Steam Vs. Air and other things

[neptune769]

Hello All,

I'm new to engines. I don't know much about them. But that is why I'm here. I acquired a lathe and I want to make a small engine. I'm either going to make a Sterling or Air powered. Something simple. On a separate subject I was wondering is there a difference in performance between Steam & Air for the same engine and air & steam pressure? Also is there a way to calculate HP for a Steam or air driven engine? Thank you.

Regards,
Dennis L.

 

[portlandron]

Engines designed for steam will also run on compressed air without any design change.

For your first engine I would suggest you build a steam engine. Sterling engines are very interesting to see run but are not that easy to get to run. They require very close fits and very little friction between moving parts and these are two thing that are hard to balance out at the same time. Steam engines do require some close fits but are a little more forgiving.

There are many casting kits you can buy but I think for a first engine you would be better off finding a set of plans that do not require casting but are built from metal stock.

If you do it this way and make a mistake you just start over with another chunk of metal rather then have to purchase a replacement casting.

Which ever you build welcome to the hobby.

 

[Blogwitch]

Engines designed for steam will also run on compressed air without any design change.

Not quite right I am afraid.

Expansion engines is just one common example, they actually have to use expanding steam to work correctly.

I am sure there are a few more as well, including steam vacuum engines, it's no use throwing in cold water if it is just air in there.


John

 

[steamer]

A steam engine will run on air, but no where near as well as with steam. There are many texts on calculating the indicated horsepower of an engine, but generally it's PLAN/33000 = IHP or Indicated Horse Power

P is the Mean Effective Pressure
L is the stroke in feet
A is the piston area in square inches
N is the rpm

If the engine is double acting, you have to multiply by 2 to account for both sides of the piston. Talking about a wobbler though, a wobbler is single acting so this equation stands

the tough part is determining the MEP or mean effective pressure. For model work I would start with half your boiler pressure. You won't be far off. Then multiply by the mechanical efficiency....like 0.5...and you'll get your brake horsepower.

The problem you run into with air is the low expansion and energy conten as compared to steam. You'll get more power with steam than with air. But if your just trying to make it run, it really doesn't matter much

Dave

 

[flyingtractors1]

Hi Dennis. For a first build you might even consider a simple solenoid engine. Many varieties are possible, and they operate very much like steam engines but employ electric energy to power an electromagnetic coil which draws the piston rather than a burst of compressed air or steam to propell it. Solenoid engines employ wired electrical switching in place of plumbing and valving. Otherwise they resemble steam engines and are fun to build and easy to operate. Many examples are available on this forum and on YouTube and other sites. Have Fun. Ralph

 

[Nickademusss]

Theirs something about live steam! I think the simplest engine might be the wobble type steam engine or as stated above the solenoid motor.

PM research have great castings for simple steam engines, and the material is easy to work with.

 

[tel]

Yes indeed, there is nothing to compare with running your engines on real steam as opposed to air.

 

[firebird]

Hi Dennis.

Have a look at this little steam plant I built a while back. It will run on steam or air quite happily.

http://www.homemodelenginemachinist.com/index.php?topic=4779.0

cheers

Rich

 

[rhankey]

If you are interested in making multi-cylinder engines that work well with compressed air or steam, then I would suggest sticking with "compound" engine - in which the steam or air supply is fed directly into all cylinders.

Expansion engines require steam's ability to produce work multiple times, by feeding the exhaust of the first (high pressure) cylinder into the intake of the next (intermediate pressure) cylinder(s), and the intermediate pressure cylinders may then feed a third (low pressure) cylinder. The steam produces less work as it moves sequentially down the line of cylinders. Compressed air on the other hand can produce work only once, so will only power the high pressure cylinder. When run on air, the intermediate and low pressure cylinders will not do anything other adding drag. The drag might be too great for the high pressure cylinder to overcome (as it is also the smallest cylinder), and to the extent it can, it will need significantly higher air pressure than it would require if run on air.

The benefit of expansion engines when run on steam is that they run more efficiently, as they extract as much useful work out of the steam as is viable. I think you can appreciate that power or efficiency of steam engines will vary greatly based on their configuration.

Robin

 

[steamer]

What multi expansion engines give you is expansion over smaller temperature differences. That reduces the condensation losses at any one stage. In a compound, there's the HP temperature range and the LP temperature range.....if it was expanded all in one cylinder, the condensation losses would be huge....and is generally why you don't see simple engines running above about 80-100 psi.

In a compound, your would see say 140 psi down to say 45 and then 45 down to say 20 inHg.

Look up the saturated steam temperature for these 4 conditions and you will see what I mean

If your not too concerned about efficiency, and just want raw power....like a locomotive...go ahead run it at 300 psi with a single simple expansion
But your burning fuel big time.

Once you get beyond a triple expansion engine, the mechanical losses start to overwhelm the gains in thermal efficiency...which is why you don't see too many Quads....or quints!

Additionally, small compounds have so much surface area compared to they're swept volume that they are steam hogs anyway....then again, if you want efficiency...buy a diesel!

Dave

 

[Mainer]

If this is your first engine, keep it simple. Even a simple engine, if you have never built an engine before, can give you fits. There is time enough to wade into a Stuart-Turner triple expansion marine engine casting kit. Find out what it's like to do something allegedly "simple."

I'd suggest a single-cylinder steam engine with an overhung crank made of barstock. Making even a one-throw crankshaft is not easy; start with an overhung crank (basically a pin in the side of a disk). Google "Elmer's Engines" and see if you can find his engine plans. An old guy named Elmer Verberg designed and made a whole series of assorted barstock steam engines, small in size but all unique in some way. The material for any of them should be easily affordable, and if you mess up a part it's a dollar's worth of brass, not a $100 casting.

As somebody said, Stirling engines are non-trivial for the reason stated; air-tight but as close to zero friction as possible. Get a little experience first.

Of course, there is always the novice who builds a fully working compound Corliss engine for his first attempt and succeeds brilliantly, but don't count on being him.

 

[neptune769]

Wow, lots of info. Thank you all for your input. So Stirling is out for now. I'm not new to machining just engines. As soon as I can get a motor I will start on my project. While I'm waiting to get started I can decide on what I'm going to make. I'm thinking maybe a simple wobbler for now.

Rich, that was a good thread. Thank you for sharing.

Regards,
Dennis L.

 

[lensman57]

Hello All,

I'm new to engines. I don't know much about them. But that is why I'm here. I acquired a lathe and I want to make a small engine. I'm either going to make a Sterling or Air powered. Something simple. On a separate subject I was wondering is there a difference in performance between Steam & Air for the same engine and air & steam pressure? Also is there a way to calculate HP for a Steam or air driven engine? Thank you.

Regards,
Dennis L.

Hi Dennis,
Sorry for asking but have you got any machining experience at all? I didn't when I bought my first lathe a year ago to machine some pulleys for my turntables and spent 3 months just to get to be able to machine a part to size.
If you have experience I suggest a simple design from Elmer's series of engines, I love the standby design and then the wobbler but the wobbler is more of a challenge. Liney Machine have a couple of simple designs as well but you need to purchase the plans, they all run on both air and steam but compressed air is more readily available and much safer to operate if not as dramatic as steam.
Regards,

A.G

 

[firebird]

Hi Dennis

Just to make a point and confirm what others have said here, even a simple engine can take some getting going. You will see my little steam engine ran fine first time on air but getting it going on steam required a few mods and more than a little patience. It was a great way to learn though.

Cheers

Rich

 

[neptune769]

Hi Dennis,
Sorry for asking but have you got any machining experience at all? I didn't when I bought my first lathe a year ago to machine some pulleys for my turntables and spent 3 months just to get to be able to machine a part to size.
If you have experience I suggest a simple design from Elmer's series of engines, I love the standby design and then the wobbler but the wobbler is more of a challenge. Liney Machine have a couple of simple designs as well but you need to purchase the plans, they all run on both air and steam but compressed air is more readily available and much safer to operate if not as dramatic as steam.
Regards,

A.G

Hi A.G.
Fair question, don't be sorry for asking. Yes. I have 13 years of machining. I have done parts that were .125 long .093 diam. with a .062 hole in one end and a .010 hole all the way thru, to parts that had to be hoisted into the lathe with an over head gantry. I have run numerous manual lathes and a couple CNC. Also ran manual Bridgeport type mills as well as a bunch of different types of CNC mills. A couple parts had a .0002 tolerance. I prefer small parts. I didn't like having to use a hoist to load the part. I have worked with all types of materials Aluminum, Brass, CR steel, Inconel, Hastelloy, 304 & 316 SS, Titanium, Copper, Bronze/beryllium, Cast iron, Graphite, Delrin, Virgin Teflon, Acrylic & Polycarbonate. I have worked for a company that catered to the refineries as well as a company that manufactured Medical Diagnostic Equipment. Several job shops as well. I also worked for a company that all they had were Screw Machines. You talk about noisy. Get about 100 machines running with bar stock feeders all running at once. The stock whips around in the tubes or the feeders. I think they were 20 foot long or so. You can say I have some experience. If you have any other question feel free to ask.

Regards,
Dennis L.

 

[blighty]

going by that lot, you should go and build your self a small 24 cylinder H configuration type engine ;D

 

[neptune769]

going by that lot, you should go and build your self a small 24 cylinder H configuration type engine ;D

LOL no I don't think sooooo!!! I have a lathe without a motor, a bench top drill press, hack saw and files. Lathe motor coming soon. I have a 4 jaw chuck so I will be able to do a little rectangular parts. I will let you all know when I start so you can wish me luck.

 

[hobby]

Hi,

With all that experiance in machining, I would like to suggest doing what I did, just for the fun and challenge of it,
First, I had no machining experiance before I started this hobby,
but going this rout to build a steam (compressed air) engine worked out real well, has given me confidence to design air engines from scratch.

Here is the rout I was talking about,

I "googled" steam engines, and found a good animation on "how stuff works" website, this animation explained and showed how a double acting steam engine worked, as with a locomotive,
this animation was so complete in detail, that I studied it until I finally was able to figure out a way to design my own.

Once you build a double acting model, then single acting models are much easier to design and build.

But that animation really makes it easy to learn when starting out in this hobby.

 

[Chazz]

Well it seems youv'e been 'around the block' when it comes to machining as it were, you just need a push out of the nest.

As to steam vs air, may I offer a few observations that are just my humble thoughts;

First, I didn't see you mention any comfort level, skill sets, regarding soldering, brazing or welding? Kinda needed for steam work.

Second, in a lot of my checking out some different 'hobby machine' exibitions, due to insurance and safety reasons, motors running indoors have to run on air (usually supplied by the shows host through a distributed header?)

Third, are you aware of 'your' local codes regarding boiler construction, testing and certification?

Beleive me, I am NOT trying to disuade you from the world of steam, but make an air motor or 2 whilst learning about boiler construction, the last thing you want to do is try to explain why little niece, nephew, grandchild has to be rushed to the hospital because your 'first' boiler blew-up while they were watching! :big:

Regards,
Chazz

 

[neptune769]

Well it seems youv'e been 'around the block' when it comes to machining as it were, you just need a push out of the nest.

As to steam vs air, may I offer a few observations that are just my humble thoughts;

First, I didn't see you mention any comfort level, skill sets, regarding soldering, brazing or welding? Kinda needed for steam work.

Second, in a lot of my checking out some different 'hobby machine' exibitions, due to insurance and safety reasons, motors running indoors have to run on air (usually supplied by the shows host through a distributed header?)

Third, are you aware of 'your' local codes regarding boiler construction, testing and certification?

Beleive me, I am NOT trying to disuade you from the world of steam, but make an air motor or 2 whilst learning about boiler construction, the last thing you want to do is try to explain why little niece, nephew, grandchild has to be rushed to the hospital because your 'first' boiler blew-up while they were watching! :big:

Regards,
Chazz

First a note on children getting hurt. I definitely would not want my 7 year old daughter to get hurt. She already has to worry about me being a member of "DADD, Dads Against Daughters Dating" ;D

Before this was posted I had decided to work on just Air driven motors for now anyway. I started reading "THE
EXAMINATION & TESTING OF MINIATURE STEAM BOILERS". There is allot I did not know or consider about steam. Plus I had no idea that there were regulations regarding building a "hobby" boiler. As for skills I have some experience with sweating of plumbing fittings and Electronic Circuit boards. I trust my PCB soldering more than the fittings. At least it looks better. As for Brazing and welding. I have zero experience with that.

I have to consider also my limitation on tooling. You can only do so much with a lathe, drill press, belt sander, scroll saw and some hand tools. I don't have access to the good tools anymore. The lathe I have is an Atlas 618. It is not even in the shop yet. My father still has it. But as I mentioned before, it needs a motor. So there is no rush getting it over here. As for tooling it has. I was told there is a 3 jaw & 4 jaw chuck, Face plate, Follow rest, QC tool post, 9 boring bars, Live center, Drill chuck & Collet set with draw bar and I think all the change gears for cutting threads. So it will get me started. I have a lead on a motor that I will check out hopefully on Thursday. I can't afford a new one at the moment so I'm looking for a cheap used one.

I would like to say one last thing. I am just in awe by some of the craftsmanship I have seen on this forum. I hope one day I will be able to make at least on piece look & work as good. I know I will never be able to build a CZ motor. That is a work of art. I do plan on trying something in the future like the Swash plate motors like Captain Jerry has made. Very cool!!!

Regards,
Dennis L.