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Author Topic: equivalent brushless motor  (Read 5756 times)

firstperkasa

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equivalent brushless motor
« on: December 03, 2015, 09:42:22 AM »

Hi I'm looking for an equivalent motor to a turnigy 2627 1200kv that has been recommended for a project I'm considering.
I can't find this turnigy motor in the UK so I'm after something of the same spec.
can anyone help ?? I still dont understand brushless despite loads of help.


Thanks Rob
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firstperkasa

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Re: equivalent brushless motor
« Reply #1 on: December 03, 2015, 09:58:39 AM »

just to add, I have seen this on the hobbyking site. I have also seen 

PRODUCT ID: NTM2826-1200 but not sure whether its a similar spec.
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TomHugill

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Re: equivalent brushless motor
« Reply #2 on: December 03, 2015, 10:29:02 AM »

What you need to do is find a motor of a similar size, kv and power.

http://www.hobbyking.co.uk/hobbyking/store/__8141__Turnigy_2627_Brushless_Outrunner_1200kv.html

http://www.hobbyking.co.uk/hobbyking/store/__8503__Turnigy_2632_Brushless_Motor_1500kv.html

There's nothing difficult about brushless motors. Three specs to be aware of,

Kv is how fast the motor spins (higher is faster) max RPM is kv x voltage used ir 1000kv motor on 10 volts would spin at 10000 RPM

Power is obvious, more is better!

The 4 digit number is the size, first two digits are motor diameter and second two are can length . Ie 3674 size motor would be 36mm diameter and 74mm can length.

Generally bigger motors are more powerful and can swing a bigger prop.

Hope this helps
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firstperkasa

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Re: equivalent brushless motor
« Reply #3 on: December 03, 2015, 11:09:46 AM »

sort of thanks.
so if i went for that ntm motor that has quite a bit more power but only marginally heavier (6g) and a couple of mm difference in size, would that be ok ?
Presumably the power is limited by my thumb on the fast stick ?
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TomHugill

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Re: equivalent brushless motor
« Reply #4 on: December 03, 2015, 11:27:51 AM »

That should be fine
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TomHugill

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Re: equivalent brushless motor
« Reply #5 on: December 03, 2015, 11:28:40 AM »

sort of thanks.
so if i went for that ntm motor that has quite a bit more power but only marginally heavier (6g) and a couple of mm difference in size, would that be ok ?
Presumably the power is limited by my thumb on the fast stick ?

Did the explanation make sense though?
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Martin [Admin]

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Re: equivalent brushless motor
« Reply #6 on: December 03, 2015, 11:44:19 AM »


KV is how fast the motor spins (higher is faster) max RPM is kv x voltage used ir 1000kv motor on 10 volts would spin at 10000 RPM
Power is obvious, more is better!

The 4 digit number is the size, first two digits are motor diameter and second two are can length . Ie 3674 size motor would be 36mm diameter and 74mm can length.


It's good that Brushless motors do have these numbers on them, I guess we're just not used to reading numbers on the old  DC / Permanent / 'can' motors, all we did was look at the size and listened to how much it revved on 6v!
 

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Crossie

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Re: equivalent brushless motor
« Reply #7 on: December 03, 2015, 01:10:39 PM »

 
 I would advise that after choosing your brushless motor and especially if you are likely to only have electric boats, buy yourself a watt meter, they are available with all manner of functions added, lipo balancing etc. but around 20 provides all that you'll need and you can see the power that your drivetrain is drawing while under some load when the boat is in the water. This way you will be able to get a better match between the motor and the prop and battery voltage and fuses to make your whole system as efficient, safe and aslong lasting as possible.

                                          Trevor
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inertia

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Re: equivalent brushless motor
« Reply #8 on: December 03, 2015, 02:18:28 PM »

Good point, Trevor. I can recommend this one from personal experience. http://www.4-max.co.uk/wattmeter-budget.htm
DM
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firstperkasa

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Re: equivalent brushless motor
« Reply #9 on: December 03, 2015, 04:35:00 PM »

Did the explanation make sense though?
I understand the motor dimensions and the kv in terms of revs at voltage. The brushless motors are specced as watts. the wattage I dont get. the ntm motor is classed as 215w at 12v with 3 cell lipo. hows that work out ?
Dave millbourn has tried to educate me but i'm really struggling.
I'm still fixed on brushed motors in my head and struggling to compare.
For example, I'm building my schnellboot s100 1/35 with 3x mfa 385 5 pole motors. what would a single brushless be to replace the 385's ?

Cheers
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inertia

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Re: equivalent brushless motor
« Reply #10 on: December 03, 2015, 04:46:48 PM »

Watts is the power of the motor and can be calculated very simply as Volts x Amps. It applies to brushed as well as brushless motors.
There is much more useful data published about any brushless motor than there ever was about most brushed motors (except the Graupner Speed range) so choosing one should be that much easier. As regards comparing the two it's blissfully easy - just don't.
End of lesson.
DM
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boaterjim

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Re: equivalent brushless motor
« Reply #11 on: December 30, 2015, 11:53:06 PM »

Hello all, I am from the aircraft brushless world were power for flight is , watts per pound (weight of model) so around 100 watts for a one pound model will fly it slowly but no reserve power for aeros, 200 watts per pound model balistik, so 2kg model 500 watts fine flyer. more watts is better.

Can this weight to watts be applied to model boats and if so, the required watts per pound to get a boat starting to plane.

just asking
Jim
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Klunk

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Re: equivalent brushless motor
« Reply #12 on: December 31, 2015, 09:14:50 AM »

Watts is the power of the motor and can be calculated very simply as Volts x Amps. It applies to brushed as well as brushless motors.
There is much more useful data published about any brushless motor than there ever was about most brushed motors (except the Graupner Speed range) so choosing one should be that much easier. As regards comparing the two it's blissfully easy - just don't.
End of lesson.
DM
I'm on my phone but from memory
Volts  = V
Watts = w
Amps = a
So if DM is saying V x A = W
Then transposing the equation given that you know 2 of the 3 items means you can work out the third.
Ie V = A W 

Please correct if I'm wrong!!
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Tug Fanatic

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Re: equivalent brushless motor
« Reply #13 on: December 31, 2015, 09:32:48 AM »

I'm on my phone but from memory
Volts  = V
Watts = w
Amps = a
So if DM is saying V x A = W
Then transposing the equation given that you know 2 of the 3 items means you can work out the third.
Ie V = A W 

Please correct if I'm wrong!!

You are incorrect. Volts equals watts divided by amps. (Divide both sides of the equation by Amps)
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Klunk

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Re: equivalent brushless motor
« Reply #14 on: December 31, 2015, 09:48:29 AM »

God been 30 plus years since I learned that!
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Tug Fanatic

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Re: equivalent brushless motor
« Reply #15 on: December 31, 2015, 10:03:54 AM »

God been 30 plus years since I learned that!

That is why I am better at it than you. I have been digesting it for 50 years (Happy Thumbs Up & Innocent Smiley if Smiley's worked for me)
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boaterjim

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Re: equivalent brushless motor
« Reply #16 on: December 31, 2015, 10:30:21 AM »

Hi so what do I need to get a 48 inch wood fireboat using twin brushless motors, and 3 cell lipo on each, up on an easy 25 mph plane
Can you please give me your opinion on motor size and wattage required,
I was thinking about two Ntm 3530 1400vv 560watt ea
motors from hobby king?
Jim
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sparkey

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Re: equivalent brushless motor
« Reply #17 on: December 31, 2015, 10:41:33 AM »

 :-)) Hi,Jim,I would go with two NTM prop drive 30-36 875 watt motors bit more power and only 30p dearer,after all you can ease off of the throttle but if you don't have enough power you got to start again,plus if you start putting all the extra's on the boat you will a bit more umph .....Ray. :-))
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Tug Fanatic

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Re: equivalent brushless motor
« Reply #18 on: December 31, 2015, 11:29:49 AM »

:-)) Hi,Jim,I would go with two NTM prop drive 30-36 875 watt motors bit more power and only 30p dearer,after all you can ease off of the throttle but if you don't have enough power you got to start again,plus if you start putting all the extra's on the boat you will a bit more umph .....Ray. :-))

Ray

Do you mean this 35-36 rather than the 30-36 you suggested (which I cannot find)? http://www.hobbyking.com/hobbyking/store/__29489__NTM_Prop_Drive_Series_35_36A_1800Kv_875w_UK_Warehouse_.html?strSearch=875w
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sparkey

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Re: equivalent brushless motor
« Reply #19 on: December 31, 2015, 11:34:10 AM »

Sorry slip of the finger your right 35-36 ....Ray :-))
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essex2visuvesi

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Re: equivalent brushless motor
« Reply #20 on: December 31, 2015, 12:17:45 PM »

The Turnigy NTM motors are very good quality for the price, Im running 2 of them in my constellation
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red181

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Re: equivalent brushless motor
« Reply #21 on: December 31, 2015, 01:06:39 PM »

I have used ntm in planes, thet are very robust,

Boaterjim, here are the answers you want, same boat, with a load of testing etc, I only use brushless so am familiar with what you want, however 25mph is a massive ask for a 4 foot heavy old girl, mine is 22mph recorded with eagletree datalogging, faster and the hull gets very unstable. Have a read, all the answers are here, and get the watt meter dave suggested, I started with one of these, you cannot guess what your amp draw, watt consumption etc is, if you get it wrong your esc's will blow or the motors will burn out. Just getting the props wrong by a couple of millimetres is enough.

personal experience would have me saying 1400kv is too high revving, lower kv means more torque, which you need to get this heavy wood lump moving. Mine are 800kv, my Huntsman that will do 25mph is 850kv, higher kv usually is in very fast but very light racing boats, for example a tug would have low kv, so its a balancing act. When I was building my fireboat there was nothing out there for reference, lucky you :} :} :} you have a full build to use as reference!

Any questions, just ask, but read this! (looks like some of the pictures have disappeared, you need to open new link an they reappear)

http://www.modelboatmayhem.co.uk/forum/index.php/topic,39278.0.html
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inertia

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Re: equivalent brushless motor
« Reply #22 on: December 31, 2015, 01:33:17 PM »

Those very nice people at Component Shop are now advertising a 150A Watt meter, which does the same measurements etc as the budget one I use, for 17.95. http://www.componentshop.co.uk/150a-watt-meter-and-power-analyser.html
They also now have a 120A brushless marine ESC. http://www.componentshop.co.uk/120a-marine-v3-waterproof-brushless-motor-speed-controller-esc.html
DM
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sparkey

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Re: equivalent brushless motor
« Reply #23 on: December 31, 2015, 02:57:10 PM »

 :-)) I found that the most current used on my princess was 28 amps,this with the following setup a 500kv 1300 watt motor,a 100 amp esc running on 4c 14.8 volts and a most unsuitable 4 blade 55mm steam prop ( the only spare one I had at the time),nothing got overly warm and performed very well,so a little watt meter comes in very handy if only to get the fuse size right and an idea of run time.....Ray :-))     
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boaterjim

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Re: equivalent brushless motor
« Reply #24 on: December 31, 2015, 04:53:05 PM »

WOW thanks for the information lads  specially Red i81 and Sparky.
I now feel confident about what motors to get and not wasting time money and effort on something that doesn't work.
 I will get a wattmeter as well as it seems to be a great piece of kit
Thanks again
happy new year
Jim
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