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Old Sep 01, 2011, 04:31 PM
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New guy here, have a few questions.

Hey guys, I'm new here. (you can just skip the boring introduction and scroll down to my question lol) I decided to start flying my planes again and finish building a 31 year old unfinished plane my father once started.
I have a Carl Goldberg anniversary edition Piper J-3 with a .46 engine, I had this one for 12 years and it never let me down. I must have crashed it over 7 times and it's still perfect. I'm going to cover it again.
I also have a Chinese made Cessna 182, complete piece of crap. As soon as it took off the wing snapped. That one has a .40 engine and is being repaired.
I have a glider too with an electric motor, in case you need it. Haven't flown it yet.
I also had a few trainers which I crashed and destroyed lol.

And this plane. I can't remember what it's called. Acrobat something. My father built it when he was 17. He never was able to fly it because he couldn't afford an engine or servos and it stayed forever in my grandfather's house until a couple years ago that I took it home with me.
The wings and fuselage are already built. I just need to put the electronics, an engine and cover the wings and a few finishing touches.

So here comes my question. I have a barely used .40 engine (remember the Cessna?) that I could put in it. I pretty much have everything to have it flying but I'm tired of petrol engines. I want to make it an electric plane.

What brushless motor would you recommend for it? I don't want to over power it. The balsa wood has dried over the years and I don't want to over stress it. I want an engine with enough power to fly without worries.
I don't want an expensive engine either, the cheaper, the better but I don't want bad quality one either.

Oh and what battery would you recommend me for it?

Thanks and sorry for the long intro lol.
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Old Sep 01, 2011, 11:04 PM
volare est vivere
ray foley's Avatar
United States, OH, Toledo
Joined Jan 2005
2,050 Posts
hi there from Toledo

for a 40 size airplane, an Axi 412018, an 80 amp speed control, a 5s lipo 4000mah, an apc 15x8 eprop, a longer LG. This will give about 700 watts or so and is a known great package for this size airplane.

There are chinese knockoffs for fewer $$, caveat emptor.


ciao -rjf
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Old Sep 01, 2011, 11:04 PM
2 no or knot 2 no!
BC, Canada
Joined Sep 2009
765 Posts
No expert advice from me, but seeing as no one else is replying I suspect that this motor or something similar would be a good choice.
http://www.hobbyking.com/hobbyking/s..._AXi_2820.html

add a 40-50 amp esc and 2200 mah lipo and 11x6 prop and go from there.

Perhaps you could add more info such as wing type/span and wieght of airframe.

After reading the above post ( lol same time) MAYBE THE NEXT SIZE UP MOTOR MIGHT BE A BETTER (oops caps) idea.

they say Suitable for the following model weights;
Trainer: up to 2.6kg
Warbird/Sport: 1.8kg
3D: 1.5kg
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Old Sep 02, 2011, 08:03 AM
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Thanks for the help guys!
What do you think of this motor with this esc?
http://www.hobbyking.com/hobbyking/s...r_55_64mm.html
http://www.hobbyking.com/hobbyking/s...ontroller.html
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Old Sep 02, 2011, 08:19 AM
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Richmond, VA
Joined Oct 2009
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Quote:
Originally Posted by QTRPILOT View Post
Thanks for the help guys!
What do you think of this motor with this esc?
http://www.hobbyking.com/hobbyking/s...r_55_64mm.html
http://www.hobbyking.com/hobbyking/s...ontroller.html

That is a motor for an EDF jet. It will not work for your purposes. The KV is too high.

If you provide a little more information people can be more helpful. What is the wing span and weight of the plane you want to fly? Is it a tail dragger? Is it a Sport Plane, 3D plane, something else? What is the prop clearance?

A picture would also be helpful.
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Old Sep 02, 2011, 08:40 AM
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Ware, herts. U.K.
Joined Sep 2008
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Also where are you in the world?
Links are fine but postage can be a killer if you live across the water (as I do) in UK.
There may be other outlets that can supply quicker.
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Old Sep 02, 2011, 09:00 AM
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I live in Qatar (middle east) no problems with shipping for me from the U.S. or the U.K.
I'm a pilot and can have them shipped to my hotel.

Sorry, should of given more info.
Wingspan is 46"
Fuselage is 35"
It's a tail dragger, sport plane. I will do some basic aerobatics with it but not too much. The plane is 31 years old and the balsa wood is pretty dried up. I don't wanna push it.
I believe it's made for a .40-.46 glow engine.
I'm not sure about weight.

Here is what I'm working with.

The motor Ray Foley recommended is a bit pricey for me.
And the one tmb55 recommend is in back order.
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Old Sep 02, 2011, 09:00 AM
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QTRPILOT: if you can give us the approximate weight of the airframe, the wingspan and chord (or wing area) -- we might be able to give a better recommendation for the power system. The Turnigy 35-42 recommended earlier is probably good for a sport flyer up to maybe four pounds or so.
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Old Sep 02, 2011, 09:07 AM
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Quote:
Originally Posted by rafe_b View Post
QTRPILOT: if you can give us the approximate weight of the airframe, the wingspan and chord (or wing area) -- we might be able to give a better recommendation for the power system. The Turnigy 35-42 recommended earlier is probably good for a sport flyer up to maybe four pounds or so.
I'm going to take it to my neighbor's and weigh it, my scale is broken
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Old Sep 02, 2011, 09:18 AM
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Okay just weighted it. As seen in the picture above, it weighs exactly 600g. The wings weigh 240g and the fuselage 360g.
Landing gear weighs 100g. Still got to add the weight of the ailerons and rudder and the weight of the wings once covered. So approximately 800g fully assembled without electronics?
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Old Sep 02, 2011, 10:04 AM
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Richmond, VA
Joined Oct 2009
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Ok, that is pretty light.

Here are some thoughts. A 70 gram motor on 3S should do it. Your KV should be around 1000 to 1100. Here are some options. I would only go to the heavier motors if the lighter one turns out to be underpowered.

A Torque 2830T/1095 or Torque 2818T/900 would do nicely with a ~35 - 45 amp ESC.
http://extremeflightrc.com/html/torque.html



An Omega 72 or Omega 103 with 35 - 45 amp ESC.
http://www.3dhobbyshop.com/Omega-103...r_p_15516.html
or from here
http://www.adchobbystore.com/Omega-1...tor_p_257.html


Hacker A30-28S or A30-16M with 35 amp ESC
http://www.aero-model.com/Hacker-Bru...30-16M-V2.aspx
http://www.aero-model.com/Hacker-Brushless-A30-28S.aspx
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Old Sep 02, 2011, 10:22 AM
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Australia, ACT, Kambah
Joined Feb 2001
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if it was made for a .40 glow, I'd expect balance problems with a 70g motor. It looks like a fairly short nose model, so not much room to get batteries forward etc

A Turnigy G32 - in stock and $30 weighs about 220g, still a bit less than a .40 glow with muffler and throttle servo but in the ballpark.

On 3 cells and a 12x10 it drags my 4+lb Kadet LT-25 very nicely. If you couldn't fit a 12" prop, it would work well on 4 cells with as small as a 10x6 and still generate around 5lb static thrust - heaps for what you want to do
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Old Sep 02, 2011, 10:37 AM
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Good point about balance although it seems awefully light to have been designed for a .40 glow.
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Old Sep 02, 2011, 10:39 AM
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Ware, herts. U.K.
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Okay, so you're probably going to land up with a plane weighing between 4.5 and 5 pounds - so multiply by 60 for a gentle sport / scale sort of performance and we arrive at a minimum of 300Watts power required.
So we're looking for a 400W motor (to give a safety margin) which puts the Turnigy mentioned above in the right area.

It so happens I was testing a similar motor (rebranded Turnigy) for a friend yesterday so I'll give you the results here...
http://www.giantcod.co.uk/xyh3548-11...-p-403281.html
I have just bought four of these for my next build and they have quite a high kV (revs/ volt applied) so can run on less LiPos.
On 3S the current was 43A on a 10" x 6" wooden prop and 37A on a 9" x 7", but it is revving very high and a propeller is more efficient (creates less drag and so on) at lower revs, so I then tested it on 2S batteries and could then run a 12" x 8" wood prop with current drawn 38A.
This would be a more useful setup than having a small prop screaming in your ears, but the current is a little close to the 40A limit so you may wish to drop the prop pitch to x 7".
This was the ESC I tested it with...
http://www.giantcod.co.uk/speed-cont...-p-405366.html

When looking at ESCs the word OPTO refers to a decoupling system used in the unit and means that you will need to purchase a separate BEC if you use that sort of ESC. for 2S or 3S setups an integral BEC is fine. Only for 4S and above does the heat given off by the BEC system cause a real problem dictating an OPTO ESC.
As has been mentioned though, with these cheap items quality control is non-existant so you may just be unlucky and get a dud. I always figured at that price give it a try though - it's not a lot to lose if you do get a bad one.

Because this motor has a fairly high kV you can afford to have a higher capacity battery as it only has two cells...
http://www.giantcod.co.uk/loong-tipp...-p-404445.html

Hope this is helpful.
Have fun - and enjoy your shopping!
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Old Sep 02, 2011, 10:49 AM
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Okay I did some testing with some weighs and the centre of gravity is too far back with a 70g motor.
The Turnigy G32 seems to be the best match so far. I can fit a 12x10 propeller with no problems. If I need a bit more power I can switch to a 4 cell battery, right?

Is the ESC I posted any good? Or should I go with a 60-70A esc rather than a 55A?
Sorry for all the questions, I know about glow engines but don't know anything about brushless.
http://www.hobbyking.com/hobbyking/s...ontroller.html

Thanks for all the help so far!
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