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Old Feb 24, 2011, 10:26 AM
wac
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Joined Jun 2005
1,409 Posts
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Should I keep my octo or make an X8?

Hi Guys,

I just finished up my latest ship, a heavy lift octocopter and im wondering if i should convert it to an X8?

my setup is;

FCB - Hoverfly Pro
Frame- Rustys rev 7 & 8 plate mix (one level), Carbon fiber 12mm tubing
esc's - Kens Fast
Motors - Rctimer 2836-11
Props 12x3.8 APC
Batteris - 2x 4s 500mah
Camera Mount - Askman AP 360 Pro

My main problem with the current octo setup is its pretty big and not very practical for travel. From tip to tip it is 36" long and not very easy to break down.

what do you guys think the pros and cons are


Thank you
Bill
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Old Feb 24, 2011, 11:12 AM
Z06 Tony's Avatar
United States, NY, Rochester
Joined Sep 2008
7,201 Posts
I built an Octo and did not like the bulkiness and out of all the multis I have flown I like the flight charecteristics the least on the octo. Here is a vid I just shot of my Y6->
Carbon Fiber Y6 Hexacopter on 4s (4 min 24 sec)


I like the Y6 alot and you can buy a foldable Y6,X8.hexa here and they are nice and light. A little more than rustys frames though. The foldable Y6 is $270. I can say they are nice and light. I have 2 and the CF is not the same as china CF. They use more CF and less epoxy. So it is lighter and more flexable-> http://www.rchobbyhelicopter.com/sto...tom_UAV_Frames
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Old Feb 24, 2011, 12:13 PM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,713 Posts
Hi Bill,
Here are some nice foldable octo builds to consider:

Imagecatcher - http://www.rcgroups.com/forums/showp...ostcount=12785

Maximus-RC - http://www.rcgroups.com/forums/showp...&postcount=846

AZ Choppercam - http://www.rcgroups.com/forums/showp...&postcount=800

BTW, you have a typo on your lipo mah, I'm sure you meant 5000 not 500mah

@Tony,
Nice Y-6 video what board are you using?

Cheers,
Jim
Quadrocopter and Tricopter Mega Link Index
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Old Feb 24, 2011, 12:17 PM
Registered User
Gainesville GA USA
Joined Nov 2004
155 Posts
Quote:
Originally Posted by wac View Post
Hi Guys,

I just finished up my latest ship, a heavy lift octocopter and im wondering if i should convert it to an X8?

my setup is;

FCB - Hoverfly Pro
Frame- Rustys rev 7 & 8 plate mix (one level), Carbon fiber 12mm tubing
esc's - Kens Fast
Motors - Rctimer 2836-11
Props 12x3.8 APC
Batteris - 2x 4s 500mah
Camera Mount - Askman AP 360 Pro

My main problem with the current octo setup is its pretty big and not very practical for travel. From tip to tip it is 36" long and not very easy to break down.

what do you guys think the pros and cons are


Thank you
Bill
I'd be concerned about running 4s. Your motor/prop combo is good to 3s.

Model: BC2836-11
Motor size: Ф28*36mm
Shaft size: Ф4.0*49mm
Weight: 70g
KV(rpm/v): 750
Max Power: 206W
Battery: 2-4Li-Po
Test Prop: 12x6/9x6
Ri(M Ω): 0.160
ESC(A): 40A

Take a look at http://personal.osi.hu/fuzesisz/strc_eng/index.htm

Here is how I figure the RPM for the 2836-11 motors:
750KV * 14.8v * .8 = 8880 rpm (80% efficiency, I'm being conservative)

Wattage comes out to 291. Way over the rated 206W above.

Drop back to 3s and your wattage is 122.

I'm just finishing up my HF octo, same motors and props. As I get it all together, it is looking bigger than it did on paper.

Rick
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Old Feb 24, 2011, 12:39 PM
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Hamanu's Avatar
United States, MI
Joined Nov 2003
798 Posts
Z06 Tony that is a really nice looking Y6 you got there. What control board and motors are you using?


Quote:
Originally Posted by Z06 Tony View Post
I built an Octo and did not like the bulkiness and out of all the multis I have flown I like the flight charecteristics the least on the octo. Here is a vid I just shot of my Y6->
http://www.youtube.com/watch?v=V7pNh...layer_embedded

I like the Y6 alot and you can buy a foldable Y6,X8.hexa here and they are nice and light. A little more than rustys frames though. The foldable Y6 is $270. I can say they are nice and light. I have 2 and the CF is not the same as china CF. They use more CF and less epoxy. So it is lighter and more flexable-> http://www.rchobbyhelicopter.com/sto...tom_UAV_Frames
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Old Feb 24, 2011, 12:48 PM
wac
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Joined Jun 2005
1,409 Posts
Hi Rick, i didn't think that the wattage was going to be that extreme. Is the 291 at full throttle?

I think I'm going to convert the octo to an x8 and put a watt meter on one of the motors and see what's going on. If it's way to much then I might drop down to11inch props

Thank your for the info

Bill
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Old Feb 24, 2011, 12:51 PM
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Long Island, New York
Joined Jun 2008
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Hi Bill,
Don't worry about those motors on 4s, there is no problem with that combo at all. I will never go back to 3s on any of my copters.
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Old Feb 24, 2011, 01:44 PM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,713 Posts
Rick,
Not really sure what your point is. Nice calculator though Too bad they don't have a constant factor APC SF or EPP props. We need a calculator like that made specifically designed for multicopters. And here is why:

For multicopters the critical values for efficiency are wattage at the hover speed for the AUW or total flying weight. Max wattage is OK for general aircraft model specifications, not necessarily for multicopters, as we do not fly around continuously at max RPM's. For the BC2836-11 750Kv motors on 4s, yes the max rated wattage will be higher than 3s which is actually closer to the 206W listed on the www.rctimer.com site. Here: http://www.rctimer.com/index.php?gOo=goods_details.dwt&goodsid=128&produc tname= So they do work well with 3s or 4s lipos.

In operational use as measured with an EagleTree or other wattmeter we like to use watts per gram of thrust for measuring multicopter motor/prop combo efficiencies. At hover on average this works out to about 100W per motor at 14.8v and a 1.0-1.4kg multicopter. Here is an excellent link to Old Man Mike's Motor tests for multicopters: http://www.rcgroups.com/forums/showt...s#post11657593

OMM's post on motor/prop efficiency: http://www.rcgroups.com/forums/showp...ostcount=16592

Other available motor prop estimaters not optimized for hovering multicopters:
--Estimaters for electric motor and prop combinations: http://adamone.rchomepage.com/calc_motor.htm and http://personal.osi.hu/fuzesisz/strc_eng/index.htm and http://www.peakeff.com/MotorDetails....ID=2753&v=10.5 and http://www.drivecalc.de/

Cheers,
Jim

Quote:
Originally Posted by llamatrails View Post
I'd be concerned about running 4s. Your motor/prop combo is good to 3s.

Model: BC2836-11
Motor size: Ф28*36mm
Shaft size: Ф4.0*49mm
Weight: 70g
KV(rpm/v): 750
Max Power: 206W
Battery: 2-4Li-Po
Test Prop: 12x6/9x6
Ri(M Ω): 0.160
ESC(A): 40A

Take a look at http://personal.osi.hu/fuzesisz/strc_eng/index.htm

Here is how I figure the RPM for the 2836-11 motors:
750KV * 14.8v * .8 = 8880 rpm (80% efficiency, I'm being conservative)

Wattage comes out to 291. Way over the rated 206W above.

Drop back to 3s and your wattage is 122.

I'm just finishing up my HF octo, same motors and props. As I get it all together, it is looking bigger than it did on paper.

Rick
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Old Feb 24, 2011, 02:26 PM
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VA
Joined Nov 2009
2,682 Posts
There are two paths to propping a 'coptor or so I think. Overpropping and getting better efficiency at hover. Downside is load it up and you could burn out motors. If you are the only one that will operate it there shouldn't be a problem. The other path is the engineers view. Try to make it work for everyone, all the time, with no tweaking no matter what they do even strap it to a concrete pad and run it wide open and it would make no difference. I have used both methods myself just a matter of preference.
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Old Feb 24, 2011, 03:25 PM
Z06 Tony's Avatar
United States, NY, Rochester
Joined Sep 2008
7,201 Posts
The board is a KK Blue board with no accels just the board.

BTW as Tarro mentioned once you go 4S you will not want to go back to 3S. I tried 4S on my X650 and liked it so much I used the same motors on 4S with my Y6. My props are 12" Xair props.
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Old Feb 24, 2011, 03:48 PM
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Hamanu's Avatar
United States, MI
Joined Nov 2003
798 Posts
Wow thats just a KK board with no accelerometers it looks very stable what size batt are u using and whats the KV on those motors?



Quote:
Originally Posted by Z06 Tony View Post
The board is a KK Blue board with no accels just the board.

BTW as Tarro mentioned once you go 4S you will not want to go back to 3S. I tried 4S on my X650 and liked it so much I used the same motors on 4S with my Y6. My props are 12" Xair props.
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Old Feb 24, 2011, 04:25 PM
Z06 Tony's Avatar
United States, NY, Rochester
Joined Sep 2008
7,201 Posts
Quote:
Originally Posted by Hamanu View Post
Wow thats just a KK board with no accelerometers it looks very stable what size batt are u using and whats the KV on those motors?
Not sure why but Xaircraft does not list a KV rating. I am guessing about 750kv. I am using a Thunder Power 2250mAh 45C. I am waiting for the new XPS 65c to get back in stock cus all my batts are new and the Hyperion 25C batts have less punch as they should cus they are only 25C. Want to compare the TP 45C and the XPS 65C. They both have a top number of 90C so might not make a diff but they are cheaper.
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Old Feb 24, 2011, 04:51 PM
Registered User
Ironbridge (UK)
Joined Jan 2009
3,966 Posts
Quote:
Originally Posted by Z06 Tony View Post
Not sure why but Xaircraft does not list a KV rating. I am guessing about 750kv. I am using a Thunder Power 2250mAh 45C. I am waiting for the new XPS 65c to get back in stock cus all my batts are new and the Hyperion 25C batts have less punch as they should cus they are only 25C. Want to compare the TP 45C and the XPS 65C. They both have a top number of 90C so might not make a diff but they are cheaper.
yes they do Tony, you have to check the wiki here

Material:Steel, Aluminum, Copper, Magnet etc.

Weight:86.5g

Mark:850KV, 150W.

I see you cannibalised your x650 then your Y6 seems to fly really great very nice, It's made me want to build one now
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Old Feb 24, 2011, 05:40 PM
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United States, IL, Chicago
Joined Dec 2006
8,649 Posts
Quote:
Originally Posted by Z06 Tony View Post
I built an Octo and did not like the bulkiness and out of all the multis I have flown I like the flight charecteristics the least on the octo. Here is a vid I just shot of my Y6->
http://www.youtube.com/watch?v=V7pNh...layer_embedded

I like the Y6 alot and you can buy a foldable Y6,X8.hexa here and they are nice and light. A little more than rustys frames though. The foldable Y6 is $270. I can say they are nice and light. I have 2 and the CF is not the same as china CF. They use more CF and less epoxy. So it is lighter and more flexable-> http://www.rchobbyhelicopter.com/sto...tom_UAV_Frames


tony sell me your y6 :P
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Old Feb 24, 2011, 06:57 PM
Z06 Tony's Avatar
United States, NY, Rochester
Joined Sep 2008
7,201 Posts
Quote:
Originally Posted by Joshbb View Post
yes they do Tony, you have to check the wiki here

Material:Steel, Aluminum, Copper, Magnet etc.

Weight:86.5g

Mark:850KV, 150W.

I see you cannibalised your x650 then your Y6 seems to fly really great very nice, It's made me want to build one now
Thanks for the info JB. No I can afford 6 motors so I did not need to take them from the X650. Remember I have no kids. If I had a few children I would be flying 1 quad if I was lucky. Prolly with used and donated parts. All it took was 1 flight on 4s with the X650 to make me want to buy those motors for my Y6. What I like about the Y6 is no wobbling at all but not due to the FC but the motor configuration.
BTW My AHRS is messed up on my X650 and I did not crash or even land hard and it is a replacement.
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