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Old 07-28-2012, 06:17 PM   #1
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Default Newbie needs help on motor selection

Ok guys really need some help here, this is my conundrum.....

Backround- I have a greatplanes spectra sailplane with an old brushed master airscrew 05 motor and there 3:1 gearbox, as well as there 12x8 folding prop. This setup was only pulling something like 17 amps. I got some help before and was told that I could run a two cell lipo and a 14x9 prop and run around 23-24 amps and be much happier with the performance....So I bought two 2cell lipos and the 14x9 prop

Now the conundrum- before the lipos and prop came in I was range testing the model, as it has recently been rebuilt from a crash. Anyhow the motor is shot and I need a new one.... In my mind If I'm gonna spend money toward a new motor I might as well put it toward a brushless setup. Now I know I need around 200-220 watts. I have been eyeing up several of the .10 brushless motors like gp rimfire, eflite, super tiger etc. I know everyone is running 3 cell lipos with like a 10x7 prop and getting good results, but I have 2 cell lipos.

What prop would give me 25-28 amps on 2 cells(28 amps x 7.4volts= 207 watts)? And what amp pull would my new (expensive) 14x9 prop have

Thanks so much for any help I recieve
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Old 07-28-2012, 06:42 PM   #2
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A motor of about 100-120g with a kv of around 1400k should do the job. Most likely give you a few more amps than you are asking for but that shouldn't be an issue, get a 40A ESC to be sure.

Here's one that looks ok providing you can fit it in the nose of your glider: http://www.hobbyking.com/hobbyking/s...ner_Motor.html
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Old 07-28-2012, 07:03 PM   #3
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Hey there Jet....just to be clear, the specifications your recommending (100-120g, kv1400), would work with 2cells and my 14x9 folder???

I checked out that turnigy motor in the limo you gave. Looks great, but unfortunately the diameter is 2 mm too big.

Also you said it might give me a few more amps than the 25/28 I was looking for. However the gp rimfire, eflite and super tiger .10's are only rated for about 30 amps.
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Old 07-28-2012, 09:56 PM   #4
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Check out www.headsuprc.com

This will give you a very good idea of what your looking for, and how the kv rating and props will change your thrust and amprage.

A 450-480 class motor on 3 cells would easily get you the 200 or so watts your looking for, on 3 cells. You will also have a bit more power from a brushless motor then a brushed one.
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