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Old Jul 09, 2012, 07:15 PM
EDF rules... :)
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Originally Posted by Knife Liddle View Post
Very true!

The bigger the motor the better on any fan, but with the high load fans it`s even more important.

Just an example. I`ve switched the 3126 outrunner to a 2200kv on my CS-10 fan. On 6s it`s hitting 93a at about 2.1kw. But the intresting thing is that the motor is hitting 91% of it`s unloaded KV! 91% on a $20-$30 outrunner depending on where you buy it.

Those short inrunners will probably be lucky to hit 80% of their KV. The rest of the power is just turning into heat that will cause the motor tube to weaken and let the rotor hit the shroud.
+1.....

Eric B.
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Old Jul 09, 2012, 08:33 PM
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I have a L2855-2100 that un-bonded (?) its stator from the central housing 'tube', and then subsequently shredded its power leads with the stator rotating back and forth, being held in a rough region of arc by those power leads exiting the front cutaway.

I am guessing this happened either because it was poorly bonded in the first place, or the earlier posted mentions about power wastage/heat caused its failure.
This was run on 6S in the CS10 which draws approx 58A = 1200W 1.8Kg bench thrust area for that.
I would also guess that the L2855 is a bit over-stressed in that application (CS10) !!

After testing the HET2W30, and how dual batteries (to get more current capability) extended its output (and input) power by another 10% or so (1.9Kg thrust went to 2.1Kg), I wanted to re-test the L2855-2100 on the dual batteries to see if it would increase power also. But if 1200W is a problem for them already, then pushing it for more (the HET went to 1500W) could be a bad idea for it really.
And for now all my CS10's have motors in them and balanced, and no L2855-2100kv one amongst those. Two are in CS10's in a plane but I don't want to fry one of those! So that test has to wait a little while. The L2855-2100 assigned for that test will be happy with that reprieve!
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Old Jul 10, 2012, 01:40 AM
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Originally Posted by PeterVRC View Post
And for now all my CS10's have motors in them and balanced, and no L2855-2100kv one amongst those. Two are in CS10's in a plane but I don't want to fry one of those! So that test has to wait a little while. The L2855-2100 assigned for that test will be happy with that reprieve!
Peter,

my initial L2855-2100kv testing with high C large 6S packs showed that it's stressed above 60-65amps and will not last (winding temps in excess of 180F). I now only use low timing and lower C (25C or 35C) 3300mah packs and I am happy with it even though the thrust is not the maximum I could get.
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Old Jul 10, 2012, 01:56 AM
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The failed one was running in that 6S 58A max setup (due to battery limitation I would think).
They can get to very hot even at that spec, and that is still 1200W area.... a fair way over the 900W claimed spec, which is probably crap anyway! LOL. They aren't a very hefty motor at all really.

Hopefully it was just a random failure. And I can't even tell how the stator is really held on normally - it seems it would be bonded, but there is no evidence of that. And the housing and stator surfaces are clean - maybe it was a press fit? But now it slides over with ease.
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Old Jul 10, 2012, 02:02 AM
Lee Liddle
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sounds like the glue gun was empty when that one went down the line.
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Old Jul 10, 2012, 02:02 AM
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Originally Posted by PeterVRC View Post
The failed one was running in that 6S 58A max setup (due to battery limitation I would think).
They can get to very hot even at that spec, and that is still 1200W area.... a fair way over the 900W claimed spec, which is probably crap anyway! LOL. They aren't a very hefty motor at all really.

Hopefully it was just a random failure. And I can't even tell how the stator is really held on normally - it seems it would be bonded, but there is no evidence of that. And the housing and stator surfaces are clean - maybe it was a press fit? But now it slides over with ease.
Most likely a random failure.

The various L2855 motors, except for different winding lengths, are made from the same materials.

I have 2 L2855-2800 running 4S setups continuously pushing 60-65 amps in hot weather (37C) for the last 2 weeks or so.

I also use 2 L2855-2300kv on 5S and around 60amps max again all OK.

These motors get hot on anything other than low timing.
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Old Jul 10, 2012, 02:25 AM
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I get the same output (and input?) across all timings. 1, 7, 15, 30degrees.
The L2855 seems to be a very lenient motor that way. Though I have only run a few types that have had issues at various timing settings... almost none though.
But technically it should matter.

I guess I could sacrifice one 2100kv and run it on the bench for a 6S test at WOT non-stop (in a CS10), to see what happens... and when. And if it lasts... run another battery.... LOL.
And if it LASTS.... well then that was a useful test.
If it fails.... the information is far less useful in specifics. But at least will show NOT to run it at 1200W non-stop!

I'll have to change over one of my other setups tonight. There are two 2300kv setups (for 5S use) that I don't even really need for now, so one of those can be used.

I'll have to run up that HET2W30/ERC alloy on 5S to see its results too. Bound to be the typical 1.4Kg thrust area, for 52A area... I expect. But I will find out the real numbers....
I would hope it as more efficient than the L2855-2300 on 5S. Or at least either less Amps for similar thrust, or less thrust for less Amps (being 2200kv instead of 2300kv).

Though I am really looking for a 1.6Kg thrust setup for a plane, which is enough thrust for it, and the aim to keep Amps lower (than 1.8Kg uses) to get more flight time. But at the moment all I can get is either side of 1.6Kg ! Either 1.4 area, or 1.8 area.
I think I would need a 1900kv 6S, or 2550kv 5S, for that. Approx.
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Old Jul 10, 2012, 02:27 AM
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Another interesting thing is LEOPARD....
They have a huge range of motors. eg 28mm at 45mm, 50mm. 60mm. And a dozen spanning all KV's you could ever need within each of those ranges!

But WHERE do you get them?? And how much?
Fairly costly as far as I have seen the few places that do have the odd ONE or two!
They don't turn up anywhere, when looking to buy them.

They are the real solution to getting the truly capable power motor for any CS10 aim you have!
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Old Jul 10, 2012, 02:37 AM
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Originally Posted by PeterVRC View Post
LOL, yes even 4S would be way too much. And probably even pushing 3S.
A 2800 on 5S is 71A 1200W. So I expect a 3350 on 3S would be in that 1200W region too, so then 80A or so. Say 75A to 85A range... which is pretty hefty even at the lower Amp end of that.
Need a few batteries for that task!
Save that motor for a high RPM 3 or 4 blade fan.... on 5S or 6S then. Something doing 50k to 60k RPM. (I have a few [basically Wemo version clones] but I don't know if they can do those sorts of RPMs - I have never tried that).
Or really, more optimal on something lower blade count (5 or 6) 4S I would think.
The above analysis assumes that both setup will draw 1200W, which I puzzled:

2800 rpm/v * 5s * 3.6v/s * 80% = 40k rpm
3450 rpm/v * 3s * 3.6v/s * 80% = 30k rpm

The CS-10 needs >1kW to turn at 40k rpm, and >2kW to turn at 45k rpm.
There is an exponential factor in power-to-rpm ratio when driven at high rpm.

Accordingly, the CS-10 is much easier to drive at 30k rpm.
flylow2011's measurement and my estimate put the amp-draw at ~55A.

3s * 3.6v/s * 55A = 600W, which the 2W20 is certainly comfortable with.

There is indication this motor becomes inefficient for CS-10 if is driven beyond 600W.
So, this is the wrong motor choice for the majority here, for most pilot are looking at high-power >1kW setups.
For me, it is the perfect choice, since it achieves 90% of the performance of the HET 6904/HET 2W 3s setup, with the sweet sound.
I am not after super high speed. I like good speed mixed with some harrier. I can even go vertical from a harrier with the 2W20 CS-10.
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Old Jul 10, 2012, 03:26 AM
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Originally Posted by PeterVRC View Post
I get the same output (and input?) across all timings. 1, 7, 15, 30degrees.
The L2855 seems to be a very lenient motor that way. Though I have only run a few types that have had issues at various timing settings... almost none though.
But technically it should matter.
I got up to 10 more amps with high timing, 50F higher temps... albeit using an HK SS 90-100 ESC used on the test stand.

Quote:
Originally Posted by PeterVRC View Post
I guess I could sacrifice one 2100kv and run it on the bench for a 6S test at WOT non-stop (in a CS10), to see what happens... and when. And if it lasts... run another battery.... LOL.
And if it LASTS.... well then that was a useful test.
If it fails.... the information is far less useful in specifics. But at least will show NOT to run it at 1200W non-stop!
Been there done that. Run it on high timing for about 2 mins and got hot. Got
6S 4500 25C battery.
21.63Vm
68.36Ap
1538.74Wp
2.4Kg Thrust (Peak) - Settled 2.2Kg.

On Low timing on a Plush 80amp
6S 4500 25C
22.0V
60A
1300W
2.0Kg sustained thrust
These are not the Wattmeter statistics given at the end of the run but realtime readings taken over 2mins.


Quote:
Originally Posted by PeterVRC View Post
Though I am really looking for a 1.6Kg thrust setup for a plane, which is enough thrust for it, and the aim to keep Amps lower (than 1.8Kg uses) to get more flight time. But at the moment all I can get is either side of 1.6Kg ! Either 1.4 area, or 1.8 area.
I think I would need a 1900kv 6S, or 2550kv 5S, for that. Approx.
The 2100kv on 5S does 1.6-1.7Kg depending on the battery.
5S 4000 35C-70c nano-tech
18.5V
49-50Amps
920W
Starting 1.7Kg and down to 1.53Kg at the end of the 2min wot run.

I 've got a couple of 1860kv H2218 motors that I will test soon for low amp 6S - twin 70mm setups.
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Old Jul 10, 2012, 04:22 AM
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It is interesting what different results there can be.
For the same main setup aspects as below, I can't get 2.0Kg except on peak. And 1.8Kg ongoing, for approx 58A.
Battery specs are much the same (4000mAH 30C = 120A), but I would say mine is not coping as well as the volts are 21.3v area. Which is where the RPM, and thus thrust, are being lost. (Assuming the same motor and thus should have the exact same load situation for both our cases).
But at least comparing the two result sets, they align pretty well for those two likely battery differences.
And will be interesting to see what my 4000MAh x2 tests show.....

I'll have to go and re-test all timing settings, but I am pretty sure I ended up using 1deg because going higher did nothing of use and I figured that meant it should be wasting some power for that no gain. (tho it looked the same in all aspects to me when I recorded the first runs doing that test of all timings)

Sheesh, I will have to and video every motors various timing setting tests too!! 4x the efforts per motor!

I use HK SS series for all motor tests (eg 70A and 90A and 190A, as motors get bigger). Re-programming them is a big pain, seeing it is "option 5" you have to get to in the main programming cycle, and then the waiting for the timing value too. LOL (is there a programming card for them??)
And.... it you want to test PWM also... that is 8 tests per motor..... sheesh.

Quote:
---------------------------------------------
On Low timing on a Plush 80amp
6S 4500 25C
22.0V
60A
1300W
2.0Kg sustained thrust
These are not the Wattmeter statistics given at the end of the run but realtime readings taken over 2mins.
----------------------------------------------
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Old Jul 10, 2012, 04:33 AM
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Ooops... I did my 3350kv 3S numbers on 14.8v by the looks. Not 11.1v.
I use the base volts to get the RPM for comparisons, because it is just a comparison.
eg If 5S 2800kv 18.5v says 51k, and 4S 3350kv 14.8v gets 50.5k, that is a close enough ballpark to show they would need the same Watts. So if you knew the 5S Watts from real tests, then you now know the 4S Watts needed - as their RPM was almost identical. eg 5S 1200W, 4S 1170W or whatever.

But, 3S is if course not 14.8v, LOL.
Luckily more than one person does the maths to check!! Sorry.
And of course then the numbers make for a totally different, and usable, result.

And handily means I have a couple of 3200 to 3500 kv range motors that will work the CS10 on 3S !
Not that I really want to run 3S ever.... hehe (it makes the required Amp sourcing tougher).

PS: I have several test result sets that have 700W giving in the area of 1.2Kg, so 600W should be 1.1Kg area.
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Old Jul 10, 2012, 05:37 AM
Lee Liddle
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Peter where did you find prg instructions for the SS esc. Mine seems to have just 4 options and I can't adjust the timing or PWM.
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Old Jul 10, 2012, 05:40 AM
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LOL (is there a programming card for them??)
No. Just via the throttle channel.
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Old Jul 10, 2012, 05:42 AM
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Originally Posted by Knife Liddle View Post
Peter where did you find prg instructions for the SS esc. Mine seems to have just 4 options and I can't adjust the timing or PWM.
Lee,

see attached.

The 5th and 6th settings are really hard to get to. Have to concentrate hard since they don't sound that much different than the 4th.
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