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The Brushless thread
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Glen
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The Brushless thread

plenty of us are using this technology now so time for a thread me thinks Smile if we could put up experiences of every motor used and controller that would be good!

brushless power has an awesome power to weight ratio (650 gram motor is about 3000 watts at 80% efficiency or so) and are very compact so there very attractive to use as weapon drives.

but they do have some problems -

Cogging

most of the motors and controllers we use are sensorless which means the controller is guessing the position of the rotor (it applies reduced power to one coil and senses the back emf through another i believe).

problem is with a large load such as a blade or drum etc the small amount of power applied to one coil at start up isnt enough to move the motor enough to induce a large enough back emf for the controller to sense.

the only way to get around this is reduce the loading on the motor (reduce belt tension or make the setup more efficient etc) or to gear it down more. getting a motor with less KV (rpm per volt) may also help as the torque from the motor is increased.

some controllers also are better and sensing start up on certain motors then others so its a matter of experience there.

Overheating

sometimes the motors just overheat rapidly under free load and driving an otherwise minimal load..

reason being the controllers we use are more or less generic and made to work with lots of different motors. inrunners, outrunners, 2 pole 4 pole 8 pole motors etc etc. all require different timing settings.

generally the outrunners that use 6 or more poles (poles refers to the amount of magnets in the motor) require medium to high timing settings while the inrunners using 2-4 poles require much less timing.

as an example the KD45 blue inrunners most use on high timing generate approximately 3 times the heat on high timing mode with next to no extra rpm generated. be sure to experiement with your controller settings it makes all the difference in this regard.

Good motors -

KD45-17XL

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=5158&Product_Name=KB45-17XL_700kv_Brushless_Inrunner

probably the best of the cheap motors. proven to be pretty durable mechnically so far and the power is immense.

the end caps are only pressed in and need to be reglued and then a mounting system that holds the ends in devised. its also totally sealed so stops swarf being sucked in

runs very very hot (dumps nearly 600w of heat at full power) and runs great from 18v - 36v although you really have to keep your eye on the temperature.

lots of rpms made so lots of gearing needed. goes great with the new turnigy 100A HV controller from united.

Towerpro 5330

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4570&Product_Name=TowerPro5330-10T_679g/215kv/80A_Brushless_Motor

a massive motor probably the best for flat out power and torque. it is the outrunner style so its less durable then the inrunner and swarf can get sucked into it..

low RPM per volt means you dont need much extra gearing as opposed to a inrunner so its good to use when your converting a dc motor robot to brushless.

the magnets are held in poorly tho so definitely a good idea to pull it down and reglue them! also support the motor from both sides for strength

because theres so much torque cogging is not really an issue with this motor.

Sentilon 100A HV brushless controller

works good on most motors. has plenty of settings and all are pretty usefull. also failsafes properly (stops motor when no signal is present)

3 timing settings so its good for the inrunners and outrunners. and constructed pretty average in the new version (small heatsink and weak base..). pretty damn good overall for the money. very reliable so far!
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Post Fri Jan 02, 2009 4:09 pm 
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Valen
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Joined: 07 Jul 2004
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cogging has NOTHING TO DO WITH THE CONTROLLER!.
cogging torque is the ripple in torque due to the interaction between the iron in the motor and the magnets.
IE when you spin the motor by hand its the "lumps" you feel as it turns.

The problems that sensorless controlers have spinning up motors with lots of inertia attached has nothing to do with cogging. Stop calling it cogging because it just plain isn't.

</rant>

brushless is good mmmmkay
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Post Fri Jan 02, 2009 9:22 pm 
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Glen
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two meanings of cogging, isnt english awesome like that Surprised
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Post Fri Jan 02, 2009 9:25 pm 
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Valen
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except one is right and one is wrong ;-O
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Post Fri Jan 02, 2009 9:26 pm 
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Nick
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Thanks for making us COGnisant of the real meaning Rolling Eyes !

Post Fri Jan 02, 2009 11:18 pm 
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cerberus3112



Joined: 05 Dec 2005
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Does anyone listen to "COG"? Laughing
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Post Sat Jan 03, 2009 12:14 am 
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andrew



Joined: 16 Jun 2004
Posts: 3110
Location: Castle Hill, Sydney. N.S.W


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yeah that band kicks ass, now back to topic

In regards to the outrunner motor glen posted i have tried them and have had nothing but bad things with them, i have yet to see them used successfully in a heavy hitting spinner

The blue inrunners work a treat

Dylon has them in his eggbeater robot which once he gets it reliable will be incredibly nasty

they worked fine in orbit minus proper mounting which caused motor failure (this has been rectified) plus the touro featherweight robot from Brazil which competes in robogames every year uses them at some obscene speed and it seems to perform well.
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Post Sun Jan 04, 2009 12:34 pm 
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timmeh
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Just thought id throw in some controllers advertise they have a low torque start feature to save your lil gearbox in your plane which may be why some controllers dont throw enoughf into the motor to start your weapon up.

Also i dont see the 700kv motors on hobbyking?
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Post Sun Jan 04, 2009 3:30 pm 
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timmeh
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Have one of these esc's http://cgi.ebay.com.au/RC-Model-100A-Brushless-Motor-Speed-Controller-ESC-H_W0QQitemZ270324286052QQcmdZViewItemQQptZAU_Toys_Hobbies_Radio_Controlled_Vehicles?hash=item270324286052&_trksid=p3286.c0.m14&_trkparms=66%3A2%7C65%3A1%7C39%3A1%7C240%3A1318

Cost me bout $25 will see how it gose.
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Post Sun Jan 04, 2009 3:51 pm 
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Glen
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they call those ones "supersimple" escs, they have heaps more timing features and some other features but the reviews are always half work great the other half are DOA.

the 700kv motors are on a different page (last one i think) so just look and youll see em. they where out of stock last i saw Smile
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Post Sun Jan 04, 2009 4:01 pm 
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Rotwang
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Joined: 15 Jun 2004
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A long long time ago when Brett and I were thinking heavy weight thoughts and Brett was starting to play with the idea of building some ESC’s one of the possibilities we kicked around was using car alternators as blushless motors.
We decided the air gaps were too large to get any worthwhile efficiency but I am tempted to get a controller and try and see if I can get one to motor.

It’s going to take a lot to convince me that these hobby motors are worth using in a feather.
Bit expensive to be considered a consumable. Confused
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Post Mon Jan 05, 2009 6:21 am 
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andrew



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granted, the blue inrunners have a good track record though and if mounted properly with a flange on both sides to assist the press fit then they should work nicely.

Only reason motor died last event was caus my mounting was crapola and the press fit loosened and both ends of the motor flanged out.

Besides that had more than enough power to spin up the 3kg disc at 2:1 ratio and the motor didn't get too hot either
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Post Mon Jan 05, 2009 8:59 am 
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timmeh
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question Very Happy

one blue motor running 28.8v 1-4 gear ratio.

two blue motors running 14.4v 1-2 gear ratio.

Both driving same load.

Am i correct in saying the two motor setup would produce less heat and less stress on the motors?

This is an example i am aware that 28.8v would prob be pushing the blue motor.
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Post Sat Jan 17, 2009 7:35 pm 
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Nick
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Just remember you need two controllers as well.

Post Sat Jan 17, 2009 7:48 pm 
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timmeh
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Easy controllers get cheaper when your running lower voltages Very Happy
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Post Sat Jan 17, 2009 8:01 pm 
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