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Author Topic: (ENGINE CONVERSION) Converting a two cyl. air compressor into a steam engine  (Read 51343 times)
biggkidd
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« on: March 24, 2012, 11:03:07 AM »

Hi i'm New here. Names larry. Recently got a 3G phone which gives me internet for the first time in four years. We live off grid and I've been working on building a steam engine . I've gotten the boiler built and started on the eng. when I found this site. The proposed engine is an inline two cyl. cast iron 20 CID air compressor made by Emglo. So far I have the jugs off the crank case and have started making the cross head ? ( not sure that's the right term ). I plan to use the original poisons cut off flush at the oil ring groove, and the original cyl. . I have gotten a hardened half in. rod to connect the pistons to the conn. rods.
Will post more later if you guys are interested. I can sure use some help / guidance as I know nothing about steam power. I'm building this to be our main power source as gas prices are eating me alive.
   Thanks Larry
« Last Edit: September 21, 2012, 11:28:18 AM by PatJ » Logged
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« Reply #1 on: March 24, 2012, 11:21:00 AM »

Hi Larry, welcome to CSEE.

I have seen some people convert existing equipment to steam power, including old lawnmowers, refrigeration compressors, weed eater motors, etc.

One of the problems that I am aware of is getting condensed water (condensate) into the crankcase, and I am not sure how people handle that.

The engines made from such items are called single action, since steam acts on the piston(s) in only one direction, as opposed to most old steam engines where the steam acts on the piston(s) in both directions.  Single action engines work fine.

One challenge, and perhaps the larger challenge is to find a boiler that is sufficient to run the engine.  Boilers have to be operated carefully.

I know of one site online of a home powered by a steam engine, I will try and dig out that link.

I sort of perfer to be off-grid myself in many ways, and avoid some of the chaos of the world.

I will post the link of the home-powered steam engine when I locate it.

Good luck on your engine.  Can you post photos?

Pat J


Edit:
Here is the steam engine powered home generator and boiler I was referring to:
http://www.youtube.com/watch?index=62&feature=PlayList&v=xksDjfLbcQ0&list=PLCFE3A43B1AC5779D

I believe this fellow makes his own windmill and steam engine generators or alternators from hand-wound coils and permanent magnets.

« Last Edit: March 24, 2012, 11:28:33 AM by PatJ » Logged

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biggkidd
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« Reply #2 on: March 24, 2012, 02:04:26 PM »

Hi Pat
 Thanks for your reply. I've seen that link, that fellow makes some amazing things .
I didn't explain my project ver y well, let me try and do better. Its going to be double acting . I've unbolted the cylinders from the crank case and i'm taking the pistons off the connecting rods. I'm making slide rods to go between existing rods and pistons. The pistons i'm cutting flush at the oil ring and drilling & tapping to thread to slide rod. Which in turn  will hook to the connecting rod. Building  a case above and around this to seal the crank case. The slide rods will pass through this and into a tower the lower head, cylinder, and upper head will rest on. Its the valves and timing giving me trouble.  There is no eccentric on the crank to work with. May be able to make one. I'm making the cross head and tower & other parts out of mild steel. The slide rods are hardened half inch steel rod.

 The boiler is made and pressure tested. Volume of steam is Unknown.
 Thanks Larry
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« Reply #3 on: March 24, 2012, 06:27:42 PM »

Larry-

Sounds like you have put a lot of thought into what you want to achieve.

I guess my only concern would be with the top of the piston from a combustion engine being rigid enough to take stress in the upward direction.  I guess you could try it, it may work perfectly.

I did make a steam engine using a Briggs piston, but it was single-acting.

I don't pretend to understand everything about valve gear, but I have reverse-engineered the Stanley 20 hp auto steam engine, and believe I understand that valve gear pretty well.

My thoughts are that given what I know about the Stanley valve and valve gear, I can make a valve and valve gear for any given steam engine that will function well, but I would not claim that the design is necessarily perfect.

The short story on valve/port/passage design is that you size the port length at about 80% of the cylinder diameter (length measured perpendicular to valve travel).  Then you size the width of the port using a spreadsheet which takes into accout the bore, stroke, operating pressure and rpm, etc.

Having the size of the steam port, you then make the exhaust port twice that width, and make the bridges between the steam and exhaust ports equal to the width of the steam port.

Next, I lay out the valve and eccentric to allow the steam port to open a maximum of 80% when the valve is in its extreme position.  This position determines the outside edges of the valve, and the travel (throw) of the eccentric.  The target cutoff is around 70%.  The cutoff could be adjusted later if desired using the same port layout, by changing the valve and eccentric.

I have seen others generate reams of paperwork, complex calculation and digrams, but no one has ever proven to me that their design is any better than the one I mention above.  My method is simple enough for anyone to use, and I feel fairly accurate as far as setting the critical parameters such as admission, cutoff, release and compression.

The eccentric generally goes on the crankshaft, and if that places the eccentric rod too far out from the engine, then a link is made between the valve stem and the eccentric rod.

Do you have parameters for your engine and engine operation such as bore, stroke, operating rpm, operating pressure, etc?

I can run my calcs, and then others can comment and provide additional feedback if they think I am in error.

Pat J
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fredrosse
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« Reply #4 on: March 24, 2012, 10:34:53 PM »

Welcome to the forum, and best wishes with your steam engine building. 

A fairly easy conversion of a two cylinder air compressor to a steam engine is to mimic the Westinghouse high speed single acting engines of about 100 years ago.  These engines were, developed just to power high speed generators that Westinghouse was promoting at that time.  The same setup is used in the Stuart Sirus engine, and the Stuart engine was produced to run small generators for the British military in WWII.

There are some problems with converting the air compressor to a double acting engine, the reversed loadings on the connecting rod bearings (upstroke/downstroke) is something the air compressor's bearings are not designed for.  Water into the crankcase for the single acting setup is not necessarily a problem with proper design features, as witnessed by the Westinghouse and Stuart engines.

I built a uniflow domestic heat-power module (generates the house electricity and heats the house with the exhaust steam) for my home about 30 years ago, using an industrial engine as the basis for the steam engine.   The steam system, which included automatic firing with a coal stoker ran for 4 seasons  with only 4 forced outages.  There is an ASME paper describing the project, along with a diesel powered system that did the same service and ran for several years also.  Both of these systems ran unattended 24/7.


* 385365_Westinghouse-Engine.jpg (51.1 KB, 600x400 - viewed 726 times.)

* WESTINGHOUSE COMPOUND.jpg (114.71 KB, 531x749 - viewed 526 times.)

* sirus cutaway.bmp (117.24 KB, 200x200 - viewed 8813 times.)
« Last Edit: March 24, 2012, 10:39:40 PM by fredrosse » Logged
biggkidd
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« Reply #5 on: March 25, 2012, 11:15:52 AM »

Pat, Fred
  Thanks for your replys. The pics are great. I need to figure out how to do pivs with this phone. Let me try and answer some of pats questions .  First as an air compressor the compressor turned about1500 RPM . The bore and stroke are 2.5 in. bore and 2.0 in. stroke. I'm going to shoot for 600-1000 RPM @ 50-70 PSI. The RPM is not overly important as I can use pullys and belts to get it high enough. 3000-5000 RPM to keep the altenator cooling. I'm running old school AC Delco120 amp  alt..
If I knew the hp conversion for gas to steam I could tell you how much power I need to make . A 25 hp gas eng would give me plenty of power with a comfortable reserve. Our largest draws are the fridge year round an AC in the summer. 
I would  like to set the engine up to handle200 PSI. That way if i need to I can build a higher pressure boiler. I wasn't able to do any research before starting this project. Infact thats why I bought this phone so I could access the internet .
I sure appreciate any and all of your help.
Thanks larry
« Last Edit: March 25, 2012, 11:24:35 AM by biggkidd » Logged
fredrosse
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« Reply #6 on: March 25, 2012, 01:44:34 PM »

Many industrial air compressors are designed for 175 PSIG maximum, and that would be a good maximum steam pressure for the life of the engine. 

Engine power was historically calculated with the PLAN formula, where P is Mean Effective Pressure, in Pounds per Square Inch (PSI) , L is the length of piston stroke, (in feet), A is the area of the piston, ((3.14 / 4)  x diameter squared)  in square inches, and N is the number of power strokes per minute.

P x A gives the average force on the piston.
P x L x A gives the work performed by one stroke of the engine.
P x L x A x N gives the work performed by all the power strokes acting in one minute.

One horsepower is equal to the work of 33,000 ft-pounds per minute, so Horsepower = PLAN / 33,000
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fredrosse
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« Reply #7 on: March 25, 2012, 01:57:56 PM »

Your engine worked out as an example:
P = 50 PSI MEAN EFFECTIVE PRESSURE
L = 2INCHES / 12 = 0.1666 FEET STROKE
A = 2.5 INCHES BORE, = 4.91 SQUARE INCHES
N = 2 CYLINDER SINGLE ACTING @ 1000 RPM = 2000 POWER STROKES PER MINUTE

P x A gives the average force on the piston. = 50 X 4.91 = 245 POUNDS FORCE

P x L x A gives the work performed by one stroke of the engine. = 245 * 0.1666 = 40.9 FT-POUNDS PER POWER STROKE

P x L x A x N gives the work performed by all the power strokes acting in one minute. = 40.9 X 2000 = 81800 FT-POUNDS PER MINUTE

One horsepower is equal to the work of 33,000 ft-pounds per minute, so Horsepower = PLAN / 33,000 = 2.48 HORSEPOWER.

NOTE THAT A MEAN EFFECTIVE PRESSURE OF 50 PSI PROBABLY CORRESPONDS TO 70-100 PSI STEAM INLET PRESSURE, AND THAT 1000 RPM IS FAIRLY HIGH, BUT NOT UNWORKABLE.
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biggkidd
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« Reply #8 on: March 25, 2012, 05:37:49 PM »

Wow Fred
  Thanks for all the great info and formulas. Two and a half hp doesn't sound like a lot but forty ft. lbs. of torque sure does. A single acting would be a little easier to build. The rod bearing caps look pretty stout though, they also would be easy enough to reinforce.     Pat had mentioned the pistons handling reverse pressure, do you have any thoughts on that ? I would sure like to make this a double acting eng.. If possible.

Torque is a more use able figure for making electricity. If i remember correctly a gas eng Makes about 1.1 ft.lbs. of torque per each 1 hp. A steam eng seems  to be considerably higher.
Do you guys think since i'm  using aluminum pistons I need to face them, maybe with steel?
Thanks again for all the help. This has been a wet rainy weekend so i haven't  made any progress.
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« Reply #9 on: March 25, 2012, 09:55:10 PM »

Larry-

Fred is a working ME, and I am not, so generally if Fred has an idea, I second the motion.

I think the examples Fred shows in the photos would be the way to go, at least for an initial engine, since their concepts have been carefully thought out, and they were actual commercial grade, well functioning engines.

Fred's examples are also very similar to what it sounds like you have, and I am afraid that if you get bogged down in a double acting engine, you will not have a good working design.

I would say if you want a double-acting engine, then perhaps design one with that intent, and you will have a much better chance of succeeding than modifying what you have.

I saw a photo of an engine made from a refrigeration compressor, used on a launch.
I will find that and post a link.  Very similar arrangement to what you have/want.

I would err on the side of a slower speed, as you know that will probably work.
If your speed gets too high, you may have all sorts of issues, such as your shaft coupling flying apart, alignment issues which cause a problem from too much vibration, etc.

The piston valve across the top of the engine is an excellent idea in my opinion, and is not that difficult to make.  I actually used a similar valve on my first single-action steam engine that I made in high school.

The trick I think will be to get something working, and then operate it in somewhat of a "safety" mode, and then modify/adjust as necessary to refine the design to its final configuration.  It will certainly take a little tinkering.

I am off to find the link I mentioned.

Here is a link to "The Steamboating Forum", which I find very helpful since these guys (like Fred) operate full sized working engines, not scale models, and so have real-world experience with them.  Unfortunately, a lot of my knowledge is book knowledge, but I have build steam engines and boilers, and operated both.

http://www.thesteamboatingforum.net/forum/viewtopic.php?f=8&t=523&start=20

And here is a link to the page of the guy who uses a refrigeration compressor in his boat:

http://smaalders.net/barts/boat.html

And a photo of his engine:
http://smaalders.net/barts/engine.html

I think a wise thing for you to do is email this guy and pick his brain, since he has a working design, and that could save you countless hours of design as well as maybe save you from making a design that does not work well.

As far as steam on aluminum, I see no problem with that.
The only problem I have had with steam engines is forgetting to flush the condensate out of the cylinder after running the engine.  I put the engine in storage for several months, and when I tried to used it again, the piston was rused solid to the cylinder wall, requiring a total dismantle/cleaning.

Pat J
« Last Edit: March 25, 2012, 10:03:37 PM by PatJ » Logged

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