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[richardabeattie]

I'm about to build the Moray Firth cargo ship.  It's 42 inches long with a beam of 6.5 inches so fairly heavy displacement.  She will have a 40 mm three blade prop.  Is a direct drive MFA RE 540 brushed motor driven by a 7.2V battery going to keep her chugging along at a sensible scale speed? 

[canabus]

HI Richard
The 540 rock crawler motors 55 and 60 turn are lower rpm and more powerful.
I am using these in my Hellen fishing boat with a 60mm 3 blade prop.
Using 7.2 volts at 60% for scale speed.
Boat weight 14 pounds.

Canabus

[richardabeattie]

Thanks  - never heard of them!  The ebay photos seem to show no capacitors fitted across the terminals - would that matter? 

[canabus]

Hi Richard
I have not fitted capacitors and having no problems on the 2.4G Turnigy Ia6 and the Flysky I6.
Using Lipo batteries to keep the weight below the waterline and longer running time.
Also the Hobbyking Hobbywing Quickrun 60Amp ESC works well with only link setup and NO BRAKE setup.
Straight from forward to reverse, all the other ESC have a small braking or time stopping in neutral.
Canabus

[malcolmfrary]

A "standard" 540 will be deeply unhappy with a 40mm prop on direct drive.  Look for either high turn counts or 545 motors or gearing.
Repeating the "rules" for motors and props - motor can diameter should be greater than the prop diameter, the motor should have more poles than the prop has blades.  Gearing effectively increases both.

Fitting capacitors eliminates the chance of interference.  2G4 radios are less prone to interference so far, but the wiring beyond the radio isn't.

[John W E]

hi Richard - at 7.2 volts it sounds you are planning on using NiCads for your model - it may be better for you to use GelCell batteries of 6 volt 12 amp.  The reason for this, is, it aids to balasting the hull down to the water line.   I have just found the 2 lead bricks I put in my Moray Firth and the whole lot (model, batteries and the 2 lead bricks) weigh just under 14 lb.   As far as using Lipo goes and with a brushless motor, that is entirely up to yourself - but - me I would avoid them like the plague in this type of model.


https://www.mfacomodrills.com/pdfs/RE540LN.pdf



this is the type of motor I have in several of my models - namely the MV Duburg - which the same size as the Moray Firth and the same weight.   It pushes this along quite nicely.

https://www.modelboats.co.uk/albums/member_photo.asp?a=36621&p=597878

john

[richardabeattie]

John


No the 7.2 V battery pack is NiMH.  What is the difference between the MFA 540 which I have used in other rather smaller models and the MFA 540LN which you are recommending.  Does it run slower but with more poles meaning more torque?


And on a separate question, if I build using a 1/2 inch thick bottom, ply sides amidships and bread and butter at the bow and stern the boat will end up strong and heavy and needing less ballast.  So why do other people go for plank on frame?

[John W E]

hi there
if you have a look some of the 540 motors are 3 pole and some are 5 pole - that's the difference - what motor did you use in your last boat?


With regards to the difference in weight - the way you are going to build it, there will be a very slight increase in weight, but, you will find you will have reduced space inside the hull, unless you are going to do a lot of hollowing out.   Also, a Gel Cell battery 6 volt 12 amp is only going to cost you £12-£13 and should run your model for about 8 hours continuous that is if you pick the right size combination motor for the model.


Do you not fancy doing plank on frame?   Its just as easy as the way you may be going to do it?     Once you get into planking its quite therapeutic and you will feel an achievement when you have finished the hull.


All the fittings on the model I built are scratch built, apart from the ventilators and the propeller.


John

[richardabeattie]

John


Thanks.  The motor I used before was an MFA 540 RE so I suppose 3 pole?  As I understand it you are saying a motor of the same size but with 5 poles will have more torque.
No hollowing out required - as I said the whole central section will be just a long box with a 1/2 inch thick solid floor (to take the rounding off along the bottom) and ply sides - so plenty of space inside. Only the bow and stern need to be built up bread and butter. [/size]I built a 1/144 scale catapult armed merchantman on this system complete with a Hurricane - but not anywhere near to your standard.   I've done plenty of plank on frame but at  this much bigger size I don't see the benefit.
I also sail full size yachts and do not do 8 hour watches! 
If you built those winches I salute you.  I've found something near enough from an online 3D expert.
Thanks again. What a helpful forum!

[Colin Bishop]

The liner model I am currently building (slowly!) Is 42 inches long and 4.5 inches wide. I used exactly the same method of construction as you are proposing except that I used balsa. Half an inch for the bottom and a quarter inch for the sides with half inch bread and butter layers for the bow and stern. This is an effective, strong and quick method of composite construction for a hull with a long rectangular midsection and full bilge. As the photo shows, there is more than enough room inside the model for r/c, batteries and motors etc.

The reason I used balsa is that it is easy to fair the various elements of the hull into each other so you get a smooth transition at bow and stern. Once shaped I covered the hull with lengths of gum paper strip to simulate planking before sealing it but many might choose to sheath it in lightweight GRP cloth especially if the original vessel had a welded hull.

My model will be powered by twin 385 motors with 25mm props which give plenty of thrust and draw just 0.5 amp each under load. As said in an earlier post, there are lots of different 540 type motors with differing outputs and power consumption depending on the winding but a 5 pole 545 low drain geared down 2:1 using a pulley or tooth belt drive should cope easily with a 40mm 3 blade scale prop. You might want to thuink about an 8.4v NiMh pack to give a bit in hand.

Colin

[richardabeattie]

Colin


Thanks for that.  Being a bit gormless about motors I'd need the name and model number of a geared down 5 pole 545 low drain motor.  I don't even know what numbers like 540 and 545 refer to!  An earlier post from a bloke in Tasmania (what a forum!) suggested a Rock Crawler 55.   

[Colin Bishop]

Have a look at the SHG Models website.
http://www.shgmodels.com/acatalog/

This motor on page 17 of their catalogue should be OK: RE 540/1
They also sell tooth belts etc.

I'm sure others on here can suggest equivalents from other suppliers.

Colin

[malcolmfrary]

Colin


Thanks for that.  Being a bit gormless about motors I'd need the name and model number of a geared down 5 pole 545 low drain motor.  I don't even know what numbers like 540 and 545 refer to!  An earlier post from a bloke in Tasmania (what a forum!) suggested a Rock Crawler 55.

There was a thread on here a while back about motors and their numbers, but -
540 - a 3 pole motor with a can 54mm long, good for fairly fast boats weighing a few pounds.
545 - 54mm long can but with 5 poles, good for larger, slower hulls needing to turn a larger prop more slowly, but with more torque.
While NiMH are perfectly good in this application, SLA are also worthy contenders, low current and heavy weight being what they are about.
Some 540 motors come with a suffix number denoting that they are wound to give different results.


Motors with cans this size also appear as "600" series motors because some manufacturers like to change things.  Things like number of poles and the arrangement of the wire wound on them, determine what they are good for.  A fast revving 3 pole motor driving a prop that is too big will be forced into an almost stalled condition, where it will not produce much drive, but will pull way too much current and make a lot of heat.  I have seen an ill-chosen motor melt the solder off its tags, I don't know what the motor actually was, it had also burnt the label.

[richardabeattie]

Thanks to all of you for putting up with me.  The choice seems to be between:


SHG's offer of an MFA RE540/1 which is described as high torque and replacing the 545 model, or,
Cornwall Model Boat's more expensive offer of an MFA919D 540 geared motor with a 2.5:1 ratio.

Naturally I'd prefer the cheaper SHG offer if that is good enough.  What's happened to the font?

[chas]

I've used both those motors in similar models, but my recommendation is the 540 LN . it's a 5 pole motor and just about perfect for your model. The geared motor works well but is a bit noisy, the 3 pole motor will work but has less torque than the 540 LN..
Chas

[richardabeattie]

Right - that's it - thanks to all.

[richardabeattie]

The MFA540 LN motor has arrived (with a remarkably short drive shaft).  It is going to be driving a 40mm three blade prop on a heavy displacement cargo ship.  So is the Viper 15 ESC man enough or do I need to go to the Viper 20?  And why on the Cornwall site is the plug and play version of the ESC marginally cheaper than the non plug and play version?  Thanks for your patience with me!

[malcolmfrary]

The MFA540 LN motor has arrived (with a remarkably short drive shaft).  It is going to be driving a 40mm three blade prop on a heavy displacement cargo ship.  So is the Viper 15 ESC man enough or do I need to go to the Viper 20?  And why on the Cornwall site is the plug and play version of the ESC marginally cheaper than the non plug and play version?  Thanks for your patience with me!

It is likely to pull, tops, about 3A.  A 15A ESC should have plenty of safety margin.  Using a "standard" 540 as originally intended I would expect it to pull around 10A, go no faster and get very hot.
The price difference between PnP and the ones with a setup button is that writing software once is cheaper than providing a button on every ESC sold.  Same reason why modern TVs use a remote - buttons working software is a lot cheaper than a control panel when there is a lot of controlling to do.

[richardabeattie]

What does this forum not know?  Thanks again.

[DaveM]

Richard

A few of us just cheat (or know where to look). https://mfacomodrills.com/motors/motors.html
DM

[malcolmfrary]

Sadly, on that MFA site, a lack of useful information such as suggested voltage range and likely power.  I recall a simpler time when the motor listings just gave a suggested size and type of boat to be powered. Oddly, it worked very well, but nowadays the motor specifications (when given) tend to be overwhelmingly specific.  Of course, everything radio then worked on 6 volts.  And somehow, when trying to make comparisons, rarely match parameters.
As DM says, cheating or knowing where to look or having the curiosity to use a search engine to sift the information out there.

[DaveM]

From MFA website:

[RST]

Malcomfrary I know Dave Millbourn already said but the MFA website I always thought was exceptional and a reference for anyone else offering modelling motors they publish all their specs.  In no way is it short of info, for me it's the "base case", it's the one supplier who states just about everything.  A bench mark over the years for me, and a happy end-user of  some of their products.

[richardabeattie]

Yes it's full [size=78%]of technical information but a few word of text offering serving suggestions would be helpful.  TThere goes the font again!)[/size]