Model Boat Mayhem - Forum

Technical, Techniques, Hints, and Tips => BRUSHLESS Motors and Speed Controllers => Topic started by: debssnal on October 12, 2008, 10:36:41 PM

Title: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: debssnal on October 12, 2008, 10:36:41 PM
Hi everyone i have been playing around with brushless motors this year.I have had some good times with them and some bad.Now I feel I am going forwards very fast.I am getting bags of power and long running times.I have fitted them in small and large boats.I have fitted them in jet drive and prop boats.I have a Cygnus GM33 fishing boat 1:16 scale (24.5" long x 10.25" beam),and on a 6volt 7ahp gel cell battery runs for 4hours.It has a Tornado Thumper 3536 Brushless motor - 400 watt 1000 kv outrunner .The motor runs cold all the time so no power used to heat the lake.I have a 1:16 jet drive lifeboat (33" long x 9" beam).This has 2x 300watt 1700kv outrunner  brushless motors.It has 2x 2500 ma 11.1 volt lipo battery's,and runs for 3 hours.The motors also run cold in this boat.I have a 1:10 scale jet drive lifeboat (54" long x14" beam and coming in at 15kg).This has 2x Tornado Thumper 4250 Brushless motor - 720 watt 600kv outrunner.This boat runs for 1.5 hours on a 12 volt 12ahp gel cell battery.I have also tried the Tornado Thumper 4250 Brushless motor - 720 watt in my Speedline 1:12 Severn lifeboat.It went well ,at a bit over scale speed on 75 mm props,but they got a little warm.So i have two Tornado Thumper 5055 Brushless motors - 1280 watt 580kv outrunner on there way for it.The Tornado Thumper 4250 Brushless motor - 720 watt 600kv are going in a new 1:12 scale tyne class lifeboat.On the low rpm outrunner brushless motors it looks like you need 100watts of power per kg they work very well.I hope this is of some help to everyone.I will keep you posted on how the severn and tyne get on.

ALAN
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Stavros on October 12, 2008, 10:48:16 PM
OK in laymans terms (if there is some) can you give the say Graupener equivalent size motor in a table so we can see what is what.It is so difficult to know what is an equivalent brushless to say a Graupener 700bb turbo or even a MFA 850.Thanks




Stavros
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: debssnal on October 12, 2008, 11:19:53 PM
Hi well a Tornado Thumper 4250 Brushless motor - 720 watt 600kv =4.58 MFA 850'S.It will run a model of up to 8kg with a four bladed prop up to 60mm with no probs.As for 700 bb turbo it is a high rpm motor so not the same.When i had my 1:10 Scale jet drive lifeboat first on the water i had 2 x 700bb turbo with 2:1 gear drives on the 40mm jet drives and it was slow and eat batterys.Have a look for yourself at how the 1:10 scale and the 1:16 scale lifeboat run on brushless.
The 1:16 scale http://uk.youtube.com/watch?v=yas3G4BQ-Fg
The 1:10 scale http://uk.youtube.com/watch?v=gLRKH9_MKfI
The 1:10 on 24volt http://uk.youtube.com/watch?v=Jn2QxbhaJUs

ALAN
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Garabaldy on October 12, 2008, 11:30:04 PM
Ahh more brushless talk :-))

Sounds like you have a fari amount of experience in this are now debssnall?

In comparing the brushless motors to the 700bb it mite be easier to work out how much watts the 700bb produces.  So im sure thats just volts X amps?

I have just put 2 tornado thumper C3530 1100kv 340watt motors into my fireboat 39.  Hopefully they will be powerfull enough to give a good speed!

Debssnal what kind of speed controllers have you been using?  I have 2 35amp water cooled seakings.


Gary
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: debssnal on October 12, 2008, 11:51:12 PM
Hi Gary i am useing Programmable Brushless Car ESC XC60A Continue with BEC for the prop boats.I will have to get the XC100A ESC'S for the new motors for my 1:12 Severn.The ESC'S i use are fan cooled and they self program so no fuss.On the jet drive boat i only need forwards so i use plane ESC'S.

ALAN
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Stavros on October 13, 2008, 06:15:24 PM
so an I right in thinking that the thumper 4520 produces 4 times the power of a 850???




Stavros
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: debssnal on October 13, 2008, 07:01:18 PM
Hi Stavros, yes that is wright.A mfa 850 out put is 157watts,were the Thumper 4250 out put is 720watts.
The mfa 850 is only 62.3% efficient (1/3 of its power is lost in heat and friction)so 1/3 of your battery power is wasted so making a shorter running time.
The Thumper 4250 is 96% efficient so giving more power and longer running time.
This is just over 200 meters the boat is doing in 8.5 seconds. http://uk.youtube.com/watch?v=Jn2QxbhaJUs
The boat is 54"long and comes in at 15kg.
2x mfa 850 will not do this.I know this as 2x 700bb turbo with 2:1 gear drives were no were near it.

ALAN
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Stavros on October 13, 2008, 07:31:49 PM
Right then some sense at last with regards to theses brushless motors !!!




Stavros
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Weeds on October 13, 2008, 08:05:02 PM
Wow, what a thread! Lots of primo information to digest here. Forgive me, but I couldn't quite figure out which motor you say is best.

Can you recommend the best brushless motor you tried and specify the motor, propeller (direct drive), boat size, battery and guesstimate the boat's speed and runtime?

I'd be able then to go and buy same stuff as you did and have similar success   {-)

Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: nick_75au on October 14, 2008, 08:08:52 AM
Maybe Ive calculated it wrong , would that be 23.5 meters a second? or 80 odd KPH
What's your measured amp draw, say static in the water?

Ive got 2 Darke Horse (like what Pandan used to sell) motors per shaft with a total 4.5 :1  reduction, 20 amps per motor 40 amps per shaft or 960 watts per shaft as a comparison.

Regards
Nick
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Garabaldy on October 14, 2008, 08:35:52 AM
can some one explain the brake function to me?  On a boat, is it better if its just turned off?
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Martin [Admin] on October 14, 2008, 08:41:46 AM
yes!  :-))
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Proteus on October 14, 2008, 09:18:48 AM
can I ask why its better turned off, if you leave it on a soft setting surely it help protect the speed controller from large amp surge if you slam it from forward to reverse, same as delay helps stop damage I thought. but I may be wrong  :-\  ???

Proteus

Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: malcolmfrary on October 14, 2008, 09:44:54 AM
I assume that the brake function just removes the power and shorts the motor causing a sudden stop of the motor.  Being able to slam straight into reverse on a boat is your actual brakes.
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Garabaldy on October 14, 2008, 10:09:15 AM
The user manual (http://www.hobbywing.com/upload/manual/SeaKing_080628_e.pdf) which came with my speed controller is not the clearest but the way i interprated it is the brake function is more for cars.  "when using brakes when steer" helps prevent the motor going into reverse when going round corners.  I am unsure though.  Ive read teh manual 4 or 5 times and its probably still going to take me a while to get the controller set up.  With or without break?  The "double click" function bothers me slightly, i hope when the break function is switched off that goes away......
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: portside II on October 14, 2008, 10:18:51 AM
I have allways admired the way brushless motors work ,and their efficency . So far all i have read is that they are good in high speed applications,jet drives etc, but what about tha other end of the scale brute power as in a tug application .
Just a thought.
daz
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Garabaldy on October 14, 2008, 10:43:37 AM
on one of the other forums some one has fitted brushless motors to a dumas tug i think.  The torquer lower KV rated brushless motors tend to be more expensive though....
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: andrewh on October 14, 2008, 11:57:52 AM
Motor braking

Disclaimer - I have never been inside a hobby brushless speed controller and looked at what the software and hardware are arranged to do.
But I do design and make braking resistors and systems (up to about 20MW motors)

Any motor can be stopped by shorting the windings - try it if you are brave and confident! 
The currents flowing are huge and the torque released will break mountings and certainly any gears attached.

Much kinder and more controllable is to connect a braking resistor across the windings - so a DC motor needs only one, but ideally an AC motor (brushless) needs one per phase  - usually 3 in our world.  (you can  connect a brake resistor to just one (or two) phases but its a bit uneven and brutal)

How much is right? - well it depends on what you want.  My mental rule-of-thumb is that a resistor about equal to the resistance winding (in Ohms) gives a fairly "sharp" stop.   For aircraft brakes the resistor is usually set at this value approx (1 to 2 ohms), as usually it's required to fold the propellor.
The "sharp" stop (maybe 1/10 sec) won't do gearboxes any good at all - so a much higher resistance is used -  its best to start high and work down (if you ever have to do this use a length of hair-dryer wire, or car light-bulbs to find out what works and is safe)

So - the brushless ESCs may be switching in three resistors (one per phase) for the braking function, but these resistors would be quite large and visible, and would only be used for this function.
So I suspect that the designers use FETS as synthetic resistors (perhaps the same FETS used for the drive).  Although FETs have a VERY small resistance when they are fully "on" (and an infinite resistance when off) they can be driven so as to have any resistance, and would almost certainly  be pulsed so that the braking can be adjusted.

So in summary:

Useful/interesting/shut up! andrew?

Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Garabaldy on October 14, 2008, 12:35:53 PM
very interesting....  So if its really bad for the motor  mountings etc why would the manufactuer have a mode where braking is turned off?
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: andrewh on October 14, 2008, 12:47:49 PM
Sorry, I've not quite understood.

When the brake is off - all the torque on the motor mounting is from the motor running (and largest at the start) - no problem 

I was just making the point that braking by shorting the motor windings WILL stop the motor, but it can apply huge forces to the mountings and any geartrain attached  - which is why it is not done much.

Not many users of ESCs want brakes - cars, trucks and rockcrawlers, and some aircraft, so the brake function, where it exists, is often switchable off, and adjustable.

andrew
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Garabaldy on October 14, 2008, 03:16:40 PM
should i switch mine off?  Is it likely to break my 6mm ply mountings if i do? 
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: johno 52-11 on October 14, 2008, 03:19:14 PM
Hi Stavros, yes that is wright.A mfa 850 out put is 157watts,were the Thumper 4250 out put is 720watts.
The mfa 850 is only 62.3% efficient (1/3 of its power is lost in heat and friction)so 1/3 of your battery power is wasted so making a shorter running time.
The Thumper 4250 is 96% efficient so giving more power and longer running time.
This is just over 200 meters the boat is doing in 8.5 seconds. http://uk.youtube.com/watch?v=Jn2QxbhaJUs
The boat is 54"long and comes in at 15kg.
2x mfa 850 will not do this.I know this as 2x 700bb turbo with 2:1 gear drives were no were near it.

ALAN

Alan

While I find the performance of your boat on the video  impressive I am a little concerned about your figures. If they are correct then your boat is doing 45+ knots which is 20 more that the real thing. Scale speed for 25 knots at 1/10 scale is about 8 knots or 4 Meters per second.
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: andrewh on October 14, 2008, 03:56:02 PM
Garabaldy

Switching the brake off cannot increase the load on the mounting device
If the brake is inside an ESC, it is not a short circuit - it will be much gentler
If it is "on" and works OK there isn't a problem whether its on or off

Have I been guilty of being confusing, or wrong or (far worse) giving you worry?
andrew
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: debssnal on October 14, 2008, 10:59:21 PM
Hi everyone ,one thing i forgot to say i have blown up a few couplings with brushless motors they have bags of torque.
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: debssnal on October 14, 2008, 11:23:26 PM
Hi sorry everyone its just over 100meters not 200meters.
it has been run over a marked out 30 meters on 12volt.
ave on 4runs 5.3 sec.Could not do a 24volt run as i a coupling exploded into bits

ALAN
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Garabaldy on October 15, 2008, 12:14:45 AM
if we are onto brushless oops admissions i tested the starboard drive out but had forgotton to lube the shaft and i have clearly damaged the sintered bearings due to friciont/heat build up.  The motor didn't break a sweat doing this either. 

Now, how do i replace the sintered bearings? %%
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Weeds on October 19, 2008, 03:50:04 AM
Sorry for off topic question,

Can I use my TowerPro Brushless Outrunner 2410-08T 890kv http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=664 in a boat, and if so, how?
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: Martin [Admin] on October 19, 2008, 04:34:04 AM
Almost any motor can be used in a boat, just a matter of mounting it, fitting the right speed controller,
connecting it up to a shaft
and selecting a suitable propeller.... simple as that!

I don't really understand brushless motors numbers yet but the TowerPro Brushless Outrunner 2410-08T 890kv at $7 is
so cheap,  it's worth a punt just to experiment! As it an outrunner (the whole outer casing spins with the shaft), the
inner bit, (coils) is the fixed bit and also the mount mount. The motor is therefore fixed at the tail end, not the front end
like we're used to.  It's not a big motor and designed for ultra, ultra light RC planes so it won't have much guts but should
be ideal for a small speed boat, say 12-18" long. The trick is to find the right propller to match the motor.... trial and error...
.... unless anyone knows a good match?

(http://www.hobbycity.com/hobbycity/store/catalog/2410-08Ali.jpg)


My mate Bradders took a punt on one on fleabay - 20 with ESC!!!!! He's going to use it in a small balsa hydro he's building.
 Item number: 230301512227  (http://cgi.ebay.co.uk/SkyWing-980kv-Outrunner-Brushless-motor-40A-ESC-BEC_W0QQitemZ230301512227QQihZ013QQcategoryZ34055QQssPageNameZWDVWQQrdZ1QQcmdZViewItem#ebayphotohosting)       

(http://i8.ebayimg.com/04/i/001/14/f6/9d11_1.JPG)
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: nick_75au on October 19, 2008, 09:11:00 AM
That second motor is the same as the one I run in my Springer, I think it might be a little slow unless you really up the voltage to the maximum the speed control can handle. It Spins a 40 mm Raboesch prop on 12volts with a current draw of around 20 amps but is spinning that prop at 11000 rpm. At 6 volts it draws 3.5 amps but is to slow for the Hydro methinks. A fellow on another forum did not have a great deal of success with the first motor in a small PT boat hull.
Regards
Nick
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: andrewh on March 04, 2009, 12:54:42 PM
I have been searching for this thread/post for weeks :}

Weeds- this is the "bell motor" that has been powering my Brushless trial boat
http://www.modelboatmayhem.co.uk/forum/index.php?topic=14068.0

Using a Graupner s29 racing prop (2mm thread)
and working very well in my Higgins PT boat on 6 and 8 cells, 35mm 2-blade Graupner prop

Because my version is a 21T wind of about 1200KV, and the one you pictured is 890KV you need a bigger prop - probably 40mm - see what happens

Martin sed:
It's not a big motor and designed for ultra, ultra light RC planes so it won't have much guts but should
be ideal for a small speed boat, say 12-18" long

All true, but this one will swing a 10x5 prop and produce 120watts - about twice what a S600 is comfortable with

The PT boat is 30 inches long, but not heavy
(http://i222.photobucket.com/albums/dd159/andrewh_photo/blspiel/BellmotorinPTboat.jpg)

THIS is that it does in a 12 inch sillyboat
(http://i222.photobucket.com/albums/dd159/andrewh_photo/blspiel/DSC04551.jpg)

so well worth a try!
It needs any cheap 10A or 15A brushless ESC
It also sings as it runs - the rotor doesn't look like a bicycle bell for nothing :}

andrew
late, but pursuing

Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: boatmadman on March 04, 2009, 03:43:32 PM
This is all very interesting, I wonder if the ACTION man is planning an expansion into brushless?

Ian
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: andrewh on March 04, 2009, 04:45:05 PM
Ian,

You could ask him :}  but I don't think so at the moment (altho' I would NEVER presume to outguess a modest genius)

I have had many comments on the installation of the motor in the PT boat - with comments ranging from "kinda Puny" to "cheap" but its like a lot of things - the size (relative to brushed motors) is not relevant  - what matters is the revs, torque, what props it will twist at what speed. 
The entire installation cost me 20 several years ago, and could now be bought for half that, or about the price of a S600 from a "branded" source,
andrew
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: sunworksco on July 20, 2009, 08:09:19 AM
I'm using two Novak Crawler brushless motors and ESCs in my 1/32nd scale Type IX-C sub(2400.3mm long).These motors are the sensor type with programable low/high speeds and can run the prop at very low scale  rpms with very cool performance.The motors are about the size of brushed 380 motors,do not cause noise interferrence,are energy misers and outlast brushed motors.They are more water resistant as well.The ESCs can be water or air/fan cooled. I'm also using some very nice linear servo adaptors for the rudder and diving planes.8)
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: gyronuts on September 14, 2009, 10:02:28 PM
Hi,
    Anyone tried brushless on a 12v dry cell in a precedent perkasa 49" boat with a single prop? thanks. Bill
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: debssnal on September 16, 2009, 07:54:05 PM
Hi Bill,

One of our club members done it but it was twin prop. It was going around the lake just on the props.
Went very very fast. If you give me the weight and the size of the propeller I will send you a link with the motor you need.

kind regards
Alan

p.s failing that, come and see me at the Southern Model Air Show at the weekend. Just ask for Alan the Marine coordinator
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: ray123 on September 17, 2009, 07:37:06 AM
ive done it 2 600kv brushless motors on  a 12volt 4amp jell cell  lasts about 6min's  but in retern you got speed  :-)     (the only thing is my boat isnt a true planing hull  so going this fast i couldnt turn it very well %% (as good as brushless are ive decided to go back to 540s & i get 10mins plus run time!!) ;)    i have 2 brushlees motors & speed cons i might sell now!  only used 6times   regards ray
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: andrewh on September 17, 2009, 12:52:35 PM
Ray!

Its not the Brushless motors that are eating the amps  - its the props!

At every point of operation the BL motors are VERY much more efficient than any Brushed.  If you change you are giving up the efficiency.

Reduce the prop size or pitch (or both) until the run time is what you want and it will be going very much faster than with the Brushed motors (because of the efficiency)
If the motors are 600kv and the boat is really moving the props must have a big pitch so they must have a fair diameter (cos the two are related in boats (not in aircraft)) so I suggest trying some cheap plastic props

hope this encourages you
Pm me if you would like to discuss
andrew
Title: Re: LONG RUNNING TIMES ON BRUSHLESS MOTORS
Post by: nick_75au on September 19, 2009, 02:17:17 AM
Ray
I aggree with andrew to a point, its the rpm of the props, double the rpm of the prop and the power absorbed quadruples, the brushless motors are able to spin the props faster and handle the power but draw more current in the process,

Drop your voltage to 6-8 volts and come back with your results

Nick