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Hi, would prefer to see something like a stainless or brass washer. The nylon might pick up and tear, then metal to metal contact would occur. The washer has to take both the propeller thrust and rotation, so needs to be quite robust. I doubt thin nylon would last very long, it could also heat up and extrude under load. Rowen
Hi Roy, Happy New Year 😉 Twin screw rotation is case of 'Horses for courses'! It's a Black Art and much depends on the hull shape, especially at the stern and the orientation of the rudders to the shaft lines. What you write is correct for slow, short fat displacement hulls, like tugs and rig supply ships etc needing good slow speed manoeuvrability. Especially those with one rudder per shaft. For long thin hulls (naval ships) and deep V and planing hulls (Fast launches and power boats etc) inboard turning screws are preferred to concentrate the thrust behind the centreline of the hull instead of dissipating it out into the open water. It also concentrates the thrust onto the rudder when only one rudder is fitted on the centreline. Outboard turning screws tend to push the stern up and bow down. Inboard turning tends to suck the stern down and raise the bow. So making planing easier. You only made one mistake in your description: "when using the props to assist a turn, i.e one prop turning clockwise and the other anti-clockwise". The props turn in opposite directions when both are running ahead, or both astern. When turning, one ahead and one astern they then both turn the same way thus producing the combined side thrust. I was advised to use inboard turning props on my H class destroyer (twin screws single rudder) by an ex RN Captain I met at the local lake here in Munich about 30 years ago! @ Chris: What type of boat / ship are you building? Cheers Doug 😎
Props by ChrisG Chief Petty Officer Posted: 2 months ago
Many thanks to Mark, Doug and Roy for the information on prop rotation. I will now be confidant that each prop is on the correct side of the boat, wiring the motors and connecting the ESC correctly is a task for the future to say nothing of connecting the R.C. Thanks again👍
This rotation question seems to pop up regularly. Probably for a model, rotation direction doesn't really matter, but one authoritative answer can be found here: http://modeltugforum.com/index.php?topic=5947.0, which quotes from the Ship Handler's Guide. To summarise the comments: Outward-turning propellers means the blades of the propellers are outward turning in the upper half of their circle of rotation, and, when viewed from astern, the propeller with the right-hand blades is on the starboard (right) side and again, when viewed from astern to drive the boat forward, it must rotate in a clockwise direction. This is the preferred arrangement on full-size ships because when using the props to assist a turn, i.e one prop pushing ahead and one pushing astern, the side thrust from the two propellers assists the turn. The attached image from www.slideshare.net may help. Roy
Interesting project. Difficult to give advice on the info available. Looks like a steerable powered nozzle at the rear but what motor is it and what are the specs? An Esc does all the hard work and converts the rx pulses into usable power. I have arduinos and they can be programmed to control the power and rotation of a motor but would need additional high power Mosfets as well as other circuitry to buffer the unit from the output. If you are really into arduinos then a walk in the park but I believe an ESC would possibly be more robust and waterproof. It would be good if you were to post a build blog of your progress as the subject is certainly different to any models we have seen to-date. Good luck with the build
I have recently constructed a rotating radar mast for my 1:48 scale paddle tug "Forceful" I have used a geared 6 volt 60 RPM motor which gives a realistic scale rotational speed. It is a little noisy but only when close up. it is driven by a direct shaft running up the centre of the mast not prototypical but gives a pleasing effect. I may rebuild this at a latter date to eliminate the noise
I have used the kits from Mr rc World he has option of motors and the controller that comes with it gives you the fine control to set the speed of rotation to what you want and powered by your receiver pack You can find him on flea bay or on the Web
My pleasure👍 Re motor wires; I would be more inclined to think that the red one is the positive!! You'll soon find out if you do the rotation check I mentioned in the PM! Have fun and don't blow anything up! Check twice - pay once😉 Cheers Doug 😎
Hi Paul, yes it sails at Bury and I am continuing to try different options. There has been much head scratching at Bury over the problem and the rescue boat has been out a couple of times to rescue the boat in reverse. The Y leads have been tried as you suggested. It is easy to test the rotation direction by feeling the air flow and slowing them manually to observe them.
John, Before you get any more ESCs here are a two basic things to try. 1. At the water's edge (on the stand) start the motors (both). Check their rotation. Then lower the boat into the water and see what happens. Either it should continue in the forward direction or it will stop and then go into reverse. Separately 2. Plug ESC into one radio channel and plug the other into another channel. This is a test - each ESC will be totally independent. Also we don't want use the BEC. I have had problems of a similar but slightly different nature with my Fairmile D previously, except that one of the motors would just stop after 15 or 20 seconds. Now I have each ESC running off a separate channel on the radio and the two channels are mixed so there is a master and slave channel and I use the single throttle stick to operate it. It works fine.
Can anyone advise me on correct prop rotation direction. I will be using 2x45mm props 1 clockwise and 1 counter-clockwise. My thought is looking at the props from the rear the lefthand side will rotate clockwise and oposite for the righthand side. Please advise me if I am wrong!
What ESC were you using? My experience with 600 motors is that they are power hungry, smell a lot and get very, very hot. I had two in a Slipway Trent (they advise the ECO version, no longer available) and used to be able to smell them from the shore! Could be the ESC internals circuitry shut down and may start working again when cool. Any weed in your pond will definitely overload them, which was my problem. Too big a prop will also cause overheating. I had 40mm 3 blade brass props in the Trent. It's possible that the motor is to blame if it has cooked the coils and caused an internal short. Try running direct from the battery with an ammeter in circuit. I am assuming you have checked your propshaft for free rotation and no binding, locknuts can and do come adrift and can tighten up on the shaft, which may explain the slowing down you experienced. Please keep us posted with your progress Cheers Dave
Hi Roy, to dispel any possible confusion; by 'double jointed' I mean the true Cardan link. Which is in 3 parts connected by 2 UJs. Invented by an Italian mathematician and engineer several centuries ago to transfer rotation from one axial shaft line / level to a different (within reason) line without using gears. They inevitably create more friction by applying more side pressure to both input and output shafts, thus more wear on the motor output bearing and the tube input bearing 🤔 Plus friction and rattling/grinding generated in two 'out of line' UJs. If, as they should be, your motor and prop shaft are in (near) perfect alignment you don't need a Cardan! My maxim is 'less flexibility - more alignment' 😉 I like the coupling in the pic; called Stegkupplung in German, don't know the English for that😉 They are flexible but not floppy and totally silent👍 I once made the mistake (laziness🤔) of using a Graupner Cardan to couple up a geared Decaperm to the shaft in my Sea Scout. Never ever again 😡 After the first trials I took it apart and modded the motor mount properly. The original motor (perfectly fitted by my Dad) was a Taycol Target - the one I have recently modded for controllable forward and reverse. That will now be used in an ancient Billing Fish cutter inherited from an Aunt. Cheers Doug 😎
Good pics 👍 At first look I would say two are identical, the 'mucky' one without the outer jacket (improves the magnetic field) is probably not. Even if it is the same type without the jacket it will not perform the same. Proof of the pudding will be in the testing, preferably with a Watt meter. The red dot signifies the positive terminal for normal (forward) rotation as brushed motors have a preferred direction due to the brush wear - Bedding In! Many don't like running backwards for long periods or at high speed. The fact that the mucky one has a gear fitted also hints that it may have different parameters. For a twin screw setup I would use the two with jackets and see how she runs with all trims set to neutral. I'll see if I can trace the type/serial number visible on the mucky one. Cheers Doug 😎