Gary Murphy 1 Posted June 2, 2011 Share Posted June 2, 2011 I am into my first build and the kit says a motor of 120-160watts is needed. I ahve ordered a motor which is rated 12-16 amps and a kv of 1400. I got mixed up and thought the 1400 was in the middle of 120-160,newbie and got watts/amps and kv mixed up. I got a 20 esc to go with the motor and intend to run 3s 1300 packs or 2s if needed due to poor motor selection. But i have no idea how you work prop size out.I realise some is trial and error but what is the starting point,how do you work this out. The plane should finnish at 600g and a low wing sports 36" span.I will not f ly it yet,i am a novice,i just wanted to build. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 2, 2011 Share Posted June 2, 2011 Gary, I'm surprised Tim hasn't jumped in yet, so I'll say this first - Wattmeter! It really is an essential item if you want to make the most of electric power.Without one you have a couple of options. First there are a number of electric power calculators on the web, you feed in the details of your motor and battery, then try varying the prop sizes to find something that gives the required output without overpowering the motor.Second, search (Google etc) for the mtor you have bought. Most e-shops will list suggested prop sizes in some format.Looking on the GiantCod site I found this: A2212-10 (140W) 1400Kv SP Brushless Outrunner Motor Specifications: * Kv: 1400 (Revs per volt) * No load current @ 10v: 0.5A * Voltage: 2-3S Lipo or 6-10 Cells Ni-xx * Max Efficiency: 80% * Max Current: 16A (60secs) * Cont Current: 12-15A * Dimensions: D27.5 x L30mm * Shaft diameter: 3.17mm * Weight: 47g * Internal Resistance: 90 mÙ No recommended prop in the spec, but in the associated reviews sizes around 6*3 to 7*4 are reported as drawing 80-140W. I'd suggest starting with a 6*4 for a sporty model, or a 7*3 if it's available, both on 3s. For a 2s battery you could probably go up an inch in diameter.I'm just guessing here not having this setup myself, just as you will be guessing without a wattmeter. Edited By Bob Cotsford on 02/06/2011 07:26:32 Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 2, 2011 Share Posted June 2, 2011 Tim likes his bed Gary, maybe best to check some of the thread s and sections we have here for those new to electric.Here's a couple, but there's loads more. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 2, 2011 Share Posted June 2, 2011 Bob likes his bed too, but he's on earlies this week Quote Link to comment Share on other sites More sharing options...
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