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I Need Help with Buying a Versatile Electric Setup

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Old 08-10-2010, 09:29 PM
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Isthisnametaken
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Default I Need Help with Buying a Versatile Electric Setup

Hi, I am just getting into rc planes and I need some guidence on buying the right motor, esc, and battery. I'm the kind of person who just likes to build things so I'll probably just get one or two sets of electronics and scratch build planes to put them in. Since I'm going to be using the same internals in multiple designs, I wanted to see if someone could recomend be a basic setup that I could toy around with. I dont really know what kind of planes I'll build in the future but Im starting with foam and will move up from there at my own pace. I don't have a huge amount of money to spend to price will be a factor. Any feedback would be greatly appreciated.

EDIT: I already have a good transmitter, receiver and servos from other projects so guidance on this isn't necessary.

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Old 08-12-2010, 10:48 AM
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Default RE: I Need Help with Buying a Versatile Electric Setup

Pretty much each bird is going to use different set ups, dependent on size and what you want it to do. Would be much easier to give you some recommendations after you know what you plan on building.

I mean I can give you something for a light weight 3D foamy, but it probably would do so well in say a wing. Nor would a set up for a 60 size craft work too well if you build a park flyer. Get my drift?
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Old 08-12-2010, 12:30 PM
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Default RE: I Need Help with Buying a Versatile Electric Setup

I know that they all prefer differend set ups but I just want something with a little flexability. For reference, the plane I doing now is based on the "Mugi Evo"(www.mugi.co.uk/evo_intro.php). Depending on how I like it, I may keep building this style or try something new. The planes that interest me the most are park flyer type things, 1-3 lbs. If I buy a power system slightly too big, could I get away with it or would it create too much weight, forcing minimum flight speed up? I just want something to play around with that I can grow into so that I wont need to spend a ton of money on another power system a month from now.



How does this sound? It might be over powered but I wanted to cheat that way rather than too low.

Motor:www.hobbyking.com/hobbycity/store/uh_viewItem.asp
Battery:www.hobbyking.com/hobbyking/store/uh_viewItem.asp
ESC:www.hobbyking.com/hobbyking/store/uh_viewItem.asp
6x4 prop

One last thing, what is the difference between a 1000 mah 5C and a 500mah 10C(these are made up)?" 1000mah will last longer but what would the 500mah have on the 1000mah? All I know is that you use them to get the max amperage but is there a prefered C value for a particular motor? I cant figure out what effect it actually has on performance.
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Old 08-13-2010, 08:29 PM
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Default RE: I Need Help with Buying a Versatile Electric Setup

The "C" rating of a battery allows you to determine the maximum current you can safely draw from that battery. By "safely," I mean "without damaging the battery" or "without the battery voltage sagging so low as to unacceptably hurt performance." These can amount to the same thing where lipo batteries are concerned, since pulling too much current will cause the battery voltage to drop too low, which is one thing that can permanently damage a lipo.

To calculate the maximum current a battery can safely provide, multiply its capacity in Amp-hours times its "C" rating.

Using your two examples:

1000 mAh = 1 Ah x 5 = 5A maximum current
500 mAh = 0.5 Ah x 10 = 5A maximum current

So both batteries can safely deliver 5A maximum current. However, the 1000 mAh battery will give you twice the flight time. The 500 mAh will probably weigh less, which could be important in some situations.

NOW a very important point: Most R/Cers do not assume the claimed "C" ratings of batteries are correct. Manufacturers have been known to measure the "C" rating under favorable conditions that do not resemble the way we actually use the batteries. Many experienced R/Cers discount "C" ratings to 80% (or less) of the claimed value.

Thus, a (claimed) 20C battery is treated as a 16C battery in actual use. A (claimed) 15C battery is treated as a 12C battery.

There is no preferred "C" rating, except to say that the higher the "C" rating, the more current you can safely draw from the battery, assuming all else is equal. You must select the best battery for each power system based on the current you need and the flight duration you desire.

In summary, use the "C" rating (suitably discounted) and the capacity (mAh) to determine if a given battery can safely provide the current you need. Use the mAh alone to determine how much flight time you will get.

- Jeff
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Old 08-17-2010, 05:19 AM
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Default RE: I Need Help with Buying a Versatile Electric Setup

You are going to need to read this:

EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC FLIGHT
http://www.rcuniverse.com/forum/m_7100376/tm.htm
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Old 08-18-2010, 08:01 AM
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Default RE: I Need Help with Buying a Versatile Electric Setup

Thanks, "EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC FLIGHT''was the first place I went, I just couldn't find anything about what my limitations in size were anywhere I looked. Since Im buying for multiple projects, I wanted to cheat on the big side. That Forum Book thing helped a lot though. I already bought the setup I posted with a different battery so I'm just hoping I did my math right.

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