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What motor system should I choose

Old 03-04-2004, 08:18 PM
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crashone
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Default What motor system should I choose

I want to convert ST G75 glow engine to electric motor for my plane. The plane weighs about 15 lb and wing area is 1450 squre inch. I like to use smaller prop such as 14" or 16" in diameter. Also I hope to have 0.5 - 1 hour flying time. What motor system should I choose(motor, controller, battery...)?
Any input will be greatfully appreciated.
Old 03-04-2004, 11:45 PM
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fritzthecat
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Default RE: What motor system should I choose

Let me throw some numbers at you:
A ST75 powered plane at 15 lbs and 1450 wingarea sounds like a scale warbird.
You need at least 1000 watts for scale flight and 1500 watts for serious areobatics. Running around 30 amps will require about 30 Nicad/Nimh cells (WAG.)

Cruising at 20 amps for 1 hour requires a battery with 20,000mah capacity. Using Nimh 3000 cells would require 210 cells weighing 2 oz each for a total weight of.... 26.25 lbs. Using Lipolys requires a 12s8p pack of 2600mah Tanic cells. Thats six 4s4p 10400mah cells at U$ 465 each for a battery cost of... U$ 2790 and a weight of 2.5 lbs.

Now looking at a more realistic scale flight of 15 minutes after removing nonessential glowstuff from your plane to drop a few lbs:
AXI 4130/20 (1000watts @ 35 amps) U$ 160
Hacker 48-3P ESC U$ 170
Tanic battery pack (10s4p 8800mah) U$ 992
Astro 109 Lipoly charger U$130

Just so you know whats up.

Fritz
Old 03-07-2004, 09:26 PM
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crashone
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Default RE: What motor system should I choose

Fritz:

Thank you for those numbers.
My plane is not a scale warbird. I might call they scout, which disigned by myself. I had four prototype planes. Two was crushed. Basically, they are two types. One take off weight is 14 - 16 lb and powered by ST G75. Another take off weight is 23 - 25 lb and powered by MVVS 1.6. No any aeraobatics is needed. I just want them to take off, climb, stable flying, turn and landing even both types are able to do loop and roll.
The new one is still in building. the 15 - 16 lb is the designing take off weight. The plane actually weight wo/power system should be around 8 lb. I was thinking AXI 41 series or Hacker B or C50. Or MVVS 1.6 (over powered and viberation problem).

Could you please tell me why do you recommended AXI?
What is the LiPoly bettery life time (how many times can be recharged)? Do they have longer life time than NiMH?

Best Regards,

CJ

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