5800mAH 30C)...
That's like testing the motor with a 3300 55c

Sounds like we should stay below 40c on 3300mah and under packs on the HK motors...

The motor is already being taxed so it's no wonder going 50 - 60c gets the windings burning.
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