Marion two cylinder steam engine needs a help

[kadora]

Hello friends
I need again your help.
I am four stroke guy but this time i'm in process of machining my own design steam engine.//engine is half done//
As you can see on video engine is running on pressure 1/2 bar.
What I am worrying is high air consumption because my two cyl. airbrush compressor is not able to feed engine more than 0.5 bar air pressure.
Now I need to start machining boiler but I absolutely do not now how big
boiler should i have .
Please guys give me a hint where to look to get basic dimensions for boiler.
Thank you for any informations.
Click to see video
https://youtu.be/bJKzK2pr4bs

 

[kadora]

My first run on real steam.
Now I see how many new things I have to learn.
https://youtu.be/puJPHEdMYRQ

 

[ShopShoe]

kadora,

Congratulations.

That is running very well on real steam. I enjoy the sound of it just as much as watching it run. It's an interesting design.

I can't remember whether you posted information about your boiler: It is interesting as well.

--ShopShoe

 

[kadora]

Thank you ShopShoe
Boiler is rebuilt cooking 7 litere pressure pot
fitted with manometer , two safety valves and steam outlet valve.
I noticed that this is not good solution to power model steam engine
because the pot is designed for max pressure 1.1 Bar only .
But steam in 1.1 Bar pressure is not hot enough and contains a lot of water droplets.
These water droplets cool engine and power of engine is low.

PLEASE GUYS CORRECT ME IF MY CONSIDERATION IS WRONG.

However by rebuilding this pressure pot I got first touch with steam.
If i did not need this pot for casting /CO2 cureing/ probably I would
weld pot cover to the pot body to rise working pressure.

 

[kadora]

Hello
On the base of my steam engine observation
I have found two things to be solved.
First boiler should be as close to engine as possible.
Second to preheat engine to avoid cold start.
//cold engine spits water//
So I attached boiler and oilers straight to the inlet ports
and hot fumes from boiler preheat engine heads.
Now engine is quite compact unit.
Now I am experimenting with propane burners
for boiler heating.

 

[Mechanicboy]

Air pressure do not expanding as steam hence the steam engine do not run well at air pressure. To thing to remember: How much steam to be produced and how big is steam pressure when you are designing the boiler depending on size of the steam engine.

 

[JCSteam]

Nice job on the engine

I have concerns about you using a pressure cooker to boiler the water, but that is simply because I ain't seen it done. A well made engine will run on 15psi (1 bar) quite happily.
Even a badly made one that leaks can run on 15psi.
With running an engine on air you need to make sure there is plenty of oil. The compressed air blows it out so the piston won't be lubricated causing premature wear.

With a wet steam boiler. One that runs under 25psi. The steam that comes out is obviously as you describe wet. Some of this will condensate in the cylinder, most will be blown out the exhaust with the exhaust steam and some condensate. However it's been shown before that this condensate mixed with the oil can help to keep the piston and cylinder lubricated for a long duration, (A Mamod running for o we an hour???? With just initial lubrication).

 

[bazmak]

One thing i learned about model steam engines is that everything
can be scaled down to suit from the real full size version EXCEPT pressure