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Old Dec 09, 2011, 01:20 PM
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Originally Posted by Andy2No View Post
I looked at that GT2820 850Kv motor on Giantcod. I noticed the one review mentioned the Xoar 14x7, and wondered if it was an AMR owner
It was an AMR owner, it was me

The motor pulls about 40A with the 14 x 7 Xoar prop and a battery straight off the charger. that's with a 35c battery so your 20c batteries would probably deliver a little less. You could use a 13" prop if you wanted which would probably take the Amps down to about 30A but i cant see any reason to do so. You don't need to use full throttle if you don't want to, but having that extra thrust there if you need it can only ever be a good thing IMHO.

Steve
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Old Dec 09, 2011, 02:14 PM
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Originally Posted by aerofundan View Post
Here is an awesome how to on the PA page for learning how to do the pushrods! It was written by Radio Rookie!

http://www.precisionaerobatics.com/p..._id=38&set=USA
Thanks. What happens if you want to move the pushrods to a different hole on the servo arm? It's not going to line up at 90 degrees any more, if you can't adjust the length slightly, but more to the point, is it physically difficult to get it out of one hole and back in another?

shadow102 / JetPlaneFlyer, I have different expectations from the plane than the majority of owners - I'm not looking for 3D. I find planes feel underpowered if I can't get the pitch speed I want, but I'm quite happy flying planes with only 2:3 thrust to weight ratio. My Hyperion Sniper is the only plane I own that's capable of prop hanging as it's set up, but I still don't actually do it.

I see choosing a prop as being like having to choose just one gear to drive your car in. First or second gear might be an exciting choice, but not very practical if you want to go faster, and not great for fuel consumption... I guess this means nothing to americans because they mostly have automatic gearboxes

I have a 1.3m Ultrafly balsa decathlon which weighs nearly as much as an AMR and I use the 2200mAh 20C lipos in it, with a 100g 1000Kv motor and a 10x5 prop. It doesn't feel underpowered at all, to me. It feels a bit too fast, actually. I've thought about trying a slower motor in it so I can use more of the range of the throttle stick comfortably, and get a longer flight. I get about 5 and a half minutes, down to 3.8V per cell on landing, unless I do some gliding. I forget how much current it's drawing but I'd guess around 20A, maybe a little more.

My Parkzone Trojan is a bit lighter, and I've propped it for about 15A. That does feel a bit underpowered but I think it's more about the pitch speed than the thrust. On the other hand, it's still quite flyable and I get at least a couple more minutes out of it on the same batteries.

I'd rather have a plane set up so that full throttle won't tax the batteries, and gives me roughly the top speed I want for the plane. Plus I like to get at least five minutes of powered flight without the cells measuring below 3.8V after I land, preferably seven or eight minutes.

I never take C ratings seriously. If it's a good make of battery, it can do what the C rating says, but it still doesn't mean it's a good idea to try it too often. Also, since an ESC is really just an on-off switch that's being flicked on and off very quickly, a motor that's propped for 30A draws little bursts of 30A, even when it's averaging 15A. That still taxes the battery more than if it's propped for 20A and drawing the same average current, IMHO.

As I said earlier, I'm sure it will horrify a lot of people that I'm thinking of buying a 3D plane, then flying it more or less scale. I don't really see why not though.
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Old Dec 09, 2011, 02:27 PM
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You just remove the servo arm if you want to move the pushrod to a different hole, easy.

As for the props, each to his own but regardless of how much pitch you put on the AMR is never going to be fast, it's a draggy biplane. I guess something like a 13"x8" might be ideal for maximum efficiency and duration. Personally I cant see any reason to go smaller diameter than that, it seems like just reducing thrust for the sake of it, without any benefit. Besides, the AMR just looks so cool spinning a big prop
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Old Dec 09, 2011, 02:50 PM
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Yes, removing the arm makes sense. Thanks.

The benefit in propping it down is prolonging the life of the batteries. I have a friend with a Trojan propped for about 25A, who I guess likes to use most of that, and he has a collection of batteries which are the same make and approximate age as mine, but they're much fatter and squashier Mine still look new.
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Old Dec 09, 2011, 03:04 PM
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Well whatever 'floats your boat' but deliberate propping down so you cannot exploit the potential of top notch hardware seems akin to me to buying a Ferrari and putting a block of wood under the noise pedal to stop it going over 30mph

But its a free world and whatever way you fly it I'm sure you will find the AMR a nice plane. I often just cruise my AMR around on a whiff of throttle, it's very relaxing. But it's still nice to have the power there if and when you want it.

Steve
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Old Dec 09, 2011, 03:14 PM
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running a hacker a30 14L with a 13x6.5 prop just puttering around flying a pattern i can get around 7minutes on a 2200mah 25c turnigy pack. Its flies great this way and is extremely smooth, if i do get into a hairy situation the punch is always there and hard aerobatics/3d is just a switch flip away. I think putting a bigger motor in the plane or severely proping down will cause flight issues on the plane, like i said i have tried it on a 12x6 prop and it was very throttle sensitive from not having the thrust to move the plane around.

btw there are a large amount of americans who refuse to drive anything but stick...my first car was the only automatic i have ever owned
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Old Dec 09, 2011, 03:37 PM
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Did you happen to measure the current with the 12x6, shadow102?

I'm glad to hear not everyone there drives an automatic
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Old Dec 09, 2011, 03:39 PM
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no, dont have a watt meter yet it was being run on a 35A ESC without issue though, i have since changed that setup and am awaiting a new esc to put in so i can test it after i do that.
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Old Dec 09, 2011, 03:55 PM
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I find a watt meter is a very useful thing to have, and they're pretty cheap considering how much they can save you in puffed up batteries and burned out motors and ESCs.

I'm debating whether I should get a 60A ESC, going by the rule of allowing 50% more current than the motor is rated for. It seems a bit unnecessary when I'm not planning on going that high though. A 40A ESC should be enough, I guess.

I'd be happier with the higher current if I could fit bigger batteries in there, but I guess space is limited, plus I'd have to spend more money on buying batteries.
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Old Dec 09, 2011, 04:05 PM
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yeah your not going to get much bigger than a 2200 in there. A 40 amp esc is more than enough, i am putting a 50a ZTW esc in mine only because the 50a and 40a weigh exactly the same and its not too bad to have the extra head room.

Watt meter is on the way already
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Old Dec 09, 2011, 04:21 PM
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Good. Thanks. I normally buy Hobbywing Pentium ESCs, and the 60A one is 23g heavier than the 40A.
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Old Dec 09, 2011, 05:28 PM
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For ESC's the ZTW is the way to go. The 50A one is 23g, compared to 40g for the 40A Hobbywing. ZTW is sold under various different labels, Black mantis being one: http://www.giantcod.co.uk/black-mant...-p-403889.html
I'm using this exact ESC, it works fine.

BTW....Hacker, Extreme Flight and indeed, Precision Aerobatics, all (to the best of my knowledge) sell ZTW ESC's, re-labelled with their own brand name (and price tripled!)

As for batteries, thickness is the main restriction. I've flown the AMR with a 3 cell, 3000mAh, 25c nano-tech. it fits in fine and for sports flying and regular aerobatics performance is unaffected by the extra 50g.. I'm not a good enough 3D pilot to say if the weight makes any difference in that discipline, but i suspect very little if anything.

Oh.. i have done the cross member modification to improve battery access, but that's recommended even for the 2200mAh.

Steve
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Old Dec 09, 2011, 06:52 PM
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andy2no, I used to use a 13x7 on my AMR and found it suitable to my flying style. It was enough to punch out of a hover, and do what I wanted, and kinder on the batteries. I would suggest getting a couple of sizes to try and see what suits your own flying style best.

The 14x7 however is awesome power on this plane.
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Old Dec 09, 2011, 08:42 PM
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FYI there is a green parts AMR in the classified. I saw wings n cockpit. I think he's asking $75 + shipping
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Old Dec 09, 2011, 09:48 PM
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Quote:
Originally Posted by Andy2No View Post
Did you happen to measure the current with the 12x6, shadow102?

I'm glad to hear not everyone there drives an automatic
We only have manual transmissions in our family, here in Canada, although I'm still in LA till Sunday. Have a 14 x 7 in my AMR and a 1.3 Nanotec 4 cell, seems to have enough power when needed. Looking forward to flying it in a few days, weather permitting of course!!!!

John
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