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*HOPING FOR A BETTER 2021 AND MORE OF THESE EXCELLENT FREE EVENTS ALL AROUND THE COUNTRY!

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CANCELLED because of coronavirus. Papplewick Pumping Station, Nottingham, Sunday 12th & Monday 13th April
CANCELLED because of coronavirus. Bournville Sub Day, Sunday 10th May 2020

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(CANCELLED) Submarine, Boating & Sailing Weekend, Norwich MBC, Weekend of 25,26th July

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Model Boat Convention, Haydock Park (Cancelled this year)

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CANCELLED. Bournville Sub Day, Sunday 13th September

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    Prop shaft seals

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    Tom(ADMIN)
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    Post  Tom(ADMIN) on Fri Jul 08, 2011 8:22 am

    david f wrote:We are all a bit mad in this hobby.

    David

    Yes...
    Giovanni LiCalsi
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    Post  Giovanni LiCalsi on Tue Jul 12, 2011 8:49 am

    Let's thank Hermann for thinking out of the box, or should we say hull?
    I think that this design is similar to a Grundfos circulator pump.It is a stator core design.It can be purchased in 24 volt version.
    Giovanni
    Hermann
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    Post  Hermann on Wed Jul 13, 2011 9:25 pm

    Hello everyone,

    yes, modell submariners really seem to be somewhat mad, otherwise they wouldn't spend so much time in their workshops, face and fight a lot of self made problems they wouldn't have as a normal human. Or being at the lake even despite of bad weather like these:

    Two submarine modellers are standing at the lake with their models running. It's raining cats and dogs and their clothes are already wet through and through. One starts to talk:"Just imagine - having this awful weather my wife tried to chase me out of the house to provide some shoppings for her!"

    Concerning the wet running motors I have added a sketch for illustration (upload will succeed hopefully).
    I have also added a sketch (text unfortunately in german, hope the picture will speak for itself) and pictures of another exotic device - magnetic rudder couplers to avoid sliding seals for the rods that operate the rudders.
    Of course rubber bellows do also the job of avoiding sliding seals (if the depths are not so great).

    Kind regards
    Hermann

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    Post  david f on Thu Jul 14, 2011 8:43 am

    Very good and interesting engineering which suggests that it should be used in a really deep diving model submarine. (50m + ?)

    Ever thought about trying one?

    The problems would transfer to how you would control it at depth. (Radio would not get there.)
    Hermann
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    Post  Hermann on Thu Jul 14, 2011 8:36 pm

    Hello David,

    you are right - normal radio control transmission on 40MHz will not work in depths of more than a few metres so the only reliable way is using a cable (or using sound transmission in water but this will be a real technical challenge).

    If you use a simple wire that is even loose coupled to your transmitting antenna and down with your model it is also near the receiving antenna the radio waves will travel along the wire as this is a much better propagation path. I did some experiments.

    That class 212A submarine model is already designed for greater depths (50m+ shall be possible) and when I will have a camera and lights installed in the bow I will go again to the lake of Hemmoor (a former open mine, now flooded with ground water, about 100km from here, between Cuxhaven and Stade) and try to reach the bottom at approx. 60m.

    You may ask why doing this. Well, most modellers are searching for their special challenges (like Jermy Clarkson, "Hamster" and "Captain Slow" from Top Gear at BBC), so why not exploring the third dimension - the depth - further? For the model designer this is an interesting challenge and requires reliable solutions.

    Kind regards
    Hermann


    Last edited by Hermann on Thu Jul 14, 2011 8:37 pm; edited 1 time in total (Reason for editing : correction of a writing mistake (forgotten letter))
    david f
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    Post  david f on Sat Jul 16, 2011 11:21 am

    I'm impressed that you are tuned into "Top Gear!"

    Very interesting plans you have for deep diving subs.

    What with the rise of 2.4Ghz we have a need for a replacement control system in subs. (Sound, radio etc.???)

    Anything coming along in Germany?
    Hermann
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    Post  Hermann on Sun Jul 17, 2011 1:12 pm

    Hello David,

    yes, I am a real enthusiast of "Top Gear"! But I must confess that it was my son Christian who discovered it first via internet. It is the very best motor TV series and so different (in a positive sense) from the motor TV series here where they make tests of new car models and it seems to be more like a promotion for the car manufacturer.
    Unforgotten the items when the three converted a Renault Espace into a "convertible" or they modified 3 cars into amphibious cars (a "TOYBOTA", a narrow-boat-like VW camping bus and an Austin Herald sailing ship). And the race to the north between a motor bike, a Jaguar sports car and the new built Peppercorn pacific steam locomotive "TORNADO". Marvellous!

    Well, radio control beneath the waves might become a serious problem for us model submariners if the 40MHz frequency range would be taken away for us by the authorities. 2.4GHz control sets are also extremly rising in Germany and perhaps this might accelerate the end of 40MHz here. But 2.4GHz are definetly no replacement for us! Although I considered from therory and by firsts reports from experience by a few other modellers I did an experiment in the laboratory where I work and made measurements of attenuation of 2.4GHz radio waves in normal water. As a rule of thumb I found an attenuation of approximately 1dB per cm depth; that would mean in 20cm you have 20dB (corresponding to 1/10 ) less signal strenght, and in 40cm 40dB less (means 1/100).

    I hope 40MHz or at least 27MHz will stay a pretty long time!
    Transmission by sound is imaginable from theory but there are a lot of difficulties to solve (for industrial or military applications real solutions exist but they require complex electronics for signal processing). Imagine that you will have high acoustic noise in water so you must filter your acoustic reception signal. Reflections will occur (from the surface, the bottom, ambient obstacles, nearby other models, and so on) and so multiple reception of the same control command wit delay times between must be considered.
    As far as I know there are no special developments here for hobby model submariners (their number is not so great). But perhaps this would be a nice challenge for me after retirement...(I am 56 now).

    Kind regards
    Hermann
    david f
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    Post  david f on Mon Jul 18, 2011 7:53 am

    Well I only caught the end of last nights "Top Gear" but you have a treat in store (Rail mounted caravans!)

    Interesting that you are experiencing the same rapid shift towards 2.4 GhZ in Germany.

    Another huge advantage of 2.4 is the easy frequency sharing because of the large band width.

    Much more of a sharing problem with other sound or radio systems.

    (And sorry, Richard but we have drifted off frequency (topic?!) on this one. Do we have a section for "Top Gear?!)
    Hermann
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    Post  Hermann on Mon Jul 18, 2011 10:54 pm

    ...yes, we shouldt definetly have a "Top Gear" section. I just saw the last issue my son Christian has downloaded, with Jeremy's "sports train" - I had tears in my eyes from laughing!

    But now for something completely diferent - e.g. model submarines.

    At the moment we can have profit by the change to 2.4GHz of so many surface ship modellers. We may regain free frequency channels on 40MHz when we are at a lake with other modellers. My only fear is that the authority that is responsible for frequency licensing may close the 40MHz band for model radio control in the (perhaps near) future when it seems to become old fashioned. And how long 27MHz will last nobody knows...

    That's not a big problem for deep diving models as you will still require a cable connection for this. And you will require reliable prop shaft seals that stay tight under pressure -or a solution with a wet running motor without seals. For normal depths of our models conventional seals as discussed and sketched before will satisfy in general.

    Kind regards
    Hermann
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    Post  Tom(ADMIN) on Tue Jul 19, 2011 7:27 am

    David and Hermann, you can have a Top Gear section by all means...maybe we could have the Stig as our official sub test driver?

    Now, the radio question...(yes, I know it's wandering away from the original topic a bit)..Our very own John Robinson can convert 35mHz radios to 40mHz he tells me, this could be a way out for us and also a source of extra income for John. I had a quick look around Ebay and found several 35mHz radios(Futaba/JR/Sanwa/etc)at very reasonable prices, some of them top of the range 9channel helicopter radios with all sorts of extra functions which would very useful on a model sub.

    I'm sure that a pm to John outlining your requirements would result in a favourable reply...
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    Post  david f on Sat Dec 10, 2011 4:49 pm

    Just an update on my Simrit seal arrangements.This is the arrangement on the U Class - ORP Dzik:
    Prop shaft seals - Page 2 Orp_dz10

    You can just see the Simrit seal on the port side shaft.
    A ball race is fitted just under the Simrit seal.
    You can also see the connectors for the universal joints.
    All fairly crude but quite easy to make and works well.
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    Prop shaft seals - Page 2 Empty is the design you describe more or less energy efficient that a shaft seal (battery life)?

    Post  tarheel on Fri Feb 24, 2012 5:19 am

    Hermann wrote:Hello David,

    yes, the 7 dark circles you can see on the disc rotor are magnets indeed. They are very common ferrite magnets normally intended to hold/ stick sheets of paper at metal blackboards at the wall. These magnets have a special direction of polarisation, they are polarised in direction of the diameter so the half circle beneath the "aequator" is a south pole, the half circle above is a north pole. So the rotor (and the moulded stator also) has 14 poles. I took ferrite magnets because they had been easy to purchase (in 1993 when I built the first motor, rare earth magnets were hardly available for me). The energy density is much less compared to rare earth magnets but they are full resistant to corrosion in water.

    It's not a magnetic coupling between two magnetic rotors (one inside, the other outside the pressure hull) but a real brushless DC motor where the inner rotor is replaced by a stator system equipped with coils and driven by switching transistors. That stator system (that narrow light grey ring) is attached to the aluminium motor housing and moulded with epoxy glued. The control electronics is located inside the cylindrical motor housing that is screwed to the rear wall of the pressure hull with its flange.

    The motor has 4 terminals: 2 for power spply from the battery and 2 (signal and return) for connection to the radio control receiver.

    And you can see - there is no seal for the 5mm propeller shaft. The whole rear section of the model is free flooded.

    On the photograph you can also see the rods for moving the rudder blades. They are actuated by linear magnetic couplers, also eliminating sliding seals.

    I must confess that this is an exotic practice and a some modellers here called me mad for doing this, but why not doing things in an unusual way? That hermetical concept was just an idea and I wanted to prove that it works.

    Kind regards
    Hermann


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    Post  profesorul on Fri Feb 24, 2012 11:35 am

    @HERMANN,
    Where can be found those magnets like in the picture?. I think they can be used into a lots of aplication don"t You think?.
    REGARDS
    MARIUS
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    Prop shaft seals - Page 2 Empty Help Converting Graupner MC-19 to 75MHz

    Post  Giovanni LiCalsi on Sat Feb 25, 2012 2:23 am

    There must be someone brilliant here that can give me a wiring schematic drawing to convert my Graupner MC-19 to use a 75MHz radio module?
    I'm desperately wanting to convert.
    Thank you,
    Giovanni
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    Post  nigele(ADMIN)2 on Sat Feb 25, 2012 10:27 am

    Hi Giovanni,
    Sounds like a question for John Robinson,put a post on his page.
    nigele.
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    Post  Hermann on Sat Feb 25, 2012 3:38 pm

    Hello everyone,

    (especially Marius and tarheel to answer your questlions)

    @Marius: The magnets I have used for the magnetic rudder couplers were samples I had got from a dealer on who had been on a model exhibition selling various electronic components, tools and so on... This had been more than 10 years ago (you can see it by the coin on the photograph for size comparison, a former DM, since 2002 we have the EURO).
    Meanwhile you can buy powerful magnets in various sizes for example from ebay (look for "Neodym magnets") for almost reasonable prices. But note: for applications where they are exposed to water you shall protect them from water contact by some moulding (e.g. epoxy glue) because if their nickel plating is injured (fine cracks in the surface) the magnet material beneath the plating will start to corrode rapidly.

    @tarheel: Efficiency is a question of running speed, whether the friction of the seal or the "water friction" of a wet running rotor is more lossy. For higher rpm speed a conventional shaft seal will have less losses in comparison to a wet running motor. A wet running rotor is stirring the water around and those water whirls (that do not help for propulsion)cause losses as well.
    But the real advantage of the wet running motor is the tightness, there is no leakage at all even at extreme diving depths.

    Kind regards
    Hermann


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    Post  david f on Mon Dec 03, 2012 12:03 pm

    I've just been referring Dave from Model Boats Mayhem onto this thread and I just realise that all the shaft sealing solutions are a bit "home brewed".

    Can anyone recommend a commercially available "off the shelf" shaft seal system??
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    Post  profesorul on Mon Dec 03, 2012 12:38 pm

    @HERMANN,

    Thank You Very Much for the answer and Information.
    I think these type of transmission can be used especially for the small Sub,where the friction is low,due to the small diameter of the shaft,and from heare,the small angular speed,and the propeller speed is also low!.
    Is only My opinion.

    MARIUS
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    Post  david f on Tue Dec 04, 2012 12:17 pm

    I have just had a quick look at the Engel website and all they seem to offer is the Simmering oil seal. Good, yes but was hoping to see a housing to make it more "off the shelf".

    David
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    Post  david f on Tue Sep 30, 2014 9:41 am

    Just a word on how to fit "Simrit" type oil seals.

    As an oil seal they are designed to fit into a machined inset i.e the outer circumference is a push fit into the housing.

    You can fit them this way but you can also use the "sandwich" method I showed earlier or I have even heard of them being glued onto the outside of the WTC. The main consideration are to not use up too much of your valuable WTC space (length mainly). I have found them to be very low maintenance items - they seem to last for years.

    I have always used a ball race bearing immediately behind the seal and I think that this is a good idea to keep the shaft well aligned.

    Don't forget that you will also need some form of "thrust bearing" to take up the thrust of going into forwards or reverse. I use Collets fixed onto the shaft with grub screws. (Aircraft people use them a lot, so available from these sources.)

    I have standardized on 4mm stainless steel shafts for everything (prop shafts, push rods etc.)

    David
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    Post  timgarrod on Thu Jun 29, 2017 9:38 pm

    like the idea of the magnet linkages
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    Post  david f on Mon Jul 03, 2017 9:44 am

    They do look good for a lot of different reasons:

    - quick to connect linkages
    - completely water tight shaft seals (deep diving?)

    Having said that I haven't tried any yet.

    David
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    Post  merriman on Mon Apr 16, 2018 4:07 pm

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    Post  timgarrod on Mon Apr 16, 2018 4:59 pm

    very nice. just finished making mine for the gato.

    fingers crossed they work :)
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    Post  merriman on Mon Apr 16, 2018 6:08 pm

    timgarrod wrote:very nice. just finished making mine for the gato.

    fingers crossed they work :)

    If I can help with any specifics, just shout out.

    David

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