Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Navy - Military - Battleships: => Topic started by: ballastanksian on June 13, 2020, 09:24:10 pm
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I'm going all out with this one!
Moving turret, slaved director, Geoff firing simulator (I've ordered my thermistors %% )
I am building this particular monitor as there will be a few Marshall Soults on the lake at Wicksted next year, and I always liked the relaxed look of the American turret with it's beautiful monobloc barrels tapering to a bell muzzle.
Also, she was sunk by the Goeben and Breslau in 1918, one of only two big gun monitors lost in thirty years of the Navy having monitors. thus forming a floating memorial to the lives lost.
I will start with the turret as then everything else should be simple in comparison!
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Standing by bunks paying attention! I will be following your progress with great interest. :-))
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Hello there Ian - I will also be 'monitoring' your build log.
Coffee pot at the ready... :-)
Regards,
Ray.
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Looking forward to this one!
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The turret will be the clincher. The more so as it has to allow access to gubbins and also be a bit heat proof even with insulation. Studying Geoff's developments is the key.
The American turret has a nice rectangular roof. It curves, and has both front and back curved edges, it is a simple shallow curve without protuberances on the roof.
I will try to cast the gun barrels around brass tubing so as to get the shape and utility.
Them's the ideas :-))
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I am planning away in my usual style sat in bed listening to Gideon Coe late at night and doodling 'wiv me crayons'. I have been reading Geoff Dixon's method of building the scale gunfire system and then wondered about taking it a little further (baby steps) and incorporating gun elevation into the mix.
Raglans American 14inch guns had to return to zero degrees to reload before returning to the desired elevation to spit forth.
I have come up with a design that elevates the gun barrels individually before 'firing'. It depends on a couple issues that Geoff can furnish based on his experiences and careful design of the turret floor and mounting for the guns.
I hope that a set of cams driven by a stepper motor will elevate and lower the guns, while putting sprung levers under tension then letting them trip and push the pistons in thus forcing the fluid through the heat exchanger etc. There would be four cams probably spread unequally along a shaft depending on where the pump and elevation rockers are in the turret. Two to operate the guns, and two to operate the pistons. If I can get it right, I would make a twin barrel pump, which I reckon will be easier to make than a crossover valve, and be more economic on space.
The stepper motor would have a maximum speed not more than the Thermistor could cope with in returning to operating temperature, but it might be slowed down to stop the effect of the guns elevating in turn look gimmicky. I think the Thermistors are smaller than the ones Geoff has used, which gives me more scope to make the guns elevate and also provide room for insulation etc.
If a micro servo can operate the pump then I assume a small stepper motor would have enough gumption to do the four actions required.
The first thing I need to confirm is:
1. Is the piston inserted rapidly or sedately?
I'll ask Geoff...
I think I can achieve this but need to ask the gun fire oracle a few questions
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Its pushed in rapidly. I use a small servo (not micro) operating arm. The stroke is about 12mm but this all depends on the diameter of the pump barrel as its down to the volume of liquid you need to pump. Do it slowly and I think it will just smoke. Do it quickly and it will compress and whoosh out the barrel. Don't forget the venturi at the barrel end.
Typically the thermistors need to get to about 200 centegrade and this will take 90 seconds from cold as it also has to transfer the heat to the heat exchanger. After firing they return to 200 C in about 12 seconds, longer as the battery discharges which is why I operate it on separate channels so the timing can be varied.
There is no need to have the pump and reservoir inside the barbette - its just how Iron Duke evolved and you may find it easier to have it external thus giving you room for the breach to go down. Insulation is also important to retain the heat. I used alloy for the roof and solid ply for the turret sides. I had to replace the plastic card outside covering in ID as the heat led to de-lamination - no probs since.
Feel free to ask any questions you like. A lot of what I wrote in the ID blog was explaining why I did what I did and what worked and what didn't. Its fundamentally a very simple system to make and operate and none of the dimensions are critical.
I would counsel you build the gun complete and test outside the model to iron out any issues.
look forward to you firing back at a Mayhem future meeting!
Cheers
Geoff
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Just as an add on. With ID I have suffered some heat deformation of the plastic barrels. With Invincible I have made them in alloy and is due course will probably retrofit ID.
I wrapped the internal barrel in string using high temperature silicon gasket sealant at the muzzle to stop liquid soaking the insulation.
Cheers
Geoff
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So, the cam nodes need to be steep sided to allow the lever to snap in pushing the piston quickly. Thanks for that snippet of info Geoff as that would have caused much sloppiness if I had made the node slope gentler.
Taking your developmental discoveries in Geoff, I plan to turn a solid barrel with 4mm ID bore then mould it and insert the tube into the mould and cast around it. Therefore, the metal tube will be the same length as the barrel (plus the bit that goes into the heat exchanger.)
I will try to solder the venturii in before resin casting as that will save the heat of soldering damaging the resin casting.
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Geoff, did you make your turrets taller/larger to accommodate the internal gubbins?
I have an internal width of 54mm and an internal barbette diameter of 84mm which should be enough if the Thermistors are not too fat or wide (Must re check that.)
31mm x 21mmm x5mm. That should be alright.
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Okay, I would be careful about making a resin barrel which is in direct contact with the inner tube as the inner tube at the thermistor end will be about 200 C which may well melt the resin. This is why the 4mm internal tube is wrapped in string to both retain heat and to insulate the external barrel. You can soft solder the venturi at the muzzle as by then the temperature drops below 200 C (melting point of soft solder). at 1/96 scale you can readily buy thick walled alloy tube from B & Q.
If you have a lathe you can then taper this. Rather than offset the tailstock I put a piece of 1mm brass into the chuck such that is forced the check end 1mm towards me. The lathe did not protest and then you can use the tip slide to create the taper. Purists will note that this will be ever so slightly barrel shaped as the tube will bent a little, but not much. Once down to size I used a file to flatten it.
If you don't have a lathe then I would counsel you just use thin walled alloy tube of different thicknesses.
I used a high temperature bearing compound Loctite 648 at the thermistor end.
Okay the heat exchanger is just a block of alloy with a 6mm hole finishing at 4mm for the last 10mm. If you put a 4mm copper or brass tube in it will just fall through (or get blown out when you fire) so I put it in the lathe and used a very shallow pointed piece of steel in the tailstock with some grease and forced it gently into the tube. This gently flares the end such it will no longer fall through. Used the sealant and then used a sharply tapered drift to knock it in place and its all stayed firm. ID has fired over 6,000 shots and I haven't lost a barrel yet so I think its pretty firm.
The turrets were not increased in size and with a 14" turret at 1/96 scale you should not have any issues in fitting it all in. If for some reason it won't fit just bend the inner barrel at say 45 degrees so the heat exchanger goes down inside the barbette. Then mount the pump/servo on a sub deck using silicon tube to connect it and it will all work just as well. In fact if you are looking to elevate the barrel this is the route I would suggest.
As before none of the dimensions are critical. Fundamentally the heat exchanger acts as a heat capacitor so needs to be a certain size so when you inject the fog fluid all that energy can dump and flash vapourise the fluid. For me 6cm x 2cm x 1cm worked okay with the thermistor strapped to the top. Insulation is important as it conserves the heat and therefore conserves energy and therefor battery life.
Cheers
Geoff
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Thanks for the tip regarding the high temperature Loctite Geoff. I was concerned about the heat effect on the resin and even if it does not melt, it might rapidly perish and crack off due to repeated expansion and contraction during and after use.
I might see if wrapping the tube in thread along the barrel from the muzzle down to a point where I can use string nearer the heat exchanger to both insulate and provide a bit of spring/expansion room but still be firm. I have some experimenting to do %%
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Evening,
The Thermistors arrived today. I ordered eight of them so if this project works out, then I can use more for future projects like the Armoured Cruiser.
(https://imagizer.imageshack.com/v2/800x600q90/922/K8zGUM.jpg) (https://imageshack.com/i/pmK8zGUMj)
They are 31x21x5mm which are quite compact.
So, now the next job is to make a mock up turret and innards to see what fits where or what I have to alter to get things to work (or not).
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Hi Iain,
Shall await you results on this with great interest :-))
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I have begun to work out the turret design and internal layout.
(https://imagizer.imageshack.com/v2/800x600q90/924/zFtB6M.jpg) (https://imageshack.com/i/pozFtB6Mj)
The turret is quite narrow, despite it's barbette diameter, giving me a maximum of 56mm internal width for the two thermistors and heat exchangers.
Having drawn up a basic plan, I then bought some Bristol board 1mm thick to build a mock turret from.
So far, I have cut the floor, the front plate, and have cut a central spine from 5mm foam core.
(https://imagizer.imageshack.com/v2/800x600q90/924/8xRcYk.jpg) (https://imageshack.com/i/po8xRcYkj)
Two balsa blocks were cut to mock up the thermistor/heat exchangers with pivots from cocktail stick! (It's all Blue Peter here you know!!!)
(https://imagizer.imageshack.com/v2/800x600q90/924/yIvYc8.jpg) (https://imageshack.com/i/poyIvYc8j)
Issues I have found so far is that, having moved the exchangers forward by 5mm to give the leads more space, I cannot insert them from above once the front plate has been fixed in place. I want the front plate to support the sides and central spine to make the turret 'box' rigid for any stresses caused by the sprung injectors pushing against the cams. This means it cannot be part of the roof.
Therefore I think I can modify the central spine to have a removable section above the pivot big enough to slide the exchangers down and in.
Now I have the thermistors I can see if they char ply at 230 degrees and work from there.
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Hi Ian
As you say it’s always a good idea to do a mock up just see if everything fits. In 1/96 scale the turrets looks reasonably large but I know from experience how quickly space can be filled up!
This’ll be my job on my Invincible’s turrets next month when the rest of the model is almost finished so I’ll watch your progress with great interest. Keep up the excellent work.
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HI hope you dont mind me taggin along also as this looks very intresting
chris :-))
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Great stuff Ian! Foam & bristol board look like good materials for test runs will have to give that a go. Hope to see a line of monitors @mayhem 2021
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Make sure your scalpel blades are always sharp, as both materials dull the edge super quick.
I am working on the sub turret system to work out where the pump and mechanism will go. I would put the pump in the hull, but it needs actuating via cams that also elevate the barrels. I could do it with two sets of motors and cams but feel like a challenge %%
It looks like Geoff's pumps are made from 10mm hex bar 18mm high with an eleven mm outlet 7mm wide.
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Iain, interested in how you are going the get round the turret rotation with all this workings %)
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So am I :} I am failing at working out cam shape and all that for lifting the barrels at the mo'.
I might leave the barrels at an intermediate elevation and concentrate on the pumpage.
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If everything is attached to the inside or bottom of the turret tube, and that tube slides into a deck tube, providing the deck tube is not to long, could a clamp be designed to grip the turret tube and then rotate the assembly, the clamp operated through a deck port covered with deck furniture or over a length to the nearest structure, with a flat on the turret tube positioned when the turret is on the centre line.
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Is this similar to how you move your masts?
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Naw, started to draw it up free hand and it needs a bit more thought - DOH
Sovereign uses servo horns and a servo, Victory a sail winch and thread.
Its figuring a way to have the turret rotating servo (assuming one each per turret), more forward to engage and back to disengage with the central turret tube, so its not part of the turret assembly.
Another thought was to have the servo sat at the side with a locating plate under the turret, as it is fitted in it locates into a notch in the bottom, with the plate at the lowest part of the hull everything above is free to rotate. Bit like a bayonet light bulb in reverse. Just throwing ideas out there, ignore me if they are useless ideas or you have better ones. {-)
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I am quite limited by depth so ideally any mechanism would be best operating from the side and above the fluid level.
An idea I had, until I saw the price of the injectors, was to have a fluid circulating system like we have in our cars and a injector which opened up long enough to let an amount of fluid squirt into the heat exchanger. Then the reservoir can be outside the barbette possibly in a container so that any pipe explosion doesn't spray fluid all over the electronics and motors etc.
The power to open and close the injector could be linked to a rotating wheel with electrodes made long enough to correspond to the second or so needed to let fluid through.
It could be arduino controlled in time and duration, but that would be better for a multi turret ship I reckon.
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Would there be enough room to fit two micro servo's either side of the pivot, i.e. servo drive the pivot for each gun, could then be individually raised and lowered either by linkage or direct, the back box could then contain a servo limiter of some kind if not programmable from the ardino, the servo's down each side then are using dead space (assuming its dead space)
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I have been avoiding anything too technical for a single turret, but it may come to that.
Still, I will dabble more next weekend and see what occurs.
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To clarify, with ID I only have one working barrel per turret due to the internal space being limited and the need for insulation. Basically everything hangs off the bottom of the turret which is then inserted into a large diameter tube (75mm external diameter) with a central brass pivot tube to take the cables out on the center line. The large diameter tube then also acts as the fluid reservoir and sits flush on a false deck. The turrets are then winched round using a servo sized sail winch.
Exact details and dimensions of the pumps are in the ID thread with plans but again none of this is really critical. Probably the only thing is the pumps need to act quickly both to prime them (the valves aren't perfect) and to shoot the fluid in quickly to the heat exchanger so you get instantaneous flash vaporization which in turn pressurizes and shoots the smoke out of the barrel with an audible whoosh! The combination creates the effect as otherwise if injected slowly the smoke will pour out rather than rush out.
I would counsel you build a gun and test it as slight modification may be needed to fit. Fundamentally the alloy acts as a heat capacitor heated by the thermistor. When the fluid is injected the energy dumps and flash vaporizes. Basically it takes "x" amount of energy to flash vaporize "y" amount of fluid in "z" fraction of a second. This will also depend on the surface area of the heat exchanger so a little thought will show provided you have this combination the actual shape doesn't matter too much.
You may find if you are trying to run two thermistors off the same battery the battery may not be able to supply the initial current which could be as high as 18 amps - this also impacts the thickness of the cables etc and there may be some imbalance between the thermistors such as one drains the energy from the other and neither gets to the right temperature, This is why I use separate batteries in ID.
Its all goof fun, enjoy!
Cheers
Geoff
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I am going away from having the barrels elevate to concentrate on gun smoke. A thought I have just had is to have a battery for each thermistor. This means that ampage is reduced to the level of draw shown for a single thermistor.
But yes, I need to test all the thermistors to make sure they work and also make fluid vaporise.
I made the dimension of the barbette on HMS Raglan 92.5 (93) mm, so depending on the wall thickness and thus inner diameter, that is what I will have to play with. I can laminate a tube from thin plastic and frames.
Anyhow, off to speak 'Car' with the garage....
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When you mentioned putting fluid on the thermistors - one of these popped into my head {-) god knows how I would tackle that problem
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My internets been playing up
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Geoff has done a build log of HMS Iron Duke in Warships R&D which covers his development of smoke generation finishing up with a great system using thermistors and pumps.
Have a search for it, its pretty extensive, and Geoff is adding bits here as well while I bimble about.
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I have seen the turret system using the ardino's thread, and will leave suggestions to the more experienced O0
I have never built anything bigger than a corvette so BIG guns are an oddity to me for making them work, just got caught in the moment.
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Of course, you could always experiment with General Wolfe and her open 18" mount!
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One of the Clive's is on my long list. Nick let me have a 12inch majestic turret so that part is difficulty lessened. Mind you, an Abercrombie was also on it but got scooted ahead of Cochrane.
Not to worry Warspite, all ideas and thoughts are welcome here. I read it all and if anything pops out as useful, I will try it.
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One thing to consider is that the actual working gun is only 4mm in external diameter so much smaller guns can be made to work provided you have the room for the batteries. There is no reason why the pump and servo needs to be in the barbette (its just how it evolved with ID) and can be remote from the turret.
As an experiment I used the thermistors and a long 4mm tube and pumped the fluid in in little spurts and it went Puff, puff, puff, puff just like an anti aircraft gun!
If the barrel is bent 90 degrees and the thermistor and heat exchanger is nearly vertical it will work with much smaller turrets as the gubbins can all be below decks provided the external barrel diameter isn't more than 4mm.
At times it sounds quite complicated but in practice its really quite a simple system because of the thermistors which are self regulating.
One experiment I did try was using 3D printer heaters. They are not thermistors and have no upper temperature limit and reached yellow hot in 20 seconds - my temperature gun registered 500 C before I had to put the fire out! However once installed in an alloy heat exchanger it never overheated as the heat was drained away too quickly. Candidly I couldn't get it to work well due I think to the heat path being less efficient than a flat thermistor on a flat heat exchanger which gives a very good surface area to transfer heat.
Still at some point I intend to try again as I think it has some potential as its smaller and the maximum current draw was flat at 3.5 amps vs 9 amps at start and 3.5amps running for the thermistors so a potential saving in current which equals more shots!
Cheers
geoff
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I plan to get dabbling again on Saturday.
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Sorry not to have done any more to this since July. The new business and having eyes bigger than brain meant that I have stalled.
I hope to get back to it later this year, probably reining in my aspirations to a single barrel or fixed elevation barrels (mid angle elevation to make them look reasonable.) Mind you, using a servo to elevate them will be simpler than the cam system so all is not lost!
Happy new year folks.
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Happy New year Ian,nice to see your active again. :-))
Myself I’ve lost a bit of the modelling drive, so taking a brake from it.