2 ESC's or 1

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  • roedj
    Captain
    • Sep 2008
    • 562

    2 ESC's or 1

    To All,

    General question on ESC's - If I have a two screw ship of any type, is it better to have:

    1) ONE ESC driving both electric motors (parallel or series?) from one R/C channel or,

    2) TWO ESC's from one R/C channel each driving their own motor or,

    3) TWO ESC's each on their own different R/C channel each driving their own motor for differential steering or,

    4) ???

    Thanks for your time,

    Dan
    Born in Detroit - where the weak are killed and eaten.
  • toppack
    Rear Admiral
    • Nov 2008
    • 1124

    #2
    Depends if your model has rudders or uses props for steering, or both.
    Most Subs use rudders for steering, 1 ESC on paralleled motors, if it has 2 motors.
    Always use the 'Least' amount of electronics needed. Less to make room for and have problems with. ;)
    Last edited by toppack; 04-27-2009, 12:36 PM.
    Rick L.
    --------------------------------------------
    * Asking Questions is a 'Good Thing',
    Since Learning is Always a 'Good Thing' *

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    • KevinMc
      Commander
      • Feb 2009
      • 305

      #3
      Originally posted by roedj
      1) ONE ESC driving both electric motors (parallel or series?) from one R/C channel or,

      2) TWO ESC's from one R/C channel each driving their own motor or,

      3) TWO ESC's each on their own different R/C channel each driving their own motor for differential steering or,
      Hi Dan,

      In a nutshell:
      1.) is obviously the simplest approach. (Wire them in parallel if you do this.)
      2.) buys you is reduncancy over 1.). If you've got ESCs that are problematic you'll still be able to limp home on a single screw should one give you trouble. It presumes however that you've got space enough for a second ESC.
      3.) also buys you redundnacy over 1.) but will also give you enhanced manoeverability over both 1.) and 2.) but requires an extra channel.

      At various points in time I've tried 1.), 2.) and 3.). I have to say that I never thought that 3.) would work on my boat (1/96 OSCAR II) but it makes a tremendous difference for precision manoevering at low speed. This is also how I'm still configured. If you can spare the channel and space, it's worth trying it out at the very least. (If you're not happy with the extra manoeverability it affords, you can always pull the second ESC and save it for a future project.) What ever you do, don't let anyone talk you out of trying 3.) for yourself!
      Kevin McLeod - Oscar II driver
      KMc Designs

      Comment

      • Tachikaze
        Lieutenant, Junior Grade
        • Dec 2008
        • 20

        #4
        As they have mentioned the single ESC with two motors in parallel is you best set up, unless you feel you need to have individual prop control.
        The important issue is making sure you have a speed control that can handle the amp draw from the two motors.
        Look at the mtronik ESCs, these little guys are very water resistant ( we use them in combat R/C surface warships) and inexpensive. I have been very pleased with the three units I have running twin motor set ups in 55" and longer ships.

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        • Kazzer
          *********
          • Aug 2008
          • 2848

          #5
          I've often wondered if I should cheat with my 6 feet long S Class British Submarine and fix a bow thruster up front. The boat is like a log on the turns.

          Raboesch sent me a few samples and I think I gave them to Merriman. Must see if I can get one back and try it.



          I guess this could be rigged to the rudder servo so that some starboard stick gives a jet to port?
          Stop messing about - just get a Sub-driver!

          Comment

          • Slats
            Vice Admiral
            • Aug 2008
            • 1776

            #6
            One thing often lost in this discussion over independent ESCs is is the geometry of the propeller shafts parallel to the hull or canted (angled) out from it.

            DM educated me on this and he is right (typical).

            Take an Oberon for example the shaft lines exit the hull canted out. Reversing one motor and ahead on the other did not result in the boat engaging in a tighter turn, the result was a slewing sideways type of movement of the entire hull.

            If the shafts are parallel to the hull you can envoke tighter turns as intended via ahead on one shaft and astern the other.

            So yes all the other reasons are well worth consideration BUT consider the geometry and thrust lines of the shafts too.

            Best
            John
            Last edited by Slats; 04-27-2009, 10:42 PM. Reason: from spelt as form
            John Slater

            Sydney Australia

            You would not steal a wallet so don't steal people's livelihood.
            Think of that before your buy "cheap" pirated goods or download others work protected by copyright. Theft is theft.



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            • Slats
              Vice Admiral
              • Aug 2008
              • 1776

              #7
              Originally posted by kazzer
              I've often wondered if I should cheat with my 6 feet long S Class British Submarine and fix a bow thruster up front. The boat is like a log on the turns.

              Raboesch sent me a few samples and I think I gave them to Merriman. Must see if I can get one back and try it.



              I guess this could be rigged to the rudder servo so that some starboard stick gives a jet to port?
              Bow thruster will only work at very low speeds Mike. I have extensive experience with these in surface ships and have seen no less than half a dozen fitted to subs. The sub thrusters are no more efficient than the targets and like the targets are only of use at low speeds.

              I like the Raboesch ones, particularly the paddle design as oppossed to the new propeller design. Indeed I have two of them in Silver Cloud.

              J
              John Slater

              Sydney Australia

              You would not steal a wallet so don't steal people's livelihood.
              Think of that before your buy "cheap" pirated goods or download others work protected by copyright. Theft is theft.



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              • Kazzer
                *********
                • Aug 2008
                • 2848

                #8
                Originally posted by Slats
                Bow thruster will only work at very low speeds Mike.

                J

                I figured out thatg the actual scale speed of the 1:36 scale S Class was about 2 mph - a slow walk. Any faster would look ridiculous. It's turning circle at that speed was about 25-30' diameter. So I guess they would help?
                Stop messing about - just get a Sub-driver!

                Comment

                • Slats
                  Vice Admiral
                  • Aug 2008
                  • 1776

                  #9
                  Originally posted by kazzer
                  I figured out thatg the actual scale speed of the 1:36 scale S Class was about 2 mph - a slow walk. Any faster would look ridiculous. It's turning circle at that speed was about 25-30' diameter. So I guess they would help?
                  What I mean by slow is near a stop.
                  It will always be a case of try and see, but in all the vessels I have used these work best when the ship is near to rest. I am sure others here could describe what the physics is behind this. I guess it probably has much to do with the fact that a bow thruster works best when mass momentum associated with the hulls lateral (forward / backward speed) is not great.

                  As for the quality and effectiveness of the Raboesch ones - love em - have tried and used other brands -like these ones the best.
                  J
                  John Slater

                  Sydney Australia

                  You would not steal a wallet so don't steal people's livelihood.
                  Think of that before your buy "cheap" pirated goods or download others work protected by copyright. Theft is theft.



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                  • toppack
                    Rear Admiral
                    • Nov 2008
                    • 1124

                    #10
                    Mike,
                    I think I would increase the size of rudder, and try that, before installing a bow thruster. Is rudder larger than scale now? If scale size now, double the size.

                    Slats is correct, bow thrusters just Don't 'thrust the bow' much when moving. I've tried 2 of the twin-propellor type and I don't think you will be happy with the performance after all that work of installing it.
                    It takes a great deal of force to move a bow sideways when there's force of the water pressing equally on both sides of bow as it moves thru water.
                    Which is not so when boat is Not moving forward, so thruster works then.
                    Last edited by toppack; 04-28-2009, 10:15 AM.
                    Rick L.
                    --------------------------------------------
                    * Asking Questions is a 'Good Thing',
                    Since Learning is Always a 'Good Thing' *

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                    • Subculture
                      Admiral
                      • Feb 2009
                      • 2119

                      #11
                      Why not just fit a larger rudder?

                      If concerned about scale fidelity, then make an extension piece for the existing rudder that can be detached when the model is out of the water.

                      A modeller over here came up with a novel solution for his 1/32 WWI R-class.

                      Quite a large boat at that scale, and even with enlarged rudders, because they were out of the prop wash in small pools, operation was a real drag, so he fitted an auxiliary thruster. Rather than fit one into the hull, he made up a separate self contained unit that clips under the boat. A small TX/RX on 433mhz was built up, and used to control the thruster in a bang-bang fashion. This doesn't interfere with the boats 40mhz system.

                      The system works well, but as has been pointed out, the boat needs to be slowed almost to a halt for effective operation. The thruster was found to be most effective when clipped to the stern.

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                      • Tachikaze
                        Lieutenant, Junior Grade
                        • Dec 2008
                        • 20

                        #12
                        A rudder getting much larger than 25% increase in scale size is really going to start to slow you down through the turn. If you do do that, make sure you use the rudder to midship technique. If you pulse the throw on the rudder during the turn, you can reduce the speed loss a little.

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                        • Albion
                          Captain
                          • Dec 2008
                          • 651

                          #13
                          I've never used a bow thruster, but the velocity of water passing over the inlet (/outlet) of the thruster, which is tangential to the flow direction of the thruster would starve it of any flow. There would be negative pressure at the inlet and in effect the thruster will be moving very little liquid side to side.

                          (my college mechanical science teacher used to say "in effect" and now i'm using it damm)
                          Next time someone points out it takes 42 muscles to frown, point out it will only take 4 muscles to b1tch slap them if they tell you how mnay muscles you need to smile:pop

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                          • Slats
                            Vice Admiral
                            • Aug 2008
                            • 1776

                            #14
                            Try a bigger Rudder Mike as per the suggestions made herein.
                            Leave the bow thrusters for the tugs / tankers /and other big targets.

                            J
                            John Slater

                            Sydney Australia

                            You would not steal a wallet so don't steal people's livelihood.
                            Think of that before your buy "cheap" pirated goods or download others work protected by copyright. Theft is theft.



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