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Author Topic: Brushless Choice  (Read 326 times)

rnli12

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Brushless Choice
« on: June 15, 2022, 06:05:35 pm »

Hi,
I have had several Brushless Outrunners in 1/16th Lifeboats over the years but have a 1/16 RN P2000 model with a weight of @ 11/12 kg so much heavier and a length of 1300mm fitted with 40mm 4 bladed props.

So the question is what size brushless motor considering this is heavier? I have two new Thumper 3542/05 1250KV Tornado Thumper V3 but are they enough?
Regards,
Rich
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Regards,

Rich

Charlie

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Re: Brushless Choice
« Reply #1 on: June 15, 2022, 09:53:49 pm »

Any good at maths? It is fairly straight forward to calculate what power is required. Have a look at this:


https://www.building-model-boats.com/model-boat-motor.html

canabus

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Re: Brushless Choice
« Reply #2 on: June 16, 2022, 08:18:26 am »

The max rpm for a 4 blade is 8,800.


I think good brass prop will handle more than the max rpm.



The 1250kv on 2S unloaded rpm is 9,000.


The 1250kv on 3S unloaded rpm is 13,875.


So if get 2 ESC's which handle 3S plus, you can start with 2S batteries but upgrade to 3S if required.


Canabus
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Charlie

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Re: Brushless Choice
« Reply #3 on: June 16, 2022, 09:45:01 am »

Did a bit of Googling and maths cos i was bored! The RN P2000 is powered by CAT C18 Diesels which have a power output of 800 BHP each. Divide that by the cube of the scale, and each motor needs to produce 0.2 BHP or 150 Watts. The spec for your Brushless Motors shows they produce 710W, so they should easily be powerful enough, as long as you fit batteries that can provide enough current of course.


Hope this helps!

canabus

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Re: Brushless Choice
« Reply #4 on: June 16, 2022, 01:00:27 pm »

Thumper 3542/05 1250KV  is 710Watts on 4S batteries (14.8 volts).
[/size]
[/size]Less on 3S and 2S batteries .
[/size]
[/size]Required ESC is 30Amps, but 45Amp ones with a fan want be a better choice .
[/size]
[/size]5000mah 30C either 2S or 3S Lipo batteries.
[/size]
[/size]If you use a car ESC with forward and reverse the motor does not require water cooling.
[/size]
[/size]Canabus
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rnli12

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Re: Brushless Choice
« Reply #5 on: June 16, 2022, 04:51:27 pm »

Many thanks, will be interesting to trial in a few weeks.
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Regards,

Rich

Andyn

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Re: Brushless Choice
« Reply #6 on: June 16, 2022, 10:10:28 pm »

Did a bit of Googling and maths cos i was bored! The RN P2000 is powered by CAT C18 Diesels which have a power output of 800 BHP each. Divide that by the cube of the scale, and each motor needs to produce 0.2 BHP or 150 Watts. The spec for your Brushless Motors shows they produce 710W, so they should easily be powerful enough, as long as you fit batteries that can provide enough current of course.


Hope this helps!


Unfortunately water doesn’t scale, so this is a little irrelevant. The model won’t be a scale weight or speed either!
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