Espritmodel.com Telemetry Radio
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Old Feb 24, 2012, 09:35 PM
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Joined Feb 2010
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Help!
NEW TO ELECTRIC ( wanting to convert to electreic)

ok here is my story
i have a 3D CMP Giles 202 , about 6 lbs. i see that i am to use a motor thats around 1200watts. from there i start to get stressed out and not know what to get for a battery or speed control.
i get stressed out cause with glow i throw on the engine add the fuel give her a tuning and after some flipping and a little bleeding and its started. well until you get a dead stick .
i have heard that there is something you can use so if your esc fails you dont lose control of the plane.
also the prop, the motors that i have looked at say i should use a prop thats 14 - 16 in length. that will be too big and hit the ground, so as i said im way out in left field here and would really like some help
thanks jeff
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Old Feb 24, 2012, 09:43 PM
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Canada, MB, Niverville
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Quote:
Originally Posted by Jeffreyheslop9 View Post
ok here is my story
i have a 3D CMP Giles 202 , about 6 lbs. i see that i am to use a motor thats around 1200watts. from there i start to get stressed out and not know what to get for a battery or speed control.
i get stressed out cause with glow i throw on the engine add the fuel give her a tuning and after some flipping and a little bleeding and its started. well until you get a dead stick .
i have heard that there is something you can use so if your esc fails you dont lose control of the plane.
also the prop, the motors that i have looked at say i should use a prop thats 14 - 16 in length. that will be too big and hit the ground, so as i said im way out in left field here and would really like some help
thanks jeff
You can run a flight pack to power your servos and a seperate bec to supply steady power for your RX. Could you get away with a 13" prop? If you spec it out proper and buy a watt meter, as a rule you shouldn't blow your esc unless you buy a dollar store version.
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Old Feb 24, 2012, 10:51 PM
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I'm currently reworking a PT 40 from glow to electric. In my reconstruction I have planned on modifying it to have longer landing gear. Depending on what it slings now you might be able to get away with larger wheels.
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Old Feb 25, 2012, 02:46 AM
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Letchworth, Great Britain (UK)
Joined Jul 2004
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Originally Posted by Jeffreyheslop9 View Post
... i have heard that there is something you can use so if your esc fails you dont lose control of the plane. ...
Many ESCs incorporate a Battery Eliminator Circuit (BEC) in them that supplies 5v (or thereabouts) to the receiver, converting it down from the main motor battery. The problem with that is, if the ESC gets fried, it can also kill the built-in BEC components. One answer is to use a stand-alone BEC, which still takes it's power from the main motor battery, but is unlikely to be affected by an ESC failure. Another answer is to use a standard receiver battery, just like in glow models.

Quote:
Originally Posted by Jeffreyheslop9 View Post
... also the prop, the motors that i have looked at say i should use a prop thats 14 - 16 in length. that will be too big and hit the ground, so as i said im way out in left field here and would really like some help
thanks jeff
You may have noticed that for any particular motor power (watts), you can often get many different kvs. Higher kv means that the motor will turn at higher rpm and, thus, require a smaller diameter prop. Also, higher volts also means that you'll need a smaller diameter prop for the same power output. For an example of this you can look at the AXI 4120 motors http://www.modelmotors.cz/index.php?...kategorie=4120, for instance. The /14 model (kv=660) looks like it can possibly deliver what you need with a 12x8 propellor on 5S LiPo, whereas the /20 version (kv=465) shows 15x10 for an aerobatic model.

Having said that, there's only a certain amount of watts you can efficiently get out of a certain size propellor. I don't know what the formula is, but hopefully someone will be able to chip in with it.
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Old Feb 25, 2012, 07:58 PM
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Think about motors that are rated at least 6 lbs x 150 watts. Then add 30%.

leadershobby has a Power 46 motor that can put out 1600 continuous watts, and spike to 2300 watts. hobbyking has 190-200 A speed controllers ("opto", or without the power to the receiver and servos -- use a separate voltage regulator).

4-cell Lipos will sport fly the plane, but 6 cell voltage will be ballistic.

I use a Turnigy $5 voltage regulator that plugs into the receiver with a servo plug, and I plug a 1200 mAh battery into the voltage regulator to power the receiver and servos. This power insures that your receiver will not brownout if the motor battery runs way dawn.

I think that the body on that plane will not allow the big, flat 4S Lipos, so you will have to go with the thin long ones.

I fit 2 x 5000 3S LiPos in series to get 6S power, for the nitroplanes Giles. Ballistic, but doesn't fly for very long.
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Old Feb 26, 2012, 02:13 AM
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Letchworth, Great Britain (UK)
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Originally Posted by wuest3141 View Post
...I use a Turnigy $5 voltage regulator that plugs into the receiver with a servo plug, and I plug a 1200 mAh battery into the voltage regulator to power the receiver and servos. This power insures that your receiver will not brownout if the motor battery runs way dawn. ...
Your motor will stop running when lvc kicks in at somewhere around 3 volts per cell so, if you're using 3S or more LiPo, the motor battery will be at least 9v when the motor stops. This is more than enough to keep a BEC running to power the receiver.

So, in my opinion, if you're using a separate 2S LiPo to power a BEC to power the receiver you might as well simply use a standard 1200mAh NiMh pack or A123 pack without the BEC, and eliminate the extra complexity. With a stand-alone BEC running off its own LiPo, you can still lose your radio because the 2S LiPo has run down -- and you won't get any prior warning because the motor may still be running
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Old Feb 26, 2012, 07:01 AM
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Sverige, Värmlands Län, Filipstad
Joined Jan 2009
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Hi,

What is the weight of this Gilles 202 plane ready to fly?

Since it is a taildragger You can add larger main wheels or change landing gear to higher to get better prop clearance.

I do not know but maybe a 6 cell LiPo around 5000 mAh could be enough.
Anyway try eCalc to get some values with various motors, APC Electric props and lets say 100 Amp ESC..
http://www.ecalc.ch/motorcalc_e.htm?ecalc

/Bo
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