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Author Topic: To go Brushless or not  (Read 2495 times)

chris gillespie

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To go Brushless or not
« on: March 11, 2014, 06:59:13 PM »

It has taken a while to get my head round brushed motors and sizing etc...
 
Brushless is all gibberish and greek to me at the moment, i have put in a roxxy for a najade, it came with it so no decision neccesary....i can see the obvious advantages....
 
However, can i put a brushless in a heavier boat, 1200 long loads of weight in it.....would there be a selection of motors that can power this, also would i need to gear it down ?
 
ive uesd a mfa 540 geared 6:1 or so for Maggie M, as recommended...pretty good .....however maggie is 850, 900 long
 
thoughts please
 
Cheers

McGherkin

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Re: To go Brushless or not
« Reply #1 on: March 11, 2014, 08:20:44 PM »

Go brushless!

There's a huge range of motors out there, and you can tell exactly what speed they will spin at unloaded, through the KV rating. Multiply this by your battery voltage to get the RPM.

If that's too high, you can gear it down or you can look for a lower KV motor.
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chris gillespie

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Re: To go Brushless or not
« Reply #2 on: March 11, 2014, 08:40:37 PM »

Thanks McGherkin
 
Do these work well with lead acid ( helps with ballast ) or do i have to go fully modern with lipo's etc
 
So in theory 3000 revs / 12 v  = 250 kv   {:-{  maybe something a bit higher for loading  {:-{
 
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McGherkin

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Re: To go Brushless or not
« Reply #3 on: March 11, 2014, 08:57:11 PM »

Works perfectly fine with lead acid, not a problem.

Yeah, you've got your calculation right there. Is it 3000rpm you want? perhaps an 750-800kv motor geared down 3:1 would be a bit better :)
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essex2visuvesi

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Re: To go Brushless or not
« Reply #4 on: March 11, 2014, 09:35:05 PM »

Also a brushless equivalent will give you better runtimes as they a quite a bit more efficient than their brushed counterparts
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chris gillespie

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Re: To go Brushless or not
« Reply #5 on: March 11, 2014, 10:26:51 PM »

Yeh i like the idea of efficiency......they are a bit more expensive....but if you get an extra 25 min play time i may be worth it
 
3000 revs was just a sample.....i  dunno how many revs i would need, again depends on motor i guess  :embarrassed:
 
 
 

McGherkin

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Re: To go Brushless or not
« Reply #6 on: March 11, 2014, 10:43:57 PM »

Revs needed is boat specific, and depends on weight, target speed, blade size, number of blades etc.

What exactly is the model you're trying to propel? Apologies if I missed it in your original post.
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roycv

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Re: To go Brushless or not
« Reply #7 on: March 12, 2014, 08:33:04 AM »

Hi all, There are a lot of threads where there is a query on what kind of battery can be used to run a brusless motor.
Well it is the battery that connects to the speed controller.

What comes out of the speed controller drives the brushless motor.
If you need to know what this is read an article on it, there are many.

It is easy to tell the difference between a brushed and a brushless esc. 
Brushed esc has 2 wire o/p and the brushless has 3 wire o/p.

In the same way a brushed motor has 2 i/p connections and a brushless 3 connections.
You can connect a battery directly to a brushed motor but you can't do that with a brushless motor.

kind regards we have all struggled with these things, so don't be put off!
Roy
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admiralbb62

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Re: To go Brushless or not
« Reply #8 on: March 12, 2014, 07:13:33 PM »

I took the plunge.  I put a brushless motor in my Knox and it works great.  Here is what I used:

motor:  42mm diameter 50 mm long 500 KV (under $30 from Hobby King)
Speed Control:  Mtroniks Hydramax 30 brushless (around $85)
Propeller:  Rivabo 5 blade 50 mm diameter  ($25)
Battery:  6 V 4 Ah gell cell

Note:  I originally used a 12V 2.5 Ah battery and the hull planed at full speed, the 6 V battery gave good top speed and more capacity.


Trial run


setup


motor

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Charles

admiralbb62

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Re: To go Brushless or not
« Reply #9 on: March 12, 2014, 07:16:37 PM »

I did use a lead acid battery.  I haven't measured the amp draw but I suspect it is low.  If you are running a fast boat or overloading the motor you might need lipo batteries that can supply more amperage without damage.  I would also like to report that the slow speed control and performance is outstanding, I can make the ship crawl.
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Charles

McGherkin

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Re: To go Brushless or not
« Reply #10 on: March 12, 2014, 07:36:29 PM »

To be honest you probably wouldn't be fitting a much bigger motor than the brushed equivalent that would normally be fitted, so if anything the amp draw will be slightly less than the brushed setup due to the increased efficiency of the brushless motor.


Unless you want to plane a trawler!
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admiralbb62

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Re: To go Brushless or not
« Reply #11 on: March 12, 2014, 08:10:07 PM »

The way I picked the motor was by choosing one that had around 500KV, just so happens that the low KV motors are larger.  The one I used is about the same diameter as the brushed motor I have on other similar ships.
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Charles
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