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Author Topic: Flash steam plant control.  (Read 93323 times)

Jerry C

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Re: Flash steam plant control.
« Reply #275 on: February 17, 2015, 10:39:54 AM »

Hi, I've been watching all your posts with an interest in both flash steam/mono tube boilers AND the computer control side. From the Master FG certificate syllabus I understand(but may have forgotten a bit due to lack of use) about aspects of control of systems (proportional/integral et al) as it applies to pneumatic control systems. All totally theoretical though.
Computers now, with a view to actual programming and code is a complete mistery  to me.
I have a certain amount of Aspergers Syndrome in that if I determine a need for a certain knowledge I am able to learn it quickly and easily and (up til now), retain it for ever. Without an interest/need I block it out completely. It's hard to describe.
My education, (I'm 65), did not envisage computer use to my future, so there are NO foundations to build on or prior knowledge to call on so although I have read, and attempted to study and understand, it has I'm sorry to say appeared as fluent bollox to me. (Nothing personal the problem is all mine).
The need is now there but I can't do this myself. Also, the "standard" educator won't hack it with me. I need a special kind. I had two of these at school. One guided me to O level physics in one term and the other to Additional maths in the same time at 14.
So I will continue to follow your threads and when the time comes maybe I'll manage to get enough out of it to control my own steam plant.
Keep posting and thanks.
Jerry.

flashtwo

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Re: Flash steam plant control.
« Reply #276 on: March 29, 2015, 03:13:38 PM »

Hi Mayhemers,

With the boating season starting, Iím going to carryout some experiments (again!) on the Flash Boiler system.

This winter Iíve been building a Superheater boiler to run in tandem with the existing Saturated Steam boiler.

A problem with the single boiler is that it can go unstable when attempting to run with anything more than a few degrees of superheat. The transistion point of water turning into steam, somewhere along the length of the monotube, can suddenly move towards the cold end of the boiler, thus, exposing a lot of area to the burner flame.
 
This extra heating area gives too much superheat and the system control automatically shuts off the gas to lower the temperature.

By using a tandem boiler with its own dedicated burner, the transition point canĎt go beyond the inlet to the boiler, thus limiting the exposed heating area (that's the theory anyway!).

The Superheater boiler has about 10% of the heating area of the Saturated Steam boiler, since once the latent heat of evaporation has been supplied, it takes little heat to raise the steam temperature.

The photograph show the design is a small version of the main boiler.

Ian
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TurboTyne

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Re: Flash steam plant control.
« Reply #277 on: March 29, 2015, 08:26:30 PM »

Hi Ian

That idea for a superheat boiler is very interesting.  So is that similar to the situation in full-sized boilers where they have a control of the superheat by changing the direction of the furnace gases to control whether or not they pass over the superheater tubes? I gather they also have systems to spray water in to the steam to reduce temperature but from what you've mentioned in past posts I think you might have direct experience of these types of controls??

How do you plan to control this burner compared to the main buner? Will it respond to steam temperature and the main one to steam pressure? I have a down-loaded text book on boiler control systems for power stations. It says pressure control gives a much faster response and is usually the main control, with temperature as a secondary input. I recall you found temperature control worked best for Vital Byte but with my boiler I certainly find the response to temperature is very slow. I have a pressure sensor I want to try it at some point - after finishing what I'm doing and setting up those Xbees.

Regards

Mike
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flashtwo

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Re: Flash steam plant control.
« Reply #278 on: March 30, 2015, 01:43:25 PM »

Hi Mike,

Well, so far, I've drilled and tapped the engine steam inlet manifold and fitted an additional thermocouple. The control system has always had a spare thermocouple input for experimental purposes, so I'll be able to look at the superheated steam temperature with the new telemetry (thanks to you) system.

The first boiler's burner should be controlled on pressure, as you say, because this is directly related to the saturated steam temperature. Likewise, using the existing boilers outlet temperature should give an equivalent signal for pressure and, because of thermal lag, a less "noisy" signal. So, if I want a higher pressure I should increase the saturation temperature demand setting. At the moment the saturated demand is a function of the feed water flow - more water -higher temperature demand  - higher pressure.

The second burner should control the superheater temperature. Initially I'm going to use just manual control for the superheater burner.

This idea of a separate superheater boiler is from a system that the U.S. Navy had on warships in the Second World War. The forward and reverse turbines required different steam conditions, such that the reverse turbine couldn't handle the superheated conditions used normally for forward propulsion.

When manoeuvring in harbour, they couldn't afford the time to reduce steam temperature in the normal way of knocking out the oil burners and altering the furnace gas flow/ sprays.

By using a separate superheater burner they could quickly change the steam temperature for forward/reverse and still maintain control.

Although the U.S. Navy system wasn't a monotube boiler and had a boiler drum, I thought it would worth experimenting with on the steam launch's monotube system.

It is good to be back with the metal bashing after spending most of the winter tinkering with the software for the telemetry and Voice Command systems for the launch (all due to your question about XBEEs!).

Ian
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flashtwo

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Re: Flash steam plant control.
« Reply #279 on: March 30, 2015, 06:28:06 PM »

That was ironic - connected up the spare thermocouple to the AE-35 controller and found I had a constant 195degC reading.

Traced the problem to a bad ground connection on the thermocouple amplifier - all that bouncing around taking the launch to the Ally Pally exhibition in January caused the bad joint (that's my excuse anyway!)

At least it wasn't the telemetry system!

All ok now.

Ian

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TurboTyne

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Re: Flash steam plant control.
« Reply #280 on: March 30, 2015, 08:26:58 PM »

Was that one of those problems that takes ages to trace or did you track it down quickly?

Actually I wanted to ask about the US navy and reverse turbines. Do you know in which ships that method with the superheat burners was used? Was it in ships using very high steam temperatures (e.g. above 750 degC)? I have read that in British ships using such high temperature steam special precautions were necessary when using the reverse turbines but I have not seen what these precautions were.

Thanks  Mike
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flashtwo

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Re: Flash steam plant control.
« Reply #281 on: March 30, 2015, 10:15:21 PM »

Hi Mike,

I was lucky that there were two identical thermocouple amps  (AD595) on the board, so I could compare working with not working.

I tried shorting the input to the amps, but the suspect one stayed at 1.9 volts output. I changed the IC with a spare - no improvement. Checked the supply at the IC pins and the 5 volts was spot on, but the ground was at +1 volt. Checked the ground "daisy-chain" wiring and found a bad connection between the good IC and the suspect one. It was best to put a new ground wire in rather than re-solder the existing one.

With the new ground wire, the ground volts at the suspect IC was practically zero and the system now gave the correct temperature. It was the first fault in the controller in the five years since it was built - I hope its not a forerunner of future problems.

The U.S. Navy Fletcher Class ( http://en.wikipedia.org/wiki/Fletcher-class_destroyer ) used separate superheater boilers, which are exhaustively described here .... http://archive.hnsa.org/doc/destroyer/steam/sec06.htm.

If you look on page 58, Section (c) there it is described when not to use the superheat boiler, plus all the bell signals from engineering to the boiler room - it makes you appreciate the automation that we have now.

I hate to think of these poor boiler operators having to respond to the directives from engineering and remembering, under battle conditions, which valve and sequence to operate - any mistake and you could wreak the superheaters and be a sitting duck to any passing Jap sub or Kamikazi - I suppose that was the "job" incentive scheme!

The only precaution regarding high temperature steam, that I can think of, is that of maintaining steam flow through all the superheater tubes to prevent them failing under high temperature. The other problem is with the turbines - too high a temperature and rapid temperature change, you risk expansion and blade rubbing - too low a temperature and you risk water carryover and blade damage.

I've never had experience of reversing turbines apart from seeing the "tiny" one on HMS Achilles many years ago. You could see it only had a couple of stages from its length.


All the best

Ian






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TurboTyne

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Re: Flash steam plant control.
« Reply #282 on: March 31, 2015, 06:58:56 AM »

Hi Ian

That sounds like a very efficient piece of detective work.

Thanks very much for the links, especially to the HNSA-destroyer site.  I did not know about that and I think I'll be spending quite some time looking through the huge amount of info available there.  I had a look at the Fletcher boiler and engine pages and see what you mean about the engineers and stokers needing to keep their wits very much about them to avoid ruining the plant. Presumably the thought of all that super-heated steam that might escape and cause them serious harm must have been another incentive to keep their minds focused - even without the enemy.

I hope you'll be posting updates about how your dual boiler system works.

Regards
Mike
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flashtwo

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Re: Flash steam plant control.
« Reply #283 on: April 04, 2015, 01:02:35 PM »

Hi Mike,

Just been rummaging through an old box of memorabilia and found a blade tip cut from a 500MW turbine at Kingsnorth Power Station in 1974.

The blade, from the very last stage of the Low Pressure Turbine, was removed because of vibration problems that lead to blade shedding and considerable damage to the condenser tubes. Normally, the blade tips are constrained by the use of traditional stout wire bands, but these were replaced with properly engineered arch bands, which attached each blade to its neighbour.

The blade tips are of Stellite and show what damage water droplets can do when the tip is travelling at 1200MPH.

The new superheater boiler has been installed in the launch, though I've still have to complete the gas pipework. The boiler can be easily removed and the launch run with just the saturated boiler. The old adage is that you can never achieve superheat in the presence of water.

I've found an interesting web page discussing superheated and saturated steam ( http://www.systhermique.com/steam-condensate/services/troubleshooting/superheated-steam/ ). Obviously, with a piston engine you still need a bit of superheat to stop condensation in the pipework and engine when the steam expands.

With just saturated steam, as you can see from the article, the heat conduction is very high compared with superheated steam.

As soon as condensation takes place in the engine cylinder the pressure just falls away, so, delaying the condensation maintains the steam pressure to the end of the power stroke.

Tomorrow and Monday, I'm displaying at the Chatham Historic dockyard, Festival of Steam and Transport.

Ian
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TurboTyne

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Re: Flash steam plant control.
« Reply #284 on: April 07, 2015, 07:39:06 AM »

Hi Ian

Very interesting to see the photos of the damaged blade tip. Were the turbines at Kingsnorth made by Parsons?

Several years ago I was shown around the Parsons works by the then works manager - that was before they were taken over by Siemens and most of the huge factory buildings demolished. I remember he showed me some L.P. blades that had been eroded by water droplets and were to be repaired. I've been interested in steam turbines for quite a while. My electronically controlled monotube boiler is currently connected to a turbine that I built many years ago. This turbine is rubbish for power output but I hope the next one will be more efficient.  I plan to equip it with electronic speed measurement and overspeed protection. It is straightforward to plan all that now I have learnt a bit about microcontrollers - thanks to being inspired by your posts.

Your superheat boiler looks very neat.  How many degrees of superheat are you aiming for?

Regards   Mike
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Stoneflash

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Re: Flash steam plant control.
« Reply #285 on: May 18, 2015, 10:08:59 PM »

Hello all. I’m new to this forum but have steam experience through my previous ownership of an Edwardian Stanley steam car. I’m looking at a smaller scale but no less interesting hobby and thinking about how I would go about it. The Stanley by the way ran at 600psi with a vertical fire tube boiler, a vaporising burner fuelled with 50/50 petrol/diesel and a vaporising pilot burner on petrol. The main burner put out 500,000 Btu/hour, burning 18 litres per hour! It would do 70mph if the driver were brave enough. The pilot was identical to the silent burning diffused flame burner proposed by ET Westbury and shown on p69 of Benson and Rayman "Experimental flash Steam".

This thread is really interesting to me as a monotube gets us away from the bugbear of boiler tests etc of which I have undergone enough - but one thing which hits me from the last few posts on superheat is how much superheat can the current crop of smallish steam engines cope with? Many of them appear to have bronze cylinders and pistons - the French Antůn and Typhoon, or the TRV1A, or the Martin Baylis which has hard anodised alloy cylinders, rather than cast iron. I realise these engines run at about 30-45psi so superheat is not inevitable or even very hot, but if it does happen do they cook? Should they be confined to ordinary boilers?

I’m interested in building an 1880’s torpedo boat model, the original of which was 62 feet long but extremely low built. 1 inch to 1 foot would be about the right size for an RC model but the depth of the hull and low deckhouse height means that a D10 would be too tall (as well as too powerful). While a Stuart Sun would fit, they are not self starting or reversing so I’m looking at some of the new alternatives mentioned above, most of which are about 100mm tall. Hence my question.

My main interest is in the burner and steam generator control (although I know nothing of electronics) so would in the first place go for a ready built engine to get the hang of things.

Cheerio
another Mike
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TurboTyne

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Re: Flash steam plant control.
« Reply #286 on: May 22, 2015, 04:36:12 PM »

 Hi Mike and welcome to the forum.
I cannot help with your question about tolerance of superheat by those engines except to comment that with a monotube boiler and an electronically controlled burner you could  (in theory) protect the engine from excessively hot steam anyway.  Also, I wanted to say that Iím glad you mentioned the E.T. Westbury burner since I had passed it by before and now Iíve gone back for another look I realise it is an interesting design. You said it looks like the pilot on your carís boiler so I am just wondering - what was your main burner like? I have a copy of an article published in Model Engineer in 1932 that describes a Thorne boiler. This had a vaporising type burner where the vapour came out through many small perforated discs across the floor of the fire-box. That boiler was also fitted in a Stanley car. Was that a different system to your one?
Interesting choice of boat.  I am working towards building a WW1 destroyer and even with that, it seems it will be a challenge to keep the steam plant to be low enough in the hull. Have you decided upon a specific boat?  I have drawings of the torpedo boat No. 80. This was larger than the one you mentioned since its length is stated as 135 ft and beam 14 ft. I wonder if the hull might be better proportioned. The drawings are of the actual boat rather than a model and include 11 cross-sections. They show engines, boiler, bunks etc.  If you want a scan please contact me via a personal message since I should not post them on the forum.
Regards
 
Mike
 
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Jerry C

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Re: Flash steam plant control.
« Reply #287 on: May 22, 2015, 04:59:00 PM »

TVR engine build instructions specify 35psi max and no drier/superheat.
Jerry.

Stoneflash

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Re: Flash steam plant control.
« Reply #288 on: May 22, 2015, 09:22:19 PM »

Hi Mike and welcome to the forum.
I cannot help with your question about tolerance of superheat by those engines except to comment that with a monotube boiler and an electronically controlled burner you could  (in theory) protect the engine from excessively hot steam anyway.  Also, I wanted to say that Iím glad you mentioned the E.T. Westbury burner since I had passed it by before and now Iíve gone back for another look I realise it is an interesting design. You said it looks like the pilot on your carís boiler so I am just wondering - what was your main burner like? I have a copy of an article published in Model Engineer in 1932 that describes a Thorne boiler. This had a vaporising type burner where the vapour came out through many small perforated discs across the floor of the fire-box. That boiler was also fitted in a Stanley car. Was that a different system to your one?
 
Mike

Here are some pictures of the last version of the pilot I made to burn unleaded petrol at about 25psi. The biggest problem with the pilot on the Stanley is that it is right at the front of the car in a gale of cold air which makes it almost impossible to stop petrol from condensing before it gets into the mixing chamber of the pilot. Many people use hexane to solve that problem but I felt that was too flammable to keep around the shed so made a special pilot of which the jet was well into the hotter area of the burner casing. It worked very well. The main burner has a pair of venturi air intakes, again facing the front of the car, with jets fed by a 6ft length vaporiser over the fire which, when plied with vaporised 50/50 petrol diesel induce air into the venturis, and then via a mixing chamber beneath the main burner plate which is of cast iron with 7000 holes drilled so that the flame is more like a gas fire than a blowlamp. The main fuel is at 140psi and is controlled by a diaphragm/spring "steam automatic" which regulates the fire at the working pressure of 600 psi. One of the pictures shows the underside of the fire tube boiler, 23" diameter by 14 inches high with 750 1/2 inch copper fire tubes, swaged at either end with an inserted steel ferrule. The second, upper coil seen in the burner picture is the superheater 12 feet of 1/2 inch bore stainless steel right in the heat of the fire. It could burn 4 gallons per hour at full chat, although it averaged about 12mpg on the road and would go about 1.25 miles to a gallon of water.
Sorry to bore you with this car stuff - I'll now have to shrink my pictures to fit the forum and then come back to the boat in another post.

Cheerio
Another Mike
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Stoneflash

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Re: Flash steam plant control.
« Reply #289 on: May 22, 2015, 10:07:45 PM »

Last picture of Stanley boiler follows. This shows the superheater and the underside of the fire tube boiler - big stuff eh!! :-)
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Stoneflash

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Re: Flash steam plant control.
« Reply #290 on: May 22, 2015, 10:30:24 PM »


Interesting choice of boat.  I am working towards building a WW1 destroyer and even with that, it seems it will be a challenge to keep the steam plant to be low enough in the hull. Have you decided upon a specific boat?  I have drawings of the torpedo boat No. 80. This was larger than the one you mentioned since its length is stated as 135 ft and beam 14 ft. I wonder if the hull might be better proportioned. The drawings are of the actual boat rather than a model and include 11 cross-sections. They show engines, boiler, bunks etc.  If you want a scan please contact me via a personal message since I should not post them on the forum.
Regards
 
Mike

Choice of boat - which is not final (!) is because I just like the look of the Thorneycroft built Defender 2nd Class torpedo boat. I believe they were not much of a success in practice and one can imagine suffering a few sinkings in use as that ram bow looks very likely to cause a dive dive dive emergency - perhaps I should include a deployable  airbag! On another thread in the Warships area there are pictures of parts of Defender and all of her engine which have survived in New Zealand and the model pictured below is at Greenwhich. As I said in my first post I'm an experimenter rather than a scale modeller so it makes sense to pick something with not too much detail so I can concentrate on the side that I'm more familiar with.

Thanks Mike for you offer of a sight of the plans but I think I will probably seek the proper plan if it exists. I've yet to penetrate the NMM plans section but I imagine there will be something there. I'd appreciate being pointed in the right direction of anyone has such a plan.

Re superheat -much as I thought.

Cheerio
Another Mike
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TurboTyne

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Re: Flash steam plant control.
« Reply #291 on: May 24, 2015, 08:32:53 AM »

Hi Mike

I obtained plans and other documents for the destroyer that I plan to build from the NMM. The search function on their website gives an idea of what is available but after looking there I would send a message to them explaining what you are looking for.  The chaps in the plans section are very helpful and knowledgeable. They told me that the web-search is limited, can be misleading and does not always give a complete list of what they have.

By the way, if you plan for a paraffin burner the following thread might possibly give you food for thought. A much simpler pump and motor would probably be fine and avoiding the more usual pressurised paraffin (or gas) tanks should mean it is possible to store the fuel in a lightweight tank in the very bottom of the hull thereby helping to increase stability.
http://www.modelboatmayhem.co.uk/forum/index.php/topic,47453.0.html

Regards  Mike
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Stoneflash

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Re: Flash steam plant control.
« Reply #292 on: May 24, 2015, 11:10:30 AM »

Thanks for the link to the paraffin burner. I'd already decided to use paraffin, having read about all the fun with cooling of gas cylinders and in any case having plenty of experience with the petrol fired pilot light of my Stanley. I'll add some thoughts to the  paraffin thread later.

I must say all this electronics speak is a bit beyond me at the moment having spent some hours going through this thread in detail but maybe an old dog can learn new tricks so maybe later on?

Cheerio
another Mike
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TurboTyne

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Re: Flash steam plant control.
« Reply #293 on: May 24, 2015, 02:12:06 PM »

Well this old dog learnt the new tricks of electronics thanks to being inspired by the present thread of Ian (Flashtwo).

The following thread might also be of interest - it is by another chap who was learning the ropes regarding microcontrollers.
http://www.modelboatmayhem.co.uk/forum/index.php/topic,48245.0.html

But I suspect you could get a system working under manual control based upon standard DC motors driving water and fuel pumps and standard speed control modules without any electronic control - at least initially. I wonder if Ian would agree with this ??

Reagrds  Mike
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fredgraham

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Re: Flash steam plant control.
« Reply #294 on: January 04, 2016, 07:42:09 PM »

Hi Mike (TurboTyne)

My name is Fred Graham ( long time no post) and I am wondering if you are the guy who visited me to have a look round my workshop after having visited Paddy Freeman's regatta. I believe you were/are a member of Saltwell Park model boat club. If so please advise me as I am interested in your correspondence with Ian of Vital Byte (VB) renown.

I gather from the posts about VB that you have been attempting/succeeding in making a version of this vessel yourself and I was interested in finding out more about the project.

Please contact me somehow, I am not sure what the protocol for making contact is but I live in the Low fell area of Gateshead.

Al the best even if I have mixed you up with someone else, Fred Graham
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TurboTyne

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Re: Flash steam plant control.
« Reply #295 on: January 05, 2016, 08:28:45 AM »

Hi Fred

I'm afraid I am not the chap you are thinking of, but no matter. At present my electronically controlled steam plant is just that - no boat in sight yet. But the boiler, fuel and water pumps and steam temperature sensor are all working - at least they were last time I tried them. It is currently attached to a very crude steam turbine. For some time now I have been applying the microcontroller knowledge (that I acquired as a result of Ian's posts about Vital Byte) to building a tool for cutting steam turbine blades in the hope (dream) of building a turbine I can use to power a model destroyer.

Anyway, I'll send you a PM.

Rregards   Mike
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Re: Flash steam plant control.
« Reply #296 on: January 05, 2016, 10:01:03 PM »

Ooh O0 there was an interesting article in Mod Boats last month about model turbines. It looked at the history and products (no longer available sadly) for turbines finished off by a piece about a gorgeous all metal model of the Warspite with two turbines!!!!

Do please keep us informed about your developments and work on this subject Mike.
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TurboTyne

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Re: Flash steam plant control.
« Reply #297 on: January 06, 2016, 08:41:25 AM »

Thanks Ballastanksian - that Mod Boats issue sounds very interesting and I shall try to get hold of a copy.

Regards  Mike
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