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[tonyH]

Obviously a Grauniad reader!

There I was, ploughing through The Feast of the Poets etc.etc. for inspiration and all the time it was a typo!

Nice one Andrew!

[andrewh]

Sorry chaps - I had a "good" education in Scotland before Pontius got his wings so poetry and literature waxed large and I know, but don't speak, dodo (latin)

Yes woodworking much more useful - we had hundreds of hydulignum blades off markll Hurricanes for cutting up as wood-turning blanks
Might get back to Brushless before long!

andrew

[tonyH]

I always thought that we built a wall to prevent the Scots from learning Latin? 

[andrewh]

Crivvens, the sheer ignorance of these sassenachs

Having said that I'm one too, but brought up by the highland line.
The Romans lived and traded far north in Scotland for centuries, built the Antonine wall from the Forth to the Clyde as well as Hadrian's wall.  I've always assumed that Hadrian's wall was the last and largest but I confess I don't know the timeline well.

Onyhow, it failed!
vale
Androcles

[andrewh]

Rejoice with me
Not only has my body survived to reach its 60th birthday (mind somewhere between 4 and 6 years old, according to my womenfolk)

But also I have located the problem with my brushless CDROM motor

The its-gone-silent-without-smoke mini-tutorial
This little feller went totally silent in the middle of trial runs in Razor the BL trial boat, and I had not applied enough diagnostic science until today.
Fortunately at work we have low resistance meters by the yard (cos we make low resistances) so I was able to accurately check the resistance of all the windings (0.205 Ohms between any two leads - so EACH winding is half that)
So the problem is not electrical

Pull off the rotor (on little BL motors there is no mechanical fixing - even with an airscrew) and reverse the shaft - rotor turns like silk - its not the shaft or bearings in the stator

Apply engineers blue (actually black felt-tip) and rotate motor
Note - ALL BL motors feel very "coggy" as the powerful magnets snatch at the poles
Ssms scratchy as well as coggy, and there is blue left on two of the magnets
Eureka - diagnosis and solution

Note magnet sticking to blade of knife?
Magnets were attached to the bell with cyano - and the cyano has relaxed as a result of water, heat or both.  It appears that the magnet has got "foam" Cyano behind it - perhaps it overheated the glue while hardening?

Fairly difficult to easily diagnose - the magnet was barely loose - it just flexed inwards a little  - I don't know if it physically touched the stator - but it certainly got so close it magnetically "stopped" it
Solution - remove all the magnets (soak in acetone or cellulose thinners) replace (perhaps using epoxy and microbaloons)
Install motor in White Dwarf (thank you very much, generous donor)
Try it  and tell you

Is this a failure that you -  the great BL-using public - should worry about?
No, its Andrew's trial motor (and the first he ever built) which stopped for a predictable reason.
Commercial BL motors would not have this issue, and nor would my later ones

andrew

[dreadnought72]

Many happy returns!

(And revolutions, where the motor's concerned.)

I reached forty-six a few days ago. And so I'm switching to Martian years.

Andy, 24.5

[andrewh]

Andy 24,5
Many happy returns, too
You don't look a day over 30 ,
and you are my planking hero!

Is the 24.5 in Martian years? or is it the hat size?
Any progress on the OCB?

andrew, 1 of the 10 types of  binary mathematicians

[col426]

Hello all.
I've been reading this thread with interest, trying to learn more about brushless motors.

I've got a Cen Waveshark, like a jetski, which is 720mm long by 260mm wide into which I've put a KMB 33mm jet drive (one of these: http://www.jet-drive.de/cms/component/page,shop.product_details/flypage,shop.flypage/product_id,18/category_id,5/manufacturer_id,0/option,com_virtuemart/Itemid,17/).  It's currently running a .18 nitro engine producing about 1.184 horsepower and about 20,000 rpm.  The standard electric motor KMB run on this jet-drive produces about 19,200 rpm.

I'd like to put a brushless setup into it, as it's too much muck-around, and too messy with the nitro engine.  I'd also like to get more performance!  I've read on this thread that revs is what I need, and a brushless inrunner with a high KV rating. I've been looking at this KB45 brushless motor http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4938, with a brushless controller like this: http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=4691.  I'm looking at running it on 14.4 volts as I already have dual 7.2v Nickel-Metal-Hydride battery packs which I run in my E-MAXX monster truck.

My question is will this do the job?  Also, what is the difference between S, L, & XL motors?  Obviously they are short, long, & extra long, but it looks like the longer they get, the KV rating drops for the same number of winds.  Does anybody know what this is about, and where you would use the different motors?

Thanks for your help, any assistance would be gratefully received!

Phillip

[andrewh]

Hi, Phillip

I see you are in tasmania  - glad you are on board

Why, oh why do most of my replies start off - I don't know the answer/whole answer/question?
Sorry, but here is another "don't know the whole answer", but your question has lots of the right information built in - so lets see what research and arithmetic tell us.
Thanks for the links - they are just what is needed

First the KMB 33mm waterjet - the webpage says the power requirement is about 650watts at 15000 to 20000rpm - so it is not a crazy-revs device.  There are several motors quoted as suitable - and I tried to identify these in motocalc
http://www.motocalc.com/data/motor.html
and managed to reasonably identify the Pletts - these are about 800 to 900KV, and the reccommended Johnston 800 is 1200KV

Please don't be guided by the advertised power of your IC engine - go by KMB instead!
a few more revs will probably not harm the mechanics - Germans build solid kit!

The Brusless you have selected is an inrunner, and the highest of the KV versions of its family.  Its a huge motor - well over a pound weight and the power is written as over 3KW!  (although the discussion suggests that this, too is mythical and would be accompanied by splashing copper)
at 14V this motor would be turning at 32,000 Rpm.  Impressive, but possibly more than the water-jet bearings would like

I suggest looking at one of the more modest KV versions of this motor - around the 1500KV level which would give you the revs at 14V
In answer to your other question - the different versions are made for basically the car and aircraft users - we flyers want to direct drive huge efficient props, but sometimes the ground prevents big diameters so we need to swing a smaller prop faster, or work through a gearbox so there is always a need for several different KV motors in every size.

Plane digression - the same motor frame might have to fly a scale DVll with a 30x10 inch prop on direct drive (2200 RPM), a scale reno racing mustang with a 7x7 prop (17500 rpm), a ducted fan at 37,500 rpm,   or a heli with 30:1 main gear.  Add to that the different voltages to be used and viola! you have a big range of KVs in every motor type

  Since this is an inrunner  - it is not likely that the core length varies (but a close study of the weights would tell you that) - it is more likely that there are several different winds
 from the 2300 you mentioned - 2 turns of fence-wire
to the 650KV version    500 turns of maidenhair wire
(In fact the winds are mentioned somewhere in the literature)
OK, so I exaggerate

ESC can be any that will take the current - and follow the revs intended.  You will have no need of reverse from the ESC, as this is done with buckets on a water-jet.  (There is, BTW a purpose made ESC for water-jets which incorporates the servo movement for bucket reversing in the throttle stick movement)
The one you referred to looks the business, and none should have any trouble at 20 to 25 K revs/min

Best of luck - please keep us posted on progress - with pics!

andrew

[boatmadman]

Great stuff, by coincidence I have recently aquired one of these:
http://www.jet-drive.de/cms/component/option,com_virtuemart/page,shop.browse/category_id,11/Itemid,17/

and am now wondering what to power it with, and what to put it in - did think of a springer, but it might be a touch too fast 

The esc you mention that incorporates reverse bucket control, who make them?
Thanks
Ian

[andrewh]

Ian

How about one of the stealth warships - Visby or similar?

The Combo ESC was by (or at least from)  one of the german manufacturers  - Graupner or Robbe for one of their WJ boat kits - Martin has written about it in another thread.  I will try and find it, but my Home internet is having hiccups.

I am going to lie down in a darkened room - the thought of a 1.5 KW water-jet springer has fried my brian.
andrew

[boatmadman]

Stealth warship looks promising, anyone know where plans are available?

Andy, sorry to hear your Brian is fried 

[andrewh]

Ian,

there is a good thread on
http://www.rcgroups.com/forums/showthread.php?t=792278&highlight=visby
which might inspire you. 
I know that the gent made his own plans (origami )

Googling Visby might find you some plans
don't worry about my brian - its beyond both spelling and help
andrew

[andrewh]

News of the Andrew brushless stable:

The little sick motor diagnosed a few posts ago has been repaired and works well again, but a little stuttery and uneven.  Because I have and optical tacho I will attempt to measure the revs - and hence KV.

Homemade BL CDROM motor from a GoBrushless kit  - I was inspired and finished her off - runs smoothly and apparently powerfully.  The speed control is notably very good - I will also measure the speed and KV of this one

Might commit speedboating with White Dwarf this weekend and relay it to you with new camera
andrew

[DLM]

I've been reading the winding of Andrewh posting and wouldn't it be cheaper to buy the guts with different windings for different situations like bigger boats or pleasure boats or racers. Now i don't mind working at all but is it possible to buy the guts and do the wiring yourself. I'm  a brushed motor guy but am on a learning curve of bl so excuse my lack of bl terms. I'll continue reading on page #2. Thanks.

[boatmadman]

Andrew,
Would the water jet I mentioned above be capable of pushing a 1m to 1.5m planing hull like Visby?

I have started designing something myself

Ian

[col426]

Hello Andrew.
I trust your Brian has recovered...! 

Many thanks for your thoughts and insights on these motors.  Obviously I'm a member of the more is better club...I hate being so predictable! 

I'll have a think about your advice, and might drop back and try the KB45-10L 1800kv, perhaps with a step down to the KB45-12L 1400kv if that is too much.  I'll only be running them at 14.4v, less than half their rated voltage, so hopefully their output should be a bit calmer.  They just seem to offer so much performance (on paper anyway) for so little price (comparatively speaking).  If I wanted to buy a Hacker, etc with similar performance, I'm sure I'd be paying the proverbial arm & leg + my firstborn.  Also, most of the other cheaper brushless motors seem to be a lot lower powered, or just don't list their power rating.  The purpose-made water-jet ESC sounds interesting too, I might have to investigate that further.

I've included a couple of pictures of how the jet ski is currently, with the nitro motor & water-jet drive (it used to have normal prop drive before I got at it ).  When I get around to converting it, I'll post more pictures.

Phillip

[andrewh]

DLM,

You have hit one nail on the head - it is perfectly possible to buy a BL motor or even a kit - and rewind it to suit what you need. 
HOWEVER - it is just as easy to do exactly that with a brushed motor - and how many people do you know who salvage a 2.4 Volt motor from a 2-cell screwdriver and rewind it for 12V working with a 10 inch 4 blader tug prop?

And BL motors are cheap now, and will get much cheaper (IMHO) if the pound strengthens a bit.

Ian,
I am absolutely certain about this.
With enough power, yes.  Visby moves about smartly (the full size, that is) but not indecently fast.  Have a look at Hannu's posts about a big jet boat - I seem to remember powers in the KW range - but you don't want his radical performance.
What do you mean, you do?   Well, yes, so would I; but I remember Hailwoods law, which says " the throttle goes both ways"    the power, but use as much as seems good at any time
http://www.rcgroups.com/forums/showthread.php?t=922716

Phillip
I once heard Jock Russell, a racing driver who fitted a full race Ford V8 into a 1.5 litre Lotus F1 chassis, say "if you are going to be a bear, be a grizzly"  How true!
Thanks for the pix - I like the short tuned pipe.  I can agree with the revs you were talking about.

I think the 1800KV version might be a good bet - you will get lotsa revs at 14V, and if you feel the need for speed, go for more volts!
If you can run to it a water-cooled ESC might be a good bet - or make a cooling bed for an a/c one.  I would go for a cheap aircraft 60A unit and try and give it a cool life - poke it out into the air, or give it a battery fan of its own.
You might be able to emulate the W/J control with one of Action Electronics devices which (I believe) can mix any controls in any way - so it should be possible to do ESC from say 20% to 100 % throttle and reverse bucket servo from 20% to 0
FLJ will advise if asked, and the website is excellent

Lots of the Motor supppliers give all the performance data for alll their motors - I have mentioned the Micron R'C site before - it is excellent, and so are they as suppliers.  The area on scorpion motors has data on the whole range - and also a calculator AND a table of equivalents of the various manufacturer's products
http://www.micronradiocontrol.co.uk/scorpion_data/comparison.html

andrew

[andrewh]

Reader,

Sorry - been a lot going on in the last month, family-wise and I'm off to the Americas for a week so I thought it would be a good idea to throw in an update and stir the BL cooking pot before leaving on the big white bird.

Micro-inrunner kit!
While looking round the Car section of a Leicester model shop (Phil's models?) I found a kit of tiny inrunner brushless with reversing ESC for a BL replacement for tiny RC cars.  Motor is a 12m diameter (same as the feigao 12mm ones) but in a very short length - about 20mm
Not cheap, but it would make a tiny boat SCREAM.  I didn't notice the KV, but would guess at 7500 or so!
http://www.atomicmods.com/Products/Losi-LOSB9594-136-Xcelorin-8750Kv-Brushless-Combo__14042.aspx
I see that the cars are 1/36 or thereabouts, use 130 motors as stock and Mini-Z is  one of the types

BL Trial Boat
Heading for the water again - I have glass/epoxied the shaft hole, just to get a good base to start from, and figured out the BL motor mount system, so about an evenings work to get ready for the water

BL TUG (shameless plug)
(and it rhymes)
Did you all see Alans post -
http://www.modelboatmayhem.co.uk/forum/index.php?topic=15983.0
That is one impressive water-shifting tug, and Alan has told us all the details, motors, props etc
My impression (and it is only an impression) is that the motors are running cool, gentle and efficient with these props and Alan's well-controlled thumb.  Again the gel cell (s) are not smoking, so the current is not excessive, and duration is good
So, thanks Alan, thats one of the key corners of boat operation demonstrated

andrew
while in canada I am meeting some footy* heroes!  Excited, or what
* thats 12 inch racing yachts
 

[tobyker]

Andrew this is ever so interesting. I'm thinking of getting a Graupner minijet for a 500mm styrene hull, and putting in one of the Vortex inrunners as supplied by Tony Hill  (www.thmodels.co.uk)  as these seem reasonably priced and seem to have the revs on 10v. would I need the 480 equivalent or do you reckon I'd get away with a 400?

I've got a wee bell motor driving a 18" loa by 9" beam airboat which goes like a rocket!

I must wrap a wet towel round my head and read your primer again slowly. SWMBO thinks I'm looking at naughty things as I've spent so much time on the PC reading this thread in the past few days!

Many thanks
Toby.

[bbdave]

I'm looking at a motor the number on it is 1717 which deffinately is not the size so what do they mean? what are the differences between say an emax motor and a castle creations apart from the price?
Also if i want a 1500kv motor there is a huge difference in physical size i presume a small motor wont have the same power as the larger which has more torque simply because of the size difference is that correct?

Dave

[nick_75au]

1717
Most likely it is the size, of the stator(bit with windings on it) if its an outrunner. Kv has very little to do with motor size, Power handling is the difference between different sizes of the same Kv motor.
Nick

[roger]

Thank you Andrew. Not only especially informative but very entertaining too. If only I'd looking in the last place first!

You did say there are no dumb questions, so my "not dumb" question is: if all brushless motors need an ESC why aren't they built in to the motors?

[roger]

Hi Andrew,

Maybe you’ve moved on to other things by now, but, if you are still here, perhaps you would consider non-silly question number 2.

It’s a long time ago back to December 2008. (Actually it’s just two days ago for me since I just got here).  I follow the ABC to ACB (or swap any two for that matter) to reverse your BL.  What I don’t understand is your “Mk 1 Pencil” note “DON’T PRESS PLUNGER WHEN THE MOTOR IS RUNNING”. What happens (fried Brians aside) if I do?

[nick_75au]

Hi roger,
Maybe I can answer both questions
1, Some brush less motors do have them built in, I.E computer fans but they are not very versatile as they are fixed speed, just like a brushed motor straight off a power supply.
 The same reason brushed motors don't have one built in, different applications have requirements that vary, such as reverse, soft start, braking and RPM hold(governor) Its immpossible to make a "do everything" ESC without it being expensive and complicated.

2' the same reason you don't put your car in reverse when still moving forward, the other reason is the ESC is sensing voltage from the non active phase If that suddenly has voltage on it it may damage the esc.

Nick