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[Nick-R]

I am currently building a Billings Smit Rotterdam.  On advice from the forum, I have ordered a pair of Mabuchi 555 high torque motors.


Ideally, I would like to have full independent control of both both motors but I currently have a twin lever six channel tx so putting in two ES controllers would make control awkward with forward/reverse/speed for each motor on right and left sticks but steering also on the right stick.


As a compromise set up I have been contemplating having a single forward/reverse/speed esc controlling both motors.  Stall current on the Mabuchi is 12 amps so a 25 amp esc should do.  Between each motor and the esc I would put an on off switch on channels 5 and 6. That would allow a single motor to run forward or reverse.  No full independent control but having many years experience of full size boats, better directional control than rudder only.


A further thought is whether I can get a forward/off/reverse switch operated by a servo.  This would give independent control except for speed but with one motor anhead and the other astern, that does not really matter.


Anyone have any thoughts?  The ideal solution would be for someone to come up with a transmitter with a steering wheel and twin throttle controls like most full size twin engined boats!

[KitS]

There are twin throttle stick transmitters, or there were anyway, the Robbe F-14 Navy being one, but they're not cheap and as standard on 40 Mhz only. I've got an F-14 Navy, and another twin throttle stick Tx too, but can't remember the type of the 2nd one and I'm 120 miles away from it now too. 


Or how about a mixer on the rudder stick ? That could control the motors differentially when you're using more extreme rudder positions.

[Abandon Ship]

If your transmitter supports mixing then Kit's suggestion is what I would recommend. However there are alternatives to use switches on the transmitter.


Electronic switch that plugs into receiver - I've used these for low power, don't know if they are available at the power level you need.


Servo operating mechanical switch - have seen a toggle switch between two servo arms, servo turns one way to switch on, other way to switch off.


Vintage car speed controller/reverser (mechanical type) - look into this, could be used to switch motor on/off or forward/reverse.


Dave.

[Colin Bishop]

Many transmitters have mixing functions but they are designed for aircraft use and are not always suitable for boats. Component Shop offer a twin ESC mixer combined unit which is very versatile. Check out the data sheet on this page to see the options. It may give you all you want.

https://www.componentshop.co.uk/p94l-dual-esc-and-mixer-2-x-10-amp.html

I have this unit in some of my models and it works fine.

I have a Fishery Cruiser which uses one of the ancillary functions to switch between single stick steering where both motors respond together on the left stick and tank steering which transfers motor control to left and right sticks at the flick of a switch so for general sailing you just user the rudder on the right stick but for close up manoeuvring you have independent control. The big snag is that it uses previous generation speed controllers and this method won't work with current controllers as they do a reset every time the current is  cut. Sometimes progress isn't progress!

Colin

[Nick-R]

Thanks for the feedback chaps. I may well look at the dual motor esc as a solution but I am also attracted to a double pole double throw switch with an off position operated by a normal servo but need to find if a suitable item is available.  My tx also has a mixing function so that also needs a bit of research.

[chas]

Hi Nick, an electronic switch giving forward /off / reverse is easily and cheaply available, i tried one recently. If you wanted to use a servo to operate switches, i suggest microswitches, because they're so easy and cheap to get and install with a servo, the Taycol article in a recent model boats magazine discusses their use. That said, i would use a twin mixer, the action one is excellent.
    Collin, that's one of the nicest on the water pictures I've ever seen, very beautiful.

[Nick-R]

So excuse my ignorance.  I was into the hobby in my teens with single channel radio, etc.  I have only come back to in recent years with a near sixty year gap so modern rc is a bit of a learning curve.  My six channel tx has the usual set up of channels 1 - 4 being on the vertical and horizontal planes of the two joysticks.  Channels 5 & 6 are simple switches on top of the tx.  If I connect an on off switch to channels 5 or 6 I can see how that works but how does a three position forward/off/reverse electronic switch work?  How does that connect to the rx?

[tsenecal]

Nick-R, would you please post the exact brand and model or your R/C transmitter.  we could help you a lot more if we knew that info.

[Nick-R]

My tx is a Microzone MC6C - 6 channel.  Ch5 is a 3 position switch with reversible direction.  Ch6 is two position switch.  The twin joysticks have the usual configuration - left stick vertical plane has a ratchet and everything else self centres.


It has six settings switches.  Four reverse servo direction on ch1-4. The other two allow selecting v-tail and mix.  I might try making a test setup to experiment with what happens on these settings.


Finally, I have tried to upload a picture of the tx but it continually fails.  I have successfully uploaded pictures before and use an optimiser program to reduce the size of the file.  In this case after optimisation it is a 42kb 640x480 jpeg which should be well within site parameters so not sure what is going on.

[Nick-R]

I have come across a forward/stop/reverse relay on EBay controlled by a lever operated micro switch.  They can handle up to 10 amps so should be man enough for the job and cost about £10 each.  The setup I am contemplating therefore is:


A main esc controlling forward/reverse/speed for both motors.
One of the aforementioned relays between the esc and each motor.
The micro switches to be controlled by a servo on channel 4 turning a cam.


That should give almost full independent control on each motor except for differential speed control when both are running.  On channel 4, half deflection to the right or left on the joystick will stop either the port or starboard motor and full deflection will reverse the direction of the selected motor.  Given the self centring action, in my mind that should work reasonably well ergonomically - but not as well as the setup on the now unavailable Robbe F14. Given it seems relatively straightforward to have a TX with channels 3 and 4 both operating in the vertical plane, I am surprised some manufacturers do not offer that as an alternative to the standard layout.


If anyone has any comments I would be grateful to hear them!

[chas]

Hi Nick, i know that i mentioned the relay or servo operated switches earlier, but that was just to answer your query, i really wouldn't recommend them because in my opinion they'll mske operation of the model very cumbersome.
   What i suggest is that you get it built, and initially try what is commonly called tank steering i.e one motor and esc operated by each of the vertical axis sticks. It's an often used method of control because it's intuitive and simple to set up. If you can't get along with it then consider your mixer options. I'm always keen on the simplest solutions, it makes life much easier and you'll be sailing your model all the sooner.
Chas

[Nick-R]

By way of update, I have gone for twin escs controlling two Mabuchi 555s with direct drive I.e. not through gearboxes.  A test rig has all of that working satisfactorily.


The model is a Billings Smit Rotterdam.  The only decision is what batteries to use.  I will either go for twin lipos or a single 12v lead acid.  Does anyone have views on this plus if it’s lipos should it be 2s or 3s to give a reasonable scale speed?

[chas]

Hi again Nick, I'm glad you've got it built and working. There are a few things to consider in choosing a battery type.
 Current draw ( amps), each motor will probably take something like 4 amps so a total of 8 to 10 amps.
Weight, the fully ballasted boat will need plenty of ballast, battery choice can be part of this and be removable.
Run time on the water, there's a big difference here in what different batteries can deliver.
 Lead acid batteries help ballast the boat, but to deliver 8 amps plus for 1 hour you can't use an 8 ah battery because they lose capacity  very quickly with higher current draws. You would need at least 12 volts and 20 ah capacity, have you the space etc for those?
  Lithium batteries can deliver astonishing power for their size but need a healthy supply of common sense to look after them properly, you cant neglect them or be inattentive to charging and storage.
  Ni_mh batteries are easier to look after and still quite compact and are probably the most popular type with scale modelers.
  Its all down to personal preferences but I'd go for ni mh for that model because they're easy to use and handle.
Other opinions are available but buy a decent brand of whatever you choose, there are some dodgy batteries on the cheapo market.
Charles.

[Nick-R]

Thanks for that.  I have built a few single screw models since my return to the hobby.  My Aeronaut Queen has a good turn of speed on a 2s 8ah battery and becomes a flying machine with 3s.  More comparably, my Billings Nordkap gives a little bit more than scale speed on a 2s battery so I am inclined at the moment to go for two 2s lipos of around 5ah for the Rotterdam.  My Perkasa also gives good performance on 2s.


Is there ever a good reason to go for lead acid over lipos?

[KitS]

Is there ever a good reason to go for lead acid over lipos?

Yeah, sometimes it saves a fortune on having to buy ballast to get the model down on its waterline. 

[JohnG]

Hi Nick,
Not sure if it’s useful to you, but I just updated my ‘cheap mixer using a pico’ thread to include code to drive regular ESC’s. a single joystick controls 2 motors plus rudder – varying the motor speed to give better turning. 
https://www.modelboatmayhem.co.uk/forum/index.php/topic,68314.0.html
If it looks of interest feel free to either post or pm me. All it needs is a raspberry pi pico, a regular computer to program it, and a 5v power supply. The code can be adapted for how aggressively the motor speed adapts with the rudder position.

[Martin (Admin)]

 
This what you need!

Mercury Marine Joystick Piloting for Outboards:  https://youtu.be/LIYBHtLFZdQ?si=kFvsCTBF67clZnXI
 
Also:
https://www.modelboatmayhem.co.uk/forum/index.php/topic,2403.msg23694.html#msg23694
https://www.modelboatmayhem.co.uk/Common/Electrics/Twin_motors.htm

[Nick-R]

Hi Nick,
Not sure if it’s useful to you, but I just updated my ‘cheap mixer using a pico’ thread to include code to drive regular ESC’s. a single joystick controls 2 motors plus rudder – varying the motor speed to give better turning. 
https://www.modelboatmayhem.co.uk/forum/index.php/topic,68314.0.html
If it looks of interest feel free to either post or pm me. All it needs is a raspberry pi pico, a regular computer to program it, and a 5v power supply. The code can be adapted for how aggressively the motor speed adapts with the rudder position.

Thanks for that.  It is interesting and something I might try in the future but for this model I am going for full independent control of both motors plus rudder control.  Using a twin stick transmitter might be an ergonomic challenge but we will see.  Seems to me there is a gap in the market for a tx with twin side by side throttles on the left and a traditional joystick to the right.  I believe there was one some years ago which is now discontinued.

[Nick-R]

This what you need!

Mercury Marine Joystick Piloting for Outboards:  https://youtu.be/LIYBHtLFZdQ?si=kFvsCTBF67clZnXI
 
Also:
https://www.modelboatmayhem.co.uk/forum/index.php/topic,2403.msg23694.html#msg23694
https://www.modelboatmayhem.co.uk/Common/Electrics/Twin_motors.htm

I had real boats for many years.  My last boat was a Birchwood flybridge cruiser with twin 200hp Volvos.  This had traditional twin lever Morse controls and you could turn the boat on a sixpence.  I would seldom use the rudders for close quarters maneuvering - leave them straight and just use the engines.  Why that is not available on a RC tx is a bit of a mystery - maybe insufficient demand?

[KitS]

Seems to me there is a gap in the market for a tx with twin side by side throttles on the left and a traditional joystick to the right.  I believe there was one some years ago which is now discontinued.

The Robbe F14Navy was one such transmitter, and the two throttle sticks could be connected or not as required.


I've got another, more modern, Tx with a similar arrangement too, but can't remember the manufacturer or model I'm afraid, so they are around.