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Old Feb 22, 2014, 10:42 AM
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3542 1185kv or 3548 1100kv

I,

Lookin at the above motors to install on a godiscover, im wanting it for range.

I have a 80a esc already

Which should I go for and which prop should I choose

Many Thanks

Jonny
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Old Feb 22, 2014, 03:28 PM
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We need details.... link to aircraft, make of motor, cell count
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Old Feb 22, 2014, 04:55 PM
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http://www.hobbyking.co.uk/hobbyking...00mm_PNF_.html

Looking at running on 3s 5000mah may be 2x 3s 5000

Motor 1
http://www.hobbyking.co.uk/hobbyking...arehouse_.html

Running 11x7 or 12x6

Motor 2
http://www.hobbyking.co.uk/hobbyking...ner_Motor.html

Running 11x7 or 12x6
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Old Feb 22, 2014, 04:56 PM
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3542 1185kv or 3548 1100kv

This will be a model for distance and cruising on low amps open to other suggestions on 35 size motors
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Old Feb 22, 2014, 08:18 PM
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If long flight time is the aim, I'd go to 4s, and a minimal prop size which would still fly the plane, to reduce amp draw.

If you have the 3s packs then choose a minimal prop size which would still fly the plane, and reduce amp draw.
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Old Feb 23, 2014, 04:04 AM
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Won't be using 4s it's really doin my head in now lol, really can't decide on 3542 1000kv or 3548 1100kv, I thought going bigger prop like 12x6 would be most efficient
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Old Feb 23, 2014, 06:15 AM
Jack
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The primary difference in the motors is that one is a 120g motor and the other is a 173g motor. In the links you posted there is no 1185 Kv motor, they are 1100 Kv and 1800 Kv.

If those are the two motors you are considering the 3548-1100 Kv motor would be the best choice for the larger props and for long distance or long duration low energy flights. The heavier motor will handle the highest input power and the lower Kv will also handle the larger prop best.

The 173g motor would be able to handle an input of 520W by the 3W per gram rule.

And the testing data on the APC E 12 x 6 shows that a 500W or so motor will be enough for that prop too:

APC E 12x6 - www.flybrushless.com/prop/view/51

If you were considering a slow fly prop (generally always worth trying for the low energy flights) it might work too. There is not a lot of test data on the APC SF 12x6 here but it looks like it might do OK:

APC SF 12x6 - www.flybrushless.com/prop/view/50

Jack
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Old Feb 23, 2014, 06:33 AM
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sorry linked wrong motor not 1800kv lol

http://www.hobbyking.co.uk/hobbyking...ner_Motor.html
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Old Feb 23, 2014, 06:47 AM
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Would be nice to choose a motor / prop combo that would work fine on 3s and also 4s and just swap props as I know 4s are more efficient
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Old Feb 23, 2014, 06:49 AM
Jack
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OK, even with the smaller difference in the Kv's, I would probably make the heavier motor the first choice.

On 3S you are going to have a no load RPM of 12.3V x 1185 or 1100, that would be 14,575
or 13,530 RPM. The APC E props recommend a max of 145,000 / dia. in inches and the SF props a limit of 65,000 / dia. in inches

So on 3S you will have the SF prop way over it's limit at full throttle. If you want to use a SF prop you would really have a much more efficient setup if you had a lower Kv, about half of what you are looking at now. Look at the Kv's and weights on the motors reported in the testing data I posted a link to

Jack
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Old Feb 23, 2014, 07:04 AM
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I will try and work out charts not my strong point lol what would u recommend for most efficient set up motor/prop wise

Thankuou
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Old Feb 23, 2014, 07:08 AM
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3542 1185kv or 3548 1100kv

Think what ur saying is go for 3548 1100kv with 12x6 prop apc-e

Would I have option then to go for 11x7 on 4s later if wanted
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Old Feb 23, 2014, 07:09 AM
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3542 1185kv or 3548 1100kv

Not going to on with sf prop
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Old Feb 23, 2014, 07:28 AM
Jack
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Quote:
Originally Posted by jwmachon View Post
Think what ur saying is go for 3548 1100kv with 12x6 prop apc-e

Would I have option then to go for 11x7 on 4s later if wanted
The 12 x 6 APC E has a recommended max RPM of about 12,000 RPM but it seldom need to be used at that full value.

On 3S the 1100 Kv motor would have a no load RPM of 13,530 RPM at 12.3V. But the voltage will fall under load and as the battery is depleted and that will drop the RPM. And you will not be flying at full throttle in the interest of duration and range. So, all things considered, the 1100 Kv motor and the APC E 12x6 are a good match.

Do you know the weight of the airplane? Or can you post a link to it? A typical airplane only needs a thrust of about 0.33:1 to 0.50:1 to fly well. So if you look at the thrust curve on the APC E 12x6 test data page, you can see that full throttle and full thrust is not needed after takeoff.

It if good to have power in reserve for unexpected winds and emergency maneuvers but many planes will fly on a lot less than full throttle.

And we still don't know what a "godiscover" airplane is.

Jack
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Old Feb 23, 2014, 07:40 AM
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Lol sorry mate
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