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Discussion Starter · #1 ·
I understand basically, but how about the nuances? What about really hot weather or just mildly hot weather? I can understand that in cold or cool weather warm to mildly hot water would be the ticket, but how does this change with the temperatures? Also, seems like one condition is wanted to fill a tank and another condition is wanted for the tank to put gas forth and then another to refill so there must be some compromise. I am only months into live steam so I am just trying to get my head around this one element. Thanks for any thoughts on this. Jim
 

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Hi Jim,
I am in Australia where temperatures range from around 12 degrees C (53 F) in winter to around 38 degrees C (100 F) in summer, often much hotter, and I can tell you that in winter you need some warmth for the butane to become gas with a reasonable pressure to run the burner properly. Ambient temperature from around 16C to 30C is the best problem free running range.
COLD WEATHER If you have a water bath around the gas tank then usually water will be sufficient to keep gas tank temp stable or when really cold use warm water (not very hot or boiling!) in the water bath and that will get the gas right.
If gas tank is a stand alone, no water bath, usually in the loco cab, then the gas inside stays semi liquid until warmth from the loco boiler/gas burner in the cab heats it up, once area heated it's usually OK. Lighting from cold means gas will be semi liquid, so slow and small opening of gas valve needed until flame is stable and the flue is hot and the warmth in the cab will then make the gas tank warm to give the usual running performance.
HOT WEATHER I have found it's easy to light up when hot but for filling the gas tank in cab mounted, non water bath gas tanks, they can get really hot and on the second fill of gas less will go in as the gas is expanded by the residual and ambient heat.
So yes a colder gas tank is better condition for filling but less gas pressure from a cold tank can mean slightly poorer running and hotter ambient temperatures make for easier lighting and better running but poorer for getting a bigger gas tank fill for a longer run.
When a loco has a really big gas tank say to feed two burners for 40 minutes or more ( Accucraft K27 to K36) then the gas tank cools significantly during the run and a water bath is definitely needed to keep the gas tank at a stable temperature. Small gas tanks don't seem suffer the pressure loss/cooling effect as much.
Hope this info helps, just run you engine in varying conditions and you will get to know it's burner habits and how to adjust to temperature.
Russell
 

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Below about 50 degrees Fahrenheit (10 Celsius) butane does not convert to gas efficiently enough to get reliable burning. As noted above the tank can be surrounded with warm water to bring it up to these temperatures. The upper end is about 260 F (126 C) where the gas and liquid have the same density. Probably not good for you or the tank to get this high (grin).

You do not want to try to transfer from a colder tank to a hotter tank. The back gas pressure from the hotter tank will keep the liquid from flowing.

Hope this helps your understanding.
 

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Another option for cooler weather running is to use isobutane or a butane-propane mixture. Note that straight propane should NEVER be used in a live steam loco gas tank.
 

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use isobutane or a butane-propane
That's the usual suggestion - "Camping Gaz" from the outdoor store is the place to get it. It is about 30% propane and 70% butane but it varies. I've run in below 0 Celsius / 32 F using the mix.
(As an aside, I poured warm water on the fuel tank to get it above freezing that day, and noted when I finished the run that the drops of water on the tank had turned to ice!)

Otherwise, as Russell so well described, it's mostly a case of keeping the gas tank at a stable temperature. It will get colder as the gas evaporates, so you want to give it a big water bath if you can.
Some locos use the water bath as a source of boiler water and incorporate a hand-pump. If so, you need to keep the water level up as you refill the boiler.

Cab-mounted gas tanks are a problem to refill if the cab is hot on a hot day, for the reasons stated above. Filling it initially, when cold, is easy, but many people are confused when it won't fill again after the run until it cools down. I've been known to put an ice cube on it to speed up the cooling!
 

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There are many details, well covered in the above responses. Other then ambient temp, choice of butane (which is actually 95% butane, 5% propane) or camping gas, 10-20% propane depending on brand, I found position of the gas tank very important. And also rather conflicting. My Forney tank fills up nicely after a run, and my Accucraft dockside is impossible to fill up after a run, both tanks are in the cab close to the boiler. So you need to run your engine(s) and learn their quirks. For example, my Frank S is notorious for poor running in cold conditions. Until my buddy Eric added a steam line into the tender water bath.....now it is superb in 27F weather.

And one final note, I left my Regner Lumberjack roasting in the July sun, and when I lit it there was high pressure in the butane tank and it roasted the springs that keep the oscillating cylinders attached. Great hobby!

Jerry
 

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From my experience, the Frank S tender-mounted tank really needs the water bath, even when the ambient temperature was warm. I found that the burner simply wouldn't light otherwise.

For cab-mounted tanks, I've always cut a small piece of ceramic boiler insulation (The Train Department stocks it) and wedged that between the tank side and the boiler. It seems to reduce overheating the tank better than the minimal air gap does, although (as has been pointed out) there's a lot of variability between locos.
 

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Folks, there are some elementary misconceptions about gas tank - ambient temperature essentially does not matter at all! Only Russel pointed out (and Pete reiterated) the most important fact that gas tank will cool dow rapidly and dramatically when butane evaporates. This happens in two conditions, when gas tank is filled - while liquid butane from the can flows into the gas tank, part of butane evaporates. This makes the gas tank much cooler than any ambient temperature. Then second but slower cooling process starts when butane slowly leaves the tank to be burned. As you know, there are two ways of dealing with the problem, one is placing gas tank in the cab, or in the side tanks in the vicinity of the boiler - this is often used by Roundhouse and in smaller Accucraft locomotives. Generally, this approach works well, although refilling hot gas tank can be a problem. And in some Accucraft locomotives gas tank actually gets too hot! The other approach is placing gas tank in the tender, in a water tank. This is a very good solution and luke or even cold water should be poured into the tank right after filling it or even better, before filling it with gas. Water can be added/replenished during the run but usually the volume of water and its heat capacity is sufficient to keep the butane flowing in any ambient temperature. Of course, if you want to run near or below the freezing point of water you need to consider adding warmer water and a lot of other issues such as oil which will become denser and more viscous adding resistance to the drive train, cold cylinders etc etc. Essentially, running live steam at very low temperatures is not for beginners. Best wishes, Zubi
 

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Hello Yellow Cad, That is entirely correct! Water has very substantial heat capacity
4184 Joules/kg/K - the highest of any liquid https://en.wikipedia.org/wiki/Specific_heat_capacity
Water is amazing, from nearly all perspectives, including those supporting the 'miracle of life'.
And it is cheap! So we live-steamers win hands down. We use water! And I strongly advice to use water as a stabiliser and heat source for gas tanks. There is simply no better solution and it is not even required to add lukewarm water, simply pouring more room temperature water will replace water which gave its heat to the cooling gas tank. Of course, if you want to run at or below water freezing conditions you can consider lukewarm water (or even water with added propylene glycol - that stuff that you use to prevent your car radiator from freezing - that same stuff is used in the freezer blue pack - but its only function when added to water is to lower the freezing point of the mixture, the solution will actually have lower heat capacity than pure water! Propylene Glycol based Heat-Transfer Fluids - so once again pure water wins. With best wishes, Zubi
 

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Folks, I would like to bring your attention to this beautiful phase diagram for butane: Butane - Thermophysical Properties
This diagram contains wealth of information for both physicists like me and for engineers.
It contains most spectacular 'triple point' and 'critical point' much like phase diagrams for other substances (water is actually much more complex!)
But also people who are not familiar with phase diagrams can learn a lot from this diagram.
For example, please note that at zero pressure butane becomes liquid at -138 degrees Celsius.
In practice, this means that cold weather turns butane into liquid is a 'myth' popular among live steam community (it is the pressure that does this! temperature has pretty minor effect as you can see in the diagram - follow the purple line -and what I stress below).
What does take place, however, is a slow decrease in pressure at which butane undergoes liquid/gas phase transition (evaporates/becomes liquid) which we observe in the range from 50 to 0 degrees Celsius - the range far greater than anyone would like to run live steamers.
Enjoy running in every weather! Zubi
 

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Discussion Starter · #15 ·
On my Aristocraft Mikado 2-8-2 yesterday, my biggest problem was filling the butane tank. It was windy and the temps were in the 70s. It leaked a lot of liquid when trying to fill the butane tank and when it didn't leak, it would not spue back like it was full no matter how long I kept the fill process going. I used my hands for warmth on the butane can and at one point wrapped it in a towel soaked with warm water, but to no avail. At one point, I thought that I could even see liquid in the butane hose from the tender to the locomotive.
I can't understand why the butane filling was so erratic since the temps were in the 70s. My tender has been set up to pipe overflow water around the butane tank and I did add warm water to the reservoir around the tank. I tried to fill the butane tank before adding the warm water and after adding it. Neither seemed to work.
Any thoughts would be greatly appreciated.
 

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Just a thought, I would replace the gas filling valve on the loco gas tank as it seems it isn't venting properly when filling ("..leaked a lot of liquid when trying to fill.."). During filling the gas valve has to vent to let gas liquid in and vent out the "air" until liquid gas vents out indicating a fill. This poor filling will happen at any temperature and be worse when warmer. To test this try filling with the gas feed valve to loco just 'cracked open' to let a small feed into the loco then close it off when you think it has received some fill, do it out side not indoors and you should get a better fill but it still won't be as much as it should be. If it fills a bit better and easier this way, then replacing the filler gas valve is the way to start.
Russell
 

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Discussion Starter · #17 ·
What sizes do these come in? Are there just a few standard sizes? Without taking it out, the one in the Aristocraft Mikado looks to be about 3/16 OD whereas the one in my Accucraft Mason Bogie looks to be about 1/4. I see online 4.5mm and 5mm. Can I assume that the 4.5mm will work with my Aristocraft Mikado? And, that the 5mm will work with the Accucraft Mason Bogie?
 

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There are different sizes and threads, I don't know the size in your loco maybe contact 'The Train Department' or 'Triple R Services' as both may know the size, have valve replacements so should be able to help.
By chance does anyone else out there with this loco know the gas valve thread size???
Russell
 
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