Simple Boiler

[Tony Bird]

Hi Gedeon,

I wonder why the exhaust pipes are lagged with insulating (?) material the white stuff in fact...I would have expected the opposite, cooling the exhaust pipes to condense steam (and oil) !

Theory, well mine anyway. The oil is in the exhaust steam but not part of it. When the cooling exhaust steam hits the inside of the chimney the oil sticks to it and runs downwards, the steam either condensing or exiting out of the top of the chimney. The chimney being hot might help the steam to remain steam and condense less? The heat keeps the oil more fluid helping it to descend the chimney and leave via the pipe. The lagging is to help the thick oil stay hot so more fluid so it can exit the pipe into a receiver. Any water getting to the bottom of the chimney tends to evaporate. It seems to work whether lagging the pipe helps or not I'm not sure but it makes the model look more balanced? So far I have only done short bench tests which seem to work. Basically it is the same system that is used on 'chuff pots' used on stationary engines. I had the idea from seeing chuff pipes used on 16mm scale model locomotives to increase their exhaust sound which they do but they also tend to fill the locomotives smoke box with oil. The locomotives run cleaner but you can get interesting smells and noises from the burning oil. It will be interesting to see how it works out in use on a model boat.

Regards Tony.

 

[Gedeon Spilett]

I did get your explanation,
I already seen similar set-up in model steamers, in fact it is mandatory here (I believe) to have one during steam meetings, to protect the pond for oil traces...Up to now, i'm not impress by the efficiency, It is true that model engineers are not stingy with oil.
I'm planing to do a compound condensing engine, so I'm questioning there and everywhere!
Cheers

 

[zhang9889]

Thanks for sharing，methodical work!

 

[Steamchick]

Tony, I like it.
Small modelling done neatly and professionally. Wish I was that good...
Hope there were no smells when you finally steamed it "on the pond".
K2

 

[Tony Bird]

Hi,

Hope there were no smells when you finally steamed it "on the pond".

The one boiler did get to be on a pond, the other in a 16mm scale tram engine. Both were heated using Sterno (alcohol gel) and used the chimney as an oil separator as mentioned, which worked really well. The video shows the boat which is powered by an own design single cylinder single acting oscillating engine with a 9mm bore and 15mm stroke and is radio controlled rudder only. The tram used two double acting Mamod cylinders.



Take care Tony.

 

[Steamchick]

Splendid!
K2

 

[Steamchick]

Just an odd point for "Care and maintenance": Point#10 you show Brass bushes being used in the boilers. A pity you didn't use Bronze - as recommended by all the texts I have read on the subject. I recommend you therefore Blow-down the boilers after use, and blow through with compressed air ( a tyre pump will do) to dry the boilers after every steaming - for storage.
I once left a boiler "Wet" over the winter, and when I came to re-test the following year I found that a brass fitting at the bottom of the water gauge had de-zincified... - It was like a crumbly biscuit! ("Cookie" for the USA readers). Had to be replaced, along with some other suspect brass fittings. Some brass is worse than other grades, but all de-zincify in the presence of water as a galvanic corrosion of the brass. = including your bushes! So keep dry when not in use, and you should manage many years of service. Also, I do not know your club's certification system, but mine is for testing to Southern Federation rules, for the boilers (like yours) under 3 bar litres. Without such certification the club's public liability insurance is invalid. So take care to "cover the job in paperwork!" (I joined the Model Engineers as the Boat club did not cover steam vessels with their insurance).
K2

 

[Tony Bird]

Are you sure they aren't bronze?

 

[Steamchick]

Tony,
Looked too yellow to be bronze - to me at least. What material did you use?
Bronze is much more red - like copper - perhaps a bit more brownish... Brass is yellow from the Zinc included in the alloy. Bronze is ZINC FREE. But Aluminium Bronze can be yellowish.
Not sure it is recommended for Steam applications though.

Anyhow, my advice on drying the boiler BEFORE long-term storage applies, whatever, so you have a nice boiler when you next get it out.
Incidentally - Lovely workmanship.

K2