Changing to brushless

[lnvisiblemanParticipant @lnvisibleman]

replacement of Fawlty motors

[lnvisiblemanParticipant @lnvisibleman]

Hi all

I have had an accident whilst working on my Tintagel model that resulted in a strange brown vapour being emitted from both motors. It must have been a manufacturing fault! Honest !

This seems like a good time to try out those brushless gizmos.

The model has (had ) two 540 motors fitted . Running on 12v nimh batteries, they gave a nice performance but, in the words of Mr. Clarkson, “ MORE POWER !!! “

I am hoping that it is possible to use the existing motor mounts but don’t know if this is an option.

As always, economy is a priority so no outrageously expensive equipment will be considered.

All suggestions will be scrutinized solemnly., but I am sure that some will raise a smile.

ALL suggestions will be recorded and will be used in evidence against you.

This is a plan of the model except that it has been scaled up to 36" long and the motors are mounted forward of frame 3 to give a much shallower prop shaft angle. ( As Paul T's recommendations)

Thanks all

Mike

Edited By lnvisibleman on 13/07/2014 19:48:11

Edited By lnvisibleman on 13/07/2014 19:50:54

[Bob Abell 2Participant @bobabell2]

Hello Mike

I think this will do nicely…….

**LINK**

Bob

[Dave MilbournParticipant @davemilbourn48782]

I should point out that the motor and speed controller in the link are recommended as suitable for use in a single-screw model up to 40" long, such as Bob's Ellie and VMBC's RTTL/Fireboat. I suspect that fitting twin motors of this size would substantially over-power Tintagel, which is about the same size as Ellie.
I'd suggest starting with the article "Going brushless" by John Parker which you can find in the Features>Hints, Tips and Technical section, navigating from the Homepage of this website.
Dave M

[Paul FreshneyParticipant @paulfreshney24971]

There was an also an excellent five page article by Ron Rees in June 2013 MB on brushless motors , which included a comparison brushed/brushless chart. The fundamental problem that many modellers have, 'getting their heads around', is that a brushless motor of equivalent performance to say a 500 or 600 'can' motor is much. much smaller.

Motor mounts – most decent brushless outrunner motors come with a specification sheet. including power outputs. Those specifications can usually be found on the manufacturers/retailers website, because they are critical for aeromodellers.

For example, the Turnigy 28mm dia motors bolt into a 380 mount and larger sizes will bolt into a 500 type of mount.

If you look for the Lubeck thread on this forum you can see such a motor in a 380 type of mount. That 28mm diameter motor is of 102 watts output, but much smaller than an average 380 so yes, the model is massively overpowered!

Paul Freshney

[Dave MilbournParticipant @davemilbourn48782]

Paul/Colin B

Is there any chance of reproducing Ron's article in the Technical section here? It would be much easier to refer to than that great disorderly pile of magazines stuffed into the cupboard! I'm certain that questions like this one are going to crop up regularly as more folk decide to test the waters….

Dave M

[lnvisiblemanParticipant @lnvisibleman]

Thanks all

I have read the mentioned articles only to be left more confused than before. Every article I have read ( and there are many ) says basically the same thing " Try something and if it doesn't work, try something else *. Not very helpful IMHO. This must be the most debated subject re model boat power and yet there are no clear guides anywhere to be found. Is it that nerds like to make it more complicated than necessary or am I just an idiot?

All I want to do is replace a pair of 540 brushed motors with a pair of brushless motors. I don't want to have to rebuild the interior of the boat so as to move the motor mounting block or fit longer/shorter prop shafts. If it really is as complicated and difficult as it appears , then there is no wonder that so few folk go down the brushless route.

That's my moan over for the day !

Mike

[Dave MilbournParticipant @davemilbourn48782]

It isn't difficult or complicated, Mike; it's just new and different.
The problem is that, thus far, there are so few modellers who have gained sufficient experience in selecting and operating these things to be able to pass on any quantity of useful information. Even fewer of these have the confidence/stupidity to write an article about it!
For illustration, if you look at the Hobbyking website you will find literally hundreds of different motors available – and that's from just one supplier. It's like the old problem "I've got a 540 motor"; "Which one?"; "I dunno – it's just a 540"; "No such thing, mate. How many poles and/or winds does it have, then?" multiplied by a factor of about 100. Then there's choosing a speed controller…………………

There are other Internet model boat forums where you might drop across the answer you need. You have the same facility to research them as any of us. Try Model Boat Mayhem – there is a dedicated Brushless Motors board there. Nick Kaur on that forum (aka Nick_75au) talks a lot of sense on the subject and there are others who clearly know a fair old bit, as well as 261 different topics already posted.

Failing all else the best you are going to get is what you already have. Why not "try something and if it doesn't work try something else" yourself? You'll be the expert then.

Ref Tintagel, this might not be the best time or model to try brushless motors. I would suggest you stick a couple of Speed 600 BB motors in **LINK** and run them on 30-35mm 2-blade props. They'll fit the existing mounts and couplings and the model should go like greased weasel poo. Try different props until you get the best performance to suit you, and leave the fancy technology for a purpose-built model at sometime in the future. The nicest thing about banging your head against a brick-wall is when it stops.

Dave M

[Colin BishopModerator @colinbishop34627]

The problem with finding a straight replacement based on somebody else's experience is that you need to find somebody with almost the same setup as yours as there are so many potential variables involved. This means similar motor specifications, windings, RPM, torque et., similar prop size and (equally important pitch). battery voltage and of course, as Dave says, the ESC. This is relatively easy where kits are concerned as a lot of people have them and the manufacturers will frequently suggest an optimum setup which you can vary if you wish.

In the 2011 Model Boats Construction Special issue http://www.modelboats.co.uk/news/article/model-boats-construction-special-2011/8072 I did include an article on the knotty problem of choosing suitable motors and props based on general principles and empirical advice from Forum members at the time although it didn't include brushless motors. There don't seem to be any back issues available now but you can probably find a copy on line if you are interested. The basic data was taken from this topic: http://www.modelboats.co.uk/forums/postings.asp?th=45505&p=1

If you do a global search on 'Motors' it will also bring up lots of interesting posts to pore over! I'm afraid that generally you do need to do your homework on this as most people are interested only in the 'output' side (what works for my boat) and nobody really has much incentive to draw up lists of comparative tables, especially when many of the products are constantly altering in specification

Colin

 

Edited By Colin Bishop, Website Editor on 14/07/2014 13:32:18

[lnvisiblemanParticipant @lnvisibleman]

Dear all

I suspect that we have found the answer to a question that was posed elsewhere. "Why are so few people taking up model boat building? "

If it isn't possible to get a straight answer to a straight question then it is not much of a surprise. !! I assume that outlets do actually want to sell these motors but it mystifies me how they manage when they have no idea what will suit a clients requirements. Not IMHO, the best way to run any business.

I will take Dave M's advice and stick with brushed motors, at least until there are some decent answers available or until I kick the bucket, whichever is soonest.

I am fairly sure that bucket kicking will come around first.

Mike

 

Edited By lnvisibleman on 14/07/2014 14:49:33

Edited By lnvisibleman on 14/07/2014 14:49:53

[Diede van AbsParticipant @diedevanabs87670]

Mike,

As Dave and Colin already indicated, not getting a clear answer as to what motor to use is not strictly a Brushless issue – I have it all the time, brushless or brushed the like. Both are an educated guess at best. Brushless generally seems to get me closer to my goal though. I have four guidelines for my own choice process:

-I want an OUTrunner
-Rotational speed of the motor
-Power rating
-If possible, number of poles

I want an outrunner for the sake of torque. Inrunners are for rev-hungry speed boats that run full speed for 80% or more of the time, outrunners for scale ships (although they can still rev like hell if you pick the right one)

I typically choose a motor that will give me a loaded rotation speed at or slightly above the desired prop rotation speed, on the argument that I can always throttle back. (this is read by the Kv reading, in conjunction to the battery of choice and then corrected for load. The calc for your eyeball figure is Kv * Vbatt*0,9)

Then I look if I can find the number of poles, or at least find out if a motor has sufficient coils and magnets – the more they have, the better the control on slower speeds. If it is not stated in the specs, you can sometimes make this up from the photos.

Lastly, I generally pick a motor which I suspect will have enough power – and this is the "hardest part" if you want the motor to be loaded to the max. My motors are generally pretty much overpowered… Once again though, given the right RPM's and the right prop, that is just a matter of stick control, and it is better to have a bit of reserve power in your motor than running right at the edge of its possibilities, as it runs cooler.

The ESC is the most straightforward: I pick a ESC that has a power rating that exceeds the max current draw of the motor, and it must have a reverse that does not need braking.

If you feel too uncomfortable with these newer motors though, indeed stick to ye olde fashioned brushed motors – they come cheap nowadays, with all the brushless motors taking over.

Better experiment with brushless on a simple, single screw craft.

Good luck!

[Dave MilbournParticipant @davemilbourn48782]

I assume that outlets do actually want to sell these motors but it mystifies me how they manage when they have no idea what will suit a clients requirements.

You are looking to compare apples with coconuts, m'duck. Forget the dusty little back-street model shop with Jim that's run it for a hundred years and knows everything there is to know – with a free cuppa if you're there at tea time. The staff at your favourite Chinese-based Internet model suppliers have little idea what they're selling [we call it "glossy-box syndrome"] and so couldn't care less about their customers' requirements. Their method is to provide you with some scant product information on their website and you make your decision from that. That's it. End of. Full stop. If you chose wrong then Go to Jail or pay £200, proceed to Go and start again.
If you want to buy brushless motors and receive a modicum of advice and service then you have to go to a specialist supplier. I would suggest Prestwich Models and ASTEC Models, both of whom I've heard good things. They have a limited range of motors and speed controllers, but all are tried-and-tested and aimed squarely at the fast electric model operators. I know that either Dave Marles or Alan Shillito would be able to help but you have to be prepared to pay a premium for their expertise.
While ever the Chinese are happy to sell single items direct to end-users at the same unit prices as they quote for quantity to shops then no shops will ever carry a "general" range of brushless motors – even if such a thing were to exist. As you said earlier, until things change then it will be a case of trying different things until you hit one set-up that works.

DM (wanders off to find something to kick)

Edited By Dave Milbourn on 14/07/2014 16:42:54

Edited By Dave Milbourn on 14/07/2014 16:46:41

Edited By Dave Milbourn on 14/07/2014 16:51:13

[Andy CParticipant @andyc56856]

So what we need is a model boat shop, not an airplane shop that might sell a few model boat kits, run by people who know & build model boats, for people who want to build model boats.

Wow, we don't want much do we. But I think that is where the crux of the problem lies. Most model shops have been catering for the mass market, which unfortunately is not boat but planes and cars. Brushless motors came about due to that market place and there has not been the testing in our area of the world. Some testing can be found on Youtube from the ROV community (including using one of Paul bilge pumps as a motor).

I have wondered in the past if anyone has thought about actually doing some testing, maybe with the aid of the manufacturers, to determine what Brushed motor can be replaced by which Brushless. This of course depends on peoples time to construct the test bed and have access to the various and very wide choice of motors.

Just a thought.

Andy

[lnvisiblemanParticipant @lnvisibleman]

DM (wanders off to find something to kick)

You leave my bucket alone !! Again, I shall heed DM's advice and speak to an expert (?) before confirming the purchase of several lengths of 100 x 100 Oak timbers. I already have a set of steps and some stout rope, so a scaffold should be easy to knock up. I hear it is less painful than bashing ones brains out against brick walls.

Mike ( suffering from connecter terminal depression)

Edited By lnvisibleman on 14/07/2014 18:24:55

[Dave MilbournParticipant @davemilbourn48782]

Andy
So wise yet so innocent. Your first two paragraphs are spot on. The last one is a tad wide of the mark, as I suspect you know.
Let's get things straight from the start. Help from the manufacturers is not going to happen. At best you'd get the published performance figures for each motor, and you can obtain that already. If by help you mean freebies then forget it². I was charged a premium rate for the manufacture and posting of two sample 755 motors when I enquired about buying 1000. The idea of picking, packing and sending hundreds of free samples out would not appeal to the Brothers of Shenzheng – trust me.
99.99% of brushless motors sold to the model world are sold for aeroplanes and there is already a plethora of tables out there comparing volts with amps with torque with prop size etc etc. As far as the manufacturers are concerned we boatistas are nobody. Unless some philanthropist is kind enough to find both the money and the time to compile and test a collection of both brushed and brushless motors, together with propellers and other stuff like speed controllers then we will forever be Cindarella modellers. It's actually been that way for ages – this is just another brick in the wall (so to speak).
I'm very much afraid it's down to "try something until you get it right", to which I would add my eternal thanks to anyone who already has found something that worked and published the details.

Mike
Don't use cyano. It doesn't work very well on oak. Six inch twin-starts is the recommended fixing method for a gallows these days. You might find this useful, too **LINK**
"If I can help somebody as I go along life's way……………………….."

Dave M

[Gareth JonesParticipant @garethjones79649]

Andy,

In answer to your question if anyone has thought about doing some testing, the answer is yes, I have, but so far it is just a thought. I have put together a fair amount of performance information on my models built so far, but they all have brushed motors. When I retired about 4 years ago it was my intention to build a test rig that would allow me to measure motor voltage and current, prop rpm and static thrust in a controlled manner. I have measured these parameters on most of my models, primarily at the maximum power settings. You are welcome to that data if you want to send me your email address in a pm.

The idea was to have a simple universal hull shape which would accomodate the instrumentation, could be tethered in the water and could easily be fitted with a wide range of motors and propeller sizes. The intention was build up a data base of which combinations seem most efficient and effective for various sizes and types of models, generally displacement and simple planing hulls, not high performance fast electrics.

Unfortunately so far it is still just a thought, I have not got round to building the test rig. I am now on my third retirement and will probably go back to work again next winter, which will not help, apart from providing the funds to build and equip the rig. After three years work I have finished my latest model and have just started planning the next one, which I have decided will have a brushless motor. It might seem an odd thing to put in a model of a 90 year old barge but there's progress for you. In order to avoid a major redesign as a result of a mistake in this new technology I do plan to build the rig sometime this year so I might have some results by the year end.

In the meantime, I think Diede, Colin and Dave have provided some good, sensible and pragmatic advice. Unfortunately there are a lot of variables in any model boat propulsion system and they can all have a major influence on its performance. Its pretty well impossible to analyse the whole system from first principles (well it is for me anyway, Paul T might be able to do it), so the best option is to look at what works in your own or someone elses models and start from there.

Regards

Gareth

[lnvisiblemanParticipant @lnvisibleman]

A big thanks to all respondents.

Just so it is totally clear to me, would this statement be regarded as accurate?

Nobody has the foggiest idea which brushless motor is suitable for any particular model. Unless it has been satisfactorily used by someone in a identical model.

At least know not to waste any more time on this issue.

Mike

[Colin BishopModerator @colinbishop34627]

Not really Mike. The point people are making is that there is no special database which will automatically tell someone what he best motor for their particular model is simply because there are too many variables involved to list all the possible combinations. Even full size ship design still relies upon empirical factors by evolving one successful design into another. Experienced modellers can apply their expertise to give them a good idea of what might work. In the case of relative newcomers then if you find a setup which works well in a model with similar (not identical) characteristics to your own then you can be reasonably sure that it will work for you. If you happen to be building a kit than just follow the recommendations of the manufacturers.

As a small example of using experience, my electric powered steam yacht (see photo on the right) is fitted with an old Marx Monoperm motor driving a 25mm three bladed prop via a 2:1 geared down belt drive on 7.2 volts. It goes OK but in choppy conditions could do with a bit more power sometimes. The obvious solution would be to fit a larger 30mm prop but there isn't really enough clearance between the stern tube and rudder post and the larger prop would bring the blade tips nearer the surface where they might simply stir up froth instead of providing more thrust.

Fitting a bigger pulley on the motor might do the job but would reduce its efficiency and increase current consumption. The hull doesn't have the room or carrying capacity to fit a higher voltage battery and I don't want to mess around with the internals if I can help it as space is very tight.

The solution I have therefore adopted is to fit a four bladed 25mm prop which I estimate should give that extra bit of thrust without significantly adding to the motor load. I had already checked that the pitch of the four blade and three blade props is the same so the four blader will give me extra blade area while the pitch remains constant. I have yet to test it in the water but I will be very surprised if it doesn't give me the desired result. But you will see from the above just how many factors come into play when simply tweaking an installation to modify performance. (there are other options I haven't mentioned above but chose not to pursue)

Colin

[lnvisiblemanParticipant @lnvisibleman]

Colin

I understand all that you and others are saying, even though that may be a surprise to all readers, but as a total beginner to model making it is , to say the least, confusing. If a beginner cannot get reliable guidance from vastly more experienced modelers, how can we/I hope to get it right? or even close ?

I have learned a vast amount from the contributors to this forum and greatly enjoyed the light hearted banter that prevails throughout. It is with great regret that I am now giving much thought to returning to model railways where everything is so much more straightforward. I hate to give up on anything but finances are very limited and we can't all afford to keep trying things out just to see if they work, or not. Maybe when model boat builders have got things more sorted, I will return and have another go at a hobby that I find fascinating and challenging.

Life is too short to be wasted on questions that have no answers. Perhaps the answer really is " 42 "

Mike ( hitching a lift to a good restaurant )

 so long and thanks for all the fish !

Edited By lnvisibleman on 14/07/2014 23:59:41

[Dave MilbournParticipant @davemilbourn48782]

Well thanks for that, Mike. This is getting to be quite typical these days. Instead of taking responsibility for their own hobby and doing some in-depth research (and maybe experiment) like most of us would, people simply fire up the PC and demand an answer from the nearest "expert".
'Proper' modelling – as practiced here – isn't about opening glossy boxes and clicking shiny toys together. Even the most cursory perusal of the modelling press and internet forums would have told you that brushless technology for boats is a subject which is in its infancy, and that boat modellers are the Cindarellas of the R/C hobby when it comes to specialist manufacturers and retailers. I'm sure that if you'd bothered to follow up any of the leads you were given then you would have begun to discover more about it and gradually solved your problem for yourself. You might then have become a resource for others in the same way you expected us to be for you. As you say, however, life is too short – especially for those who demand full and instant answers as of right and then move on.
Good luck with your toy trains. You should be able to buy them without having to make lengthy phone calls to China…….at least for the time being.

Edited By Dave Milbourn on 15/07/2014 08:46:22

[Colin BishopModerator @colinbishop34627]

Mike,

As the earlier posts have made clear, there is a lot of information out there but you do have to do some homework and put the effort in. Like in every hobby, the more you put in the more you get out of it and the more you learn. Sometimes, as with brushless motors which are a major recent innovation as far as model boating is concerned, there is no 'easy' answer at the moment as even expert model boaters are still going through the learning process themselves and building up expertise.

We'd all like things to be simple but sometimes they just aren't in which case you can either accept the challenge or bale out.

Colin

[Tony HadleyParticipant @tonyhadley]

Quite a good example of a twin screw brushless installation was featured in the latest Model Boats magazine (August 2014, Vol. 64 No 765), Wildcat 53 Windfarm Support Vessel. Well worth reading if anyone is planning a twin screw brushless installation.

Don't forget we all went though a change of power installation some years ago, with the change from i/c to electric. Diesel and glow motors were powering the majority of r/c models not to long ago and a change to electric power evolved over the years. A similar change will evolve with the change from brushed motors to brushless. In years gone by there was no direct electric equivalent from an i/c to electric in a model, e.g nobody could say what would be an electric equivalent of an E.D Mk. V 4.5cc diesel. Over time though, things evolve.

Tony

[Dave MilbournParticipant @davemilbourn48782]

How true, Tony, but evolution takes time and some individuals can't accept that. Thanks for the heads-up on the 'twinstallation'. My curiosity has been stirred and my arm subsequently twisted by a certain magazine editor. In consequence a brushless motor/ESC/programmer set-up is on its way to Milbourn Towers. We experts have to keep abreast of these things, you know.

Dave M

[Diede van AbsParticipant @diedevanabs87670]

Hi Mike,

I think it is sad that you kick the bucket so quickly on the brushless motors (or model boating in general), because it really is not that hard. It is actually about as easy or difficult as brushless motors. It really does not need to cost you the rest of your life's spare time, and there certainly is no need for a timber frame with a rope dangling from it. Come on man, don't give up so easily!

Just find yourself a brushless outrunner of about the diameter of your prop (motor can be a little bit smaller, not too much) that gives you about the right RPM given the battery you are going to use, and make sure that it has enough power, and you should be fine.

As for your Tintagel; If you can give me the size (and shape) of your props, and some data of your current (smoked), motors I might give you an example advise based on the principles I described before.

Did you have the motors water cooled, BTW?

[lnvisiblemanParticipant @lnvisibleman]

Hi Diede,

I ain’t dead yet ( much to the annoyance of some )

Not many read the post correctly. Here is the relevant section.

“I am now giving much thought to returning to model railways”

The motors presently smouldering are these

http://www.componentshop.co.uk/540-standard-dc-motor-mounting-bracket.html

They were not water cooled but that option is available. I was actually doing some bench tests when th escape of vapour occurred.

And the props are Rivabo 3 Bladed R & L Hand 30mm.

My current thinking is that if I get a pair of pokey brushless motors and they turn out to be unsuitable, then I will build a model that they will suit !! Simples.

Mike

How did the font grow ??

 

 

Edited By lnvisibleman on 16/07/2014 13:50:00

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