# Most powerfull steam engine?



## jan019 (Sep 29, 2013)

Hi guys,

Newbie calling out for some advice. First of all I am absolutely new to these things, but it all looks very interesting. For a long time I was wanting to make some sort of engine to power my hand coffee grinder. Yes I could use a drill or something to power it, but I rather wanted to create something and now I have a school project to make a steam engine that will power something and thus the question is solved, I will try to build a steam engine to power my hand coffee grinder.

I did quite some research and found out there are quite a few different types of motors. The thing I need to know, is which one is most powerfull, or in other words which one will be strong enough to power a grinder? I originally wanted to make a osciallting steam engine, but I've read that it might not be strong enough, although it was never directly pointed out this way, so I just want to be sure. Thank you for the answerws 

John


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## Tin Falcon (Sep 29, 2013)

O K you need to power something.
 You want to power a hand operated coffee grinder.
measure the torque and rpm of you operating the machine.  

The power of a steam engine is (P*L*A*N)/33,000

Pressure on piston 
length of stroke
Area of piston
Number of stokes in a minute. 

My suggestion is start looking at a marine engine that is twin cylinder and double acting with a piston size in the 12-24 mm range.  Now realize this is a huge range of scale .  As the larger engine will require 8 times the material. and put out eight times the power. 


Now you need to decide if you want to go with an engine with a steam chest and sliding valve. a piston type vales or an oscillator. 


John :
It would really help us if you post an introduction in the welcome are .

Tell us a bit about yourself. your shop and your interest in model engines. And where in the world you are from. 


Tin


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## BronxFigs (Sep 29, 2013)

John:

Try "BOGSTANDARD'S PADDLEDUCK STEAM ENGINE" ... a tutorial...showing how to machine a two-cylinder steam engine.  And for a far more simple design, try: "THE LITTLE HUSKY"...a single-cylinder, all bar-stock design, that can very easily machined, and be quickly built.  You'll be grinding your coffee in no time at all.   Scale designs up/down to suit materials that you have on hand.

What about the boiler to steam your new engine?????  Compressed-air might be an alternative.

Good luck.


Frank


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## OrangeAlpine (Sep 29, 2013)

Oscillators have gotten a bum rap because they have been used so much in cheap toys.  But they have a long history of producing large amounts of power in a very compact and reliable package.

Bill


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## Tin Falcon (Sep 29, 2013)

the problem with large scale oscillators is inefficient valving .
that is why the Corlis valve engines were so popular for large industrial engines.
save steam  = saving fuel = saving money. the other consideration with an oscillator is limed pressure. You not not run an oscillator on more than 30 psi. for a small steam toy that is a good thing it has a built in safety. For large industrial power big disadvantage.  
Tin


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## jan019 (Oct 5, 2013)

I was out of reach from my computer so I couldn't reply, sorry guys. At the same time thank yo uvery mcu hfor your replies.

My situation is a bit different than most of you think, I have no shop, no machines, pretty much nothing. my plan is to make a prototype of the model I'll want so I know exactly what parts I need and so on and then I'll have it made somewhere, not sure where yet, but that shouldn't be a problem. 

Okay so I probably won't be making the oscillating one. I was thinkign about making this one . I've made a quick design of what it could look like - in the attachment. It's probably still a bit to complicated and I'll redo it into a simple version, but I'd imagine this could work better than the oscillator. 

To the attachment - the top cylinder is the piston cylinder itself while the lower one is the valve, it's done based upon the diagram i posted. What do you think, would this be better?

John


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## Charles Lamont (Oct 5, 2013)

Tin Falcon said:


> the problem with large scale oscillators is inefficient valving.



Oscillating engines were popular and successfull paddle steamer engines from about 1840 to 1860. They were built up to 100" bore & 12ft stoke and developed up to 4,750 indicated horsepower. Admittedly, they were fitted with slide valves & Stephenson's valve gear, rather than the simple porting arrangement used in models.

Corliss valves would hardly be a beginner's project.


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## BronxFigs (Oct 5, 2013)

John:

The diagram that you show, if flipped 90 degrees vertically, is the same as the cylinder/valve arrangement for  "The Little Husky" steam engine.

Also, take a look -on this forum- at a thread called: "Model eng. from Levenworth"... and see many nice, simple steam engines, for your coffee grinder.  : )

Frank


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## jwcnc1911 (Oct 5, 2013)

John, when you get ready to start making it, pitch it here.  There are many many people here who would probably make some or all of your parts... for less than a regular machine shop.

Just an idea.


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## jan019 (Oct 6, 2013)

Thanks for the information and recommendations. Unfortunately I am from the Czech republic, so it would be a problem to get the parts to and from some of you. I will have to deal with that somehow. I will probably start working within the next two weeks, so once I do start, I will defintely post updates.

John


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## jan019 (Dec 21, 2013)

Hi guys,

The time to start working on my project has come and with that come questions. As I mentioned earlier, I have no work shop, no machines, pretty much nothing, so I will be making the engine out of what I can find, buy and easily change to my needs. 

The material I want to use for the cylinder and valve is copper. Is that a good choice? 

The other question is what is the best way to connect a copper cap to the tube? Is soldering the only way?

Will heating from for example solid fuel cubes generate enough pressure? 

And lastly, how much pressure can copper hold and what pressure can I get from boiling water, from steam? 


Thanks
John


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## abby (Dec 21, 2013)

Copper is no good at all for cylinders or valves , brass ,gun-metal or cast iron are the usual choices and it is good practice to avoid similar metals working against each other.
Accepted practice is silver brazing for boiler construction and for joining many of the metals used in model engineering ......other than screwing/ bolting together.
How much pressure can you get from steam ? how long is a piece of string ? the hotter the steam the greater the pressure , the thicker the copper the more pressure it will withstand.
But beware using steam at high pressures requires high quality design , materials and construction , the energy contained in superheated steam can strip flesh from bones .
The efficiency of heating will depend on the heat transfer from the burning fuel to the boiler water , any fuel will provide enough pressure if you can burn it quick enough and use all the heat.
I would suggest that you limit your project to around 40 psi of steam pressure and use copper of 1.5 mm thickness for your boiler construction. 
Obviously the boiler will need to be large enough for a constant supply of steam to the engine at the chosen working pressure , it will also need a feed pump to replace the water evaporated .


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## jan019 (Dec 21, 2013)

Thanks for the info. Copper is the easiest to get, so would it really be that bad to use it? Other than that I could probably get steel tubes, would that be better?

I'm attaching an image of the design I would liek to build. What do you think, could it work? There are three "wheel" because that's the simples design I could think of given the materials I have. The outter disks would be made from wood, while the smaller, grey disks are normal washers that would provide strength for the wood. All 3 disks would be glued/connected to the middle axis so that the valve and cylinder system would work. The cylinder on the side with the smaller washer is the valve. The middle blue hose would connect the valve with the boiler. Other than that I think it's self explanatory. Thansk for any imput.

John


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## Tin Falcon (Dec 21, 2013)

Take a look at this old design. I think it will work for you .



http://npmccabe.tripod.com/olddesign.htm

Tin


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## Swifty (Dec 21, 2013)

John, what you have designed is a double acting piston, air pressure is introduced alternately at either end, you will need some way of exhausting the air in the cylinder when you are introducing air pressure in the opposite end. The engine that Tin has put a link to is single acting, air pressure is only put in one end of the cylinder and it relies on momentum of the flywheel to complete the return stroke.

Your current design is like drawing air into a syringe, then holding your finger over the end whilst trying to depress the plunger on the syringe, you must exhaust the air in the other end for it to work.

Paul.


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## Swifty (Dec 21, 2013)

If you google " simple model engine slide valve" and view the images, you will see a lot of designs for these valves.

Here's a link to a basic image. http://www.igg.org.uk/gansg/00-app3-4/slivve.jpg

Paul.


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## abby (Dec 22, 2013)

John copper is a soft metal and unsuitable for moving/wearing components , brass would be far superior and is readily available.
You may not know that steam is totally unlike air. When steam is admitted into a cylinder the pressure will push the piston , just like air will . Unlike air the steam expands as it cools , so it is normal to close the inlet valve when the piston approaches around 50% of it's travel , the expanding steam provides the remainder of the thrust.
Your valve gear should be designed so as to take advantage of this expansion and enhance overall efficiency.
Reciprocating marine steam engines were usually " triple expansion " each of 3 cylinders wa larger than the proceeding one , steam was exhausted from smaller to larger ensuring every last calorie of energy was turned into power , the steam leaving the last cylinder went into a condenser so that a vacuum was created thus the largest piston was not only pushed by the steam it was pulled by the vacuum.
Hope this somewhat simplified explanation goes a little way to explaining some of the principles of steam engineering.


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## jan019 (Dec 26, 2013)

One more question. What is the best and easiest way to connect two brass pipes like in the attached picture? At the same time safe for a steam engine. Thanks


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## Jyman (Dec 26, 2013)

That would depend on what it's used for, but I would use silver brazing to connect them


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## jan019 (Dec 28, 2013)

@Tin Falcon

Do you think that engine, being single-acting, would have enough torque to grind coffee? This might be an absolutely stupid question, but it just seems to me that relying only on the mommentum of the fly wheel would make it very easy to stop on the "unpowered" run. Thanks


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