Model Boat Mayhem - Forum

Technical, Techniques, Hints, and Tips => BRUSHLESS Motors and Speed Controllers => Topic started by: dodgy geezer on August 02, 2009, 08:46:44 AM

Title: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 02, 2009, 08:46:44 AM
All the advice here seems to cover large and powerful motors (and why not!).

I am putting together a trial 'starter' boat for children out of balsa in the old EeZeBilt style - you can see it under the Pictures section of http://modelboats.hobby-site.com . It is 20" long - the frame you see weighs 1 1/4oz at the moment, and I suspect it will end up at about 4-6oz.

These boats used to potter sedately around with a 4.5v flat battery and a small Mabuchi brushed motor, however I suspect that modern technology might improve matters a bit. I am looking to keep the build very low-cost, but I thought there might be a lightweight aircraft brushless and ESC for perhaps £10-£15 which would make it plane on 4 cells. Has anyone got any advice....
Title: Re: Recommendation for SMALL brushless....
Post by: monarch on August 02, 2009, 09:28:13 AM
Hi
Not an easy question to answer, so many types - Outrunner tend to be large low revs high torque, Inrunner tend to be faster revs less torque.
If you want the boat to reverse watch what ESC you get most a/c and fast electric are forward only.
Hope someone can help a bit more on suitable recommendations.

Monarch
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 02, 2009, 11:14:33 AM
Hmm....

I've never used a brushless, but the impression I get is that they rev very fast. I suspect that, for a 'sports' boat, low revs/high torque is better. No reverse would not be a killer, but I would need the ability to go full, half, dead slow and stop. Do cheap brushless motors (probably intended for aircraft) have throttling issues when used on light boat loads?
Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 02, 2009, 03:06:00 PM
Quote from: dodgy geezer
Do cheap brushless motors (probably intended for aircraft) have throttling issues when used on light boat loads?
The motors don't.The cheap controllers can't give low revs without gearing.

The cheap controllers get hot on two lipo cells(thats ~ 7 volts).It is down to the choice of P-ch transistors used.
Title: Re: Recommendation for SMALL brushless....
Post by: andyn on August 02, 2009, 03:30:43 PM
http://robotbirds.com/catalog/product_info.php?cPath=56_102&products_id=961
Title: Re: Recommendation for SMALL brushless....
Post by: Mi Amigo on August 02, 2009, 03:37:04 PM
My friend has one of these, it works well, (in an aeroplane), never had a problem yet, he's had it about 6 months now.

http://www.brchobbies.co.uk/?page=shop&action=additem&item=184 (http://www.brchobbies.co.uk/?page=shop&action=additem&item=184)

£12 is good value for a motor with esc.

Neil

Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 02, 2009, 04:43:35 PM
That IS good value - worth getting (as I just have) purely to experiment with these motors! This looks like a shop which will go in my bookmarks...
Title: Re: Recommendation for SMALL brushless....
Post by: jimtrellis on August 02, 2009, 04:52:45 PM
The cheap controllers get hot on two lipo cells(thats ~ 7 volts).It is down to the choice of P-ch transistors used.

I've been following this thread with some interest, but then you threw this in and you have confused me completely.
What is a P-ch transistor? Do the adverts tell you which type of P-ch transistor is fitted, and what are the types to avoid? If the type fitted isn't stated then how do we know whether or not a speed controller is going to get hot, and does it matter?
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 02, 2009, 05:46:45 PM
Do the adverts tell you which type of P-ch transistor is fitted, and what are the types to avoid? If the type fitted isn't stated then how do we know whether or not a speed controller is going to get hot, and does it matter?


Without knowing anything whatsoever about brushless motor controllers, I can state categorically that, in common with all other advertising, the adverts will:

- only tell you about the 'good' things their product has
- avoid mentioning anything about the downsides of what they offer
- indicate that their product is the peak of desireability, and that no other product can match it.

I am constantly surprised by the way companies generally manage to provide a product line of several grades of product at different prices, and yet each one is the absolute best....
Title: Re: Recommendation for SMALL brushless....
Post by: Captain Povey on August 02, 2009, 07:16:38 PM
H Dodgy, I have posted some stuff on here of my experiences of fitting a small brushless motor, Fusion 1100rpm/volt, in the Mantua Mincio. Whilst the motors are a good price the cheap controllers are not good value. In the end I had to buy the proper job which was programmed for a boat and had reverse. Cheers, Graham.
Title: Re: Recommendation for SMALL brushless....
Post by: andrewh on August 02, 2009, 07:27:29 PM
As Neil says - good value

My friend has one of these, it works well, (in an aeroplane), never had a problem yet, he's had it about 6 months now.

http://www.brchobbies.co.uk/?page=shop&action=additem&item=184 (http://www.brchobbies.co.uk/?page=shop&action=additem&item=184)

£12 is good value for a motor with esc.
Neil
This is a "bell" motor - the 21T version has a KV of 1200 and has been extensively used in by Brushless trial boats from 12 inches long (razor and White dwarf) to 18inches (hellkitten) and my 1/35th Higgins PT boat
Details and photos in http://www.modelboatmayhem.co.uk/forum/index.php?topic=14068.0
and http://www.modelboatmayhem.co.uk/forum/index.php?topic=13538.0

Dodgygeezer - your desire and quest are perfectly reasonable and possible - Brushlesses come from 1gram weight to hundreds of tonnes - there is one in there for you.  I would strongly reccommend a cheap aeor speed controller
 - can't possibly agree that their low speed is poor - they are designed and made to allow Andys to fly, hover and reverse in the air.  As always you get what you pay for (and weep for as long as it cost when the smoke comes out)  in my case at Wicksteed I wept for a few picoseconds while i found the fried FET

Please consider making your own motor :} :}
The "bell" motor is approx a 2209/XXT wheere XX is the KV.  For cheerful pottering  - with a prop like an EZbilt prop and a few cells (say 5 or 6 pencells for power) you should be looking for a KV from 1000 to 2000.
GOOD NEWS - this is what all the little motors are - unless they are inrunners (You don't need an inrunner)

Have a look at micronRC anyway - thy also do good deals with bell -motors but also sell  the GoBrushless kits you can wind these with any KV you like from  about 300 to 3000.  A CDrom motor taken straight from a disc drive will run with a cheap brushless ESC and is near-perfect for what you want.  With replacement magnets (which come in the Gobrushless kit) it is perfect - low current, fairly low KV (turns a sensible prop) and VERY cheap
http://www.micronradiocontrol.co.uk/gb.html

Go for it - I will help all I can
andrew

 


The Bellm otor
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 02, 2009, 08:58:37 PM



Please consider making your own motor :} :}
The "bell" motor is approx a 2209/XXT wheere XX is the KV.  For cheerful pottering  - with a prop like an EZbilt prop and a few cells (say 5 or 6 pencells for power) you should be looking for a KV from 1000 to 2000.
GOOD NEWS - this is what all the little motors are - unless they are inrunners (You don't need an inrunner)

Have a look at micronRC anyway - thy also do good deals with bell -motors but also sell  the GoBrushless kits you can wind these with any KV you like from  about 300 to 3000.  A CDrom motor taken straight from a disc drive will run with a cheap brushless ESC and is near-perfect for what you want.  With replacement magnets (which come in the Gobrushless kit) it is perfect - low current, fairly low KV (turns a sensible prop) and VERY cheap
http://www.micronradiocontrol.co.uk/gb.html
 

Hmm....a lot there!  I think buying a cheap brushless +ESC just to find out what all these acronyms mean is a starter for 10... Have you seen the aim of my site? I was looking to get kids interested in building - looks like they may be building motors as well! I have disk-drive motors coming out of my ears - I should be able to get 20 or 30 just by going into the attic... so that might be a good route to go...
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 05, 2009, 02:54:48 PM
I've picked up a cheap brushless now, a 2408-21T-3A, at £12 from BRC hobbies and here are my first impressions:

These things are complicated! With a brushed motor, as soon as I got it out of the packet I could connect a few volts to it and see how it ran, from any old batteries which were lying around, or a power supply if available.

With this, you must connect it to its ESC, then to a receiver, then get a transmitter. Your batteries must be fully charged, otherwise the Auto Detect will not work. Once connected, the transmitter throttle position, auto motor calibration (timing?), cell count (?), voltage cut-off and lost signal protection are set up automatically. Only then can you see how it turns. I have not done this yet -I don't know if the motor is safe to run with no load, and there are no instructions which might tell me...

The mount is intended for an aircraft, so will need modifying. I will have to mount it somewhere for testing. Unlike a brushed motor, I suspect you can't just hold this in your hand while test-running it with a few volts...

When I turn the motor it is very notchy, and requires much more of a 'hand twist' to turn than a brushed motor. The impression I get is that this is going to be very powerful...

There are warnings all over the instructions which tell me NOT to fit bigger props than specified, and to keep within Watt limits - use a wattmeter at all times. I had hoped to keep the speed within managable limits by fitting a suitably large prop - it looks like this is forbidden....

The data on power is designed for aircraft use, and compares prop size, number of cells and thrust. It expects you to use Li-Po - there are only two rows showing Ni-Cad, and both assume 8 cells. I had hoped to use 4 cells, or 2 if the motor turned out to be very powerful - it looks like this is forbidden... 

You are also warned to 'fly the motor until fully discharged' - probably something to do with the ESC automatic settings. If you are to do multiple flights you must make sure the battery is fully charged prior to each. For a small boat you might want to do a few runs, potter about a bit, pause for a sandwich, potter about some more.. it looks like this is also forbidden....

I suppose my first question to the Brushless experts is - can I use a small pack of 4 AA Nicads with this? And what will happen if the Nicads are not fully charged?

Title: Re: Recommendation for SMALL brushless....
Post by: nick_75au on August 06, 2009, 09:19:45 AM
Hi Dodgy Geezer

In answer to some of your points

"With this, you must connect it to its ESC, then to a receiver, then get a transmitter."
A servo tester will work equally well in place of the transmitter/receiver for testing, still need the esc though, it acts as the commutator.

"When I turn the motor it is very notchy"
Motor is notchy as they use Neo' magnets which are far stronger than the ferrite magnets found in most motors, gives more torque.

"There are warnings all over the instructions which tell me NOT to fit bigger props than specified, and to keep within Watt limits - use a wattmeter at all times"
Unfortunately with boats there is little detail on what prop is good with what motor, it would be nice if there was a table that matched air propellers with boat props that give similar watts. Fit a small prop to keep watts down. A good base line is a prop smaller diameter than the diameter of the motor.


Most esc's will run on 6 volts if its 2 cell lipo capable, I use mine on a 6 volt gel cell and just set the battery type to ni** and the cutoff to the minimum possible (0.4 V per cell) which gives a theoretical lowest voltage of 2.4 volts. Cutoff can be disabled on most esc's as well so it then will just want power and servo signal.

If using Lipo, this is important any other "usual" cells wont make any difference.

It may work with 4 cell nicad, I think you may need 6 though, good thing about brussless is a lower KV motor can be selected which will lower the rpm.

Regards
Nick

Of course you might have an ESC that is not overly programmable or sensitive to voltage
Title: Re: Recommendation for SMALL brushless....
Post by: nick_75au on August 06, 2009, 10:29:16 AM
Forgot to mention, no problem with running the motors unloaded
Nick
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 06, 2009, 11:15:25 AM
Nick,

Thanks very much - your responses give me a bit more confidence!

I understand the theory of why an ESC is needed, but I was reporting on the impressions that a 'standard' motor guy would have on seeing these things for the first time! Unlike a brushed motor, it's a non-trivial process to test-run a BL motor.

Your advice to use a small propeller is very helpful - the impression I have is that BL motors are high rpm, and noisy. The one I have makes quite a loud whine if I just twirl the rotor with no power applied! In a small scale boat I wanted to cut noise, so I thought over-propping the motor would slow it down and cut the noise, while running off 4 cells would limit the wattage.....

To get a motor running slowly, say, 3-4k rpm, on 4.8V I would need a KV of about 1000. I presume I would have to wind that myself - is there an easy calculator to indicate how to do this? I have lots of dead hard drives and CD-Roms available to me...

Why is there a voltage cut-off? Is it to protect the LiPo cells? Of course the ESC probably won't run with less than +5v, and you want to maintain control, but if you were feeding your motor from gel cells you could run flat with no problems. My ESC is cheap (£12 for motor +ESC!) and it has an 'auto' cut-off - I wonder what that means, and how I can influence it? I probably can't disable it....

   
Title: Re: Recommendation for SMALL brushless....
Post by: nick_75au on August 06, 2009, 11:59:05 AM
Assuming your motor is the tower pro,

your motor is a 1400 Kv motor so is probably ok with a fine pitch prop and 6 Ni** cells, there is a tower pro 2410-12T-3Y which has a Kv of only 600 and quite a few in between

http://www.hobbyking.com/hobbyking/store/tp_motor.html

and the ESC is

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=656&Product_Name=TowerPro_n18A_Brushless_Speed_Controller

Bit of extra information if you read the reviews on setting up the ESC. You will want the Ni** setting which will reduce the cutoff voltage. The cutoff is to protect the batteries from over discharge, Lipos don't have anywhere near the slowdown like gels and Ni**. By the time a lipo powerd motor is slowing down the cells are damaged hence the requirement for a cutoff.

Not sure about the whine bit, should be silent if your spinning it by hand, something loose/rubbing or dry bearing?

Regards
Nick

Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 06, 2009, 12:05:46 PM

Why is there a voltage cut-off? Is it to protect the LiPo cells? Of course the ESC probably won't run with less than +5v, and you want to maintain control, but if you were feeding your motor from gel cells you could run flat with no problems. My ESC is cheap (£12 for motor +ESC!) and it has an 'auto' cut-off - I wonder what that means, and how I can influence it? I probably can't disable it....

   
You couldn't run a simple hobby brushless controller with 4 NiXX without a voltage cut-off.It would overheat to destruction.
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 06, 2009, 12:24:11 PM
Hmm... not sure about that. I simply bought this combination, as advised above:

http://www.brchobbies.co.uk/?page=shop&action=additem&item=184

This is advertised as a 15A ESC, and a 2408-21T-3A motor. There is no information provided on 'setting up' the esc - I was going to connect it to an old 27Mhz futaba receiver and drive it from that, so there will be no 'computer' input from the transmitter. I will look for more info on this requirement. I will try it on 4 NiCads initially, unless you think that will damage anything...?

If you spin a small brushed motor you will typically hear a faint 'clicking' sound, as the brushgear slides over the commutator. When I rotate the BL, instead of complete silence, or slight ball-bearing noise, I hear a low 'thrum' of vibration as the magnets notch round the stator. If I spin the shaft between finger and thumb, that noise increases in pitch to a whine - about the same volume as a brushed motor, but I had been expecting a dead hush...

I have one immediate question - how do you connect the ESC wires to the motor? The motor has a red, blue and white set of wires, the ESC just has three black wires. No wiring diagram was provided - does this mean you can connect any wire to any other wire? I enclose a shot to show what I mean...
(http://img190.imageshack.us/img190/9385/35170160.th.jpg) (http://www.postimage.org/image.php?v=gxPzdNJ)
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 06, 2009, 12:32:06 PM
You couldn't run a simple hobby brushless controller with 4 NiXX without a voltage cut-off.It would overheat to destruction.

How does that work? The cut-off is for LOW voltage, isn't it? Are you saying that a motor will be OK on 6volts, but will overheat if given 2v?

The only way I coulod see that happening is if the ESC stopped working at some low voltage, and this left one phase energised continuously (though that would be a poor ESC design).

Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 06, 2009, 12:33:58 PM
How does an audio amplifier work?
2v would need an N-channel bridge.

Simple brushless controllers have got the equivalent of three  half bridges (http://www.datasheetcatalog.org/datasheet/vishay/72281.pdf).
Top of page 1 shows the connection and the table shows how at 2.5 volt the resistance increases.
Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 06, 2009, 12:43:25 PM
that's three complementary half bridges with N and P
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 06, 2009, 01:08:17 PM
How does an audio amplifier work?

Um...lots of different ways? They tell me my Quad uses a clever triple cascade design. But I still have valve amplifiers here... :)


Simple brushless controllers have got the equivalent of three  half bridges (http://www.datasheetcatalog.org/datasheet/vishay/72281.pdf).
Top of page 1 shows the connection and the table shows how at 2.5 volt the resistance increases.

Yes, but the amperage has gone down. Aren't we talking about I2R heating here? I had hoped to save weight by using 4 cells, but if 6 is really essential I suppose I can squeeze them in...
Title: Re: Recommendation for SMALL brushless....
Post by: OMK on August 06, 2009, 01:19:44 PM
And so good that it had to be said twice.

Don't you just love repetition?
Don't you just love repetition?

Quote
Do the adverts tell you which type of P-ch transistor is fitted, and what are the types to avoid?

No, and BC109s.
Maybe better still, elbow the P-ch transistor and bung in a P-ch FET instead?

How does an audio amplifier work? Easy. It works in the same way as a radio. You start off with two wires, bung one of the wires away, then you end up with a wireless.
To make the audio louder you connect two loudspeakers in parallel; negative to negative and positive to positive, then connect both neg's and pos's to 240 a.c. and holler into loudspeaker #1, then wrap the green wire around your Tx antenna, about five or six turns. Don't worry about the inductive foldback loop issues because the yellow wire takes care of that.
Title: Re: Recommendation for SMALL brushless....
Post by: andyn on August 06, 2009, 01:25:52 PM
How about Li-Po's instead? I have a suitable one for sale.
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 06, 2009, 02:43:18 PM
How about Li-Po's instead? I have a suitable one for sale.

I'm looking for a cheap, simple build, suitable for kids. The boat so far has £3 worth of balsa - probably needs another £1. Propshaft and rudder will be a few quid, and I was expecting a £50 radio. If I went for a conventional brushed motor that would be perhaps £4, with not much for batteries - I assume every house has a charger and 4 AA nicads. A speed controller, though, would be about £20-30?

A brushless motor, on the other hand, might be free if we use a CD-Rom, with £8 for a cheap ESC. I got a motor+ESC for £12. If this could be run off 4 nicads, we could have a very cheap system. Cheap LiPos would cost about £15, plus a charger?
Title: Re: Recommendation for SMALL brushless....
Post by: andyn on August 06, 2009, 04:12:21 PM
http://www.modelboatmayhem.co.uk/forum/index.php?topic=18933.0
Title: Re: Recommendation for SMALL brushless....
Post by: malcolmfrary on August 06, 2009, 11:21:13 PM
The CD motors that I have used in the past have all been brushed types, running on a fairly conventional ESC.  There may be a change in motor technology that I haven't run into yet.  I haven't taken one apart yet, but it could well be that floppy and hard drives may well contain brushless motors.  What their performance would be, who knows?
Title: Re: Recommendation for SMALL brushless....
Post by: jimtrellis on August 07, 2009, 09:46:50 AM
So if I can try to pull all of this together -
•   Brushless motors and/or speed controllers aren’t very good at slow speeds without having a gearbox
•   Brushless speed controllers only work in one direction, so you can’t reverse the boat
•   If you just happen to have a spare CDROM drive then if the motor still works it might just be the right sort of motor (three “ifs” here)
•   The DIY kits from Micron all seem to be out of stock
•   You must avoid speed controllers with the wrong type of P-Ch transistors but you won’t necessarily know what type is fitted when you buy one
•   Lipo batteries are dangerous if they are allowed to go too flat and cheap speed controllers won’t stop that from happening
This does seem like a lot of different people all beating their own drums in different rhythms at the moment – very jumbled and confusing. If it’s all largely fact then there’s not much here that would encourage me to try a brushless motor yet. For those people who don’t make fast electric boats simplicity and reliability are important, as are slow-speed control and reverse.
I also wondered about the figures quoted, so I’ve looked at one popular website and found that a 7.4v 2200 mah Lipo and mains charger costs £35 while a 2400mah Nimh battery and mains charger is £13. That gives a price advantage of £22 in favour of the brushed motor when it comes to buying a speed controller. Also the Micron kit to make a small brushless motor is £6.60 while a 360 brushed motor can be bought for £3.50. I might not be the world’s best model boat builder but I can count.
I have seen models go with brushless motors and it is impressive if speed is your main concern. They do seem very limited in other ways, though. Perhaps when there’s more collective experience and therefore more agreed wisdom on this technology then a more even balance may be achieved.
Title: Re: Recommendation for SMALL brushless....
Post by: nick_75au on August 07, 2009, 11:29:51 AM
No drum beating on my part or at least I dont think I have {:-{
Dodgy, any of the three wires can go in any combination, if the rotation is wrong swap two of the three wires :-))


I have a total of 2 brushless motors so I'm not an expert (drip under pressure?) but I have taken the time to understand what the different numbers mean.
 1 motor is high speed 3200Kv  and the other is low speed 1000 Kv, both outrunners same diameter as the CD style motor but longer which improves torque.
I use the 1000 kv on 6 volt gel cells in a Springer tug which achieves a massive 4.6 Kph the other motor was in a GG Miami crashboat on a 2.3:1 gearbox and 25 Kph on 10 Nimh cells. Not a Lipo in site

(well actualyIi do have 1 lipo which..... I happen to use on a brushed motor set up :o) I use it because its light not because its Lipo ;)

Im not sure about the overheating thing, for P12 (Aussie Keyboard, never found that pound symbol :D) why not suck it and see. work out the cutout so its the minimum and on Nixx. My bets are it will work on 4 cells. As far as I know most ESCs brushed or brushless need 6 volts or greater anyway so the BEC can work with some exceptions of course. On the Hobbycity website there are tiny brushless escs that will work on a single 3.7 lipo cell so will be happy on 3 Nixx cells as well

Jim, in same order as your post
" see above , Springer, I can set the motor so I can see the bell rotating,  lower Kv motor if slower speed is required
"I have a reversing brushless  esc, Mtronics produce  a 15 and 25 amp version, there are a number of others available, expect to pay the same as a good quality brushed ESC with reverse.
"CD rom motors work but not nearly as much torque as a hobby motor due to only having fridge magnets rather than Neo" magnets(yes I've tried)
"dont Know
"IHNFI short for I have no idea what that's all about
" Lipos will be damaged (not usually dangerous) by over discharging, most brushless escs have protection regardless of price, electronics are available for any ESC that doesnt, Lipos do require more care than other battery types but all batteries have dangers if mistreated

It makes no difference what type of battery you use for brushed or brushless motors your battery price comparison has nothing to do with what motor you use.

The confusion is perhaps because the brushless esc's tend to be aimed with Lipo's in mind, this is possibly due to the fact that most brushless systems are aimed at electric aircraft which benefit from the light weight of Lipo batteries

The Brushless basics thread is an excellent read.  http://www.modelboatmayhem.co.uk/forum/index.php?topic=13538.0

Regards
Nick

 
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 07, 2009, 12:09:56 PM

So if I can try to pull all of this together -


With a nod also to nick_75au - thanks for the useful tip...


I wanted to find out if Brushless was a good way to go for a simple cheap 'small boat' motor. My understanding, gleaned from this thread and a bit of research, is as follows.

Short answer - at the moment, probably no.

Medium answer - probably yes, in the future. At the moment the cheap market is entirely for aircraft, so you have to pay a lot for anything which isn't hi-power/lightweight/LiPo

Longer answer - Brushless motors are probably the way ahead. They are much more efficient and can be optimised for hi-torque or hi-revs. There is no reason why a brushless motor should not outperform any equivalent brushed motor; they can come in any size, and can easily be rewound for any specific application. They should be cheaper than brushed motors - they are simple: I can probably get, or easily make, an ideal brushless motor at the moment.

What I can't get is an ideal cheap brushless ESC. I might want to use 2 Nicads or dry batteries for a small motor, or a gel pack for long duration. All the cheap ESCs assume you are using LiPo batteries, and they have LiPo safety features built in, which means they will detect the initial battery voltage at switch-on, and cut out when this has dropped to about 70%.  Typically, they do not have reverse (though I don't see this as a huge issue. Also, I suspect the current ESCs would not like the motor to be stalled if, for instance, weeds are hit.  There is no reason why an ESC should not be designed which has better marine characteristics, but they are complex beasts, and they are only cheap because of volume hobby aircraft production. Ours will probably always be expensive...

So, if you want a fast power boat with LiPo batteries, lucky you. You can get a high performance unit cheaply.  If you want a little motor for pottering around, you either buy a simple brushed system, or do complicated things with gears and expensive brushless EScs which have reverse, and can be programmed to use different battery types...
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 07, 2009, 12:32:18 PM
The CD motors that I have used in the past have all been brushed types, running on a fairly conventional ESC.  There may be a change in motor technology that I haven't run into yet.  I haven't taken one apart yet, but it could well be that floppy and hard drives may well contain brushless motors.  What their performance would be, who knows?

Some useful things you can get from a dead CDRom....

1 - flat sheet metal
2 - flat and curved plastic
3 - an assortment of bolts/nuts
4 - 4 anti-vibration mounting grommets
5 - various electronic components and connectors
6 - micro limit switches (see picture)
7 - various good quality gears
8 - an IR laser diode, a magnetically-suspended lens mount, and a powerful magnet embedded in the CD mount (see picture - red)
9 - two small 12v brushed motors (for opening the cd-slide and moving the laser reader) See picture - blue.
10 - one small brushless 12v motor for spinning the CD (see picture - yellow)


I would agree with nick_75au - the brushless motor looks as if it will be lower performance than the hobby ones - it's not notchy at all, but it will probably also be dead quiet?
(http://img188.imageshack.us/img188/467/43999938.th.jpg) (http://www.postimage.org/image.php?v=Pq1LV94i)
Title: Re: Recommendation for SMALL brushless....
Post by: jimtrellis on August 07, 2009, 12:50:49 PM
So, if you want a fast power boat with LiPo batteries, lucky you. You can get a high performance unit cheaply.  If you want a little motor for pottering around, you either buy a simple brushed system, or do complicated things with gears and expensive brushless EScs which have reverse, and can be programmed to use different battery types...

It looks like we've arrived at the same point here. My thanks to the folk who've bothered to offer simple explanations. I'm still wondering about P-Ch transistors, half bridges and triple cascades, although I've concluded that they probably just cloud the issues and so are no business of mine.
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 07, 2009, 01:34:52 PM
It looks like we've arrived at the same point here. My thanks to the folk who've bothered to offer simple explanations. I'm still wondering about P-Ch transistors, half bridges and triple cascades, although I've concluded that they probably just cloud the issues and so are no business of mine.

The 'triple cascades' was me, was a tongue-in-cheek comment about audio amplifiers, and has absolutely nothing to do with ESC electronics.

Nick_75au's comments make a lot of sense to me. I am sure brushless are the way ahead - the issue at the moment is that the cheap ESCs are optimised for LIPo flyers.

The ESC is the equivalent of the commutator. Cheap motors just have a couple of brass strips touching three segments of copper. Once a multi-phase ESC becomes cheaper than two strips of brass all motors will go brushless - that probably means that we have to wait for a single-chip ESC. At modern speeds of development, that will probably be next month.....

I will continue trialling a cheap brushless with 4 cells, and perhaps rewind the CD-Rom motor, if I can find a wiring calculator... 
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 09, 2009, 07:01:20 PM
Well, I can report the first (short) trial of this brushless motor I am trialling to see if they will work for small models...

I first tried it with 4 NiCads. Stallspeed had commented that it probably wouldn't work with these, so I was not surprised to find that the ESC beeped, but otherwise did nothing. (Later I found that one of the NiCads was dud, so that was even less surprising)

Then I tried 6 Nicads. The ESC woke up and beeped a lot more at me. It beeped once, then once again. Then it beeped twice, then twice again. Then a pair of three beeps, and back to one again. I believe this is a standard feature of brushless ESCs - you're supposed to move the transmitter throttle at some point to program it. But there were no instructions with the item I bought, so I just moved the throttle at random. Suddenly, there was a single low beep, and the motor started.

The throttle response was, unsurprisingly, odd, given I did not know how to program it. One half of the throttle throw did nothing at all, then at half way the motor started and accelerated up to full when the stick was fully forward. Compared to a little brushed motor the power was phenomenal, and being delivered at higher revs. I was interested in the low speed regime, so tried to run it slowly, and found that I could. It would run at what I would call a medium tick-over - not a crawl, but quite slow, certainly lower than planing speed.

Getting this low speed was a bit tricky. It was only available at one or two click positions on my throttle, and the motor rapidly accelerated if I upped it a notch. If I put an excessive load on the motor with my fingers when running slowly it would stop, and then I had to return the throttle to zero before bringing the motor back up to speed again. Setting up the ESC is definitely a critical point for brushless operation.

I noted that my cheap ESC was specified as 'between 6 and 10 Nicads'. I could have bought one for 'between 4 and 8 Nicads' but at three times the price.

The noise was not high - it was quiet and vibration-free at low speeds, while a medium-pitched whine developed when I ran it fast. It was probably quieter than a comparable speed brushed motor.


So I am wondering whether to install this motor/esc pair at the moment. The motor will be fine for about half its range (when I have worked out how to set it up, but the boat will probably be grossly overpowered at the top half of the range, and there will be a need to strengthen the prop shaft mounting...
Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 09, 2009, 10:03:10 PM
Did you switch on the boat with the throttle at the half way point?

However hard you try with transmitter settings you can't get down to a crawl with a cheap 3-wire brushless.
To do that you can gear down and yet still maintain the top range with a larger prop.

If slow speed is required something similar to the robotbirds gearbox  (http://robotbirds.com/catalog/product_info.php?cPath=56_102&products_id=961) is out your budget then you could purchase gears and make one.

If budget and weight is a priority you could chose a brushed 385 (http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2389737) or 360 (http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2389715) and six to eight high capacity pencells.
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 10, 2009, 12:59:04 AM
Yup - now I understand the basic programming set-up - had to find it on the net, though - nothing in the instructions...


I have still got a few things to try with brushless motors before going brushed...

Without a tach, I estimate that I can run this motor at 1000-2000 rpm on slow (no load). It will go slower with a load, but then I would probably want to up the speed a bit for safety. Unlike Brushed motors, the ESC will stop the motor if it's overloaded, and you have to drop to zero throttle to start it again. But 1500 rpm is quite slow...

I see quite a few 5-cell brushless escs advertised, and some 4-cells, though these are usually not at rock-bottom prices. Then there is always the option of rewinding a motor for a lower kv - I might try that with the cd motor I have. At the moment I would be happy with the slow speed I have, if only it weren't quite so damned powerful at top speed!

Budget, space and weight are the drivers - ideally I want to run on 4 cheap NiCad pencells. The original EeZeBilts ran on a 3 cell dry battery of 4.5v...
Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 10, 2009, 02:12:06 AM
By a crawl I was meaning about 60 rpm with no load,That is possible with a brushed motor.

Rewinding will only effectively change the motor voltage.The same effect would be be more easily obtained by reducing the supply voltage.....that's if you can get hold of a controller.

Title: Re: Recommendation for SMALL brushless....
Post by: sunworksco on August 10, 2009, 05:51:19 AM
Here is what I am using in my www.scaleshipyard.com 1/32nd Type IX-C Submarine.Runs cool,silent,slow scale speed,instant reverse/forward,battery miser,no gear reduction required,no bec required or noise cancellation resisters.
Title: Re: Recommendation for SMALL brushless....
Post by: nick_75au on August 10, 2009, 06:23:36 AM
My Springer motor spins at 600 rpm with load, the boat barely moves at this speed so Im happy with my slow speed performance. Granted a sensored system will be better and will go slower, great for cars but not the cheap setup wanted for this project. Who runs props at 60 RPM?, maybe a paddle wheel perhaps
Nick
Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 10, 2009, 12:26:16 PM
[
Who runs props at 60 RPM?, maybe a paddle wheel perhaps
Who runs props at 60 RPM?
model tugs (http://www.modelboatmayhem.co.uk/forum/index.php?topic=18835) when they have no tow line.
In relation to their size they have greater power which needs to be throttled back on occasion in relation to their size.
Quote
My Springer motor spins at 600 rpm with load, the boat barely moves at this speed
That is a factor of two improvement which could be achieved with a lower kv motor with more poles than dodgy's one.
Aye,just like a cdrom brushless. ok2

Title: Re: Recommendation for SMALL brushless....
Post by: andrewh on August 10, 2009, 12:54:48 PM
DG

Rewinding CD-ROM motor - near infinite information in both the Gobrushless forums and on
http://www.rcgroups.com/electric-motor-design-and-construction-361/

If you need specific help - PM me and I will try and help.

Basically there are levels of mods to a CDROM as howked out of a computer:

So I think your best option is to change the magnets - let me know if you need help or would like to borrow a bell with hot magnets on to try.
andrew
Title: Re: Recommendation for SMALL brushless....
Post by: andrewh on August 10, 2009, 01:05:20 PM
<<The Brushless basics thread is an excellent read.  http://www.modelboatmayhem.co.uk/forum/index.php?topic=13538.0>>

I would have to agree, wouldn't I :}

Any merit it has came from the wonderful Do-How contributions from Nick and others :}

THIS thread is interesting, too - you are asking a new and good question, DG - and doing the trials to get some foundations installed on the subject.  Thanks and well done!

Could you please post where you found the programming instructions for your ESC - I can see that being helpful to me and others

BTW - I mounted my bell-motor on an SHG 380 motor mount using self-tappers to hold the bulkhead mount to the upright bit, and the bell clears the base easily - its a straight drop-in replacement at least on my PT boat.

It may be worth bearing in mind - all of us that power produced by a prop is NOT proportional to the revs at all (probably a cubic function) - there may be little point in achieving VERY low revs, only low enough to reduce the resultant power to the low level you want.
andrew

Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 10, 2009, 05:55:06 PM

Could you please post where you found the programming instructions for your ESC - I can see that being helpful to me and others



No problems - I just googled on 'Brushless esc Beep' to get quite a lot of data - here are some example instructions:

http://www.2dogrc.com/ecommerce/os/catalog/Documents/Xcontroller.pdf
http://www.beatyourtruck.com/bytstore/index.php?main_page=product_info&products_id=232&zenid=502a01688fc65ac9728a3dc1e94a3219
http://www.bphobbies.com/pdf/bp/BP-60A-ESC.pdf
http://www.horizonhobby.com/ProdInfo/Files/20

It ought to be easy to make a brushless motor creep - they are pretty similar to stepper motors, which can go very slowly. I suppose the most common escs are just designed for high revs. Perhaps if we treated them like a stepper motor and used a stepper driver....
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 10, 2009, 06:04:47 PM
whoops - sorry - last url should be http://www.horizonhobby.com/ProdInfo/Files/20A-BrushlessV2.pdf

Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 10, 2009, 06:54:40 PM
It ought to be easy to make a brushless motor creep - they are pretty similar to stepper motors, which can go very slowly. I suppose the most common escs are just designed for high revs. Perhaps if we treated them like a stepper motor and used a stepper driver....
It is impossible to make your 3-wire brushless motor creep.There is no back emf feedback at low revs.If you want creep with brushless you have to use a sensored motor/controller combo.

You couldn't use a stepper motor driver as brushless windings are too low a resistance and the windings are in threes.Cdrom motors have three hall sensors.You could use a sensored brushless controller chip but there are complications there too.

How many pencells do you want to use in total?
Title: Re: Recommendation for SMALL brushless....
Post by: andrewh on August 10, 2009, 07:41:46 PM
I'm only a simple mechanical engineer, but it seems to me that if you feed the beast slow pulses you will get slow rotation to follow the pulses - exactly the same as a stepping motor.  there is no need for locking or position holding - there is a strong magnetic "notch" which will hold the position between pulses

Worth a try, anyway.

The Hall sensors are there for speed control, because the CDROM duty is quite different to our DG's requirement and. for that matter, mine.
andrew
Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 10, 2009, 09:41:13 PM
I'm only a simple mechanical engineer, but it seems to me that if you feed the beast slow pulses you will get slow rotation to follow the pulses - exactly the same as a stepping motor.
Despite some physical similarities in the motors,the controllers don't work the same way.

If dg wants slow speed brushless control and willing to consider stepper motor circuits then sensored cdrom drive,using the hall sensors and the IC's meant for the purpose, is the logical path for future experiments.
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 10, 2009, 10:48:16 PM

If dg wants slow speed brushless control and willing to consider stepper motor circuits....


I drive one of the axes of my telescope using an L293D driven by a PIC16Fnnn - I supose all I need to do is code that up to go faster (though that is a bi-polar driver..).  There is probably a practical speed limit on the top speed for the telescope stepper driver circuit based on the clock speed of the PIC. I wonder what the limiting factor is which determines the slow speed for these three-phase drivers? You would think it was quite possible to put out a pulse every 1/10th sec or so...?
Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 10, 2009, 11:21:18 PM
I meant if you are going to the bother of rigging up your own controller you may as well use the correct chips when they exist.
You wanted two pencells for the motor and  I presume you have four for a receiver so why not just use six on a brushed bec esc with a 360 or 385?

Your present brushless controller works at a fixed frequency of 8kHz but changes the duty cycle
The limiting factor is the driver or controller cannot pick up back emf at low brushless rpm.

For low speed control,you need feedback sensors,whether hall effect or optical encoder, for the controller to perform the commutation electronically.The coloured cables on the Novak rock crawler motor are the sensor wires.




Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 11, 2009, 01:25:37 AM
That makes sense, and would explain the difficulty in setting low speeds. I find that the throttle signal gets quite touchy, and if the ESC loses synch it has to restart with a little surge before coming back down to the bottom end speed again. So about 1000 rpm is a practical limit with sensorless - Nick-75au is doing well to run at 600!

From the weight and space point of view, 4 NiCads would be better than 6. I have seen 4 Nicad cell escs advertised, though, as you pointed out, never 2!

I would normally have gone brushed with a bec esc, but I became interested in brushless because:

1 - the price seemed to be very low; I could not get a brushed motor and ESC for £12
2 - if I can rewind a CD-Rom prices become even cheaper
3 - in small boats the small size and weight of a brushless motor is an advantage
4 - small EeZeBilt boats never had planing performance. Brushless motors would offer that
5 - small boats cannot carry big batteries, so suffer from endurance problems. High efficiency would help that. 

I imagined a small light boat cruising at a good non-planing speed for a fair time on 4 2200MAH NiCads or NiMH, and being able to shoot up onto the plane a few times - the whole thing for pocket-money prices. No complex charging regime or expensive power packs. In fact, I think we're most of the way there - the ability to go dead slow is not absolutely critical. Getting a good low-drain efficient run is important - this will depend on the prop as well as the motor, of course...
 
Title: Re: Recommendation for SMALL brushless....
Post by: Proteus on August 12, 2009, 03:55:31 AM
you can get cheap, small  brushless speed controllers with reverse, and the work OK


http://www.r2hobbies.com/proddetail.php?prod=rcps81707_30


Proteus
Title: Re: Recommendation for SMALL brushless....
Post by: FullLeatherJacket on August 12, 2009, 08:40:57 AM
Delivered price to UK is $38.05 = £23.19; you'll probably avoid the VAT, which should be on top of this. If HMRC do spot it and the Royal Mail have to collect then say cheerio to 15% VAT plus an eight quid "handling charge" from Postman Pat. A useful link but even tax-free it's a bit outside the parameters of £12 including the motor.

I'm still not sure if the objective here is primarily a cheap power train for an Ee-Zee boat, simple enough for kids to fit, or an experiment with brushless motors. If it's the former then it's a no-brainer; brushless just isn't there yet - certainly on the parameter of price. I would also be reluctant to accept that an average 12-year old might be capable of rewinding a CDROM motor when a fair proportion of adults seem incapable of wiring up a battery the right way round - even with a coloured diagram to show them how it's done.

Cynical? Moi?? Nope - just sadly wiser than I used to be.

FLJ
Title: Re: Recommendation for SMALL brushless....
Post by: kiwi on August 12, 2009, 09:13:09 AM
Brilliant FLJ
But how true.

Even if I think DG is going in the right direction

vnkiwi
Title: Re: Recommendation for SMALL brushless....
Post by: stallspeed on August 12, 2009, 09:43:00 AM
Now that I've had a look at the photos,I'm sure I have seen something similar to the 10 1/2 inch Terrier.
It was fitted with a 540 motor,7.2 racing pack and servo op. microswitch.Far from sinking the model,the 540 allowed it to skim along like a tunnel hull boat.
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 12, 2009, 09:57:26 AM
....
I'm still not sure if the objective here is primarily a cheap power train for an Ee-Zee boat, simple enough for kids to fit, or an experiment with brushless motors....
FLJ

Well, it's both, really. While I have been wasting my life away from modelling technology has changed a bit, and when I (was encouraged!) to put up a few pages in memory of the EeZeBilt range I wasn't sure where it would go. I couldn't work out if brushless would be a cheap possibility without a bit of experiment...

What I can see happening is a development in two directions. I would like to maintain and distribute data on the old EeZeBilt kits as a historical service. That means producing (saving!) original die-cut sheets and artwork where possible, and maybe some research later. All contributions gratefully received, by the way - I have Triton diecut sheets up, am working on reconstructing the sheets from a 1960s Terrier, and have a promise of a Curlew to come. If you want, you can now reproduce an original model from 12"x3" balsa, a cheap motor, a 4.5v battery, some brass tube and paperclips....

But a major feature of the EezeBilt kits, and others of this kind from Veron and elsewhere, was that they introduced young kids to the hobby cheaply. So it would be good to encourage that as well - several people have stressed that we have a gap in this area. Simply putting up the original die-cut sheets is of limited value to kids who aren't so interested in the history, because:

- People get different sized balsa today - why cut it down?
- You can't get the original propshaft/rudder
- You can get much better power units
- You can get cheap'ish' radio

so I thought I would see how we could 'improve' the range to offer what it used to do - a simple cheap introduction to model boating. This will be the '50+' range that I have been trying out - EeZeBilts for the 21st century! I would expect these to:

- Cost about £5 in materials
- Maybe another £5-£10 for motor and battery
- Be big enough to carry lightweight radio
- Be just as easy to make, using the original EeZeBilt eggbox technique
- Be between 15"-20" rather than 10"-17"
- Offer lots of opportunity for simple mods and self-built accessories
 
These are probably where the brushless motors would come in. What I think I have found is that we are quite close - some end-of-line BL motors and escs are around the cost bracket, but cheapness rather rules out LiPos (with their costly chargers) and size limits the number of cells. So we are at one edge of an envelope. Which is always fun...


Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 12, 2009, 10:38:26 AM
Now that I've had a look at the photos,I'm sure I have seen something similar to the 10 1/2 inch Terrier.
It was fitted with a 540 motor,7.2 racing pack and servo op. microswitch.Far from sinking the model,the 540 allowed it to skim along like a tunnel hull boat.

Sounds a bit like a shark - the boat will stay above the water so long as it's moving forward...!
Title: Re: Recommendation for SMALL brushless....
Post by: Proteus on August 12, 2009, 01:52:51 PM
Delivered price to UK is $38.05 = £23.19; you'll probably avoid the VAT, which should be on top of this. If HMRC do spot it and the Royal Mail have to collect then say cheerio to 15% VAT plus an eight quid "handling charge" from Postman Pat. A useful link but even tax-free it's a bit outside the parameters of £12 including the motor.

I'm still not sure if the objective here is primarily a cheap power train for an Ee-Zee boat, simple enough for kids to fit, or an experiment with brushless motors. If it's the former then it's a no-brainer; brushless just isn't there yet - certainly on the parameter of price. I would also be reluctant to accept that an average 12-year old might be capable of rewinding a CDROM motor when a fair proportion of adults seem incapable of wiring up a battery the right way round - even with a coloured diagram to show them how it's done.

Cynical? Moi?? Nope - just sadly wiser than I used to be.

FLJ


I read the thread and saw he was after a reversing brushless speed controller but was told in reply 28 that brushless speed controllers don't have reverse so I was pointing out that you can and they are cheap .

Sol how many people who have bought from this sort of company small items have had to pay VAT, I have bought lots and never had to, he also sells them on e-bay.

Proteus
Title: Re: Recommendation for SMALL brushless....
Post by: dodgy geezer on August 12, 2009, 03:53:53 PM

I read the thread and saw he was after a reversing brushless speed controller but was told in reply 28 that brushless speed controllers don't have reverse so I was pointing out that you can and they are cheap .

Sol how many people who have bought from this sort of company small items have had to pay VAT, I have bought lots and never had to, he also sells them on e-bay.

Proteus


Well, reversing would be nice. But originally, what I said was

"I thought there might be a lightweight aircraft brushless and ESC for perhaps £10-£15 which would make it plane on 4 cells. Has anyone got any advice...."

I was looking for small, light and cheap. 4 cells turns out to be a bit of a problem for brushless, but there are cheap combos available as offers - £12 for a motor+esc was a good example. Once I get a cheap prop-shaft and connector I will be trying it out.

My understanding for purchasing abroad is that the magic number is £18 - the cost of the item must not exceed this. Once it does, you are liable to be assessed for tax, on the cost of the item + postage! In practice, single items frequently come through a bit higher without attracting attention, but this must depend a lot on the person on duty, whether a new policy is being enforced, and luck. I have never paid any extra tax yet, and have had items of around £30 delivered.

I suspect that if you go for specialist shipping you are more likely to be stung - I have heard stories about DHL and others in the past. The problem is that, as well as charging an import duty, your shipper is also allowed to charge you an administrative fee for collecting this money from you and passing it onto Customs. This is usually unspecified beforehand unless you ask about it, and, for a grasping commercial company it can be quite high! Royal Mail will also charge this admin fee, but the postie is usually uninterested in collecting it - they don't like the extra work involved in handling money. I have had a package with a 'money to pay' sticker just pushed through my letterbox while I was out, and no one came round later to collect anything...

There's lots more compexity, but you get the idea....