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>> Home > Tags > rotation

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contra rotating
HMS HOOD by Trumpeter by RNinMunich Fleet Admiral!   Posted: 6 days ago
Even tastier with the Frankfurters, and Colemans Mustard I trust😜😋 Steve: I found a cheap way to mechanise the two aft turrets of my H class destroyer Hotspur, using one servo with a pulley, a couple of smaller pulleys on the turrets, about 2:1 ratio to give at least 180° rotation at the turrets, and a spring loaded nylon cord around the pulleys. I'll see if I can dismantle her over the weekend to make some pics. I plan to try something similar with my 1:350 Hood, also Trumpeter and also excellent detailing. Another way is to use one micro servo per turret, connected with Y cables if you want a synchronised Broadside; A+B and X+Y turret. Then use the servo travel adjustment at the TX to maximise the rotation. You can then move all four on one channel or two channels for 'Independent Firing" fore and aft. I will use the two pots at the top of the Turnigy i6 TX for this. On Hotspur I used the left stick left/right. I plan to do this in my Graf Spee, Belfast, Hood and Bismarck. Maybe also the ack ack turrets on Ark Royal!? Will knock up some test jigs sometime 🤓 Cheers Doug 😎

Graupner ranzow refitting by kmbcsecretary Captain   Posted: 18 days ago
Here we have the working crane for lifting the buoy's into/out of the water. Again this was converted to working by using three micro motors rated at 300-1 plus one gear box at 5-1 to operate the rotation and a 4-1 gear box to operate the lift and lower first pic shows the crane completed second pic shows the line winch motor which is just a 300-1 micro motor. third pic shows the lift and lower arm with the motor and gear box is hidden in the crane body fourth pic shows the micro motor and gear box that controls the rotation, there is a similar layout that controls the lifting arm the final pic shows the micro speed controllers that you can do the fine control of setting the required speed that you want. Ron

Aerokits Patrol Torpedo Boat by MouldBuilder Lieutenant   Posted: 1 month ago
Hello RNM and others. The 20mm gun arrived today. I am really pleased with it. To my surprise, it does move up and down. It has no rotational movement. I will attach pictures at the end. I bought the "beast" motor that you suggested Canabus. I will have to see how it fits in. Do you think the universal joints I am using now are suitable or should I upgrade these considering the RPM. One other question I have for today is about paint. Can you suggest a suitable paint to use on my boat. I am not concerned about the colour, just the type/make at this stage. I read an article here earlier that suggested to use Holts car spray cans. What are your thoughts on this. I have an air brush if this is more suitable, but would like help on a suitable paint choice. I will attach the gun pictures now. If there is a particular angle you would like, please reply and I will try to add tomorrow. Thanks. Peter.😉

Graupner Elke HF 408 by Dave M Fleet Admiral!   Posted: 2 months ago
Hi Allen Mabuchi no longer list details of your motor and as it is from an ex flyer chances are it has been cooked at some time in its life. I agree it is not easy to check for shorts but a reasonable meter will show any major problems. Your battery sounds fine. Pitch is often marked on the props near the boss but an explanation I have seen on the web: Pitch: theoretical distance the prop travels on each rotation. This is theoretical because water is not a solid medium and the prop slips. 10 to 30% is normal, the lower numbers are found only on hi-performance props, specially prepared. Constant Pitch: the pitch is the same across the entire propeller's working surface, or blade face. Progressive Pitch: the pitch is lower at the leading edge and increases progressively along the trailing edge. Consider a prop that runs in a liquid media with a constant pitch, the tip of the prop rotates faster than the hub. Conversely, if the angle at the tip is lower, the water speed on all prop surfaces will be the same. In this case, the performance is far better. Progressive pitch props offer better planning performance. So if you were to get some graph paper or paper with 1mm markings and set the prop on a shaft over the paper and measure the start point then rotate thro 360deg and measure the finish point this will give you the theoretical pitch. Over the years I have amassed a fair number of props and usually try various before I decide on the best for the model. Try what you have with the 6v battery (looks just right for the model) and see how it sails. From experience I know that this type of model is difficult to get going and all our club models have coarse pitch brass props. Speed will depend on the motor but with a geared motor you should be able to reduce the revs to give scale speed. I look forward to hearing how you progress in a couple of weeks.

Graupner Elke HF 408 by RNinMunich Fleet Admiral!   Posted: 2 months ago
Re Prop (or screw pitch) ... If the prop blade was a complete screw it would advance through a solid at the rate of NP, where P is the pitch of the blade (prop) and N the rotation speed (Revs) of the driving shaft. Therefore for given revs of the motor a coarser pitch will result in more speed. Conversely finer pitch = less speed. Which is why I suggested perhaps a 'scale' prop with finer pitch. Of course the above refers to motion through a solid. Ya gotta start somewhere😉 I can provide the maths for extrapolation to slip (slip ratio) in a fluid medium ..... if anyone's really interested 😉

MV TEAKWOOD by RNinMunich Fleet Admiral!   Posted: 2 months ago
PS: Trouble with so called 'Smart' phones is that they sometimes outsmart themselves and us!😲 if you had 'Auto rotation' ON then the pics will ALWAYS look right on the phone, no matter which way up you happen to be holding it! 😁 Whether from my Samsung phone or my Sony digital cam I always upload to my PC, check the orientation (correct if necessary using Irfan View) and then upload to the site. But then I don't like the mobile App anyway 😡

Test fit the Rudder! by RHBaker Fleet Admiral!   Posted: 2 months ago
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

Props by RNinMunich Fleet Admiral!   Posted: 4 months ago
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: 4 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👍

Props by Trillium Captain   Posted: 4 months ago
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:, 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 may help. Roy

12v esc for trolling motor build by Dave M Fleet Admiral!   Posted: 4 months ago
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

rotating radars off mast by marlina2 Petty Officer   Posted: 5 months ago
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

rotating radars off mast by kmbcsecretary Captain   Posted: 5 months ago
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

Twin Esc/Mixer by RNinMunich Fleet Admiral!   Posted: 5 months ago
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 😎

Twin motor control problem by John Fleet Admiral!   Posted: 6 months ago
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.