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Old Mar 04, 2011, 11:05 AM
wac
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Joined Jun 2005
1,364 Posts
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X8 is only flying for 5 minutes, is this right? Maybe some help with numbers?

Hi All,

I just recently built an X8 with rc timer 2836-11 motors with 12x3 apc props and seem to have pretty low flight times.

Yesterday i flew with one 4x 5000mah pack and it gave me 5:35sec before it had no more power to fly, and i charged that battery back up with 4015mah.

I was planing on using 2x 4s 5000mah packs but im thinking that will only give me at the most 10minutes and i was hoping for at least 12-15min.

Are the short flight times im getting normal?

Here are some stats from my watt meter

Lowest voltage 14.06

Watt-Hours Wh 1646.2w

Amp -Hours Ah 4.785

Peak Watts 71.35w


Thank you
Bill
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Old Mar 04, 2011, 11:11 AM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,249 Posts
Hi Bill,
You are definitely experimenting here. Are the upper and lower rotating in the same direction? What is your AUW? 3s or 4s? Perhaps APC1365 props are a better match? How old are your lipos and what is the C-rating? Some Gents were using APC1365's on similarly sized Pulso motors getting only 4 minutes on a 4.5kg hexa using a 4s 5000mah c-rating? lipo putting 3200mah back: http://www.rcgroups.com/forums/showt...1#post17048665

Cheers,
Jim
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Last edited by jesolins; Mar 04, 2011 at 11:24 AM.
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Old Mar 04, 2011, 02:55 PM
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United States, CA, Orange
Joined May 2007
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i think you're pushing these motors hard with 4S and 12" props, try a 3S or prop down to 10"
i personally would try 2 x 3S 5000 with 12"
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Old Mar 04, 2011, 02:58 PM
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Looks like motor's KV is too high (1100). I got 16 min hover with 4S5000 quadro from MK with DT750. What is the weight?
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Old Mar 04, 2011, 03:02 PM
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Quote:
Originally Posted by AlcoNaft43 View Post
Looks like motor's KV is too high (1100). I got 16 min hover with 4S5000 quadro from MK with DT750. What is the weight?
RCTimer 2836-11 is 750KV
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Old Mar 04, 2011, 05:59 PM
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It could be the props being too large, but I personally don't think so. I'm flying on these motors and I'm hitting 30 minutes hover time no problem (with a 1.5kg hexa). Here are their performance graphs with 11" props.

Your math doesn't look right - a battery with U = 14.06 V, C = 4785 mAh should have energy on the order of 67 Wh, not 1646. That's about 242,000 Ws, or 242 kJ. Now assuming your rig hovers at 71 W (which doesn't sound right either), you should be able to hover for almost an hour (E/P = 3411 s).

Or was that a per-engine figure? In that case your 5ish minutes are correct. How much does your rig weigh? Mine hovers at around 25 W per motor.
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Old Mar 05, 2011, 11:05 AM
wac
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Joined Jun 2005
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Hi Jim,

I appreciate you chiming in...

Im not sure about the overall weight but it was loaded down with 2 4s 5000mah 25c, askman pro 3 axis camera mount, 900mhz wireless video system, gopro hd camera and a canon hv20 camera (brick).. Im working the next couple days but after ill try and run down to the post office and get it weighed..

My hover is about 1 click above half throttle.. Ill try and provide some more numbers this monday or tuesday..

Thank you
Bill




Quote:
Originally Posted by jesolins View Post
Hi Bill,
You are definitely experimenting here. Are the upper and lower rotating in the same direction? What is your AUW? 3s or 4s? Perhaps APC1365 props are a better match? How old are your lipos and what is the C-rating? Some Gents were using APC1365's on similarly sized Pulso motors getting only 4 minutes on a 4.5kg hexa using a 4s 5000mah c-rating? lipo putting 3200mah back: http://www.rcgroups.com/forums/showt...1#post17048665

Cheers,
Jim
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Old Mar 05, 2011, 11:12 AM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,249 Posts
Hi Bill,
Your using the words "1 click" when you mentioned your throttle makes me have to ask if your throttle has the model plane ratcheting still on it? Most Gents do the simple mod to remove that ratcheting which a heli Tx does not have to make it easier to hold a hover. If you need help getting rid of the ratcheting, let me know and I will point you to some mod threads. FWIW
Cheers,
Jim
Quote:
Originally Posted by wac View Post
Hi Jim,

I appreciate you chiming in...

Im not sure about the overall weight but it was loaded down with 2 4s 5000mah 25c, askman pro 3 axis camera mount, 900mhz wireless video system, gopro hd camera and a canon hv20 camera (brick).. Im working the next couple days but after ill try and run down to the post office and get it weighed..

My hover is about 1 click above half throttle.. Ill try and provide some more numbers this monday or tuesday..

Thank you
Bill
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Old Mar 05, 2011, 11:19 AM
wac
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Joined Jun 2005
1,364 Posts
Hi Jim,

Im sorry but its not actually one click, its one line up from center on the throttle stick.

Bill


Quote:
Originally Posted by jesolins View Post
Hi Bill,
Your using the words "1 click" when you mentioned your throttle makes me have to ask if your throttle has the model plane ratcheting still on it? Most Gents do the simple mod to remove that ratcheting which a heli Tx does not have to make it easier to hold a hover. If you need help getting rid of the ratcheting, let me know and I will point you to some mod threads. FWIW
Cheers,
Jim
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Old Mar 05, 2011, 11:20 AM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
14,249 Posts
No problem Bill...I had to ask...
Cheers,
Jim
Quote:
Originally Posted by wac View Post
Hi Jim,
Im sorry but its not actually one click, its one line up from center on the throttle stick.
Bill
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