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Author Topic: Elec motor equivalent to a 46 I.C motor  (Read 2899 times)

marklincs

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Elec motor equivalent to a 46 I.C motor
« on: August 05, 2012, 03:30:22 PM »

All,

1st sorry double post I got the 1st wrong one in the wrong section  {:-{ {:-{


I have a Fireboat Aerokits I'm refurbing and Research has revelled I could ideally do with an electric motor equivalent to a 46 I.C motor

Thinking Brushless and do not mind out runners either, then a decent ESC to handle it all.  Prop needs to be a 2Blade X type 45mm

anyone got an recommendations ?
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tugs62

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #1 on: August 05, 2012, 03:48:20 PM »

ive got the 34inch one and run that on a 600 electric but have a 1480kv brushless and thinking of converting it
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marklincs

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #2 on: August 05, 2012, 04:15:14 PM »

ive got the 34inch one and run that on a 600 electric but have a 1480kv brushless and thinking of converting it

Hi
 what does she run like on the 600 ?

I've seen an 850 motor but would it be enough.....

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tugs62

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #3 on: August 05, 2012, 08:17:51 PM »

hi she runs fine i use a 7 cell pack some times and that realy lifts it and run times arnt bad
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dodgy geezer

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #5 on: August 05, 2012, 08:21:44 PM »

I put this answer up in the wrong section - so I'll duplicate it here:

I've never worked up at that power before, but it's worth putting some estimate figures together so that you can check that you are in the right ball park. Here are my guesses:

A 46 motor puts out about 1.5HP. That's about 1KW. You would be using 1KW if you had a motor running at 20V taking 50A. Modern brushless are pretty efficient, so go for a 60-70A motor at 20V - a 6S. Pro Rata for lower voltages. You should be able to get one from Giant Shark for 40 odd. Here's one at 33 - but I don't know enough about the 250 KVA implications to know it it will be any good - 5000rpm may be a bit slow....

http://www.giantshark.co.uk/xyh6354-250kv-outrunner-p-404607
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tugs62

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #6 on: August 05, 2012, 08:31:15 PM »

ive had a look for a picture of mine on the lake but as yet there isnt one  but my sea commander runs on the same set up

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nick_75au

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #7 on: August 06, 2012, 06:37:11 AM »

The Kv depends on the voltage and the RPM you desire, a 45 mm prop will want about 10 000 RPM for a fast subsurface drive, I would expect such a prop to draw about 45-50 amps at this RPM on 11.1 (3 cell Lipo). a 1000-1200 Kv motor capable of handling 50 amps should be about right.

Cheers
Nick
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dodgy geezer

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #8 on: August 06, 2012, 09:16:49 AM »

So something like this might do at 20v:

http://www.giantshark.co.uk/xyh5055-580kv-brushless-outrunner-p-403285.html

That's 1.5KW and 580Kv - and only 20!
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nick_75au

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #9 on: August 06, 2012, 10:55:49 AM »

Well that's equivalent but.....I think you don't need 1.5 Hp to drive a 45 mm prop at a speed suitable for subsurface drive, My Ski Boat takes 440 watts to drive a 40 mm prop, given its a lower pitch and slightly smaller. The 45 mm prop will not load up the motor to 1100 watts, it will be more like 600 watts. Plenty of people drive that prop on a 700 brushed which is not really capable of more than 300 watts without extensive cooling. 

Its the same with the IC motor, it may be capable of producing the power but in reality the load put on it is considerably less and the range that the motor can produce that power is very narrow, electric motor produces more torque over a much wider RPM range.

Nick
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Circlip

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #10 on: August 06, 2012, 11:29:26 AM »

Oh for the good old days, Bee, Hornet, Racer and Hunter. :-))

  Regards  Ian.
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dodgy geezer

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #11 on: August 06, 2012, 02:05:13 PM »

Well that's equivalent but.....I think you don't need 1.5 Hp to drive a 45 mm prop at a speed suitable for subsurface drive, My Ski Boat takes 440 watts to drive a 40 mm prop, given its a lower pitch and slightly smaller. The 45 mm prop will not load up the motor to 1100 watts, it will be more like 600 watts.

Hmm... on the other hand, the 1.5HP is probably power in - power out will be lower. The 48" Aerokits Tender is a big heavy beast (no fibreglass hull!) so it could probably do with a bit of poke. And I expect it's a good idea to err on the side of too much capability - you can always drop the voltage or cut the throttle, but our friend says he wants a good fast boat, the price looks good and it's got good reviews.....
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marklincs

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #12 on: August 06, 2012, 04:09:21 PM »

Well I went for the Hobby king combo stuff and ordered a 4s li-po to come with it as well  :-)

Now for me having a bit of extra power if required is always nice

Example I fly RC Planes so if the kit says 40-60 engine you stick a 60 in it you never go for the low end because you get into trouble the engine just doesn't help you out, not good and you tend to find you have to have the dam throttle nearly always at 100% to do anything. As for scale models bloody things can become nasty without the right power  %)

And the ability to not race around at 100% is always nice but I'm aiming for cruising around 1/2 to 3/4 throttle should be good with the option to open her up

it will be running on 4s packs as my planes also fly on these and i'll 4 packs with the option to double 2 up to give me around 7800ma to play with

or on one battery 3300/3900/4000ma depending which pack I use

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HS93 (RIP)

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #13 on: August 06, 2012, 05:35:52 PM »

that will make it plane,it will give you all the power a fire boat will handle, but start small with props (plastic 2 bladders) and check the heat of everything, you will probably know that the speed ctroler will only dissipate the amps if watercooled.

Peter
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bj

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Re: Elec motor equivalent to a 46 I.C motor
« Reply #14 on: January 31, 2013, 05:03:26 PM »

If you look on the OS Engines ELECTRIC motor web page they give an equivalent I/C engine size against each of their brushless motors.
Their OSMG 9540 and 9550 motors are equivalent to an I/C 40 and 50 respectively.
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