Simple Steam figures

[Blow]

Hi all

Can some one advise me on a simple rule of thumb method of calculating how long my boat / steam engine would run?

I'm aware that steam calculations can go on and on for every little detail but there must be a general rule of thumb to give a rough guide,  Assuming the boiler is working @ 40psi the engine is twin cylinder double acting 11mm bore 18mm stroke running @ 500-600rpm

The boiler capacity is 0.75 liters and I'm thinking it would need topping up after 50% so how much steam would .36liter produce?
and how efficient or how much steam would a 11X18mm bore use per stroke?

Any offers

[sandy_ACS]

 

Hi PD's.... NO I'm not DEAD

Blow

Sorry to read that your first boiler ran into difficulties (we all have such things happen) and I hope your new one will behave it's self.

Anyway, welcome to the mad house, I am sure you will find a lot of interesting stuff to keep you on your toes.....

I have placed an answer to your question on steam consumption under the 'Live Steam' heading, since I think this is the best place for such threads and it saves Eddy having to move things about.

I hope you find it informative.... I expect I will get some OZZIE STICK though....

Best regards.

Sandy.

[Eddy Matthews]

Hi PD's.... NO I'm not DEAD

Sandy.

Good grief, hello stranger! 

[sandy_ACS]

 

Hi Eddy,what a big hull you have....

I'm keeping an eye on you lot...not sure you can be trusted by yer selves yet.....

regards.

sandy

[Eddy Matthews]

Hi Eddy,what a big hull you have....

Well thankyou kind sir...... I didn't want to brag, but your quite right, it is BIG isn't it!

[Bierjunge]

Can some one advise me on a simple rule of thumb method of calculating how long my boat / steam engine would run?

I'm aware that steam calculations can go on and on for every little detail but there must be a general rule of thumb to give a rough guide,  Assuming the boiler is working @ 40psi the engine is twin cylinder double acting 11mm bore 18mm stroke running @ 500-600rpm

The boiler capacity is 0.75 liters and I'm thinking it would need topping up after 50% so how much steam would .36liter produce?
and how efficient or how much steam would a 11X18mm bore use per stroke?

Hi,
Sandy has perfectly walked you through some simple calculations in http://www.paddleducks.co.uk/smf/index.php?topic=3343.0

An alternative, not to start these calculations everytime from scratch, would be to use my simple excel calculator attached to http://www.paddleducks.co.uk/smf/index.php?topic=3262.msg14351#msg14351

Since it has no direct rpm input, you will have to play around a little bit with the paddle wheel or propeller dimensions in order to get your desired 600 rpm at your given cyl dimensions and 2.75 Bar (which is 40 psi). I would further set the cylinder filling to at least some 75%, because oscillating engines are full pressure engines.
If you do so, you will end up at a mass flow rate of six-hundred-something grams per hour, which would give you a running time of roughly half an hour. Pretty much the same result as Sandy achieved.
Of course there are many uncertainties involved, especially in guessing mechanical efficiency, so a rough estimate of running time is all you can expect.

Another question would be: Where do your 600 rpm come from? My little excel calculator would allow you to check if this is plausible at your given assumptions.

Best regards, Moritz

[Blow]

 Hi

Thank's for the excel calculator this look good and will be very usfull but I will need to studdy it a bit more.

I'm sorry about the placement of the question but I'm very new to Forums and find it daunting with all the different sections, I'm getting better and starting to under stand the layout a bit more, I tired searching but came up with not allot.

My reason for trying to establish the running time was to help me decide where or not to build a small feed pump to keep the boiler topped up. If the answer was less than half an hour and I would but as it is about that and this is for my first project I think I won't bother as there are several other things I would / will change for the next project.

I'm still on a very steep learning curve but I'm really enjoying the challenge.

Thank you once again