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Author Topic: facts on Brushless Motors  (Read 13078 times)

colin-stevens

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facts on Brushless Motors
« on: August 30, 2007, 10:19:26 AM »

I am building an Atlantic 75-RIB. I want to powwer it via the uotboards. settled on 1/10th scale as this will give me a larger outboard. But to fit in the  motor  i have decided to go Brushless. Dont want reversing so settled on a 28 vesion,including speed control. low end just to see what it would be like. If it works and gives enough power then i wil get another to power the other outboard. If it aint man enough then i have only wasted one motor, and go up in price a bit.
So the question is, do they produce much heat, how are they if they get wet, and how accident proof are they, and as i am removing the supplied shaft and fitting a longer one so i dont  need a coupling, will it stand up to the shaft maybe beeing out of true?
colin
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MCAT

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Re: facts on Brushless Motors
« Reply #1 on: August 30, 2007, 01:50:55 PM »

Colin   cannot answer this question but thought i should point out I believe you also need a ESC especially for brushless motors
so you my be wasting more then just a motor. Im sure you know this but wont hurt to mention it.

will we be getting some pic's of the build ??
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colin-stevens

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Re: facts on Brushless Motors
« Reply #2 on: August 30, 2007, 02:23:17 PM »

the brushless motor came witha speed control.
just wondering how "acident" proof the motors are
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cbr900

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Re: facts on Brushless Motors
« Reply #3 on: August 30, 2007, 03:49:29 PM »

You can always suck it and see, then tell us all so we don't have to waste money ............. ??? ???



Roy
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dougal99

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Re: facts on Brushless Motors
« Reply #4 on: August 30, 2007, 08:46:19 PM »

Colin,

my maxim "plan for the worst and you'll never be disappointed"  ::)

Doug
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Captain Povey

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Re: facts on Brushless Motors
« Reply #5 on: August 30, 2007, 10:27:04 PM »

Hi all, I am never sure about the field durability of the brushless motor. We have had one running on trial continuously at work for about ten years without a problem but everytime we build one into a product and let it into the hands of a user it lasts about ten hours. Something to do with Hall sensors I am told. Also the motors cost about 20 and the controllers 200. Cheers Graham. :(
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colin-stevens

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Re: facts on Brushless Motors
« Reply #6 on: August 31, 2007, 08:27:15 AM »

Roy,Glad i am going to be the guinepig. O0
Doug, yer doing that. I always try to build so that things like the motors shafts ect can be removed.
its a totalll heath Robinson build, bits of brass tube, cut up helicopter shafts and spares.
should be "interesting" >:( :'(
colin
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Welsh_Druid

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Re: facts on Brushless Motors
« Reply #7 on: August 31, 2007, 09:44:10 AM »

Colin

I have used a couple of brushless motors for the drive props on my RNLI hovercraft. I extended the shafts and supported the ends through Tamiya ball races (see attached photo) - no problems with vibration or heat build up, though it does not get run for long periods, and of course being mounted high up they do not get wet either ;).   Lots of power and torque.

Don't know if that is any use or interest ?

Don B
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colin-stevens

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Re: facts on Brushless Motors
« Reply #8 on: August 31, 2007, 11:06:18 AM »

well at least someone else has done something else with the shaft, vibration is one of the issues i was wondering about
by the way, how about some more photos? looks realy good.
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johno 52-11

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Re: facts on Brushless Motors
« Reply #9 on: August 31, 2007, 01:15:08 PM »

Colin

I have some info on how I built the outboards for my 1/12 Atlantic 21 if this is of any help to you. http://www.lifeboatmodels.co.uk/atlantic.htm the 2 links at the top of the page give a detailed build upto the point of shaping the gearbox.

Welsh_Druid would love to see some more pic's of your Hovercraft what scale is it.

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Welsh_Druid

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Re: facts on Brushless Motors
« Reply #10 on: August 31, 2007, 01:50:56 PM »

box.

Welsh_Druid would love to see some more pic's of your Hovercraft what scale is it.



Johno

I thought you were at the Southport RNLI meeting last year when I had it out on the very rainy Sunday ? (it won third prize in the scratch built class)

Irs 32 inches long, 17 inches wide so that makes it 10th scale.

Anyway here's some pics for you.

It doesn't get used much - the other club members complain its too noisy  ::)


Don B.
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colin-stevens

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Re: facts on Brushless Motors
« Reply #11 on: August 31, 2007, 02:30:18 PM »

Johno, it was youre site that gave me the idea.
havnt been able to find the Bevel gears you mentioned.
colin
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Welsh_Druid

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Re: facts on Brushless Motors
« Reply #12 on: August 31, 2007, 03:33:24 PM »

Colin

Squires list 12mm 45degree bevel gears in their catalogue if thats any help ?

Don B.
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colin-stevens

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Re: facts on Brushless Motors
« Reply #13 on: August 31, 2007, 03:55:06 PM »

too big, looking for a lot smaller
Ta
colin
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Colin Bishop

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Re: facts on Brushless Motors
« Reply #14 on: August 31, 2007, 04:05:07 PM »

Try here: http://www.hpcgears.com/

(the other) Colin
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colin-stevens

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Re: facts on Brushless Motors
« Reply #15 on: August 31, 2007, 04:13:41 PM »

Saw the sizes, thought goodie, their. Then looked at the prices. 13approx each. stick with what i have. bur thanks anyway. put the link in my favourites, never know. must sort out my favourites, getting a bit unweidly, cant find a thing.
colin
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colin-stevens

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Re: facts on Brushless Motors
« Reply #16 on: August 31, 2007, 04:15:43 PM »

Guys, realy appreciate the help, but getting a bit of topic. could do with knowing if Brushless get very hot. its going to be in a very small box. will mount it on an ally plate, might help.
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johno 52-11

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Re: facts on Brushless Motors
« Reply #17 on: August 31, 2007, 05:14:13 PM »

Colin

The ones I used were from HPCgers part number ZEB0.5-16 and are priced at 89p each. they are Moulded hostafoam http://www.hpcgears.com/newpdf/bevelgears_pdfs/moulded_bevel_gears_0.5_2.0mod.pdf not sure if they will be able to take the load of a bigger motor but they work ok with a 400.

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colin-stevens

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Re: facts on Brushless Motors
« Reply #18 on: August 31, 2007, 08:40:39 PM »

johno, you are a gent. will carry on with what i have for now, but will order a pair asa back up
thanks
colin
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colin-stevens

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Re: facts on Brushless Motors
« Reply #19 on: August 31, 2007, 09:56:23 PM »

just a quick sot of crude progress
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justboatonic

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Re: facts on Brushless Motors
« Reply #20 on: August 31, 2007, 10:54:37 PM »

You dont need a brushless ESC for brushless motors.

You only need a 'special' ESC when using Lipo cell packs instead of NimH or Nicad packs. This is because Lipo's have different characteristics and must be switched off when the voltage gets down to a certain level else the pack is ruined.
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malcolmfrary

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Re: facts on Brushless Motors
« Reply #21 on: September 01, 2007, 12:04:09 AM »

A look at
http://en.wikipedia.org/wiki/Brushless_DC_motor
might be useful.  Not all brushless motors are equal, some low power ones having integrated electronics which will allow a normal controller, higher power types might not, and, having rather more wires to connect that a brushed motor, will require a dedicated controller type.
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Subculture

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Re: facts on Brushless Motors
« Reply #22 on: September 03, 2007, 03:53:11 PM »

Brushless motors tend to be a tad more efficient than brushed type,as there is no commutator or brushes to worry about. This also cuts down on maintenance, which is virtually zero (bearings wearing out......).

One disadvantage of brushless electric motors are, unless they are sensored, is poor low speed working and an odd delayed throttle response. So they're not such a good choice for scale models that may need to run slow sometimes.

Sensored motors need a special controller, and these are much more expensive. Sensored motor and controller combinations give you the power and maintenance free running of brushless motors, with the low speed running characteristics of a brushed motors, at a price.

Andy

Stavros

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Re: facts on Brushless Motors
« Reply #23 on: September 03, 2007, 10:27:06 PM »

Right then if you dont need a special esc for a brushless motor how do you connect them up, as they have 3 wires commign from them

Stavros
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wombat

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Re: facts on Brushless Motors
« Reply #24 on: September 04, 2007, 08:41:20 AM »

You do need a special ESC for a brushless motor of the type used for model boats. There are brushless motors that do not require an ESC, but these tend to have the electronics built in to them already - many don't have speed control, or have very limited speed control. CLassic examples of these are spindle motors on hard drives or in PC fans.

A brushless motor ESC has six fets in a three phase bridge arrangement rather than the normal ESC which has 4 FETs in a single phase bridge, or a single FET and a relay. The outputs for a brushless motor consists of three squarewaves spaced 120deg (1/3 of a cycle) apart. To vary the speed, the frequency of the squarewave is changed - this correspnds pretty much directly to the desired speed. (Though because the brushless motor is essentially a 3-phase induction motor, they don't run well at low speeds without some jiggery pokery not necessary in most model boat applications). For a traditional ESC, the speed is varied by varying the mark-space ratio of the signal applied to the motor, which varies its effective average voltage.

One mototr type will not work on the ESC for the other type.

Wom
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