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Old Mar 07, 2016, 06:59 AM
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Denmark, Region Syddanmark, Odense
Joined Aug 2015
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Build Log
T960 Heavy lift dodecacopter

This build started a while ago. (I think it was last year in October)
But some stuff happened.
This should probably be able to carry like 15-20kg payload with no batteries. I am using these motors http://www.ebay.com/itm/281519696721...AIT&rmvSB=true with 1855 propellers which should give me at least 3.5kg of thrust with 22.2v
The frame is a tarot T960 COPY http://www.ebay.com/itm/T960-Multico...35f&rmvSB=true (not the real tarot because Hobbyking didn't have them in stock)
I will be using the Foxtech Pivot v3 landing gears and these ESC http://www.ebay.com/itm/221605136380...AIT&rmvSB=true
The motors will probably draw about 300-360 amps on full throttle in total so Im using this power board http://www.uavshop.co.uk/catalog/pro...roducts_id=383
All this will be powered by four 10 000 Mah making a total of 40 000 Mah.
I hope to get around 20-30 mins of flight time
The dodecacopter is about 5kg and 5kg batteries. So there should be room for 10-15 kg payload.
The copter's maximum takeoff weight should be around 25 kg on 70% thrust if the coaxial setup makes it 20% less efficent.
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Last edited by prutealex; Mar 08, 2016 at 01:44 AM.
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Old Mar 10, 2016, 08:09 AM
Cereal_Killer is offline
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United States, OH, Columbus
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Quote:
Originally Posted by prutealex View Post
The copter's maximum takeoff weight should be around 25 kg on 70% thrust if the coaxial setup makes it 20% less efficent.
This is not correct. A PROPERLY setup coax setup provides ~5% MORE efficiency than a flat configuration but you have to properly size the motors / props. Having the same IS NOT correct. You need to have a ~1" smaller diameter, and 1.5" higher pitch prop on the bottom. If that's not possible you need to spin the lower prop faster.

The inefficiency figure you mention (that I'm guessing you read here) is only if you're using the same prop / motor upper and lower which causes the lower to freewheel in the upper's downdraft. It also takes away a bunch of control authority.

Read this
http://ecalc.ch/calcinclude/help/xco...help.htm#hints
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Old Mar 11, 2016, 01:58 AM
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Denmark, Region Syddanmark, Odense
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To be honest I don't really need more thrust. But thanks for the tip.
Also got my landing gears on the copter.
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Old Mar 17, 2016, 02:33 PM
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Can you provide a source for this increase in efficiency? Having 2 props on top of each other will reduce efficiency, regardless of size and pitch. This is because they BOTH have a much larger induced drag because of the downward velocity imparted to the air by the other motor.

Quote:
Originally Posted by Cereal_Killer View Post
This is not correct. A PROPERLY setup coax setup provides ~5% MORE efficiency than a flat configuration but you have to properly size the motors / props. Having the same IS NOT correct. You need to have a ~1" smaller diameter, and 1.5" higher pitch prop on the bottom. If that's not possible you need to spin the lower prop faster.

The inefficiency figure you mention (that I'm guessing you read here) is only if you're using the same prop / motor upper and lower which causes the lower to freewheel in the upper's downdraft. It also takes away a bunch of control authority.

Read this
http://ecalc.ch/calcinclude/help/xco...help.htm#hints
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Old Mar 31, 2016, 02:02 PM
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Getting ready for maiden.
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Old May 05, 2016, 12:56 PM
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nice work!
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Old May 06, 2016, 12:19 PM
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Quote:
Originally Posted by zatorax View Post
nice work!
holy crap I thought you were gone forever.
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