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Author Topic: Brushless motor for a Perkasa 48" long.  (Read 7427 times)

nick_75au

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Re: Brushless motor for a Perkasa 48" long.
« Reply #25 on: January 17, 2013, 10:51:51 AM »

OK I'm curious about what motor you have used, KV size ect, It looks too small for the boat.


Gel batteries are useless for fast boats, I would run it at light trim, remember the full sized boats probably have a foot or more difference in draft from beginning of patrol to end so its not out of scale to have a bit of antifouling exposed.


You can run into problems with longer wire lengths between battery and ESC (and this is regardless of battery chemistry), its safer to run "extended" wire lengths from ESC to motor or alternatively the high power guys run extra input capacitors to solve the issue, unless your extending more than 8-12 inches over the wires already attached to the battery and ESC then there wont be an issue IMO .


The only suitable switch is the largest one but I wouldn't use any switch, use the plug on the battery to isolate power, shouldn't be leaving the batteries in the boat anyway ok2


Cheers
Nick
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Big Ada

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Re: Brushless motor for a Perkasa 48" long.
« Reply #26 on: January 17, 2013, 03:10:55 PM »

Hi Nick,
Its a 3000kv one, I was not planning on leaving the Battery in it, the switch was for isolating the Battery before I lift the boat out of the water.
Regards,
 
Len.
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Subculture

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Re: Brushless motor for a Perkasa 48" long.
« Reply #27 on: January 17, 2013, 04:34:39 PM »

You asked for a recommendation above, and you've purchased something completely different. I'm going to assume you know what you're doing.

Lancejsy

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Re: Brushless motor for a Perkasa 48" long.
« Reply #28 on: January 17, 2013, 04:38:53 PM »

You keep asking the questions and ill can read all the answers as they will be use full to me as well bud ;D ;D ;D


Cheers Len :-))


Lance
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Re: Brushless motor for a Perkasa 48" long.
« Reply #29 on: January 17, 2013, 05:50:46 PM »

Well the first thing you need to bear in mind, is that a 3000 KV motor is going to wind 36000RPM on 12 volts, assuming the battery can supply the necessary juice, which is unlikely from a gel battery. Lipos will supply the required juice provided they're of the correct C rating.

On a 55mm prop, which is probably going to be in the 1-1.4 pitch range, you're looking at over 50mph with 25% slip on the mildest pitch.

Doubtful it'll do that, but the motor will have a good try at trying to, and pull a tremendous amount of amps in the process. I don't think the hardware in the boat looks upto the task, and those chocolate block connectors are likely to be a source of problems.

The 1000-1500KV range I mentioned before was much more suitable for this type of boat, and would have provided ample performance. The motor shown in the install will need to geared down about 2.5-3:1 or run with a smaller prop (less efficient) e.g. 30mm.

Big Ada

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Re: Brushless motor for a Perkasa 48" long.
« Reply #30 on: January 18, 2013, 05:52:03 PM »

You asked for a recommendation above, and you've purchased something completely different. I'm going to assume you know what you're doing.

Absolutely Not, so how do I get what I have bought to work, sorry I did not follow your suggestions, I got side tracked over availability in the UK store.
I just want the boat to go forwards and in reverse, so do I just add Lipos, I have some Turnigy 3 cell 2200.
I can change the prop,.
 
Len. <:(
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Subculture

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Re: Brushless motor for a Perkasa 48" long.
« Reply #31 on: January 18, 2013, 06:48:23 PM »

Very small pack for a boat that size. You'll only get a short running time.

What sort of duration are you after?

Big Ada

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Re: Brushless motor for a Perkasa 48" long.
« Reply #32 on: January 19, 2013, 03:39:37 PM »

I bought these for a motorised Kite that I made, I have 4 of them.
What sort of duration would I get from one, I do not expect to use full throttle all the time, could I link two together or is that dodgy with lipos.
Thanks
Len.
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Subculture

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Re: Brushless motor for a Perkasa 48" long.
« Reply #33 on: January 19, 2013, 05:53:07 PM »

I would estimate about 10 minutes on a boat that size, maybe slightly more, or less, depending on what sort of prop you're using.

But that's all immaterial- the motor you have fitted is grossly mismatched for that type of boat- you should follow the link I gave earlier, that shows a motor far better suited.

Big Ada

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Re: Brushless motor for a Perkasa 48" long.
« Reply #34 on: January 20, 2013, 02:12:05 PM »

you should follow the link I gave earlier, that shows a motor far better suited.
I have one winging its way to me at this moment.
Just what would the one in the boat suit, An Air Boat, A Hovercraft, both of which I am interested in building ( I have built an Airboat ).

Thanks Subculture.
 
Len.
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Re: Brushless motor for a Perkasa 48" long.
« Reply #35 on: January 20, 2013, 03:22:53 PM »

You could use it on either of those. You want to run a fairly small prop, a two blade say 5-7" maximum diameter, so as not to bog the motor down.

You'll have to experiment with prop pitch, can't be more specific, as I don't have that motor.

Big Ada

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Re: Brushless motor for a Perkasa 48" long.
« Reply #36 on: January 20, 2013, 03:56:20 PM »

Thanks for that. I am planning to use the water cooled one as planned, so what sized ESC should I use for the 3000kv job now destined for Airboat or Hovercraft?.
Thanks for your help.
Regards.
Len.
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Lancejsy

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Re: Brushless motor for a Perkasa 48" long.
« Reply #37 on: January 20, 2013, 07:04:42 PM »

Don't build a hovercraft mate that's how this forum started, anyway I will be building one soon bud LOL!!
Cheers Len
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