Topic: HMS Agincourt build project (Read 182776 times)

Bob K · « **Reply #425 on:** February 12, 2018, 10:21:25 pm »

Iain, it seems strange that something this voluminous does not demand vast amounts of ballast. When the six SLA batteries go in I will be very close to the 29kg you all loaded aboard her at Wicksteed last year to take her to the waterline, but if necessary I can take her a little deeper draft. That is why I am going for four turrets firing, not all seven. That would take another three big batteries. Even a square metre of deck planking is significant.

I was in Mantua Models last week, which is close to where I live, and we weighed lengths of tube in plastic alloy and brass. I am using the largest standard Plastruct tube, which is the lightest of the three, but solid wood dowel was lighter than even alloy tube. A local model shop can sometimes be more convenient than buying online.

ballastanksian · « **Reply #426 on:** February 18, 2018, 06:18:13 pm »

How interesting! I know you didn't pug that much filler and Milliput into the hull when fitting the location tubes, nor did you use hefty slabs of wood for the bulkheads.

Bob K · « **Reply #427 on:** February 18, 2018, 07:43:21 pm »

The hull joining methodology did not help. 19 mm thick bulkheads each side of the join (the other four are only 9 mm). plus nine lengths of 1.6 mm wall thickness stainless steel joining tubes total almost 3 kg. Four big Buhler motors at a kilogram apiece.
Six large SLA batteries totalling 12 Kg. You are looking at twenty kilograms for that lot in total.
That leaves just 9 kg for everything else, including the 2.2 m f/glass hull. It adds up rapidly.

Sorry, not much progress lately. Family matters have limited my workshop hours recently.
To come: More work on the superstructure, plus laminating up the fixed barbette outers.

Colin Bishop · « **Reply #428 on:** February 18, 2018, 07:51:53 pm »

Bob,

Would you be better in using lighter LiPo batteries?

More expensive but more flexibility weight wise. Additional weight was always a bugbear in the original ships.

Colin

Bob K · « **Reply #429 on:** February 18, 2018, 10:16:11 pm »

Thank you Colin, but all the batteries have to be 12V, and the ones powering the gun fire thermistors have an initial current of 13A. This drops rapidly to 2A as the thermistors heat up.

There are LiFePO₄ batteries which are a third of the weight of SLA's but cost £199 for a 12V 12AH one.
Not sure if I want to spend mega £'s on batteries.

High discharge large NiMh batteries are also expensive but I do not feel comfortable ganging them in parallel for high initial current.

cos918 · « **Reply #430 on:** February 18, 2018, 11:04:04 pm »

Have you looked on Hobby King Uk website .
best place for batteries
John

Geoff · « **Reply #431 on:** February 19, 2018, 01:41:50 pm »

Bob,

I have also considered Lipo's for the gun thermistor units but you would need some "eletrickery" to avoid over discharging the Lipo's. With lead acid you can effectively keep going until they just run down but if you did this with Lipo's you would destroy them.

As a reminder dreadnoughts draft varied a couple of feet depending on how much coal they had on board as they invariably anticipated hours and hours of steaming (sometimes days) before any action commenced. Also the lower level of the armour belt should be about 4 feet below the normal water line to protect against underwater hits.

Also as you say cost comes into it but a mixture of battery types could be an elegant solution to keep costs reasonable.

Cheer

Geoff

Bob K · « **Reply #432 on:** February 19, 2018, 04:22:50 pm »

Geoff: I agree about LiPo's not being suitable for the gun fire thermistors, and could cause major problems. I will stick with SLA's for those (1 battery per gun), as you say they will be far more forgiving on cumulative discharge.

I may however consider using a 12V 16Ah LiFePO₄ for the four Buhler motors. I have spoken with TracerPower and they claim these can operate at much better ranges of discharge than SLA's and the 16Ah one should run two hours with ease as the motors are not being run full speed continuously. However, it costs £224 c/w power leads case and special charger. They have a built-in charge indicator.
Costly, but could save 3 kg over twin 9 Ah SLA's.
In fact I can put the 1.9 Kg LiFePO₄ (4 motors) alongside a 1.7 Kg 5Ah SLA (gun fire) battery.

https://www.tracerpower.com/tracer-12v-16ah-lifepo4-battery.html

Colin Bishop · « **Reply #433 on:** February 19, 2018, 06:09:49 pm »

Is a 16ah Lipo equal to two 9ah lead acids though? You should not normally discharge a lead acid below 50% of its nominal capacity as a rule of thumb but I believe that a LiPo can be more deeply discharged than a lead acid so you might only need say 10-12ah of Lipo to get the same performance. No doubt somebody will be able to confirm that or otherwise.

Something else that might be worth checking is whether two smaller LiPos, each running two motors would be cheaper than one big one. The LiPo chargers (not special ones) often have more than one output so they could be charged simultaneously.

You can also get 10ah tagged NiMH D size cells now which would would be a lot cheaper than your £224 LiPo, last longer and probably still save significant weight over the SLAs. You would need two 10 cell packs of course. I swapped out the 4 lead acid Cyclons in my Fishery cruiser for NiMh replacements and saved both space and weight for the same performance.

I can't remember, but have you tried out a Buhler motor with a prop on the end in water to see what the current draw is at various voltages?

It's certainly worth checking out the various possibilities.

Colin

unbuiltnautilus · « **Reply #434 on:** February 19, 2018, 06:48:55 pm »

Maybe you could use the LiPo option for the gunfire side of your set up. They are designed primarily for high current work and should easily handle the 12amp initial surge current incurred by your firing system. I assume the firing system is only drawing current while in a live and firing sequence? If that is the case, then you will have minutes while the system is 'hot' and minutes when it is not. This should be within the capability of decent quality LiPo packs. You just need to check the C rating of the cells first.
As far as over discharging the cells, you can always fit a LiPo alarm into the balance lead, or in the main circuit, depending on type. This will give an audible alarm when you are approaching a flat battery situation.
Although I am currently avoiding a LiPo option for my own proper firing pyros, not too keen on direct shorts to blow fuse wire! I know that is what fuse wire is for, it's just LiPos still make me nervous......

Bob K · « **Reply #435 on:** February 19, 2018, 07:43:38 pm »

I said "LiFePO₄", not "LiPo". a huge difference. Lithium Iron Phosphate.

Guaranteed for 1,400+ cycles. Discharge cut-off voltage: 10V.
This battery type was mentioned in a much earlier Post from Across the Pond as "SLA Replacements" but at a third of the weight. At that time I could not find them available over here.
The disadvantage is the very much higher price.

Colin Bishop · « **Reply #436 on:** February 19, 2018, 08:15:30 pm »

Sorry, didn't realise the difference. Expensive though, as you say.

Colin

Bob K · « **Reply #437 on:** February 20, 2018, 10:43:18 am »

The more I think about, the most I am leaning towards a LiFePO₄ (Lithium Iron Phosphate) battery for the main propulsion.
The 3 kg weight saving could make all the difference.
Instead of two 9 Ah SLA's, (one each side of the central tube) I can fit the new 1.9 kg battery one side of the centre, and one of the 5 Ah gun fire SLA's (at 1.7 kg) the other side. Almost balances.
This also brings the rear half to within 2 kg of the front half. Better weight distribution.
Additionally this gives me almost 3 kg in hand for the remainder of the build, so I can keep it to waterline.

£224 is a lot of money for a battery though, but it may be the best option.

derekwarner · « **Reply #438 on:** February 20, 2018, 11:36:40 am »

It's OK Bob

....

Just think of it a message from the War Office confirming a request from the Admirals [as approved by Whitehall] for a minor technical propulsion revision

Derek

Geoff · « **Reply #439 on:** February 20, 2018, 01:09:31 pm »

Bob, I think I'd wait until Agincourt is afloat and sailing before deciding on a final battery decision as you may be surprised in a number of ways.

Cheers

Geoff

Klunk · « **Reply #440 on:** February 20, 2018, 01:23:49 pm »

bobk
found this also do an 18amp

http://www.allbatteries.co.uk/lithium-iron-phosphate-battery-lifepo4/12v/16ah.html

Bob K · « **Reply #441 on:** February 20, 2018, 02:49:49 pm »

Thanks Pete. That looks interesting. I will check it out.

Geoff: At the moment as I am building each half I am regularly checking them on my scales.
I am also keeping a detail spreadsheet itemising the known weights of items to be added to each half.
I know the final displacement as my hull was loaded with lead at Wicksteed '17, 29kg took it to the waterline.

unbuiltnautilus · « **Reply #442 on:** February 20, 2018, 06:34:32 pm »

Quote from: Bob K on February 19, 2018, 07:43:38 pm

I said "LiFePO₄", not "LiPo". a huge difference. Lithium Iron Phosphate.

Guaranteed for 1,400+ cycles. Discharge cut-off voltage: 10V.
This battery type was mentioned in a much earlier Post from Across the Pond as "SLA Replacements" but at a third of the weight. At that time I could not find them available over here.
The disadvantage is the very much higher price.

I was just broaching the subject of LiPos having the grunt to work your firing gun system. If they were an option, that would free up volume, displacement and pound notes for other jobs! I would still rely on the big gel cells for main drive, you won't be pulling big amps with those motors and you would benefit from their weight.
Over to you and Geoff on that one..

RST · « **Reply #443 on:** February 21, 2018, 11:31:46 pm »

Really sorry but been reading this build for ages and have to ask. "Thermistor units"? A thermistor is usually just a small temp sensor -it doesn't draw much if any current (it's pretty much a small resistor), couple of magnitudes less than what you're talking about anyway. I see references made to the system in other boats and I appreciate it's part of a bigger system? Could you provide a link or description for a proletarian please? Sorry if it's been asked before.

Bob K · « **Reply #444 on:** February 22, 2018, 06:58:41 am »

Hi RST: A thermistor is a type of resistor whose resistance is dependent on temperature, in this case a self-regulating heating element. The heating element is used to heat up a small amount of Fog Fluid, boiling off the water to produce a puff of fluid smoke from the gun barrel. It draws a lot of current when cold, but much less when it reaches its optimum 220 degrees.

Geoff · « **Reply #445 on:** February 22, 2018, 08:35:21 am »

There are different types and sizes of thermistors but fundamentally two different types:

1) NTC (Negative temperature coefficient) as they are heated the internal resistance reduces - these are used in many applications but the obvious is a car temperature sender unit. As the engine warms up the temperature increases and it allows a voltage to flow which moves the voltmeter (temperature gauge)on your dashboard.

2) PTC (positive temperature coefficient) these are exactly the opposite as a voltage/current flows through them their resistance increases which in turn produces heat. These can frequently be used to keep coffee warm on a hot plate and are used in industry.

Specifically these are designed to have certain characteristics such they can only reach a certain temperature and are self regulating so can be used as heating units in certain applications.

The advantage is that they are self regulating so don't need any feedback circuits to maintain a constant temperature. PTC's are designed for multiple applications and can have maximum temperature settings from 60 degrees up to 250 or in some cases 400 degrees!

Sizes range from a few mm to 60mm x 25mm x 5mm.

If I may, have a look at another thread for Iron Duke on this site under warships R&D. Start at the end of the thread and work backwards and it shows the development process of this system and how it came about in more detail together with plans and pictures. Iron Duke has now fired well over 5,000 shots and works consistently. I typically get 300 to 350 shots in a session and because its totally no pyrotechnic can be used anywhere.

Below is a link address for some I have on order.

Hope this is of interest

Cheers

Geoff
https://www.amazon.co.uk/gp/product/B00M85KTO2/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Geoff · « **Reply #446 on:** February 22, 2018, 08:37:53 am »

Sorry, wrong link! I'm experimenting with these as well!

Correct link below!

Cheers

Geoff
https://www.amazon.co.uk/gp/product/B01N7SSYH5/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

Bob K · « **Reply #447 on:** February 24, 2018, 10:36:45 pm »

Excellent description Geoff.

Bilge keels?
Something else I need to consider before the superstructure is permanently fitted. Bilge Keels.
Was HMS Agincourt fitted with them? My 3 sheets of plans only show the side view down to the waterline.
The prototype model does not appear to have them, but several illustrations do, in various forms.

Where they go (if fitted) is fairly straightforward, on the curve between the vertical and horizontal hull planes.
If I fit them I should do so now, whilst the hull can be placed at an angle or upside down.
Maybe three thicknesses with supporting pins through the centre plane, and slightly curved.

What do think? Fit them, or not?
With the shape and size of the hull it may not make additional effect to stability.

derekwarner · « **Reply #448 on:** February 25, 2018, 01:41:29 am »

This is an interesting dilemma Bob........as you note, certain text suggests that 'Bilge Keels' were not fitted .......[due to the Dock size or limitations

., ........I have difficulty in understanding the logical basis with these written words ]

It is clear, that the Battleship Class builds after the first Dreadnaught incorporated 'bilge keels' in their hull design

One could type 10 pages on the facts, omitted or un-scribed notation....... however ...

I would be inclined to consider the copy the bilge keel design [net effective length x height x profile etc] as installed to the following vessels such as the Iron Duke

Derek

Akira · « **Reply #449 on:** February 25, 2018, 02:08:14 am »

Bob,
Consulting "British Battleships of World War 1" by R A Burt, on pages 272-273, shows inboard profile sections of Angincourt, circa 1918. Clearly shown are bilge keels running from frames 111 to 243. I suspect they actually extended beyond these noted frames however. On American ships, bilge keels ran parallel to the keel, so measuring with a flexible rule at the widest point will allow an easy transfer of the bilge keel lines for the full extent of their run as a constant measure from the keel centerline.
I will be happy to scan and send you copies of the pages, if you like.
Jonathan

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Author Topic: HMS Agincourt build project (Read 182776 times)

RST