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Author Topic: The ship that never was - G3 - HMS Indomitable  (Read 43450 times)

marmoi

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The ship that never was - G3 - HMS Indomitable
« on: June 19, 2009, 01:52:25 pm »

Well I thought I had built the largest model I would ever build (HMS Dreadnought) until the "Belly Dancer" saw the G3 hull at Ron's show last year and bought it for me for Christmas!

Not being perturbed by mere facts like "Darling, I have already got HMS Dreadnought, it's collier and Tug and HMS Kent in the car, where am I supposed to put a nine foot hull?" or words to that affect. We did manage to slide the hull down the centre of the car and all the way home all I saw was the top of her head and a "light" snoring sound.

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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #1 on: June 19, 2009, 01:56:56 pm »

So I thought, I have a big hull now, what next?

Research

The National Maritime museum has a full set of plans for this vessel and after they had liberated quite a lot of money from me I received 6 detailed drawings of the G3 at 1/96 scale, which made each full size sheet ten feet long (I am going to need a bigger workshop!)

The G3 was going to be the biggest ship the Royal Navy had ever had, so big in fact that the docks where she would tie up, were going to have to be extended. Thankfully the Washington Treaty put an end to the repeat of the arms race that lead to the first world war from happening again in the 1920's.

The drawing below shoes the proposed layout, which was later adopted in a shortened version for the Nelson & Rodney.
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #2 on: June 19, 2009, 01:59:11 pm »

Over the winter, I started work on the mechanical and electrical design for this model. I looked hard at the requirements and decided that with the room that I had to play with this time, I would use it to it's full extent and build in as much as I could to give me ultimate control and realism of handling.

1. Engines

I would need a lot of power at both high and low revolutions, but I was not sure how such a large hull would behave, so I opted for 4 motors with medium range, and to give me the control I went for 11 pole Buhlers that could be run off a 24V supply.

2. Drive train

To give me flexibility I went for the same belt drive system that I used in HMS Dreadnought, it's quite, easy to line up accurately, and by changing pulleys can alter the drive ratio easily.

3. Propeller shafts

The shafts are going to be quite long, so I order some stainless steel (316L marine grade), Bronze and Brass to make my own.

4. Speed controllers

With the requirement for low and high end control I went for 3 Electronise variable frequency controllers, and I will explain why 3 and not 4 later.

5. Fogger

Last but not least I wanted the realistic look of smoke coming from the stacks. I spoke to Mark of Marks Model Bits and after a bit of discussion we came up with the concept of the super fogger. 5 nebulisers, two fans and an ESC, all running off 24V.

So it was soon down to some design time on the computer to work out the layout of the motors and tubes.
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #3 on: June 19, 2009, 02:02:30 pm »

Now I am getting into the swing of things, I thought it was time for some prototyping.

I always build and mess about away from the model as I am not often happy with the first attempt.

The first part of this build was going to be the engine room, so with a large piece of wood I set about putting the components together.

The scale of this engine room can be judged from the standard size servo acting as the rudder, just in front of the pulleys.
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #4 on: June 19, 2009, 02:06:42 pm »

It is now that I had chance to try my first experiment. Now it is not going to be easy to explain as you really need to see the results in action, but here goes.

I recently treated myself to a 6 channel 2.4 Ghz Futaba 6EX. This set is designed for aircraft and so has flaps and aileron control built in. It also has a relatively good computer and most importantly two programmable mixers.

I setup the two central motors on one of the speed controllers as per normal, but the other two motors were connected to the remaining two speed controllers and then plugged into the aileron and flaps channels. This gave me the opportunity to drive them together in the same direction (flaps) or in opposite directions (ailerons).

Now this is where it gets complicated! By using the two in built channel mixers on the transmitter, I was able to mix the flaps with the throttle and get all four motors operating at full power without the loss you sometimes get when using electronic on-board motor mixers. The by using the second mixer I was able to combine rudder and ailerons which gave me the ability to change the speed and direction of the two outer motors as the rudder turns.

I still have the ability to use the flap and aileron controls independently for maneuvering, but the combined channels give me supreme control of the models power on one stick.

I am contemplating a bow thruster through the forward torpedo tubes to give me good docking control as the bow is nine feet away.
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ronkh

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #5 on: June 19, 2009, 02:52:33 pm »

Hi Marmoi,

Looking forward to this build. :-))

Ron.

PS. I am not the Ron mentioned in your first post!!
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riggers24

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #6 on: June 19, 2009, 03:20:43 pm »

Have you thought of using a mixer like the ACTion P40C http://www.action-electronics.co.uk/pdfs/P40C.pdf

Just a thought

Riggers
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #7 on: June 19, 2009, 03:27:48 pm »

Hi Rigger,

If I use the mixers on the Transmitter, I can switch them of at a moments notice and use the two outer motors on their own as a fine control.

Mark
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riggers24

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #8 on: June 29, 2009, 10:15:36 pm »

Hi Mark,

All four motors would be running all the time, do you not think with the length of the hull you will be needing all four. I believe the mixer would be a great help, I have seen other long hulls with the mixer fitted dancing on a six pence and other with huge turning circles.

I have been away last week so sorry about the delay in responding to you.

Marc
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #9 on: June 30, 2009, 08:09:44 am »

Hi Marc,

Now this is where the mixers on the transmitter start to be very helpfull, once moving at a decent cruising speed, at the flick of one switch the mixers are turned off and only the two centre motors will be running on the throttle stick, the outer motors can be activated if required on the right hand stick. To bring them all back together I just have to flick the switch again.

It is very hard to explain and it took a lot of thinking to get it working, but once had built the test bed it all came together and even I understood it better.

I have been reprogramming a friends 6EX the same way for his twin prop type 42 and the model performs and handles a lot better. We have also found that by reducing the mixing ratio in the programming, the mixing is less violent and more controlled at lower speeds.

Regards

Mark
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riggers24

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #10 on: June 30, 2009, 03:57:13 pm »

Hi Mark,

Another thought I had if a mixer was fitted is reduces the number of channels you are using so if you want to fit anything else i.e. swing the turrets you have that option.

Just a thought

Marc
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #11 on: June 30, 2009, 05:15:29 pm »

Hi Marc,

With the mixers turned off, I can use the Action 4 way switcher on the rudder channel. I have used this system with good results for many years. The rudder signal passes through the switcher and is virtually unaffected with the quick flicking for the switching. I have also built a rudder servo slower into the circuit on this model as I want the rudder to turn realistically, so the switching will have little effect.

If I have the mixers turned on, then I will be doing some manoeuvring and therefore won't be wanting to switch anything on or off at that time (I hope).

This is all going to be a grand experiment and I will not garanttee it will all work, but that is half the fun. I experimented with my Dreadnought for 3 years and I am still not happy with the mixing.

Mark
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #12 on: June 30, 2009, 05:27:57 pm »

I have had some time free in the workshop, so I thought it was time to start the rudder.

Because it's a big model and the are going to be 4 x 55mm props pushing on the rudder, I decided to go for belt and braces and machine the rudder from solid Aluminium. Good old ebay came to the rescue again and I got myself a block of Aluminium that should do for the rudder and it's support.

Steps:

1. Draw the rudder on CAD and plot to paper. Cut out plot and stick to Aluminium.
2. Cutout blank with saw and milling machine.
3. Mill the blade section out.
4. Burn hands repeatedly while linishing machine marks out and produce smooth profiles.
5. Give a quick protective coat while building the rudder support.

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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #13 on: June 30, 2009, 05:27:57 pm »

More
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John W E

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #14 on: June 30, 2009, 06:18:05 pm »

hi  there;
May I just take a moment of your time so I can make sure I have this clear in my mind your control set up?
So, what you are basically doing is you have 3 x speed controllers which control x 4 motors?   2 outboard motors, I take it, are ganged together on 1 speed controller & the 2 centre motors are on independent controllers?

These 2 inboard motors are the only ones being mixed with the rudder function?

So, these are controlled by 2 channels on your handset?

You have a 3rd throttle channel, which controls your outboard motors - and you have a 4th switching channel which switches this channel in and out - in actual fact you are using 5 channels to control the movement of the boat.

What Riggers is trying to explain to you is; with the ACTion P94, you would be able to control 2 pairs of motors - in other words 4 motors.  This is because there are several facilities on the P94 and 1 of them is to add an extra speed controller - so, you would still have the mix of the 2 outboard motors or inboard (whichever you prefer) and the 3rd speed controller would not be affected by the mix, it would just respond to the throttle settings either ahead or astern.
The other function is that you can adjust up to 50% of the mix between rudder and throttle.  This would eliminate the harshness of the mix.   Now, the next piece which I shall mention is my own experience, from when I built a model of HMS Ajax.
  
HMS Ajax is also controlled similar to the way you are doing it, only instead of the Futaba 2.4  6EX mine is the old 40 mg version – same sort of mix facilities on it; and by only using your inboard props mixing you are going to find it difficult to turn the vessel.   What I found was, you have to have the motors ‘ganged together’ in pairs.   In other words one speed controller controlling the motors on portside and one controlling starboard side.
You will possibly find, that having 1 set of props sitting idle, whilst the other 2 are trying to do the work will be more of a hindrance than a help.  
The last thing I would err caution on is slowing down rudder movement;   the model you are building is going to be a fair weight when you have completed it.    Natural momentum of the vessel going through the water, with its weight – it is going to take something to stop/ turn it.  You will therefore require all the power you need and all the movement of your rudder as quickly as possible.
The model I made of HMS Leeds Castle at 1:48 Scale will be something in the region of a similar weight to yours – she carries 3 x 12 volt x 12 amp wheelchair type batteries.  When she is under way, believe me – she takes some stopping  ask Riggers to show you the photograph of the ‘chunk’ out of the side of lake and the state of the bow of the Leeds Castle. 
Food for thought; and I can appreciate where you are coming from – because like me – you like to experiment with your radio gear and so forth.   Best of luck.
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riggers24

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #15 on: June 30, 2009, 06:46:39 pm »

one damaged bow
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John W E

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #16 on: June 30, 2009, 07:24:42 pm »

 %% %% they don't build em like they used to son....   {-) {-) {-) {-) {-) {-) {-) {-) {-)
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The long Build

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #17 on: June 30, 2009, 08:16:28 pm »

Hi Marmoi (Mark)
If I am wright in thinking it is your HMS Dreadnought in this months MB as displayed at the Ellesmereport show last March, and if that is anything to go by this build should be just as stunningly spectacular.

Larry
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #18 on: June 30, 2009, 08:23:02 pm »

Hi Larry,

Yes that's my Dreadnought in July's MB and she has come on a bit since then, the radio aerials are now fitted and the crew is on board.

Mark
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #19 on: June 30, 2009, 08:35:49 pm »

Hi Bluebird,

The four motors are on 3 speed controllers. The outer motors are on individual controllers and the centre pair are on one. The middle two motors are controlled on the normal throttle, the outer two are set up on the flaps and aileron's. The flaps are then mixed to the throttle, giving full control of all 4 motors on the throttle stick, the ailerons are mixed with the rudder, which gives me mixing on the outer pair.

I have been experimenting with my Dreadnought for quite some time and have got the controls working quite well now. If you want to learn how hard it is to stop a battleship that has very small props, then build yourself a Dreadnought   %%

I aim to get my models acting as near as possible to the real ship, I have found that I do not get enough control over preprogrammed mixers, but with the 6EX I can set the amount of mixing for each model and save it.

It may go all wrong when on the water, but experiments so far with other models have proved very successful.

Mark
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #20 on: September 25, 2009, 08:48:26 am »

Sorry things have been quite, the show season was very busy this year, but I have been quietly working away in the background digitising the original plans and building the superstructure up in 3D (yes,  will be putting some images on the forum shortly).

In the mean time here is a short movie of the massive foggy unit that MMB built for me.

http://www.youtube.com/watch?v=iAXpWRQQlCY

Mark
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #21 on: September 25, 2009, 03:19:35 pm »

Here are some renderings of the superstructure virtual model. This has been drawn to a scale of 1/96 from the original admiralty plans.

Mark
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marmoi

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #22 on: September 25, 2009, 04:58:06 pm »

And here is a quick virtual tour  :D

http://www.youtube.com/watch?v=gAkvwzu_OaQ

Mark
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GG

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #23 on: September 25, 2009, 07:26:40 pm »

Mark,
       Let me say how refreshing it is to hear of someone prepared to use a "computer" RC outfit to its full potential.
I still find it puzzling to see modellers who have such outfits buying extra items when their transmitters could do the same job.  Perhaps they do not read the instructions?
Good luck with the model, I look forward to reading about your experiences and seeing the finished model perform.  My own ambitions, sizewise that is, have never exceeded about 4 feet, the width of the back seat of our cars.  But, having now bought a car with a hatchback it looks I might be able to go up to 6 feet and a bit.  Please no one tell my wife about these plans!
Regards, GlynnG
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Brian_C

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Re: The ship that never was - G3 - HMS Indomitable
« Reply #24 on: September 25, 2009, 09:31:43 pm »

heres some of the  G3 BATTLESHIP  will post a few more :-))
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