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[tonyH]

Can them that knows these things advise? I'm contemplating a brass shunt from under a <1 litre boiler to a thin brass warming plate beneath a disposable gas cartridge. The safety valve is set at 60 psi so theoretically the temperature in the boiler, if my sums are roughly right, about 200C and the external temperature could be a bit lower. Am I in the right ball-park or am I being a total twonker? If I'm right, then soft soldering to the boiler would be a rather stupid idea

[1967Brutus]

60 psi is about 4,15 bar and from this: stoomtabel_300_bar_voorbeeld.pdf  it follows a water and steam temperature of 153 deg C.

Metal temperature externally will be by and large the same, maybe 5~10 deg C lower.
Tin soldring has no place with that kind of temperature.

But if your intention is to get heat to the gas tank in order to maintain fuel pressure, there are easier options.

Easiest is to reroute (a part of) the exhaust steam from the engine, to a heating coil touching the gas tank. Advantage is that the temperature of that exhaust steam is exactly defined (100 deg C). Therefore this solution allows for fairly easily "tailoring" the heatsupply by increasing or decreasing lenght of the coil in contact with the tank, in order to keep gastank temperature in check, because you really REALLY REALLY do not want that tank to overheat: pressure build up is exponential...
Another option that is fairly easy to achieve is to place one or two ceramic resistors under the gastank, and heat the tank that way. Use 0,1W per gramme of gas used per hour, for example a burner that consumes 60 grammes per hour, fit a 6W heating resistance under the tank. Use actual consumption numbers (averaged numbers will do), NOT the stated max capacity, which can be much higher.
As an example: my own installation, max capacity of the burner is unknown butprobably significantly in excess of 100 g/h. Max consumption at full speed is about 90 g/h, average consumption during normal use is about 60 g/h. I used a 5W heating element, and that was "just about right", given that the tank always picks up some radiant heat from the installation.

But very VERY recently, I discovered "liquid feed", and oh boy.... done right, all your woes and worries WRT fuel pressure are a thing of the past.
https://www.modelboatmayhem.co.uk/forum/index.php/topic,70510.0.html.
In hindsight, that was something I should have done from the get-go, it works brilliantly...

[tonyH]

Thanks Brutus. I'm re-planning a simple warming set-up with brass sheet which in principle is the same as using exhaust steam but I couldn't remember the formula from many years ago!
Cheers
Tony
 

[1967Brutus]

There are many ways to skin a cat

As long as it works!

[Geoff]

I always position the oil seperator (condenser/waster water collector, call it what you will) such that it is just touching the gas tank. At the end of a run the gas tank is consistently hand warm which is perfect. It does not overheat because the actual contact point is very small. Bear in mind that in practice it is prudent to get the boiler up to pressure and then turn the gas down a little. At this stage the gas flame will not be at its best as the gas tank is cold. As every thing gently warms up in sailing the gas pressure will slightly increase giving a larger flame and more heat. This works well and I have been using this set up in my steam models for over 20 years with no issues. It has the benefit of using waste heat as well.


Cheers


Geoff

[tonyH]

The problem I've faced is that I'm rebuilding a French spar torpedo launch into an English version armed with Whiteheads. This has a water cooled condenser cylinder built into the hull. They're almost identical dimensionally but I've had to reverse the boiler end to end to get the funnel in the right place. This means that the gas tank is now about 16 inches from the condenser so probably too much heat loss. The reason for the initial question is that I assume that heat transfer from the outer face of the boiler to any warming device is affected by how closely any individual parts of the link are connected. Soldering should, for example, be better than holding together with a clothes peg! The length and thickness of the link are also relevant as is the material used. Now I know the input temperature I can get a handle on the next bits of the cunning plan using thin brass strip which should be easily trimmable/adjustable. According to the canisters the maximum operating temp is 50C but I'm going to aim for about 15C. I'll let you know
Cheers
Tony

[1967Brutus]

That to me sounds like an excellent excuse to try liquid phase feed

(A bit tongue in cheek of course, don't do what you do not want to do, but it is less complicated than it would appear...).

[ooyah/2]

Geoff


Please check your P.M. in box


George.

[Geoff]

George, I just checked and nothing there. Cheers  Geoff

[ooyah/2]

Hi Geoff,
There has been some strange happenings on the forum and I have asked Martin to investigate.
If you go back to your first post in trying to fit an MBH boiler and engine into a Clyde puffer I was going to ask if you would like to see some pics of puffer that I built some years ago and fitted a steam plant into it which would help with some ideas in your project.


My model was built 1/2" to the foot giving a 33" long hull hence my asking as to the dimensions of the puffer that you have.


If you wish I can post what I have for your perusal on your post off fitting an MBH  steam plant into a Puffer


George