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Old Jan 30, 2013, 01:41 PM
chuck
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sounds familiar , i posted exactly that a ways back. now given the motor is balanced , all the other issues will show up motor balance is a must, but fine tuning beyond that will bring all the other deficiencies into play.

chuck.
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Old Jan 30, 2013, 02:10 PM
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Re Locktite
I have used it to secure the motor shaft to the inner race on another outrunner and had good results. It eliminated the play and made balancing more predictable. This 2855 shaft play doesn't seem too bad though. With the smooth running motor, clocking the fan, then the spinner gets it running pretty good. I needed two drops of thick CA inside the spinner to make it perfect.

I have been experimenting with twin 10 blade fans running 2855 2100kv motors and was pleasantly surprised with the amp draw. The combined draw was 108A/2350watts with a full single 6S 25C 5500mah battery dropping to 100A/2000watts. A single fan drew much higher current (over 65A) which this motor wouldn't take very long but the 50A range (twin setup) seems promising. More testing needed before committing them to an airframe.
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Old Jan 30, 2013, 04:54 PM
Life begins at transition
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Now you're talking true dynamic balancing! Weight in two planes, not just one.

The 6s setup sounds great, I'm looking to stick that in a FW Su35, but using the stock battery. That's almost perfect...
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Old Jan 30, 2013, 05:20 PM
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I ran twin L2855-2100's in an Su-35 on 6S 5000 & 5800 30C.
Both fried in short order.....
It was around the 100A area or so in total.
But say 55A at 22v is 1200W and THAT is the issue.... too high a power for them.

But I use the 2300kv's in numerous jets running from 43A to 55A areas, and they have all lasted long term. That is on 5S though, so the power total is less than the 6S was.

The main issue is the "keep it under 1000w"... pref to 950w area. Which 5S does perfectly with these in CS10/12s.
Amps.... something about "keep it under 60A area"... pref 55A area.

You can somewhat limit that power total via battery C, and/or (even better) ducting restriction. eg 5S Vampire 2300kv will only run 45Amps due to its ducting restrictions.

The L2855's are not up to powering the Su-35 adequately. In any cell count form.
Use some decent inrunners for that (6S 2200kv etc)
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Old Jan 30, 2013, 06:49 PM
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Quote:
Originally Posted by PeterVRC View Post
I ran twin L2855-2100's in an Su-35 on 6S 5000 & 5800 30C.
Both fried in short order.....
It was around the 100A area or so in total.
But say 55A at 22v is 1200W and THAT is the issue.... too high a power for them.

But I use the 2300kv's in numerous jets running from 43A to 55A areas, and they have all lasted long term. That is on 5S though, so the power total is less than the 6S was.

The main issue is the "keep it under 1000w"... pref to 950w area. Which 5S does perfectly with these in CS10/12s.
Amps.... something about "keep it under 60A area"... pref 55A area.

You can somewhat limit that power total via battery C, and/or (even better) ducting restriction. eg 5S Vampire 2300kv will only run 45Amps due to its ducting restrictions.

The L2855's are not up to powering the Su-35 adequately. In any cell count form.
Use some decent inrunners for that (6S 2200kv etc)
Peter,
Can you tell me what ESC settings you had in the pair of motors that fried on 6S? Was it with 10 blade or 12 blade fans.

Also, did the ESC's fry too? What rating were they?
Thanks Eric
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Old Jan 30, 2013, 08:03 PM
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It would have been 'high' settings. Probably 15deg. In CS10's... stock plastic housing, seeing you can't even really use them in alloys in any easy manner (machining required).
I pre-test everything... timing made no difference to power or amps. Or at least negligible and didn't warrant detailed stuffing around with. I start at lowest (1deg) and move up through them to check motor smoothness etc (and PWM) and 15deg seemed best to me.

One motor lasted one flight... the other about three flights.
The thrust in the Su-35 with these 2100kv's is nothing great. They are just a bit weak, even when they are surviving. And if you had to run them at lower power, somehow (via airflow restriction) it would just get more lack lustre of course.
It did fly fine enough, at that 'ducting as it comes' power level.. but fried them. You really want more like 2000W at least, towards 2200w.... or more for spread freaks, LOL
To do this reliably and efficiently you are then heading to HET, Leopard, Tacon, DrMAD, CyclonePower 2200kv motors that can do it with reasonable ease and give what the 2200kv can theoretically give. (So it has a pair of HET 2W30's in it now)

Sheesh.... I guess I would have to go an re-video the motors bench tests with every test combination of Timing and PWM! To have proper records of EXACTLY what each of those really does. Recharging the common battery for every test.... sigh. hehe
I do happen to have a ready to go L2855-2100kv CS10 lying around..... (was for 5S in something, but not enough power for what I wanted - so back to a 2300kv in that).
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Old Jan 30, 2013, 08:12 PM
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Hi Peter,
I'm still wondering if you perhaps fried the ESC's (first) along with the motors? Also wondering if it was 12 blade fans or 10? I'm seeing about 7% higher draw with the 12 blade vs 10. I am also running low timing to keep draw low as possible. Not loolking for a powerhouse, just something that is happy with 6S around 2000w (total for 2 fans). The ESC's I'm running are 100A red bricks which seem pretty adequate so far.
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Old Jan 30, 2013, 08:27 PM
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No... my ESC's were both fine. Only the motor fried each time. (Smoke and wrecked windings). Which maybe was lucky it was just that too!? Went OC and didn't bother the ESCs I guess.
(Though my atrocious 'no power' glide in - which would have been totally fine if done better! - ended in a tip stall, crash, from about 10ft up still. DOH).
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Old Jan 30, 2013, 08:31 PM
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At 1000W each... irrespective of timing, it is just power.... they won't be happy.
I would say in the 'grey area' of might survive ok, but is above the 'safe area' which is sub-1000W and more like 950 to 900W range.
And even then, that higher power area is only at WOT, so it would depend on how much you use that, and how long.
Though even my 'assessments' come largely from planes using them long term successfully... and those are 90)W WOT area, but not used at WOT all the time either. Though one I did a lot of WOT % for a long period (many weeks)... 5S 2300kv 900W area. And that one is still going fine! (I use a lower WOT % these days... to keep batteries happier!)

I took off (WOT of course) and came back from a "U", still WOT all the way.... maybe 30secs? Then a smoke trail ....
So that first one didn't last long at all in length of flight terms. But it would have been bench tested before too... and also some in-plane thrust testing. So X minutes of WOT probably.... 5mins in total?
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Old Jan 30, 2013, 08:41 PM
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Thanks Peter,
Was it 12 blade or 10 blade fans? Will likely test a pair to destruction, as they are no use to me unless they can take 6S.
Cheers Eric
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Old Jan 30, 2013, 09:13 PM
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10 blade
But I got identical result in the 2300kv from the 10 and 12 blades.
Maybe that is a 'fluke' occurrence if you use a motor that is nearing its limits? But a more adequate motor might show fan differences better.
If anything the 12 is likely to be a bit more load by its LOOKS..... which is not very technical or objective, LOL.
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Old Jan 31, 2013, 04:29 AM
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Been reading this post for some time now and appreciate all the info! It has helped me achieve a sweet flying bird, Exceed F-18/ CS 10/ HET 2W25/ Efflux shroud/Hobbywing platinum Pro 80amp esc/Skylipo 4s 40c 3000. Took my time balancing it all and modified the ducting(which took away a lot of the "Woosh" but now has impressive vertical, more build pics in my blog and heres the maiden, Thanks again to everyone!

http://www.youtube.com/watch?feature...&v=RNrJuSbmXC8
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Old Jan 31, 2013, 06:02 AM
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Quote:
Originally Posted by PeterVRC View Post
....The L2855's are not up to powering the Su-35 adequately. In any cell count form.
Use some decent inrunners for that (6S 2200kv etc)
How heavy is the Su-35?

2 x 2300kv L2855s on 5s 40c packs = ~ 7.5 8lbs total static thrust... ~2k watts

Turnigy L2855-2300kv - 5S - CS 10 Blade Test (2 min 11 sec)
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Old Jan 31, 2013, 06:19 AM
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6-7lbs for most, around 12 for Pete's flying Tankski!

I'd like 3kw, so it's good to know the L series aren't up to snuff. I much prefer inrunners, but at least now I have an idea what kv to hunt for.
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Old Jan 31, 2013, 06:20 AM
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OMG, a sad end to a test that was looking pretty good here tonight.....

I dug out my Turnigy XK2850-2060kv inrunner to set it up in an ExtremeRC alloy housing to run on 6S. I had balanced and bolted it all together a few days ago and ran it up just for balance tests..... all was good.

Tonight I started on a 'lowly' 6S 3000mAH 20C (!!) (just 60A "capable") to see how that would cope for use in a plane.
63A 20.7V (!) 1308W and 1.8Kg Thrust... slowly fading, but initial peak was over 2.0Kg! 45 secs later and I stopped it to check the battery temp.... just warm, so that was good (considering its duress really). The motor at 50degC but climbing, in post run heat soak.... it got to 60degC and that was it - I didn't cool it down as I wanted to see what it did get to, but I would then have run it slow if it went over 60degC. But that was the max temp seen.

I was very happy with that test!! A cheap combo for good power! Though it would need a bit more testing to verify the battery coping (heat etc).

So next was to test with a 6S 4000mAH 30C (120A "capable"), which is a far more capable battery for the job. But bigger and heavier too!
That test did not get too far.....
The numbers were very much the same as the 20C !! Just a fraction better - but I expected it would maintain better power... less 'fade'....

Just 3secs into the test there was a major failure!!! Though I am not sure what CAUSED the problem for sure.

Grrrrrr, bzzzzzz. pfttttt..... smoke......

So far I cannot confirm the ORDER of what happened.
Immediately after the main 'noise' process, the rotor "fell" off.... it is in a vertical test stand.
The shroud has a 'burnt plastic' ring around it from the fan blade ends.
The rotor nut was on the ground nearby.
The motor is fried and 'catches' if you try to turn it.
Nothing else is loose (motor screws, shaft adaptor screws).
I DIDN'T put loctite on the rotor nut.... which may or may not even matter in this result really... I am not sure. But it meant the nut could undo.

The way a motor and fan spin makes a nut do up tighter, not loosen.
But if a fan 'suddenly decelerates' then its rotation direction then makes it 'drive' in the direction to try to undo a rotor nut.
As far as I can see this situation would not happen unless there was some reason the motor slowed dramtically in the first place - and the rotor 'keeps going', thus driving the nut loose(r).

The 'plastic burn' on the housing is right in-line with the rotor being on in its normal position.... HUH???

Checking the video, in 2.5secs it hits 86A 22.1V 1900W 33,240RPM 1.9Kg thrust then it goes to crap! Noises.... a jump to 122Amps(!!)... rapid deceleration and numbers drop, and the rotor falls off.

I reassembled it, to check things, and the fan is still dead centre and equal clearance all the way around.
If not for the smelling burnt, and notchy motor feel, it would be as per normal... it rotates centrally and all correctly.
If the motor shaft was bent, that would explain it.... but it isn't.
To get the 'plastic burn', at the fan fitted position, means it must have hit the sides whilst STILL in its correct position on the shaft adaptor. And that would jam and then fry the motor.
But HOW did it do that if all is fine checking things now!!???

Every blade seems to have approx 1.5mm clearance as of now... and that was what it was like before really.
To me it seems most likely that "1.5mm" is NOT ENOUGH blade clearance when it runs to 2.0Kg initial thrust area... ???..... and that was 34k RPM area..... the fastest I would have run a CS10 in this shroud ever I expect.

Note that even though the KV meter is set for 2 poles (which is really for a 4 pole motor), and the RPM seem about the right area versus selecting 1 pole or 3, which then are no way near correct numbers reported.... I am never convinced it is truly correct! 2.0Kg Thrust area... wouldn't that need more towards 40k RPM area?? So I would take that 33,240 RPM number with a grain of salt.

...
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