Little boiler questions

[paul]

Just starting the uber-simple little boiler to run my mini engines. It'll be horizontal format, about 6" long x 2" dia and will be a simple pot boiler with no additional tubing.

I'm sticking a boss on top for the safety valve and steam take-off, the only other option might be bosses for a pump and some sort of water level gauge.

So the questions:

1 If adding water while in steam, where should the boss be located - below nominal water level, above water level, does it matter?

2 Is any sort of gauge a practical proposition given the small size?

3 Is adding cold water likely to consume too much energy given the small size?

TIA

[baggo]

Hi Paul,

I'll put my pennies worth in.

It shouldn't make any difference really where you feed the water into a boiler like that. Most boilers have the clacks below the water line. Obviously some loco boilers have top feeds where the water enters the boiler at the top and then trickles over trays (in full size) to spread it over a large area before it hits the water in the boiler.

You should be able to fit a conventional water gauge on the end of the boiler quite easily - the glass doesn't have to be that long. Some boilers (wilesco?) have a flat piece of glass over a slot in the end of the boiler held on with a cover plate and sealed with a gasket.

Adding cold water will cool down the boiler and lower the pressure initially but so long as you only feed it in slowly a bit at a time instead of a lot all in one go it shouldn't be too much of a problem.

John

[mackintosh]

Hello Paul Just a suggestion have a look at the way the 16mm boys top up there small boilers. They have a neat
little valve on top which is filled with a hand held garden spray pump modified with a tube where the nozzle fits.
I have a drawing if you are interest. As for the other points John has it covered
Bob

[modeng2000]

Hi Paul,

Dave Watkins has a drawing of a boiler top up valve on this page :- drhttp://www.davewatkins.pwp.blueyonder.co.uk/sheet6.gif

Good luck, John

[teakfreak]

Onn the whole, I find that vertical boilers work better than horizontal ones - more heating surface if you have a centre flue - and if fired by meths I have found the flames can lick around theboiler and out of the top of the casing. Tubal Cain's "Polly" design can be modified to include three flame tubes instead of the single one if you extend the shell a bit to alow a smokebox to be created, then you can arrange the meths burner so there is a wick beneath each flame tube. Because I build these boilers for kids I usually arrange an extra bush about half way up for a feed from a hand pump and include a small water tank to pump from. I also fit an inexpensive water gauge so they can see the levels of water they have to maintain. I also fit a mamod safety valve as these seem quite reliable.

Finally, I screw the whole lot toa heavy baseboard so there is no possibility of anything falling over.

Even so, these boilers don't seem to have a lot of capacity and will barely keep pace with a 1/4-3/16" bore wobbler.

[modeng2000]

You might not have come across this site Paul. Not directly about boilers but should interest you.

John

[dickdastardly40]

Another site I'm a member of has plans for a 3 1/2" dia 6" long boiler available to download. Not sure if you have to be a member.

www.homemodelenginemachinist.com/index.php?topic=1072.msg9458;topicseen#new

You could either add hot water or design an economiser in to pre-heat the water before it enters the steam drum for a 'Rolls-Royce' solution.

Al

[paul]

Baggo: Helpful as ever, thank you!

Bob: Yes please any and all drawings welcome

Modeng2000: Nice link.. and useful plans

terakfreak: thanks for that. I made a vertical but it isn't a great 'looker' and it has other bad points (don't ask!). I'm shooting for simplicity this time. How do the small gauge glasses cope with the bubbling water in such a small boiler? Is putting on the end of a 2" tube likely to be a waste of time?

Al: see PM

[mackintosh]

Hello Paul I hope this drawing is OK if you would like a printable copy PM with your email address
Bob

[teakfreak]

Paul,

I don't have any problems with gauge glasses on these boilers. I guess the narrowness of the glass tube helps to damp down the effervescence of boiling. The water level does move a little, biut no more than it does on bigger boilers, e.g. 5" gauge locos

[paul]

Couldn't do any boiler bashing/filing or sawing today due to a cut right on the end of the pointing digit. Ouch.

Still I did manage a simple new safety valve even if I did buddha up three 1/4" bronze balls in the process - aint' it a pig getting them to sit and stay just so in the chuck, even with a stub behind? And isn't de-burring little bits like this M3 nut a fiddly game? Tch!



Better add a washer at the bottom end and test it I guess.

[chris vine]

Hi Paul (again),

The safety valve looks fine to me.

It is just a thought, but rather than make a top filling valve, you could make a small hand feed pump as your next exercise. It is most satisfactory to be able to fill a boiler while it is running the engine. If you have a pump you can feed a little and often and so not knock the steam pressure to much.

If you find the adding of water beats the boiler/steam pressure, then you just need more flames!!!

Chris.

[steam4ian]

G'day Paul,

In that you are making a "simple" pot boiler, have you considered adding quills to make it a porcupine? The quills are said o greatly enhance heat transfer.

Regards'
Ian

[paul]

This is very roughly what I envisaged:



...the boiler tube completely concealed within a steel sheet housing held in place at either end with nuts on studding soldered to end plates (perhaps). I suppose a gauge could be fitted to one end if it was close to the housing.

Teakfreak: is it possible to disassemble are the gauges you buy and if so can you post a link please?

[teakfreak]

Not sure what you mean by disassemble - they are inexpensive plain gauges - see MaccModel Engineering Supplies cat p20; I use the 3/16" x 40/4mm glass size for these little boilers, but if you want to make your own I'm sure there will be LBSC designs in this size bracket, just as there are hand pump designs.

My horizontal boiler is based on a Tubal Cain design and has one end exposed so that there is room for a water gauge mounted diagonally across one end. The boiler sits in a brass cradle at this end. By the way, I think that another writers suggestion of porupine quills to improve heat transfer is worth thinking about. I recently came across them on a boiler design for a G-scale De Winton VB locomotive.

There used to be a seller on E-bay where one could pick up these items cheaply from time to time - it just depended how much competition there was on the day. This is where most of my collection of fittings came from. Main problem was that the seller, although based in the UK, charged in $US and got to the point where he would only sell using Paypal, which I'm not keen on. His postage rates were very steep for single items but hew was willing to combine items to reduce costs.Don't think he trades any more

[paul]

Thanks all for help and suggestions. I've files away all the links/drawings etc but for now I'm sticking with the simplest 'pot'... I currently have four engines and no steam so I need results fast (wrong attitude for model engineering I know but I have steam withdrawal symptoms!)

Got the barrel and the first flanged plate done this afternoon before the fluorescent tube in the 'workshop' decided to pack up. Grrrrr!