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Author Topic: Advice on brushless drives for scratch built models  (Read 1101 times)

wigs

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Advice on brushless drives for scratch built models
« on: December 03, 2013, 11:00:59 PM »

Hi

I am new to this site and am looking for advice on selecting brushless motors for two scratch built boats I have made.

The first is an Interceptor 42 Pilot boat that is 93cm long.  The hull alone weighs just under 3kgs.  I had two direct drive 12v speed 600 motors in it with 40mm 3-blade props, but the performance was not that great.  I would like to get a bit more performance out of it The other boat is a new scratch build of a semi scale Damen Twin Axe catamaran.  It is 90cm long and 34cm wide (Scale of 1:29).  Any idea of what motors and prop to give it a scale speed of 26knots.  I have never used used brushless motors before and have know idea how to spec them, so any ideas would be much appreciated.

 For both boats I would prefer to use 3cell Li-Po batteries(11.1v) system to match all my other boats. Regards Anton
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McGherkin

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Re: Advice on brushless drives for scratch built models
« Reply #1 on: December 03, 2013, 11:35:09 PM »

I would just look at other models that are a similar type and size to yours and see what they run for similar speeds. The interceptor sounds like it'd be quite similar to a 1/16th Tamar class lifeboat in terms of size and performance, and you left out what the second model actually is!
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nick_75au

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Re: Advice on brushless drives for scratch built models
« Reply #2 on: December 04, 2013, 02:49:07 AM »


Hi Antonwhat voltage speed 600 motors are you using, and what voltage are you using?



http://www.modelboatmayhem.co.uk/forum/index.php?action=dlattach;topic=42249.0;attach=120907


use the Max RPM graph on the chart or even a little higher


At a guess though some 28 mm outrunners have been very good on 12 volts and 40 mm props,


This hull Im using 750 Kv bell motors but also tried  750 Kv 28 mm outrunners with 40 mm 5 blade Raboesch props its 1150 mm long and about the same weight


http://www.youtube.com/watch?v=tbXt4Clk8QA&list=UUOv1BWZzfbDtDS7fZRDK9MA


Nick
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Guy Bagley

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Re: Advice on brushless drives for scratch built models
« Reply #3 on: December 04, 2013, 08:38:26 AM »

i have an interceptor from models by design- hull is GRP -  and i have had 2 x brushless set ups in it,
 
firstly i had a pair of 800 kv  turnigy  motors, but i  reduced the prop size, http://www.youtube.com/watch?v=1a-0A4OJQNM
 
smaller props (40 mm) allow the higher revs, and the motors ran cool and fairly efficient- no need for water cooling  - i get about 35 to 40 mins from 12v  5ah cell pack- this is as it was in the you tube video...
 
 however after talking to andy griggs at MBD - he advised returning to the kit props and using a pair of 580 kv   - which i have now done, - speed not massively different , slightly  better duration on the  batteries, slower revving motors , but more torque- but bigger props so speed not really affected.....
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all in all its just another brick in the wall......
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