Brushless motors

[harry smith 1Participant @harrysmith1]

Hi Bryan

So the brushless motor trip ended OK !!!

What size prop and blade number are you planning for the Huntsman.

One of our club members is running a Phantom cruiser with a G60-500kv on 6S with a 4 blade 70mm prop.

[Dodgy Geezer 1Participant @dodgygeezer1]

Try an outrunner at a somewhat lower kv – perhaps 1500. The bigger boat could do with more torque for a bigger prop…

[BRYAN ASTONParticipant @bryanaston57723]

Greetings Dodgy

Thanks for the reply, do you or anyone know of a suitable brushless outrunner motor and matching esc for a boat ,

as all that I can find are for aircraft. Etronix do not appear to list outrunners.

Can you tell me what would be the effect on a brushless inrunner if I fitted a too larger prop to it ,would it burn out?

Bryan who knows nowt

[Dave MilbournParticipant @davemilbourn48782]

If it's of any help the prototype Huntsman 31 46" model had an HP 61 glowmotor, running an X55 two-blade prop at a no-load speed of around 15000RPM. Claimed power output for the motor at that speed was 1.5BHP – not too shabby for 1972! On that basis you need an outrunner of about 1000-1400W power output, maybe 750kv, running on a 5-6S LiPo. A 45-50mm diameter motor sounds about right. I can recommend both the Turnigy and Leopard ranges of motors. I might be tempted to try one of these  http://www.componentshop.co.uk/lc5055-6t-720kv-leopard-outrunner-brushless-motor.html  with a 120A ESC http://www.componentshop.co.uk/120a-marine-v3-waterproof-brushless-motor-speed-controller-esc.html

As there are no brushes to burn out and the rotor is sensorless then I can't imagine what might happen to an inrunner which was overloaded, save that the speed controller would probably shut down due to excess current and/or temperature. Quite unexciting really………..unless the bearings seized…..

DM

Edited By Dave Milbourn on 19/04/2016 10:06:20

[BRYAN ASTONParticipant @bryanaston57723]

Greetings Harry

The brushless trip went superbly, but I have no idea what size a Phantom cruiser is , is a G60 the make of the motor and is 500kv fast enough and as for what size prop to use I was hoping someone would suggest one, please see reply to Dodgy

[BRYAN ASTONParticipant @bryanaston57723]

Thanks Dave

Watch this space, to quote General Mc Arthur ( I Shall Return) It always comes out right in the end

Bryan( who needs all the help I can get)

[harry smith 1Participant @harrysmith1]

Hi Bryan

Misspelled MFA Fantome and yes the G60-500kv is a brushless motor.

I use Hobbyking gear.

A few motor I use are Hobbyking 3639-1100kv (800watts) or D3548/4-1100kv(910watts) with 2 blade 40-55mm props.

Running on 5800mah Lipo batteries, on 3S 12210rpm or on 4S 16280 rpm.

Also use a 3648-1450kv(1600watts) on 3S(16095 rpm) or on 4S(21460rpm).

I use the Hobbyking car ESC,s 60 or 100Amp with the program card which runs on all the HK-30,45,60 and 100 Amp ESC's.

Very easy to setup!!!!

Also use XT-60 connectors as they have no bare pins sticking out from them to short out.

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by Dave Milbourn on 19/04/2016 10:02:05:

……

As there are no brushes to burn out and the rotor is sensorless then I can't imagine what might happen to an inrunner which was overloaded, save that the speed controller would probably shut down due to excess current and/or temperature. Quite unexciting really………..unless the bearings seized…..

DM

.

My understanding is that any brushless, in or out-runner, will simply absorb as much current as the battery provides and the back EMF allows, until the ESC stops, the wires melt or the magnets fail. Which means it is hard to specify a precise power output from them – you can always push them a little further – until they die.

In practice they seem to die because the magnets lose their power as they get near the Curie point – which is somewhere between 100C and 200C depending on whether you have bought a cheap brushless or an expensive one! When this happens, odd things occur and you get runaway thermal issues (code for catching fire). A burnt-out brushless will probably need new magnets as well as new wires if you want to mend it…

The practical power you can get out is therefore limited by the cooling you can achieve. I think it is better to run a motor well below maximum power and not need any cooling. But if you think your boat is a bit sluggish and you want to, say, double the voltage (something you can do with a brushless much easier than a brushed motor) remember to check the temperature you are running at.

I suspect that all the maximum power figures given with brushless motors refer to it operating in a cooling wind at the front of an aircraft. Enclosed boat spaces are not the same, and boat operators need to pay attention to the maximum temperature achieved. Wouldn't it be nicer to run with the old AlNiCo magnets – their Curie point was about 800C? Even Samarium-Cobalt can do about 400C….

 

Edited By Dodgy Geezer on 19/04/2016 15:01:37

[Dodgy Geezer 1Participant @dodgygeezer1]

Whoops – I did the Curie points from memory, and, on checking, find that the Neodymium alloys they use nowadays start to deteriorate at about 80C, but only go completely at 300C-400C, depending on the grade. And it looks as if they can get Samarium alloys up to 800C as well…!

I must stop living in the past… But it's still a good idea to arrange SOME ventilation for a brushless…

[Dave MilbournParticipant @davemilbourn48782]

I must stop living in the past… But it's still a good idea to arrange SOME ventilation for a brushless…

If you say so, old dear, but using them at well below their melting point does seem sensible – even to a clod like me. It was Bryan who posed the question; I'm far too much of a coward to risk my model/money by running electric motors at speeds designed for gas turbines or dental drills.

I know nuffink about Curie points, but didn't she discover radioactivity?

DM

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by Dave Milbourn on 19/04/2016 17:21:40:

I must stop living in the past… But it's still a good idea to arrange SOME ventilation for a brushless…

If you say so, old dear, but using them at well below their melting point does seem sensible – even to a clod like me. It was Bryan who posed the question; I'm far too much of a coward to risk my model/money by running electric motors at speeds designed for gas turbines or dental drills.

I know nuffink about Curie points, but didn't she discover radioactivity?

DM

The one we're talking about here is her husband, Pierre Curie. Funny family – He was magnetic while she glowed in the dark…

Of course SOME people will want to use brushless motors at their maximum capability – racers, for example. This was just a friendly warning to sports users that, just because the motor you have has a maximum output of 1hp that doesn't mean you can use it to generate 1hp without considering cooling. Use it to generate 0.25hp and it will probably be fine without it….

[Dave MilbournParticipant @davemilbourn48782]

DG

Then we are, as some pretentious twerp once said, "singing from the same hymn-sheet" , although I'm certain that we had proper hymn books when I sang in the choir.

I would imagine that Harry remains to be convinced……but I think of him – almost fondly, my little possums – as 'Harrikin from Moonee Ponds'.

Sorry, Bryan, but we've got a long way off topic (unless you're a Barry Humphries fan). Will you ever forgive me?

Dave M

[ChrisBParticipant @chrisb29081]

Hi Bryan, I have just shoved a big brushless into my huntsman, and it goes "very well!".

The set up is : turning your D3548/4 1100kv motor, through a hawk esc ( I use them as I have a programme card for them) 6s lipo ,and the prop is a 30mm k series two blade graupner job.

The motor does get hot yes, but I have yet to change to a water cooled mount etc. As this is still in 'experimental' mode. But first impressions are good.

Chris

[ChrisBParticipant @chrisb29081]

Hi Bryan, I have just shoved a big brushless into my huntsman, and it goes "very well!".

The set up is : turning your D3548/4 1100kv motor, through a hawk esc ( I use them as I have a programme card for them) 6s lipo ,and the prop is a 30mm k series two blade graupner job.

The motor does get hot yes, but I have yet to change to a water cooled mount etc. As this is still in 'experimental' mode. But first impressions are good.

Chris

[Dave MilbournParticipant @davemilbourn48782]

Chris

I run a 32mm 3-blade prop on my 1/16 scale Huntsman (half the size of the big Precedent model) with a 2817 1050kv motor on a 3S LiPo. I'm considering reducing this to a 2S.
Your motor is running a tiny prop at a very high speed (>24000RPM). Maybe it's getting hot because it's trying to boil the lake?

Dave M

[BRYAN ASTONParticipant @bryanaston57723]

DG,DAVE, CHRIS

Thankyou for all your help and tips , I am at this moment in time trying to digest all the info and after a few hours Laying down in darkened room I will come to a decision. Onward and upward.

Bryan

[BRYAN ASTONParticipant @bryanaston57723]

Chris,Dodgy and Dave

I have just sent off for a Turnigy outrunner D3548/4 1100 kg motor, I have now to find a suitable esc to go with it

If it is disappointing , I will swop it over for the Etronix in the Sea Commander,any suggestions for a suitable esc would be appreciated..

Onward and upward

Bryan

[harry smith 1Participant @harrysmith1]

A 60 Amp is on the data for this motor, but, I run 100Amp.

Also to motor will take up to 5S batteries.

[Dave MilbournParticipant @davemilbourn48782]

Bryan

The motor is rated at 50A maximum. I have used FUSION Hawk marine speed controllers in 18A and 30A sizes and have been very pleased with them. The 50A should do the job for you **LINK**

Don't forget to buy the programming card at the same time – it's shown further down the same page. Those who didn't bother usually regret it, and you can use it on any Hawk ESC subsequently.

Alternatively I've also used and can recommend the brushless ESCs and programming card from Component Shop. The 60A ESC is a little more expensive than the 50A Hawk, but it has the facility for water-cooling; is waterproof, and the programming card is a lot cheaper! **LINK**

Dave M

[BRYAN ASTONParticipant @bryanaston57723]

Dave.

Stupid question,I assume that using nihm 7.2v batteries are ok ,as lipos always seem to be recommended for brushless kit,

The Etronix runs alright on Nihm.

Bryan

[Dodgy Geezer 1Participant @dodgygeezer1]

Posted by BRYAN ASTON on 21/04/2016 10:47:38:

Dave.

Stupid question,I assume that using nihm 7.2v batteries are ok ,as lipos always seem to be recommended for brushless kit,

The Etronix runs alright on Nihm.

Bryan

Brushless, or brushed, motors will run on any electricity provided from anywhere, so long as there's enough of it.

It's just that motors take a lot of power, so the old zinc-chloride 'dry cell' batteries run down very quickly, and are not recommended, except for small 'toy' boats. Even then they are an expensive choice…

Lead Acid can provide the power, but are heavy (and sometimes can't provide HUGE amperage, particularly in the smaller model sizes. So we use these for big hulls with big motors, but not for anything that moves fast…

Nicads, and the modern equivalent, NiMH, are quite light and can provide quite a bit of power. So we use these for faster boats. Note that you can get a wide range of output from different NiMH batteries – some are designed for continual low output, some for short high output. You need to buy the latter type if you want fast speeds.

Lipos are VERY light, and can have VERY high outputs – enough to make them quite dangerous. Since brushless motors are also very light and can take much more power than an equivalent brushed motor, Lipos and Brushless tend to go together if you want huge power in a light package. This is what aircraft want, which is why you will find aircraft all using this combination. To get the best out of a high-amperage brushless you need a high-output battery, which means top-end NiMHs, or Lipos.

Since boats seem to be a minority interest, no one outside the hobby spends much time recommending specific batteries for boats. Because Lipos require a LOT of care in use, and weight is not so much an issue in most boats, NiMH is usually the battery of choice for the marine world…

[Dave MilbournParticipant @davemilbourn48782]

DG

99.9% agreed. I would only dispute the word "usually" in the very last sentence. "Often" would more accurately describe my personal observations, but we're down to splitting hairs now. As long as we can wean people off those Great Grey Bricks for such models – in the mistaken belief that bigger batteries can supply more current for longer – then we're back to that hymn sheet.

DM

[BRYAN ASTONParticipant @bryanaston57723]

Thankyou Dodgy,Harry, and Dave

I thought apart from the amperage , all nihm batteries were the same. Life is a constant learning curve.

Dave the price of the 50amp Hawk esc and program. card, is the same as the component shop 60amp and program. card, so I will go for the Component shop, on your recommendation

[BRYAN ASTONParticipant @bryanaston57723]

Greetings all

Taking into account the size of the Huntsman and motor size how large should the prop be for decent performance, ?I forgot to ask before.

I will now go quiet for a while, I think.

Bryan

[Dave MilbournParticipant @davemilbourn48782]

I would suggest you start with a 2-blade plastic X55. The prototype 1/8 scale H31 went very nicely with one of those fitted, and they aren't as expensive as cast metal props.

Dave M

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