| Building
a Model Steam Engine |
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I became interested
in Home Shop Machining about a year ago when I ran across
a website one evening. I haven't been able to find it since
but it was one of the things that inspired me to start this
page. When I visited homepages and saw really neat miniature
steam engines that actually worked I was fascinated. My ultimate
goal is to someday build a ¼ scale model of a Ford V-8 engine.
I knew that in order to someday do this I would need both
the skills and the machines and to that end I've set about
acquiring both.
You can look through
some of the other pages on my site and you'll see that I've
started accumulating the tools and knowledge. Once I had the
basic machine tools the next step was to learn how to build
working model engines. I'm going to document the steps and
the engines that I hope to build. I have 4 sets of castings
and plans, including a very nice Stuart that I'll be
starting on after I have 2 or 3 other engines under my belt.
I'm always looking for
plans for more engines. After I build a few steam engines
I plan on trying my hand at Internal Combustion and making
some hit & miss engines. I may try a Stirling engine just
to have a neat lid for my coffee mug.
This first steam engine
that I'm starting is a small vertical oscillating engine.
The castings are available through PM research for anyone
wanting to build the same. It's an excellent beginners project.
The kit comes with all of the castings, a small parts kit
that includes the screws but not the steam fittings.
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| This is
what the kit includes. A few of the parts have been started
on but very little work has been done at this point. Most kits
also include a detailed blueprint that show all parts to be
machined and an assembly view such as this. |
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| It's up
to you to take it from paper to metal. |
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| Shown above
are the completed piston rod and the incomplete crankshaft.
Below is the partially finished flywheel and piston. |
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I've spent a lot of time and effort tooling
up to make some of these toys that I've been thinking about
for so long. Now the shop is pretty close to where I want
it and I have all the tooling to start and finish the
engine kits that I have now and what I learn building these
engines will be needed when I move to Internal Combustion
and larger scale models.
I'm going to make more time for my models now.
They were the whole reason I started the shop in the first
place. The process of buying machine tools and accessories
then building all the attachments I couldn't afford to buy
was fun and educational but now I want to start devoting more
time to the basic reason I started my shop. Every time I build
something of my own I regret not being exposed to machine
work 20 years ago.
This is the finishing step for the crankshaft;
I'm putting a bevel on the ends of the shaft.
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| The hub
of the flywheel has been dyed for marking and a center square
is used to find the center. |
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| After finding
the center the flywheel is secured in a 4" chuck to start the
drilling operations. First a center drill is used to locate
and start the hole. This is done to keep the long drill bit
from "walking" when it tries to start a hole. 3 machinist's
squares were used to mount the flywheel squarely on the chuck. |
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| Now
we can start. |
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| Once the
center drill has started the hole the drill bit can be chucked
up. Since this was an aluminum flywheel and the center hole
wasn't going to be that large I skipped the pilot hole and went
directly to the 15/64" bit and started drilling. |
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| And the
final step in the process is to ream the hole to its final dimension.
A ¼" reamer is being used here to give an accurate and smooth
bore for the crankshaft. |
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| Now to
clean up the sides and outer diameter. |
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| A few minutes
on the polisher and flywheel, piston rod and crankshaft are
complete. |
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| With the
first three parts finished it's time to start on the steam chest.
Everything in this kit is small enough that a 7" lathe with
a 4-jaw chuck is all that would be needed. Having a mini-mill
though I just had to use it :) The top, bottom and back of the
chest have to be machined flat. |
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The castings for this
model are aluminum. This is a very easy metal to machine but
great care must also be taken not to fracture or break the
castings by clamping them to forcefully. I suspect that replacement
castings are available at reasonable cost but haven't had
to look into it yet. Maybe someone who knows can drop me a
note and let me know.
I've been looking at
other models and thinking about my own and still haven't decided
what color to make it J. Seems kinda trivial
I know but hey, there's a lot of work in even the most basic
model as I'm hoping to show. I for one want it to look as
nice as I hope it will run. While I may not have decided upon
a color yet I do know that I'm going to be powder-coating
it instead of painting it. After all, why have a powder-coating
rig if you're not going to coat everything you can stuff in
the oven?
The beauty of learning
to do all this on my own is that I get to do everything my
way. I've never been to trade school (Ok, I have, but Commercial
Diving doesn't apply here) and I've never taken a class on
machine work so I'm self-taught from the beginning (and it
shows as I am so often reminded) and tend to order my operations
in a haphazard way. I've gotten some of the machine work done
on the model and I'm satisfied with that for right now. Knowing
that I'm going to powder coat the model I'll probably do the
pieces in batches as I finish them rather than doing all the
machine work and then all of the powder coating. This way
I get to see some of the work all colored and shiny and it
makes me want to jump back to the machines and finish the
next batch of parts. I know, I know, I wouldn't last a week
in a production environment but doing it my way seems to keep
me more satisfied over the whole length of the project and
I find that I'm less apt to lose interest and put it on the
shelf for something more interesting.
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The castings for this
model are aluminum. This is a very easy metal to machine but
great care must also be taken not to fracture or break the
castings by clamping them to forcefully. I suspect that replacement
castings are available at reasonable cost but haven't had
to look into it yet. Maybe someone who knows can drop me a
note and let me know.
I've been looking at
other models and thinking about my own and still haven't decided
what color to make it J. Seems kinda trivial I know but hey,
there's a lot of work in even the most basic model as I'm
hoping to show. I for one want it to look as nice as I hope
it will run. While I may not have decided upon a color yet
I do know that I'm going to be powder-coating it instead of
painting it. After all, why have a powder-coating rig if you're
not going to coat everything you can stuff in the oven?
The beauty of learning
to do all this on my own is that I get to do everything my
way J. I've never been to trade school (Ok, I have, but Commercial
Diving doesn't apply here) and I've never taken a class on
machine work so I'm self-taught from the beginning (and it
shows as I am so often reminded) and tend to order my operations
in a haphazard way. I've gotten some of the machine work done
on the model and I'm satisfied with that for right now. Knowing
that I'm going to powder coat the model I'll probably do the
pieces in batches as I finish them rather than doing all the
machine work and then all of the powder coating. This way
I get to see some of the work all colored and shiny and it
makes me want to jump back to the machines and finish the
next batch of parts. I know, I know, I wouldn't last a week
in a production environment but doing it my way seems to keep
me more satisfied over the whole length of the project and
I find that I'm less apt to lose interest and put it on the
shelf for something more interesting.
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| Once the cylinder casting is drilled
the nest step was to ream it to .50" and give it a smooth bore.
After finishing the bore, 4 more holes were drilled through
the cylinder casting to secure the caps. This is the bottom
cap being reamed to size after drilling. |
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| The cap was clamped to the cylinder
to mark the locations of the screw holes. |
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| With the cylinder almost complete
I started on the base casting. I had to mill both the top and
bottom of the casting to get flat surfaces to work with later.
The casting was clamped to an angle plate and then transferred
to the mill. |
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| I made light passes with a ¾" 2-flute
end-mill and leveled the feet. The casting was then flipped
over and the top surface was completed. |
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| Finding the centers for the crankshaft
& cylinder pivot turned out to be something of a task. I
didn't have an easy way to locate the centers on the casting.
Realizing that the "back" of the casting has 3 flat surfaces
on the same plane I took the simple shortcut of taping a photocopy
of the blueprint to the casting itself to correctly locate the
holes. |
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| The photo above shows the working
print for the engine, the photocopy that I made and the cutout
glued to the casting. I had previously lapped the back of the
casting so the surfaces were well suited to this technique. |
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Once I realized the
blueprints were 1-to-1 I figured I could just Cut-and-Paste
in a real world sort of way. It seemed silly at first but
after thinking it over and trying it out I like the idea.
I may try this again on the other models. The next one in
line is the PM Research #3A mill engine followed by a Midwest
Products oscillator/boiler combo and then my Stuart 10V. What
a difference when I look thru the kits, the first three are
all similar but the Stuart is in a whole different league,
I'm really looking forward to building that one but I realize
that I need the practical experience of building the first
three to develop my abilities.
I'll say this, machine-work
teaches you patience. Unless you have a tremendous natural
ability you'll either learn to be patient and take your time
or you'll make a whole bunch of scrap. That may not be so
bad with designs based on using various stock sizes of material,
but when you're working with castings it's a whole different
ballgame.
Once the centers were
marked on the main casting I clamped it to the small drill
press and drilled the undersize holes.
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| And then the other. |
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| After the holes were drilled and
reamed to the correct size I lapped the hole for the crankshaft.
I have a small set of laps for just this purpose. |
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As soon as the mounting
holes and steam passages are drilled this casting is finished.
Since this is a learning
process I'm trying different techniques as I go along. The
original cylinder casting was scrapped when the mill dropped
1/8" while machining and flung it from the vise. Like I said,
a learning process J.
I decided to use the
lathe when I started in on the replacement cylinder so I'm
able to show you the two different ways I machined the same
part.
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| I have to say that using the lathe
and 4-jaw was much faster and easier than doing the same job
on the mill. Now maybe if my mill were larger, more rigid and
dialed in better I would have gotten improved results but as
things are and using the machines I have the lathe is the way
to go on this one. |
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| I also drilled and reamed the cylinder
on the lathe. |
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| Since the MT2 in the tailstock doesn't
use a tang to prevent rotation of the tool there has to be a
way to ensure against it. The taper itself is usually sufficient
to hold when drilling (aluminum and steel, brass tends to grab
the drill bit more often and also requires use of the dog) but
I wanted to be sure that the reamer wouldn't spin when I cleaned
up the bore so I put a lathe dog on the shaft of the reamer
and flipped the toolholder upside down in the toolpost to act
as a stop for the dog to rest against. It supported the dog
for the entire length of the operation. I was pleased with it
and will probably use the dog this way in the future. I had
been planning on bolting something to the side of the tailstock
to accomplish the same function but this seems to work well
and doesn't require any modifications to the machine. |
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| The next step was to drill and tap
the eight holes for the screws that hold the cylinder heads
on. |
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| I used the same cut-n-paste for the
crank casting. |
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| I'm planning to build the PM Research
3A engine kit next and will explore this technique more fully.
I think that paper templates can be used for the main casting,
cylinder casting the crank and both cylinder heads. For someone
just starting out I think this will be a tremendous help. With
most copiers able to scale in either direction it shouldn't
be too difficult to produce one-to-one copies of the prints
to act as cut-n-paste templates for each workpiece. |
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Still plenty of work
to do but it's starting to take shape. While I haven't done
so yet, it looks like many of the cast pieces could be easily
fabricated from aluminum round stock. The whole Idea behind
building this engine was for it to be a learning experience,
and boy am I learning. Mistakes are easy to make and learning
how to fix a mistake is all part of the process. I've picked
up a replacement cylinder casting for the original that I
scrapped and I also stole the upper cylinder head from the
#3A model to use on this one, actually it's a bit nicer with
a lathe "PM" cast into it. I'm waiting to see how it runs
but I may have to replace the cylinder head yet again. If
I do I believe I'll take a shot a just making one from a piece
of aluminum round stock.
After being forced to
consider ways to replace scrapped castings I started to see
how easily an entire engine could be created from bar stock
instead of castings. I may alter my intended "build schedule"
of steam engines to include one or two scratch-built engines
before I tackle the Stuart. The Stuart is the nicest engine
I have actual plans to attempt and I'm somewhat intimidated
by it. I know I'll feel a great sense of accomplishment when
it's done but I want to have a better handle on my skills
before I attempt it. This is also based on practicalities.
The Stuart is an English casting kit and replacements will
be harder to find and more costly than the "cruder" domestic
model kits I have at the moment.
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This engine calls for
2 different bushings. One is pressed into the main casting
for the cylinder casting to pivot on and the other is pressed
into the piston rod connector to allow it to spin on the crankshaft.
The "bushing" is just a piece of 3/16" round stock that is
drilled out 1/8" on the inside. A collet was the most accurate
way to do this. After facing both ends and center-drilling
one end I mounted a 1/8" drill bit in the tailstock and drilled
out the rod which was later cut into the 2 needed bushings.
Doing the layout work
for the model is probably the most important aspect of building
it. If you don't get your layout right then forget it, nothing
will be the right size and holes will be misaligned. There
are a lot of different ways to lay out your work; I'll try
to show you some of the ideas I used.
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The connector above attached the piston rod to
the crankshaft and according to the print it needs to be 7/16"
long. To get the right length I used the decimal equivalent
and set the digital calipers to .4375". Once the calipers
were set and locked I transferred the measurement to a set
of hermaphrodite calipers and then transferred the measurement
to the brass key stock, which has been dyed with blue layout
fluid. Once the proper length is determined and marked, the
connector is placed in a square hole collet and turned on
the lathe. A 4-jaw chuck would usually be use but since this
is such a small piece that the collet is a better choice when
one is available. This is exactly the kind of operation that
I was thinking of when I set out to equip my 7" lathes with
a 3C collet closer. Pictures and details of the closer can
be found elsewhere on this site.
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| Now that it's the right size the
real work can begin. Once again I used a paper template
made from the prints. |
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| The bushing hole was center drilled,
drilled and then reamed on the drill press and then it was back
to the lathe to mark and drill the hole to be tapped for the
piston rod. |
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The connector now needs
to have the hole for the piston rod threaded and the bushing
pressed in.
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And presto, one completed
piston rod connector. It can be surprising just how much work
goes into making just one part of this engine. Fortunately
there aren't too many pieces to this engine, which is what
makes it such a good beginners project.
I didn't stumble upon
this method of laying out my work until I was about ½ way
finished, but I plan to make more use of it in the future.
With most copiers able to scale the copy either up or down
it should be easy to obtain the size print that you need for
the part. Paper templates have been very useful in this project.
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As I do more and more
work I'm sure my layout skills will increase and at some point
using templates such as this won't be necessary but for now
while I still have so much to learn I find that they save
me a great deal of time, aggravation and disappointment.
With the bushings and
connector finished the list of unfinished parts grows smaller
each day. I only have the steam passages to drill and the
piston to make and all of the machine-work is finished. The
next step when the parts are all finished will be to individually
clean and inspect all of the parts a final time. The engine
will be assembled to test fit everything and to identify any
problems. With everything assembled I'll put some compressed
air to the engine to get it chugging along. When everything
is together and working smoothly I'll take it apart one final
time to polish all of the brass parts and powder-coat the
rest. I won't do any of the polishing or coating until I know
that the engine runs and won't need to be taken apart again.
Almost
there, this is how it's looking so far.
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| I still have a few things to do and
last minute modifications. Since this is just going to be a
display engine and won't be powering anything I don't need the
extended crankshaft. Before the final assembly I will shorten
the shaft to make for a cleaner appearance. I still haven't
decided what colors to finish it in. I have a small variety
of powders and don't know yet what will look best. Something
colorful perhaps. I an engine turned finish on a scrap of brass
and think it would be a great look for the sides of the flywheel
but I need more practice applying the finish before I try it
on a model. Maybe when I build the 3A or another 2A like this.
I also need to start thinking about how I want to display it.
I'd like to build a boiler to run it from for the best effect.
While compressed air is simple there's just something about
running one of these on steam. |
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| Here's a picture of the first piston
that I started. It remains unfinished although it may be salvageable.
This first attempt has as usual, taught me a few things. The
first is that I nee a netter tool for cutting the grooves the
piston rings will sit in. I originally used a modified cut-off
blade but as you can see it tapered to a point. This made it
impossible to get the side profile of the groove correct. A
quick construction note here, I did all the work on this piston
looking through a 10x jeweler's loupe. Watching what was happening
so closely and clearly was very educational and showed that
I would have to make a better tool in order to make a better
cut. |
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| After making the initial cuts I had
to grind a second tool to try and square the sides of the V-grooves
that I had just cut. I was able to square everything on the
top groove but I'm afraid that the ring is going to sit too
low and I stopped before finishing the second groove to reconsider
everything. I don't want to waste any further time on a scrapped
part but would also rather salvage this ten start from scratch.
Since the piston itself is only .25" I think I have enough left
on the machines stub to make a second without having to make
any more cuts, I could just part off this piston and start again.
I'm not sure yet, have to see how well the existing piston &
ring fit the bore. |
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| Finshed |
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