Advice on ESC and RC Equipment

[Sam GoodchildParticipant @samgoodchild89422]

[Sam GoodchildParticipant @samgoodchild89422]

Hi

I am planning to convert a 1/250 scale model of the Battleship model to RC and need some advice.

The kit is one made by Arii/Micro-Ace and has been unmade in my loft for at least 12 years. I have managed to find a running gear set for it (2 rudders/ 4 Prop-Shafts/4 Motors) but need some advice on what ESC or ESC(s) to buy, how to wire them. and also some guidance on Transmitter/Receivers.

Motors are specified as:

Specifications of motors:
Voltage : 7.2V
Unloaded speed: 19,000 r/m ±12%
Unloaded current: ≤ 0.9A
Loaded torque: ≥ 957.7 g/cm
Loaded current: ≥ 27.8A
Shaft diameter: 2.3mm

Any Help would be useful.

Thanks

[Sam GoodchildParticipant @samgoodchild89422]

Sorry Battleship Musashi

[Dave MilbournParticipant @davemilbourn48782]

Sam

A quick Google shows that the model will be about 1m long, which is a reasonable size for R/C conversion. I don't build military ships so I'll have to bow to the superior knowledge of those who do.

HOWEVER I do 'do' electrics – and the spec for those motors sounds horrible! 19000 RPM might sound impressive but it's grossly unnecessary for a model battleship. If you fit four of them you'll not only boil the lake but with 110A combined current-drain the batteries will last for seconds. I'm happy to be over-ruled but I would be looking at maybe four RE385 motors MFA motors. These will spin at a much more sensible and practical 7000RPM on 7.2v and draw maybe 4A total from the batteries. That means that a decent NiMH pack would last well over an hour.

I would personally run them in parallel pairs (2xPort and 2xStarboard) from an ACTion P94, which combines forward and reverse speed control and will "mix" the motor speeds with the rudder control, so that when you apply a turn the motors on the inside of that turn will slow down and assist the rudders. For a radio then you have a choice of hundreds. I'd suggest a non-computerised basic set like the Planet 2+2 . This will operate the ESC and rudders and has two additional channels which you might use for lights and/or a sound effect.

As I said, I'm happy to bow to the Plastic Magic experts but DO put those motors aside – or stick 'em on Flea-Bay.

Dave M

[Paul TParticipant @pault84577]

Sam

I totally agree with Dave as those motor specs sound impressive but are way over specified for your model, I say specified as I came across this link

I presume that you have done some research and found the same ebay site, all I can suggest is that you do further research but strongly advise you to follow Daves recommendations.

Paul

[Colin BishopModerator @colinbishop34627]

Just a bit of a lateral thought, but there is no reason why you couldn't simply use just two motors each propelling two shafts using pulley drives whcih is a configuration which has been successfully used. The simplest method is to use the motor to drive one shaft directly and connect the two shafts via pulleys (if there is room on the inboard end of the shafts) or otherwise mount the motor between and above the two shafts and have a small pulley on the motor and larger ones on the shafts which gears down the motor to make it more efficient.

Pulley drives will work fine on this type of model.

Colin

Edited By Colin Bishop on 28/04/2020 18:32:07

[Sam GoodchildParticipant @samgoodchild89422]

Thanks, very helpful.

Dave you are spot on that is the running gear set I had found. Mostly bought it for the customised rudder and running gear. May consider stepping the motors down as you suggested. I have no prior experience with RC boats, so a bit of a voyage of discovery.

thanks!

[ashley needhamParticipant @ashleyneedham69188]

Sam. On the homepage if you scroll down a bit there is an in depth electrics article from DM which is a must-read.

Ashley

[Malcolm FraryParticipant @malcolmfrary95515]

Unless it is intended to race the model, a collection of 15 volt 385 motors run on a much lower voltage will do the job. 4 motors each driving its own shaft is mechanically simplest, 2 motors and pulleys will work just as well. Might want a few more volts because each motor is needing to supply more power (2 shafts plus pulleys as opposed to one shaft)

Scale boats need scale power,

150000 HP on the real thing (from Janes Fighting Ships) equates to about 10 watts at 1:250. The HP figure is power out of the system. Electric motors are rated by power in, so allowance needs to be made for motor efficiency, plus any shaft losses and whatever the props are doing.

A reasonable guesstimate would be 20 watts. Divide that by whatever voltage its going to run off and you have a good idea of the total current the control system will need to handle. Whatever the motors need to turn unloaded plus what the load is going to impose, still not much.

[Charles OatesParticipant @charlesoates31738]

To give you a comparison, I've a 1.14 meter long cruiser. It runs on 2x 385 motors, 1 speed controller and 7.2 volts. That's about 15 watts drawn from the battery. Flat out it's well over scale speed, I run on about 2/3 throttle, the reserve gets me out of trouble when I steer badly. Long thin warships don't need much power, and over powered ones can look ridiculous.

Chas

[Sam GoodchildParticipant @samgoodchild89422]

Hi all,

Points well taken about scale speed and power draw. I was already concerned about the speed of the motors included with the running gear set. Looking at the RE385 Motors, what is the difference between those that are Noise Attenuated and those that are not? Would I still need to solder on RF dampening capacitors?

Next question I suppose is Action P94 controlling 4 motors in pairs or a pair of ESC from Mtroniks and one of their V tail Mixers? https://www.mtroniks.net/prod/RC-Accessories/VTail.htm

Found this Diagram for the Action P94, would it be appropriate for use with the RE385 Motors?

https://action-electronics.co.uk/wp-content/uploads/2019/04/Graupner%20HMS%20Hood%20-%20John%20Tew.pdf

Thanks for all the advice so far!

Sam

[Sam GoodchildParticipant @samgoodchild89422]

Hi,

Dave, just realised the Plan if the Hood I put up is one of yours!

Sam

[Dave MilbournParticipant @davemilbourn48782]

Sam

The MTroniks unit requires you to buy two separate speed controllers while the P94 is self-contained.

The LN version of RE385 is a lot less powerful but draws very little current. On balance I'd go for the standard 385s as used by Chas Oates. If you're using a 2.4GHz radio then RF supressors aren't necessary.

That diagram is perfect for your installation. If you buy a P94 then have a guess who assembled it! I'm also very good with screw-top jars and washing-up – or so I'm told.

Dave M

Edited By Dave Milbourn on 29/04/2020 18:08:19

[Sam GoodchildParticipant @samgoodchild89422]

Thanks Dave, Much appreciated!

Also found one of you diagrams that mentioned turret servos…..could I get away with a single turret servo and use mechanical linkages do you think?

Thanks, Sam

[Dave MilbournParticipant @davemilbourn48782]

I've sent you a Private Message, Sam.

DM

[Malcolm FraryParticipant @malcolmfrary95515]

While in theory capacitors are not needed on an installation with a 2G4 radio, because the motors cannot generate interference that upsets the radio at the frequency that the radio works at, there are a couple of other considerations.

One is others sailing near you who are using more traditional radios. You probably don't want to find one of them suddenly lose control and head for your boat. A thin possibility, but boats on water do have a peculiar magnetic attraction for each other.

The other is keeping back emf voltage spikes generated by the motor out of the power supply. The ESC should stop them, but might not. a nice new well made motor "should" be OK, later in its life as wear and tear take effect, less so. Voltage spikes getting into the power supply have the potential to have a bad effect on the timing components that everything depends on. ESCs rely on stable power, as do servos, switchers and everything else that plugs into the radio. And the radio depends on stable power to give stable timed signals out.

Soaking up potential interference at the motor before it has a chance to go elsewhere and do its evil is good practice. Soldering a capacitor across a pair of terminals is nothing of a job compared to rebuilding a boat, either because poor control broke it, or there was the need to pull the motors out to fit supressors.

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