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What does all the jargon mean???? Need help

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Old 12-22-2005, 09:04 PM
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fab4272
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Default What does all the jargon mean???? Need help

Hi All,

I'm new to electric flight and have been flying an Art-tech Cessna 182 for about 4 months now. I enjoy it immensely but would like to now upgrade the motor and battery.

It currently has a speed 480 direct drive motor (cheap can motor). I have a 3 cell li-po, but how do I work out what sort of brushless to buy? What sort of brushless motor, what does xxxxKv mean and what does it do? Does it have to be geared? If I gear the motor, how do I know what sort of prop to get? What does 7x4 for prop sizes mean?

See, I have a million questions but can't seem to find a website that explains this all in one easy spot. Does anyone know of such a website?

Thanks for your help...

FAb
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Old 12-23-2005, 12:17 PM
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jdetray
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Default RE: What does all the jargon mean???? Need help

FAb-

I'm not familar with that aircraft, so I can't recommend any particular brushless motor for it.

You can get a brushless motor for your plane that will work in direct drive configuration. One of the Axi outrunners would probably work fine, but I don't know exactly which one. You can review the Axi motors [link=http://www.hobby-lobby.com/brushless_axi.htm]here[/link]. Brushless motors can be used in gearboxes as well.

kV is a motor constant corresponding to no-load RPM per volt.

Low kV motors develop more torque and are used for spinning a large prop at relatively low RPM.

High kV motors develop less torque and are used for spinning a small prop at relatively high RPM. High kV motors can also be used in gearboxes, in which they can spin larger props.

The prop specs are diameter and pitch. A 7x4 prop is 7 inches in diameter and has a pitch of 4 inches. The pitch in inches is the distance which the propeller would screw through the air in one revolution if there were no slippage.

- Jeff
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Old 12-23-2005, 01:27 PM
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lwatson
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Default RE: What does all the jargon mean???? Need help

To determine the right brushless to buy, determine the weight of your current airplane (current All Up Weight), then get a brushless that will deliver about 1.5 times the thrust, 1.0 would be enough, but something tells me you are going to want this brushless in your next plane, and that one is going to need to be more aerobatic.

For an ESC get a Castle Creations 10 or 25 Amp. Many web sites offer motor ESC combo's that can save you about $30.

If you give us the weight we can tell you a motor, but be aware there are lots of options in your weight class so don't let different opinions overwhelm you. For instance, most people on this forum are only going to recommend motors they have used. (I am one of them)

Some motors are also going to be easier to mount in your current airplane, so you might want to share how the motor is mounted.

Larry
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Old 12-23-2005, 09:55 PM
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fab4272
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Default RE: What does all the jargon mean???? Need help

Thanks for the help guys. You've both been really helpful. One day when I build up more experience I hopefully can pass on help to someone else that is new.

Thanks again.
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Old 12-24-2005, 08:33 AM
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Default RE: What does all the jargon mean???? Need help

Fab4:
check out the balsa Products BP 21 brushless and it will show the speed controller to go with it. Fellow flier has one on a GWS Tiger Moth 400 which is about the same size. Still going strong after about a yr. I have one on a large homade shocky that works well. Not the lightest or most efficiet but very reliable and trouble free. no gearbox needed. Swings an 8-6 prop on 3 lipos. Hope this helps.
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Old 12-27-2005, 02:51 AM
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Default RE: What does all the jargon mean???? Need help

I have the same plane. I put the Mega direct drive 16/15/7 with a Jeti Advance 18 ESC. It was a direct replacement and took about 20 minutes. Also using the APC 7-5e prop with a 2s 1800 lipo. The thing flies great for 15 minutes. Waiting for my new 3s kokam and 8-5e prop. Good luck. Ken
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