View Full Version : Level of skill req'd. to build model steam engine??

brian Rupnow
05-19-2008, 12:11 PM
How many of you have built a working model steam engine? I have looked at some SIMPLE kits that are relatively inexpensive (as in under $100). According to the sales litrature, they contain "sand castings", all required fasteners, and all necessary gaskets. I have done enough with my lathe to feel fairly confident about #1-turning a shaft to a finished diameter. #2-facing a part. #3-drilling and boring to a finished inner diameter. My capability to get a real smooth finish is still somewhat questionable, My success in threading a 3/4" diameter rod was very "iffy"---couldn't get the lathe to run slow enough--when "picking up the thread" I was okay for the first 3 or 4 passes, then messed up and started cutting in a different place. (slowest my lathe will turn is 115 RPM.) Just how good does your skill level have to be before trying to machine one of these kits?

05-19-2008, 12:32 PM
Any completed project is nothing more than the culmination of a series of simple machining procedures. A steam engine is no different.

It does help to have a concept of how the completed project functions. This gives an understanding of the relative accuracy neded in each step. As a general rule, a larger engine is simpler than a smaller engine as they are somewhat more forgiving. A simple oscillating engine is a good place to start. Once a working engine has been completed, you are usually hooked, and can move on to more complex styles.

05-19-2008, 12:32 PM
Skill doesnt matter. Its porportionatly sized after your scrap box. After some scrap your your scrap box will be much smaller. :) Either that or your not learning anything.

p.s. scrap parts are used to make smaller usefull pieces or ineviably smaller scrap up to the point of 100% chips!!!

John R
05-19-2008, 12:41 PM
My first real project was a steam engine. It came out fine. The more difficult parts you just take slow and easy.
Good luck
John R

brian Rupnow
05-19-2008, 12:43 PM
I don't have any problem with understanding the concept of how a steam engine works. I am a design engineer, and I design custom built machinery for a living. www.rupnowdesign.com I do however, wonder about my own machining capabilities. I have been designing machinery for 43 years. I have been playing at my new lathe for 3 months. Believe me, there is a big difference between knowing the theory behind using a lathe, and the actual hands on experience of running one. I am a pretty handy fellow with "hands on" machine building, and I see building a model steam engine as a good way of improving my skill level. Just not sure I'm ready to take that step yet.

05-19-2008, 12:45 PM
You might want to try a simple engine made from barstock first; then if you spoil a piece you won't need to go through the hassle of getting another casting, and you won't have the difficulty of setting up castings for machining.

Or try a simple kit. You need to start somewhere! The most simple kit will teach you more than you might believe possible. The first engine I tried to build, I never did finish...but I learned enough so I could build the second one.

What kits are you looking at?

On threading: if your lathe doesn't have a thread dial, you can always leave the halfnuts engaged and run the lathe in reverse to get back to the start. However, that's not always possible to do if you're threading up to a shoulder.

05-19-2008, 01:01 PM
The hardest part to make will be the crankshaft and there are several ways to do that. Doing machine work requres some common sense to figure out a solution. Think everything out and work out all the problems before you start on each part.

Yep, you can do it but don't get in a hurry. Also, it's not easy working with castings. I am working on a small steam engine and a hit and miss engine for two friends now. You have to do carefull planing when machining a casting so know the overall end result BEFORE you start to machine it. Things don't always come out as planed with a casting.

BTW, you can change the pulleys on the motor and headstock to slow the lathe down and that won't affect the feeds and threading.

05-19-2008, 01:10 PM
hello. looks like we share a common background (www.sigma-f.com)
I had a look at your site and got a real kick out of that "guard-railer"
(name?) listed as "Prototype Machinery"! To be completely honest
I couldn't stop laughing -- very clever! (Maybe its me, I've never seen
such a thing before) -- whats the min turn radius on that thing??

As far as the steam engines go -- there are much more experienced
people here than I, but I have tried my hand at a few of the
Elmer's Engines. Really fun. I've got a biggish lathe and turning some
of the smaller parts was a real challenge.

Plans are available online, just try a search engine. I've never
tried my hand at anything that required castings, though.


brian Rupnow
05-19-2008, 01:51 PM
Tony---That critter had a turn radius of about 8 foot. It was intended to be a "cross over" machine, something between the very small curb laying machines that do an 8" high curb, powered by a 3 HP. gas engine, and the big industial curb machines powered by a 4 or 6 cylinder engine that do up to 16" curbs. It did work, but the man who was developing it either ran out of money or got caught up in other enterprises. I find that happens a lot. People come to me with some great idea they wish to develop, have enough money to build one 80% successful prototype, then fade away before the final 20% is fully worked out to the point where the machine is marketable.

05-19-2008, 01:58 PM
i built a wobbler as my first engine.. there are lots of plans on the internet for really simple bar stock engines. with the wobbler, my first one needed almost 100psi to run, now im on my third and i can blow into it and it will run. it was good practice at making things smooth ans fit properly. the first one didn't fit very well, the piston was too loose inside the cylinder, and i lost lots of air pressure around the cylinder.

i would give that a try, it uses about $0.30 in scrap to make, and you can use almost any material you wish. theres one called "Lucy" (i don't remember who made it) where the crankcase is machined out of a block of Lucite (Plexiglas).

and seeing an engine that you made form bar stock run for the first time is pretty cool too...


these are pics of the first one i made, after the aluminum piston and cylinder welded together.. i sleeved them just so i wouldnt have to use a solid block of brass. and the flywheel is made from a VCR head....

05-19-2008, 03:08 PM
This is the first steam engine I built:

I was fortunate in picking this as my first engine rather than one of Ray's other designs. Since that engine I have built several more of his engines and they were all a challenge. But, they do use barstock and the plans are very reasonably priced. There is also a Yahoo newsgroup that covers these engines:

05-19-2008, 03:51 PM
I'm also an engineer. Your drawings that you create in solid works will improve in the dimension/ease of fabrication area. You'll be thinking more about how the parts will be manufactured vs make it like this and dimensioning accordingly

05-19-2008, 04:08 PM

have a look round my site http://www.davekearley.co.uk

I started a few years ago on a Stuart Turner kit (10v) and i only had a tiny Unimat SL lathe and zero knowledge of machining. Admittedly i had to ask a friend to help with the bigger bits.

When i got a decent lathe i built a Stuart beam engine as practice for my main desire:- a 3" scale traction engine. This engine is now nearly done and i have even written and published a two part series of books dialoguing the build progress from a beginners point of view.

As soon as this one's running, I'm starting a 6" scale one!

What i am trying to say is, get a bit of practice, read lots, ask lots and dive in. It seems daunting to look at a running engine but when you take it all apart, most of the bits are quite basic.

As others have said, a simple wobble-engine from scrap is great, i made one at school and still have it somewhere, it was ugly as hell but did work.

Good luck

Quetico Bob
05-19-2008, 04:27 PM
Don't think it's so much a matter of skill, rather more patience. If you can comfortably run your machine you're skilled. If you know how to set up and cut your work, you have the knowlege. When you can build your part without any boo boo's to exacting tolerances, then, you have mastered the art. Unfortunately for most, that's a lifetime of experience.

For the rest of us, and its just my opinion. Jump in head first and give it a try knowing your going to make mistakes. I agree 100% with ahidley. Works for me and sometimes I even surprise myself. Still using scrap with partially cut cam lobes and journals in it.

Built this last fall after several attempts just so i could say I did it. Would it ever run? Don't know. Didn't have any plans but researched the concept. Hardest thing was figuring out how to make it in a 3 jaw chuck, don't have a four, but thats half the fun. For me it's a lot of trial and error to get comfortable with turning something. Some day I will get a kit and give it a try, but before I cut into the $100 casting I'll keep working on scrap till it's comfortable. Would love to build my son a working engine some day. There's no reason you can't practice on your own design of a crank, piston or cylinder even if there's no chance it would actually work, as in my case. The principle is there.

Sounds like you already have the "skills" won't know for sure till you try.

Best of luck,
Cheers, Bob




05-19-2008, 05:56 PM
You can Do It!!! That is the whole reason I got into this hobby was to build steam engines. If I can do it Youy Can!!! I started with oscilators and have progressed to bigger and better and more complicated. Each one has taught me new techniques, new tools and new challenges that I never thought I could overcome. Get to work!!! Don't put it off! It is like the potatoe chip, bet you can't do just one!!!! I have 14 done and running and as soon as you are done with one you are tackling the next one. I try to stick with the plans from bar stock because if you screw up a casting....you're done and lost the whole ball of wax. Dive in, The water is fine (frustrating but fine). Fred

brian Rupnow
05-19-2008, 07:01 PM
I have downloaded a free plan for a "wobbler" from the internet, and it is made of bar stock. It is made from aluminum (got that) steel, (got that), and brass (which I will have to buy). this engine has a 3/8" bore and a 1/2" stroke and looks fairly simple. I assume that a reamer for the cylinder bore is an absolute necessity???? I will model it in 3D cad, just to get a good "feel" for it. The amazing CAD package that I use (solidworks) will let me animate it and actually make it run.

brian Rupnow
05-19-2008, 08:41 PM
Son of a Gun!!! This is really neat! This is the "wobbler" I downloaded from the net earlier today. I converted all the plans to 3D CAD solid models, and I can actually run it on my desk top. I think I can save it as a file that anybody can open, and it will show the engine running. I will do that tomorrow.---Brian

brian Rupnow
05-19-2008, 08:51 PM
Holy Cow!!!---Check this out!!http://i307.photobucket.com/albums/nn294/BrianRupnow/th_FULLASSEMBLY-1.jpg (http://s307.photobucket.com/albums/nn294/BrianRupnow/?action=view&current=FULLASSEMBLY-1.flv)

05-20-2008, 12:09 AM
Yup,you got the addiction now:D

05-20-2008, 03:38 AM
If you have a small boring bar, then dont worry too much about the reamer. I find boring gives me an excellent finish.


05-20-2008, 05:38 AM
How many of you have built a working model steam engine? I have looked at some SIMPLE kits that are relatively inexpensive (as in under $100). According to the sales litrature, they contain "sand castings", all required fasteners, and all necessary gaskets. I have done enough with my lathe to feel fairly confident about #1-turning a shaft to a finished diameter. #2-facing a part. #3-drilling and boring to a finished inner diameter. My capability to get a real smooth finish is still somewhat questionable, My success in threading a 3/4" diameter rod was very "iffy"---couldn't get the lathe to run slow enough--when "picking up the thread" I was okay for the first 3 or 4 passes, then messed up and started cutting in a different place. (slowest my lathe will turn is 115 RPM.) Just how good does your skill level have to be before trying to machine one of these kits?

I made my first steamengine when I was 13 years, last fall I made my 2nd, a rotary valve steam engine, see link. Runs like a champ:) recoment building it;)


05-20-2008, 08:23 AM
I am in the middle of building "Georgina," an engine kit from Brunell Models. It is an overcrank model and is accompanied by a "how to" book by Tubal Cain. Busy Bee Tools has another book "Building Simple Model Steam Engines," also by Tubal Cain. These are all pretty simple designs. I am presently building a little two cylinder crane engine together with my grandson, (16,) and the book emphasizes that fit and finish are not THAT critical. If the fit is a bit iffy then it uses more steam! I am another engineer,but chemical/environmental, and that gave little machining experience. I jumped in by answering an add in HSM and bought a lot of eight Brunell engine kits. The biggest surprise was that these things are not built in a few hours, (or I am REALLY slow!) These British kits are great but quite expensive if you dont find a bargain resale. PM me if you want to chat further about these, I grew up near you. Duffy

brian Rupnow
05-21-2008, 12:49 PM
Jeez!!! I'm glad that I am building this steam engine mostly out of scrap I had laying around. I just went out at noon and bought some of the miniature taps and dies required, a couple of small diameter drills, and a small die holder---it cost $82.00!!!!!! The money I saved on buying a casting kit has now been spent on tooling.:eek: :eek:

05-21-2008, 03:31 PM
Jeez!!! I'm glad that I am building this steam engine mostly out of scrap I had laying around. I just went out at noon and bought some of the miniature taps and dies required, a couple of small diameter drills, and a small die holder---it cost $82.00!!!!!! The money I saved on buying a casting kit has now been spent on tooling.:eek: :eek:

Thats just the beginning:D

Its addictive stuff. I have probably spent more on tools and bits than i have on machinery. The first engine was really expensive:eek:


brian Rupnow
05-21-2008, 04:09 PM
test (trying to add signature)---wow---it worked!!!

05-21-2008, 06:08 PM
Brian,have a look here:
An excellent site,with plans for a twin cylinder steam engine built from scrap stock.I've just started that one myself.If a dimwit like me can do it,you most certainly can:D

J Tiers
05-21-2008, 09:39 PM
As far as I can explain, you learn by DOING EVERYTHING THAT COMES UP.

DUCK NOTHING...... unless you genuinely do not have the tools required.

If it's hard, you really need to learn and work.


Best not at first when you have only one part and it must be right. But then, that can focus your mind wonderfully....... somewhat like an imminent hanging, with you as the star attraction..... :D

05-21-2008, 10:43 PM
Thats just the beginning:D

Its addictive stuff. I have probably spent more on tools and bits than i have on machinery. The first engine was really expensive:eek:


yes that is just the beginning, got a chuck out of that one. have patience, keep looking and like those serendipity books eventually you will have tools come your way like magic just because you want them; somebody you know is cleaning out a relatives place or an old boy retires and hears you're interested, or you buy some old tool box on kijiji for next to nothing or you spot them a garage sale (no interest in that one myself, to much garbage to sift through looking for the needle), whatever. Often there's not much liquidity for this stuff so it goes cheap, make your interest known, network and stuff will find you......almost adds to the fun of it :D

brian Rupnow
05-22-2008, 08:36 PM
I am beginning to have an appreciation for a good selection of parallels. I have the "milling set up" on my vice right now, with one of those Harbour Freight clone ugly nasty $39.0 milling vices. You were all correct---it is only marginally better than holding the peices of aluminum in my teeth while milling them. I am making progress, but having a difficult time keeping my milled faces parallel. I am sure this will improve somewhat as I accumulate a better selection of parallels and develop my set up skills.--And maybe SOMEDAY---an ENCO milling vice for use on the lathe instead of the P.O.S. I am learning with.

05-22-2008, 09:05 PM
A basic wobbler can be made with nothing more than a drill press , file and a hacksaw.

This one is super easy to do, I built it vertical and never realy used the prints just eyeballed everything.



brian Rupnow
05-23-2008, 08:11 AM
The engine I am building uses a brass cylinder (which I make) with a 3/8" bore. How do I make that bore and get it smooth enough to run a piston in it. Can I just drill it with a 3/8" drill and then machine the piston (which I am making) to fit whatever the bore size turns out at? I don't have a boring tool small enough, and I don't have a 3/8" reamer. If I make the bore with a drill, can I put the piston into the bore and lap it with toothpaste?---How do I do that?

05-23-2008, 08:20 AM
You may be lucky with a drill but they are not known for their precision abilities:(

How about a 3/8 milling cutter? drill the hole slightly undersize then carefully run the miller in, still not as good as a bit of HSS ground into a mini boring tool or a reamer i'm afraid.

Hmm, toothpaste? never tried that, possibly not abrasive enough, sticky as well:rolleyes:

Thinking of the hole again, if you ask nicely, maybe a machine shop will bung you some dud endmills out of which you could easily grind up a boring tool, even a broken twist drill can be pushed into service.


05-23-2008, 09:03 AM
wooden dowel with toothpaste or milling paste or fine sand paper wrapped around it.

05-23-2008, 10:29 AM
laddys way will work but is time conuming. First I would try drilling undersize by a 1/64 and then getting one of thoes flapper sandpaper thingies for a dremel tool and smooth the wall. then try laddys way. It needs to be round as well as parallel. Without boreing it and honeing it it will be tough.......

Charlie C
05-23-2008, 01:19 PM
Here is a occulating cylinder engine that was featured in Home Shop Machinist some years ago. Not too hard to build and kind of fun to run.

The tooth pick is holding the cylinder in the vertical as I broke the solder connection between the base and the up right cylinder plate.


brian Rupnow
05-25-2008, 11:31 AM
This weekend, just as I was preparing to make the "throw" on my model steam engine crankshaft, the on/off switch buggered up on my lathe!!! If I hold the green button on with my finger, the lathe runs, but as soon as I let my finger off the button, the motor quits. I thought it might be the centrigugal switch in the motor, but my neighbour who is an electrician said that the relay in the start button that is supposed to "latch in" to keep the lathe running is not "latching in". I phoned Busy Bee in Toronto on Monday morning, and they sent me out a new switch (free) the same day by mail. I hope to be up and running again later this week.

brian Rupnow
05-29-2008, 08:08 PM
Well, my lathe is up and running again. I made the throw for my crankshaft tonight and pressed it onto the shaft. ---Haven't tried my hand at silver soldering yet. I can not get over how small this engine is. I have never built anything this small before. I have a devil of a time machining to size on my lathe. I try to sneak up on the measurements with my lathe, but there is a mighty fine line between "just a little more" and "Oh Damn---too much"!!!! I have the connecting rod finished, so I guess the next thing will be to machine the cylinder. I did buy a 3/8" reamer, so I will hopefully finish the cylinder first, then machine the piston to fit it.---Brian

brian Rupnow
06-03-2008, 07:23 PM
Well, I'm 95 percent finished. The finish isn't quite as horrible as it appears in these digital photos, but it certainly has room for major improvement. Today was my first experience with silver solder---it worked okay, but damn, its messy stuff!!! I got silver solder everywhere that I wanted to, and a whole lot of places I didn't want to. Fortunately most of it was in places that were easy to clean up with some carefull file work. The piston really dragged in the cylinder, so I sawed a slot into an end of 3/16" mild steel rod, wrapped some 400 grit sandpaper around it, and "honed" the inside of the brass cylinder with the rod chucked in my variable speed drill. When everything was first assembled, there was a lot of friction. I put a little wheel bearing grease on the piston and the bearing surfaces and kept working it by hand untill it freed up quite a bit. I may rig up a wide rubber band for a drive belt and use my electric drill to drive it for half an hour to "wear the bearing surfaces in". I'm certain that these things must have to spin really freely to work on 5 or 6 PSI of air. I still have to make an air inlet adapter to screw into the #6-32 steam port, and I have to track down a proper compression spring to hold the brass cylinder block tight against the side of the aluminum frame. I have been building custom cars, drag racing cars, and hotrods all of my life as a hobby, and I don't ever remember building anything this small before. I quickly found out with this project how limited my machining options are with a lathe, so this week I went in and ordered a milling machine from Busy Bee, where I purchased the lathe.---This has been an exceptionally good year for my business, so I thought that I could probably afford some "write-offable" machinery.

06-03-2008, 11:03 PM
Man, I'm glad I dropped back by to see what's been happening here. This is the best thread I've seen in a while. Guess I'm gonna have to order that 8 X 14 Lathemaster after all. :D

brian Rupnow
06-07-2008, 05:45 PM
IT RUNS!!! IT RUNS!!! My God---its setting beside me right now, running like a ---well---like a steam engine!!!! I got the steam port machined and drilled this afternoon, and took apart an old mechanical pencil for the spring that holds the brass cylinder block tight against the side of the main frame. I ran up to the hardware store and got a peice of 1/8" i.d. polyurethane tubing and machined a small coupler and silver soldered it into an air chuck fitting. I tried it at a real low air pressure, and it wanted to run, but there was just a bit too much friction. I kept turning up the air pressure, and flicking the flywheel, and finally it started to run all on its own. I immediately had to call my wife down to the workshop to have a look, and then my next door neighbour!!! After it ran for about 10 minutes, it must have worn down some of the friction points, because I was able to turn down the air pressure significantly. I am totally stoked!!!

06-09-2008, 02:10 AM
Congrats, its always good when a project works.

Got the bug now, whats next??



06-09-2008, 03:03 PM
You could have stopped the silver solder from getting away from itself by using typewriter correction fluid as a "Stopper" Brian. To REALLY bed your new engine in give it a good solvent (Acetone) washdown, re-oil with a light oil with some Graphite dust mixed into it (HB Pencil lead dust) and run for extended periods, washing and re-oiling all the operating faces,pivots and cylinder bore. When It's fully bedded in it should work on just blow power.
Regards Ian.

brian Rupnow
06-09-2008, 03:31 PM
Circlip---Not to take anything away from Elmers design, but there is a lot of potential for binding in this little engine. The relationship between the center of the cylinder bore and the face of the cylinder which seals against the frame must be extremely accurate, otherwide the end of the connecting rod describes an eliptical path as it follows the crankshaft throw around its travel . This in turn is transmitted thru the rigid piston/connecting rod to the "throw" on the crankshaft, causing a bind between the connecting rod and the "throw". The ideal solution would be a self aligning ball bushing in the end of the connecting rod where it connects to the crank to alleviate this issue, but they don't make self aligning ball bushings that small. There is also a high potential for misalignment between the centerline of the piston and the centerline of the connecting rod, as they are made of two seperate peices connected by a threaded area. If I made this engine again, I would make the piston and connecting rod from one peice. I am really thrilled that the engine runs, and runs well. However, to make my engine run on breath power alone would require both hands over my arse and 3 men squeezing me!!!

06-10-2008, 03:46 AM
Sorry Brian, Elmer didn't invent the oscillator or wobbler as you guys over there call them, and to operate a FULLY bedded and free running example will NOT require the assistance of three of your mates.:rolleyes: :D

06-10-2008, 07:40 AM
Bet you can't build just one! It is a very addictive hobby. Frustrating when you have spent alot of time and it won't run and then weeks of fiddling with it and remaking parts, then shelving it for a while to return to it later. Great job! Fred

brian Rupnow
06-10-2008, 04:14 PM
I ran my new engine on and off over the last 4 days. One of my silver solder joints let go, where the crankshaft throw attaches to the crankshaft counterbalance. I took it apart and resoldered that. It ran okay after that fix, but it didn't want to run at anything much below 20 PSI of air pressure. (It never did.) In an attempt to get it to run at a lower pressure, I machined a larger, heavier flywheel. Even with the larger flywheel it doesn't want to run on anything less than 20PSI. I have been working all day on the computer, and the engine has been chugging away all day next door in the garage. I am pleased with the engine, and for a "first ever" I judge it to be a success. Hopefully, when I get my new mill, and get better at holding parallelity and tolerances, I will eventually build an engine that will spin on lung power.

Quetico Bob
06-10-2008, 04:49 PM
I'm just new to the steam thing as well but from what I have read so far it might just be a slight timing problem. Is there any way you can put a small blob of solder on the port (s) to shift them one way or the other ever so slightly? But then again I could be wrong, never could get the engine I built last fall to work. It wanted to go but would just lock up on pressure.

Cheers, Bob

06-10-2008, 05:22 PM
At the Cabin Fever Steam show in York, Pa A guy had alot of the steam engines that I have built out of Elmers Engines and Rudy Kouhoupt. I looked and his were all running on 2-5 lbs of air. All mine take more like 10 and up. We got to chit chatting and I asked him how? He said he never intends to run his engines on steam, only compressed air. So he makes his pistons out of a chunk of teflon. They ran so smooth and you really could blow into them and they would run. I thought it was really neat but I still want the steam option. Fred

06-10-2008, 05:44 PM
Hello, this is an interesting thread since I had one of my manufacturing classes last semester build this very engine. Of the 24 students that I had in the class, all, except one, managed to build working engines. Most of the students took their engines home as quickly as I could get them graded, however, I do have a couple on my desk that haven't been picked up yet and I'll take a couple photos so you can see their work.

Over the last three times that I have taught this class I have used steam engines as a means of capturing student interest and I think they have proved to be very successful to this end. I always find a different engine to use each year and generally build a prototype and redraw the plans, altering it as needed to meet my course objectives. On this particular engine I changed some of the features on it to cover different topics with my students.

One example is that we made the base plates from hot rolled mild steel that the student had to cut to rough size on the bandsaw, mill, drill, and tap. A later activity introduced the surface grinder which the students used to finish the top and bottom surface of the plate. Following this they used bone and wood charcoal to color case harden the plate. All of this provided a platform for students to experience different manufacturing processes and than reflect on them individually.

I'll try and get some photos taken tonight so you can see the student's engines.

06-10-2008, 05:52 PM
Some of my students ended up drilling the port holes in the wrong location and many of them we were able to fix by soldering plugs in the holes and than re-drilling. Of course we were using brass for our frames that made that option easier, but you could still drill and tap a plug that would work fine. If the engine you are referring to is like the above one they aren't too fussy. Most of the problems that I have encountered with them were the result of poor fits between cylinder and piston and or the piston rod length. Most of these engines worked on the first spin, but some of them needed some work-in time before they ran reliably.