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Author Topic: Brushless - how ggod at fine speed controll?  (Read 1746 times)

bbdave

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Brushless - how ggod at fine speed controll?
« on: May 21, 2010, 12:05:16 AM »

I have tried brushless in a couple of boats but i'm not convinced you have the same fine control you get with a brushed system brushless seems fine for fast electrics but anything scale they seem all or nothing.............Discuss


Dave
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FullLeatherJacket

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Re: Brushless - how ggod at fine speed controll?
« Reply #1 on: May 21, 2010, 07:48:39 AM »

Everything I have read tells me that selection of the right motor and speed controller is paramount if you want good low-speed control. There is a type of wheeled model called a rock-crawler; nearly all of these use brushless motors and the name rather elegantly describes their low-speed performance. There's probably a few hundred dedicated websites and maybe even a forum......go Google?
FLJ
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bbdave

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Re: Brushless - how ggod at fine speed controll?
« Reply #2 on: May 21, 2010, 02:04:39 PM »

cheers FLJ i already run an axial crawler but i use a fifty five turn novak brushed for the same reason the thing with crawlers is gearing so the motor still runs very fast. It's hard to explain but i can get a brushed motor to turn very slowly and smoothly where brushless seems very jerky and they seem to struggle.

Dave
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tomo55

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Re: Brushless - how ggod at fine speed controll?
« Reply #3 on: May 21, 2010, 02:23:55 PM »

Ive got a axial with the novak 55 set up.it works well but the new Losi comp crawlers seem to be going for brushless setups ,(more money).
The site to look at is     "ukrcrc"
Chris
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HS93 (RIP)

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Re: Brushless - how ggod at fine speed controll?
« Reply #4 on: May 21, 2010, 04:59:22 PM »

these  will do it and are repairable, but they are expensive, but so easy to set up and will controle the amps they say they Will.


http://www.castlecreations.com/products/products_boat.html


http://www.castlecreations.com/products/products_drive.html

Peter
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Subculture

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Re: Brushless - how ggod at fine speed controll?
« Reply #5 on: May 21, 2010, 06:57:43 PM »

There are two ways that brushless controllers work. The most popular and inexpensive solution is to use sensorless, the controller monitors back emf in the windings and asseses the postion of the motor and switches the feed to windings accordingly.

The second type uses hall effect sensors which are positoned at 120 degree intervals (to represent the thee phases) around the motor, and sense the magnetic fields feedign back to the controller.

These give much better low speed control, as good as a brushed motor, but the controllers are expensive, and limited in voltage range.

For scale applications a good brushed set-up is difficult to beat. Very high quality motors like Buhler, Pittman, Maxon that will out last the owner in model applications and are available for peanuts if purchased surplus, and a suitable controller is inexpensive too.

They offer superb low speed running with multipole armatures, and are very efficient.

bbdave

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Re: Brushless - how ggod at fine speed controll?
« Reply #6 on: May 22, 2010, 11:03:13 AM »

Back EMF that brings back memories of my college days knew it would come in usefull one day  :-))
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johno 52-11

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Re: Brushless - how ggod at fine speed controll?
« Reply #7 on: May 23, 2010, 05:41:12 PM »

I have recently upgraded my Atlantic 21 to brushless and I have aceptabled slow speed control. The reason for the upgrade was that it was not possible to get the performance in a brushed motor for the weight. I have swaped two speed 400's for two brushless motors half the size and half the weight. I can get the same slow running performance with the brushless as I used to with the brushed motors but have a much better top end performance.

 On the other hand I have brushed motors in my Arun and that has the top end performance that I need and give's me the slow speed for manovering that I need.

Knowing the slow speed I can get from the brushless controller and the slow speed I can get from the brushed controller I do think you you can get slower speeds from a brushed controller I would say as low as 20 to 30 RPM while I would say the brushless starts at about 150 RPM.

I think the main thing to remember is that brushless motors in model boats is a faily new thing and controllers can only get better over time but as we also know model boating is a minority hobby and until there is the demand the development work will not happen.

I have come to the conclution that if you can get the performace you want from a brushed motor then that is still the best setup to use and you will get the slow end performance. If on the other hand you have requirment for a high end performance that you can not get with a brushed motor because of the weight then brushless will give you that with a resonable slow performance.

 
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Martin [Admin]

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Re: Brushless - how ggod at fine speed controll?
« Reply #8 on: May 23, 2010, 05:50:43 PM »

Topic renamed  :-)
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red181

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Re: Brushless - how ggod at fine speed controll?
« Reply #9 on: May 23, 2010, 05:59:46 PM »

without boring all that have read the topic, look at the build of my Huntsman 28, its brushless, and the esc ,linked earlier by HS93 will give tickover speed, forward and reverse, its a myth that brushless setups dont deliver this, mainly due to little or no info regarding scale boats with brushless setups. Most brushless setups are just out and out speed, mostly with no reverse, and the esc's that deliver this are generally cheap ebay/chinese ones with limited set up, most being intended for other uses such as RC helicopter etc.

I have such in a couple of jetboats, whilst they are proportional it does not feel like it when driving, whereas the Huntsman will tickover real nice and slow, unfortunately its my brain that only have 2 speeds, fast and stop :D
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andyn

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Re: Brushless - how ggod at fine speed controll?
« Reply #10 on: May 23, 2010, 07:44:46 PM »

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