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Old Jan 23, 2013, 05:55 PM
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Joined Jul 2011
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Stuttering Motor with a twist

Hello,
I have a scratchbuilt foam plane, about 1.2 lbs. It is powered by"

Turnigy D2826/6 2200KV
Hobby King 50A Fixed Wing Brushless Speed Controller
800mAh Turnigy LiPo, 3s
Orange 6ch RX
Spektrum DX6i

I have one flite on it. I went for about 8 minutes and then died mid-air. The plane is a slow flyer, and was not pushed hard.

Flite 1:
ESC arms properly, RX Bound to TX. I could not open the throttle above 15% as the thrust was too great and the plane becomes unmanagable. Plane was trimmed and flew mostly in lazy circles. Flite ended 8 minutes due to LVC on ESC. Crashed gently into wood structure.

Programmed ESC to make sure the correct range of throttle is inputted. No change to throttle response.

Flite 2: Didn't make it into the air. Everything armed and bound OK. Engine would get to 20% throttle. Increasing amounts of throttle beyond 20% did not increase the rpm's of the engine. Instead, engine surged and stuttered. When control input is made, engine shits off. Servos respond without problem. This was replicated several times.

The ESC is barely warm to the touch. Batteries are new and fully charged.

Any ideas? Thanks FC
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Old Jan 23, 2013, 06:30 PM
Jack
USA, ME, Ellsworth
Joined May 2008
16,925 Posts
What prop are you using? That 2200 Kv is going to call for smaller props and higher RPM, that contradicts your statement that the plane is a slow flyer.

You stuttering might be a timing issue if you are using a small prop and high RPM, it might be a voltage drop and/or over voltage protection kicking in if you are using too large a prop.

The testing data on a similar motor here at flybrushless.com shows the maximum prop sizes for that motor on 3S as being down around the 6 x 4 or so size:

http://www.flybrushless.com/motor/view/460

Jack
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Old Jan 23, 2013, 06:31 PM
Wake up, feel pulse, be happy!
C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
12,410 Posts
What prop are you using? It's every bit as important as the motor or battery, yet it's consistently left out of this type of post More details on the plane (which means 'post pics') would also help.

Your setup needs help anyway. The motor, ESC, and battery are quite poorly matched regardless of which prop you're using. I'd ask for an explanation of how you actually chose those components, but my guess is that you were just stabbing in the dark on HobbyKing and that's what you ended up with... You'll definitely want to change at LEAST the battery or motor, but an ESC swap might be beneficial as well, especially since this is supposed to be a slow flyer.

To run that battery down to the lowest safe level (20% remaining), you'd have 640mAh of capacity to work with. 640mAh across eight minutes of runtime equates to an average draw of around 4.8A. You said you didn't exceed 15% throttle, but without knowing what prop you were using these numbers are meaningless.

I would guess that the motor is overpropped, which could cause most your issues. It's hard to give accurate diagnostics without knowing all the important information, though.
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Old Jan 23, 2013, 06:32 PM
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C₄H₁₀'s Avatar
United States, AK, Fairbanks
Joined Aug 2009
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Looks like Jack posted while I was typing.... Hmmm, I think I see some familiar concepts
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Old Jan 23, 2013, 07:39 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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Great minds flounder around in the same ditches...

Jack
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Old Jan 23, 2013, 10:04 PM
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Joined Jul 2011
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Yes, the first prop was big. 11x6 (or so) by APC. I knew that it was too big when I ran out of juice so soon. Subsequent props for testing were much smaller (GWS 9x4.5 and 7x6) produced same results. Ditto for prop off test.

Yes, the engine is too much for a foamy. I had it, and it fit the plans criteria. Trying to do this inexpensively because money is tight.

Yes, the plane is a slow flyer, and calls for GWS props in particular.

I cannot speak as to why others do not include all information. As for me, I don't want to make the posts insanely long. People skip over passages/posts that are too long. Brevity is important. I figure if I left something out that is critical I would be asked.
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Old Jan 23, 2013, 10:09 PM
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Chattanooga, Tennessee, United States
Joined May 2003
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Holy smoke! a 50g 2200Kv motor (on 3s, suited to 5x5 or 6x4 max.) and you are using 11x6, 9x4.5 and 7x6!!

I give up!
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Old Jan 23, 2013, 10:23 PM
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Quote:
Originally Posted by Dr Kiwi View Post
I give up!
Give up on what?
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Old Jan 23, 2013, 11:07 PM
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United States, WA, Seattle
Joined Jan 2007
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On you.....you obviously don't understand KV and props.
Pretty much the absolute MAX size on a 2200kv motor on 3S would have been 6x4.
You are frying your electronics.
In addition your battery is pathetically small for the load you asked of it.
I suggest you don't even bother flying again until you do some studying on setting up power systems and get a wattmeter unless you like buying parts.
Trying to set up electrics inexpensively without some attention to matching components ends up being expensive.
The devil is often in the details.

Selecting Electric Power Systems
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Old Jan 23, 2013, 11:08 PM
Wake up, feel pulse, be happy!
C₄H₁₀'s Avatar
United States, AK, Fairbanks
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Quote:
As for me, I don't want to make the posts insanely long. People skip over passages/posts that are too long. Brevity is important. I figure if I left something out that is critical I would be asked.
Not around here we don't. It's generally preferable to have one long post with all the info than to sit here and have to keep wheedling it out of you bit by bit For instance, exactly which plane is it? A link would be very helpful.

The motor's specs on HobbyKing even state a 5x5 as a recommended prop for 3S operation. How'd you come up with an 11x6 for it? You might be able to use that motor with the 7x6 prop (max) if you run a 2S ~1500mAh battery, but 3S is gonna be dicey no matter how you slice it. I'd say it would be best to get a similar-sized motor around 800-1000Kv and use it with 9"-10" diameter props on your 3S 800mAh pack (assuming it hasn't been permanently damaged already).

In short, you have options. It would be a lot easier to make suggestions if we knew what plane we're dealing with... Remember, LINK, or at least pictures. Sometimes we say "What plane is it?" and get nothing but "17.6oz, 37" wingspan, 25" long, painted blue" as a response... Which doesn't work so well.

You might have started to notice by now that power systems require some care and attention when you put them together in order for everything to work right. No worries; that's what we're here for
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