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Old Nov 25, 2012, 11:29 AM
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Thanks DB, I was shocked at how long she flew. I was running 2x2650 mah 3s Skylipos in series. When I put them on the charger they where around 3.8 volts per cell. Throttle was pretty mixed. It was really windy that day, but helps out a lot on takeoff and landing. Couldn't get RCSPEEDO to pick up sound so not sure how fast she is. I think to prop version is faster though. I may get a flight in today. If so, I'll turn the heat up some... Was just getting the feel of het on the last vid.
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Old Nov 25, 2012, 11:42 AM
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I didn't check the amps /watts with the Wemo.rotor, but the HET rotor with the.2w-25 was 69.1 amps and 1524 watts. The Wemo should be a bit less amperage. I've soldered my serial connections so it is now impossible to connect my watt meter.... With Dean's connector anyways..
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Old Nov 25, 2012, 12:49 PM
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Correction, the batts were down to about 3.5 volts per cell. They took 2400 mah to charge. The first ones were from maiden flight....
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Old Nov 26, 2012, 04:32 PM
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USA, CA, Long Beach
Joined Jan 2009
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Het komet timing

hello,
I was flying my Komet with HET 2W -18 with 80 Castle Phoenix
& Blue Lipo 4S 3000 mAh . Readings: 880 watts 67 amps.
It flew OK.
I wanted a little more speed so i switched to a 4S 3300 mAh NanoTech Battery and got 1112 watts 80 amps (static)

problem is i get lot's of surging and an uneven RPM 'acceleration' and then ESC shuts off.

Castle said i seem to be going over 320,000 computations per minute,53,000 max rpm and This is throwing timing off.

If i get a Hobbywing ESC which claims 70,000 RPM for 6 pole motor might this work? anyone tried this?

other than getting a lower KV motor or lower C rating any suggestions?
i know i am pushing it but will use throttle management.

thank you.
pg
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Old Nov 26, 2012, 04:47 PM
chuck
santa barbara, CA
Joined May 2009
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Quote:
Originally Posted by plainguy View Post
hello,
I was flying my Komet with HET 2W -18 with 80 Castle Phoenix
& Blue Lipo 4S 3000 mAh . Readings: 880 watts 67 amps.
It flew OK.
I wanted a little more speed so i switched to a 4S 3300 mAh NanoTech Battery and got 1112 watts 80 amps (static)

problem is i get lot's of surging and an uneven RPM 'acceleration' and then ESC shuts off.

Castle said i seem to be going over 320,000 computations per minute,53,000 max rpm and This is throwing timing off.

If i get a Hobbywing ESC which claims 70,000 RPM for 6 pole motor might this work? anyone tried this?

other than getting a lower KV motor or lower C rating any suggestions?
i know i am pushing it but will use throttle management.

thank you.
pg
my guess is yes , if thats what's happening. have u checked the voltage under load compared to the lvc setting? 80 amps is a serious draw on that size battery, imo.

chuck.
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Old Nov 26, 2012, 06:16 PM
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plainguy's Avatar
USA, CA, Long Beach
Joined Jan 2009
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battery can handle it for a bit. the weak link seems to be the ESC
i am hoping someone can share their experience with similar set up.
reading past links no one seems to be pulling that kind of amps.
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Old Dec 02, 2012, 03:23 PM
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Australia
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Dump the CC and get an HW 80A esc, far superior, the fets are way underated, I use one on the bench to build and balance fans, running it at up to 100A up and down the throttle range dozens of times, it gets too hot to touch but powers on, 2 years now with the same ESC on the bench.
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Old Dec 02, 2012, 10:41 PM
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plainguy's Avatar
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Joined Jan 2009
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Thank you very much for confirming my suspicions.

Should i get the HW 80 A Pentium or the HW 80 Platinum?

Pentium is smaller and lighter but Platinum has heat sink.

could you confirm setting recommendations?

again, most grateful.

raul
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Old Dec 03, 2012, 04:58 PM
Extreme CNC Alloy EDF
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Pentium more than enough, low timing, highest cutoff, brake off, thats all you really need to worry about.
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Old Dec 03, 2012, 11:39 PM
chuck
santa barbara, CA
Joined May 2009
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Quote:
Originally Posted by Extreme_RC View Post
Pentium more than enough, low timing, highest cutoff, brake off, thats all you really need to worry about.
interesting, we always use the lowest cutoff possible. here is the thinking: we never go to lvc and in the odd event that something might cause us to get in that lvc area i would rather ruin a battery than have the plane go deadstick at the least opportune moment. so far i havent had to try out the theory yrmv.

chuck.
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Old Dec 04, 2012, 05:36 AM
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I watch people kill batteries every week because they dont set the LVC high enough, modern lipos will hold their voltage until 99% depleted, all you are doing is screwing yourself, setting highest cutoff (3.1-3.3v per cell depending on ESC) and hard cutoff means the motor cuts when you hit LVC, you close the throttle and start her up again at mid levels, come round and land, gives you that reserve in the pack that would often not be there were the cutoff too low. Also makes the packs last a lot longer especially the cheap ones.
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Old Dec 04, 2012, 09:45 AM
chuck
santa barbara, CA
Joined May 2009
4,019 Posts
agreed, the lvc is a good tool for those who dont put in the time to figure there timer setting correctly, but imo most esc's dont have a high enough setting for high amp draw systems anyway.

i have thousands of flights and have never over discharged a lipo except when i forgot to unplug it after a flight

chuck.
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Old Dec 04, 2012, 03:50 PM
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Australia
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Yup one thing the ESC manufacturers have not kept up with is the ability of current lipo cells to hold voltage until they are 95% discharged. 3.3v per cell would be a nice setting these days, 3.1/3.25/3.4v setting options would be great.
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Old Dec 05, 2012, 03:05 PM
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thank you extreme_rc for your great help.
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Old Feb 09, 2013, 08:12 PM
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I've been having a great time flying my Komet.
with HET 2W-18 3650 KV and Hobby Wing pentium ESC.
plane flies and sounds awesome.
unfortunately I keep blowing the 70 mm Skyworld rotor after about 6 flights or so.
I've had good landings. kept clean intake, balanced rotors smooth. Good sound, good performance.
All i can think is that rotors can't take the power. (I've replaced twice)
Any other fan out there that's similar or better characteristics . I hate to say it by the Skyworld sounded better... more woosh, less whine, and faster than wemotec.
but i want a good system that wont blow up every few launches.

thanks.
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