The Steamboating Forum

Hi All,
Can someone possibly confirm the steam output of the SBA Blackstaff boiler.?

I have read, 5 pound/hr unforced, and 10 pounds/hour forced, and I have also read comments questioning the figures so I am not sure . (I bought the plans a couple of years ago).

To force the boiler when required I plan to preheat the feed water, and run an air fan, blowing air up the stack- is there a better way/any thoughts on that.?

I would really like to know before I build the boiler, as their is nothing worse than not having enough steam in a steam boat

Martin

Hi Martin,

i dont know the SBA Blackstaffe-Boiler, but you can calculate the steam output of such a watertube-boiler. Calculate the evaporating rate with 12 - 15 cm³/water/100 cm²/minute heating surface (water side of the pipes).

The steam output of such a boiler is very high. I have run my HASBROUK #10 with my little LOCKENWICKLER.

https://youtu.be/AgGv3aA5R78

To preheat the feed water is a good way to increase the steam output.

Dietrich

Just realize that showing a video of an engine without it driving anything doesn't say much about the steam output of a boiler. Don't get me wrong such an arrangement is great for testing and playing around.

Just depends on what you are trying to accomplish.

Before I put Nyitra together I was using my engine to run a Permanent Magnet Alternator producing 500W continuous (Incandescent 12V lightbulbs), that was near the limit of my PMA. Every 750Watt is 1HP. The nice part of that is if you can get a boiler+engine to make an electrical load run continously a load it's a great way to quantify things and show end to end (there are intermediate losses that the steam plant is handling but they are not included in what your ampmeter is reading).

-CB

Thanks for your replies Dietrich and Cyberbadger, I am old school and looking for pound/hour output.

In hind sight perhaps I should have at least introduced myself, (some of you may know) I have been interested in building a boat for a number of years but due to ill health the steam boat got shelved. Just saying.

I am a fitter and turner and done quiet a lot of work in power stations. All been good I hope start building soon. I also hope to check the forum regularly & contribute to the forum where possible.

At the moment i am trying to decide on an engine and also a boiler to suit.

Before posting I looked back through previous posts with out finding any evaporatiin details for water tube boilers, So, If someone with experience could comment about the steam output of water tube boilers, I would appreciate it.

Martin

If you look into the FAQ sections of this forum you will find the answers to your questions.

Boat Power requirement, Propeller sizing, Engine Output Capability, Engine Steam Flow Requirements, Boiler Sizing, Output Capability, Output Testing

Note that boiler surface area should always be calculated based on the heat transfer surface exposed to the hot gas of the fire.

"....... was using my engine to run a Permanent Magnet Alternator producing 500W continuous (Incandescent 12V lightbulbs), that was near the limit of my PMA. Every 750Watt is 1HP.

Actually one English (and USA) horsepower is equivalent to 746 Watts, but that does not consider the efficiency of the generator, typically around 70% to 80% of the input shaft horsepower is converted to electric power. So a generator producing 500 Watts electric power will require about 650 Watts input shaft power.


The converse is also true for motors, 70% to 80% of the input electric power is converted to shaft power, so if 746 Watts electric power is fed to a motor (one horsepower electric input) the actual shaft power output is only about 3/4 horsepower.

Thanks Fred,
I didn't see those FAQ's.... The screen on the old 4S iPhone is pretty small (and my only Internet access).

Is their anything on the forum for calculating the proportion/volume of compound cylinders, re steam pressure (different HP LP cylinder volumes for different steam supply pressure & how to calculate what the volume of the LP needs to be). Hope that makes sense..!

Or should I repost the question.

Martin

Are you familiar with the P.L.A.N. formula for steam engines?

Yes thx Wesley I am familiar with PLAN/33,000.
I didn't write the question very clearly, I wanted to check the cylinder volume ratios on a compound for a specific steam pressure, and can't find the formula on the net.

"Is their anything on the forum for calculating the proportion/volume of compound cylinders....."

This is actually a complex issue, however for typical launch engines, the volumetric displacement of the low pressure cylinder(s) is around 2.5 to 3.0 times the volumetric displacement of the high pressure cylinder. This is for smaller launch compounds, such as the Stuart 6A (2.5x4.0x3.0).

For larger engines, presumably operating with a good vacuum exhaust pressure, the ratio increases to around 4.0 to 4.5, such as the US Navy K engine (3.5x7.0x6.0).

If you are thinking of designing a custom compound engine, there is a host of design issues well beyond the cylinder displacement ratio as a function of main steam pressure, and I would recommend you simply copy an established successful engine's dimensions and operate near the design basis steam conditions.