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Author Topic: Building a Small Vertical Double Acting Engine from Castings  (Read 23258 times)

fredrosse

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Building a Small Vertical Double Acting Engine from Castings
« on: March 23, 2011, 12:24:55 AM »

This topic covers building a simple engine from an unmachined kit.  This is a bronze MS kit, 3/4 inch bore and stroke, very similar to the Stuart V10 engine kit.  Every year I try to have at least one steam engine build project.

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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #1 on: March 23, 2011, 12:36:26 AM »

First steps, the bronze engine base is filed flat, mounted in the milling machine, and the flats for the main bearings and engine frame are milled.  Then the bronze bearing caps are soft soldered into the bearing pedestal locations.
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #2 on: March 23, 2011, 12:45:38 AM »

The bearing caps and engine base are drilled and tapped for 4-40 cap screws, the tapping goes well into the engine base. Then the caps are drilled to match the Outside Diameter (OD) of the 4-40 cap screws.

The second photo shows this from the underside, note there was some milling away of material in the base to make sure the drilling/tapping had a clean exit hole.  Depending on the base casting thickness, this may not be necessary.  It reduces the probability of drill or tap breakage.
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admin

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #3 on: March 23, 2011, 01:04:21 AM »

Fred-

That is a neat trick with the soft solder.
I will have to remember that one.
Now I have to see how the rest of the build turns out.

Nice wood base too!
I guess you built your wood boat.

« Last Edit: August 01, 2017, 09:58:54 AM by admin »
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #4 on: March 23, 2011, 01:38:53 AM »

Now to drill and ream the main bearings.  A fixture that bolts onto the bearing caps is made from a few scrap pieces of steel, which will accurately guide the drilling - reaming operation.

After this operation is completed, match marks are made so that each bearing cap is mated to its proper side of the base.  If I were a better machinist the caps could have been made perfectly interchangable, but that level of precision is not in the cards for me.
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #5 on: March 23, 2011, 01:49:47 AM »

The bearing caps are now unsoldered from the base, and residual solder is cleaned up from the surfaces with a file.  I only use single cut files for almost everything, the double cut files will not produce a smooth surface.

Now that there is a place for it, the crankshaft is next on the list.  This kit came with a nodular iron crank casting, and it was very easy to machine.
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #6 on: March 23, 2011, 02:00:16 AM »

Machining the connecting rod bearing surface requires making a small fixture that can clamp firmly on the main crankshaft journal, and be located accurately in a four jaw chuck.  The slot allows firm clamping action onto the already machined crankshaft journal.

One has to be careful here, not to strike the crank webs with the cutting tool.  I turn the lathe over slowly by hand to see that there is enough clearance to make the entire cut.  This is much better than ruining the piece under power lathe operation.
« Last Edit: March 23, 2011, 05:35:53 AM by PatJ »
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #7 on: March 23, 2011, 02:08:04 AM »

Now the crankshaft can be mounted into the engine base, and tested for good fits, etc.  And there is something that rolls at last!
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #8 on: March 23, 2011, 02:20:11 AM »

The eccentric rod and eccentric that work the valve gear is next.  The eccentric rod casting is cut in half across the big end bearing, these pieces are then soft soldered together, drilled and tapped for two 4-40 cap screws, the same process that was used for the main bearing caps.

Then the assembly is mounted in the milling machine vise (or on a lathe faceplate if you wish) and bored out to the eccentric journal diameter.  I don't presently have a precision boring bar, so I take an approximate journal diameter.  Later, the eccentric will be machined to match this diameter.

Finally, the side faces of the eccentric rod are milled smooth.
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #9 on: March 23, 2011, 02:32:55 AM »

Machining the eccentric is a simple job that requires no explaination.  Done in a four jaw chuck with no special fixtures.  On a previous engine I made the mistake of machining a brass eccentric, which is generally not happy with a brass or bronze rod.  Steel against brass or bronze works much better.

The main connecting rod is done the same way, except I used 6-32 cap screws for the big end of the main rod.

One thing I forgot to mention, when cutting the rod bearing journals, use a fine jeweler's saw, rather than a common hacksaw.  For such a small engine the jeweler's saw provides a fine cut, and does not remove too much material.
« Last Edit: March 23, 2011, 05:39:28 AM by PatJ »
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farmerden

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #10 on: March 23, 2011, 03:16:57 AM »

Thanks Fred   I've had this small engine kit for years and have been afraid to start!  You make it look simple! ::) What size mill were you using?  Thanks Den
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #11 on: March 23, 2011, 04:03:24 AM »

I have a Smithy 12 x 20 Combination Lathe - Mill - Drill, made in China.  After searching for most of my life for a good used lathe, I bought the Smithy new ($1946), it is a decent machine, but I only use the Mill-Drill now.  Of course, just after buying the Smithy, good used lathes started falling into my lap one after another (I think they call this "Murphy's Law").  I got an old Atlas 12 x 36 lathe, and plenty of tooling for $700, which I do most of my work on, because it has back gear, the quick change gearbox and half nuts, and real American (inch) dials.  Then a few 6 inch Craftsman lathes at flea markets and yard sales.  So I decided last year not to buy anymore, I had built my sidewheeler engine, and didn't need another lathe.

But I walked into Harbor Freight and there was a new 13 x 40 Geared Engine Lathe, which someone had ordered but could not pay for.  Rather than shipping it back (it weighs 1200 pounds), Harbor Freight was asking $850 for it, so of course I had to buy it.  I have to say that the 1-1/2 inch thru the headstock has come in very handy in preparing all my boiler tube ends.
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admin

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #12 on: March 23, 2011, 05:43:32 AM »

Fred-

Nice writeup on the build, and great photos (photos can be hard to do in a shop environment).
It is nice to get some details of how it is done.
I learn a lot every time I read a build post.



« Last Edit: August 01, 2017, 09:59:09 AM by admin »
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #13 on: March 23, 2011, 05:08:45 PM »

Next comes the most difficult part of the machining process, the crosshead guide.  This piece needs to be bored with a fine cut, setup is critical.  For this engine, the good casting and heavy flange on the cylinder end of the crosshead guide allowed chucking the casting tightly enough to bore a good 0.625 (5/8 inch) hole.  Often this setup is done on a faceplate with multiple clamps to hold the casting in place, that setup takes more time.

The boring process must use many fine cuts and a sharp tool, because of the openings on the bore hole to allow access to the crosshead after the engine is completed.  The boring tool pounds the open edges twice on every revolution, and if the piece is knocked loose, the casting may be ruined.
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #14 on: March 23, 2011, 05:21:28 PM »

After boring the crosshead guide, I was able to mount a piece of 5/8 inch drill rod in the lathe headstock taper, using a draw collet.  This stabilizes the setup and makes it much more rigid for the next machining step. The main frame feet were then faced to match the baseplate. 

Then the casting is turned around and the top flange is machined, again using the 5/8 drill rod to center and hold rigid the casting.  A small clamp keeps the casting from rotating.  Do not cut left to right with this setup, and use a cutting tool with little or no rake, to insure against possibly gouging the flange face.
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admin

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #15 on: March 23, 2011, 05:32:37 PM »

I just figured out what my next boring bar will look like.

Thanks Fred.



Edit:
Your build photos are just outstanding.
In focus no less.  How good is that.
« Last Edit: August 01, 2017, 09:59:20 AM by admin »
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #16 on: March 23, 2011, 05:51:55 PM »

The crosshead guide could have been soldered to the baseplate for drilling and tapping four anchor bolts (4-40 cap screws), but it is not difficult to just layout and drill-tap the holes with reasonable accuracy.

Now for the steam cylinder, it is centered in a four jaw chuck, bored and one flange faced. Mark this flange face, for it will be used to align the cylinder to the crosshead guide. 

Then the cylinder is turned around, and the other flange faced.  The two flanged faces should be parallel, and square to the bored cylinder, (but the first flange face will always be the better one).  The parallel faces are assured by seating the first flange face onto the face of the chuck, or onto unground tool bits that bridge over the chuck center hole. 

The bore is lapped with a soft copper rod and fine abrasive, be sure the lap metal is softer than the cylinder metal.

Finally the cylinder is moounted in the milling machine and the valve face milled flat.
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #17 on: March 23, 2011, 05:58:20 PM »

The last picture in the previous post shows the cylinder with the exhaust passage drilled in, exhaust flange bolt holes tapped, and the valve face tapped for mounting the valve chest.  Fairly simple layout and drill press work.

However, I did break a tap in one of the exhaust port flange bolt holes, but that is another story.  Be careful, as an error like that can cost several hours, and possibly a ruined part.
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #18 on: March 23, 2011, 06:09:24 PM »

The valve chest is next.  It was filed flat on two main surfaces, plus the steam inlet flange face.  This could have been done on a milling machine, but these castings were good enough not to require this.

The valve chest is then setup in a four jaw chuck for drilling and tapping the valve rod stuffing box.

The valve rod gland hole is tapped 1/4-28 NF, and the tap is run thru to the other side, also tapped 1/4-28.

Next two pictures, cylinder and valve chest in progress.
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #19 on: March 23, 2011, 07:28:30 PM »

Continuing work on the cylinder casting.

Valve seating face is milled for cylinder ports plus exhaust port.  Then cylinder is mounted for diagonal drilling of cylinder port. Fairly simple stuff, but be careful not to drill thru to the exhaust passage.

The cylinder covers are simple lathe work.  Note that the bottom cylinder cover is made with a close fit to the cylinder bore, and a close fit to the crosshead bore.  This aligns the cylinder to the crosshead, and is important. Both of these steps in the cylinder cover are done at a single chucking in the lathe for accuracy.

Then the cylinder covers are drilled for their flange bolts, clamped to the cylinder, and the tapping holes in the cylinder are marked.  If you are accurate, parts are interchangable, however the level of accuracy needed for this is beyond my old eyes, so I make liberal use of "match marks".  If a flange hole is a little off location, the parts still go together properly.

Note the small milled recess in the cylinder cover, gives more free steam flow into and out of the cylinder.
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #20 on: March 25, 2011, 04:52:13 PM »

Some of the pieces that are very simple turning/drilling/milling work. The flywheel has been faced and bored, crosshead made from a small piece of 5/8 rod, etc.

The valve chest, valve and valve rod, packing gland, all straightforward machining operations.  The valve rod is fitted with a small collar (from model airplane fittings) to position the valve. A couple of brass spacer washers take up most of the free play.  The valve has to float on the cylinder casting valve surface, so some small clearance is required.

Pipe flanges are made with a file, and copper tubing (1/4 OD)  silver soldered to them.

Piston is turned and pressed onto piston rod, with grooves cut for graphite/oil twine packing.  This type of packing is ok for a small model engine.

All the metal pieces finally done.  Note the crude temporary wood base, made for assembly checks, and needed because the flywheel diameter is large, and the flywheel extends below the base.
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #21 on: March 25, 2011, 05:05:16 PM »

I found some nice Walnut wood, and made this display stand.  The recess for the flywheel was cut on the mill with a fly cutter.  Wood machines so much easier than metal.

The completed engine is shown.

Having made this engine, I see that bronze castings are more difficult to machine than the cast iron ones. The bronze is much tougher than brass, which is easy to machine.  The advantage of bronze-brass is no rust.  I am told that a small operation can handle making bronze castings much easier than brass or iron.

For me, this engine project was a bit small to suit my machining skills, and requires better eyesight and better dimensional precision than I am accustomed to.  Engines with bore and stroke of at least a couple of inches are an easier job for me.
« Last Edit: March 28, 2011, 09:22:54 PM by PatJ »
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admin

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #22 on: March 25, 2011, 05:43:50 PM »

Fred-

Nice looking engine, and great build record.

Since I am a beginner/intermediate machinist, there are a number of proceedures I have not done, and don't have a good technique developed yet.

So as I review your photos, I have had several "ahh haaaa!" moments when I finally see how to do something I have not yet machined.
An example is the inclined vice, where the passages are drilled.  Did not know that one.

Thanks for laying out the steps, this is very helpful for machinist wanna-be's like myself, and I am sure very helpful to others who are getting into the hobby.

I have heard that brass/bronze is much easier to cast.
Many cast with aluminum, which I think is the easiest to cast, but if I get into casting, I will use brass/bronze in order to get the "high-mass" feel.




Edit: Looks like you have the woodworking thing down too.
« Last Edit: August 01, 2017, 09:59:37 AM by admin »
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admin

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #23 on: November 22, 2011, 08:58:33 PM »

Fred-

I ran across this post, and am bringing it up again, since I need a refresher course on machining castings (I have not tried that yet), and I see others who need the guildance.

This is good info.

« Last Edit: August 01, 2017, 09:59:51 AM by admin »
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #24 on: October 28, 2012, 02:10:56 PM »

A bit late with these replies, please forgive me.

Q: what was youre reasoning to have a through and through for the valve stem through the steam chest, rather than having just one inlet to ther steam chest?
ANS: With no crosshead for the valve stem, better bearing stability results with the valve stem being supported at both ends of the valve chest, quite necessary unless the lower bearing and stuffing box is made considerably longer to arrest sideways motion of the valve stem.

Q:  do you use a bronze bearing for the valve stem or do you rely on the stuffing to be the bearing for the valve stem on each side of the stuffing box?
ANS for a model engine, the brass valve stem guides (screwed into the valve chest) are adequate to act as the bearings.  Bronze would be better, but not warranted for a small model engine.

Q: Would you use the same process for say a 2 HP engine?
ANS: Generally Yes

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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #25 on: October 28, 2012, 02:17:33 PM »

Socket head cap screws on this engine are considered by some an "abomination", and I am beginning to agree.  I would like to replace all of the cap screws with proper studs and hex head nuts. 

The problem is that the hex nuts I find are somewhat out of proportion for the model, generally having the hex wrench flats a larger dimension than would be proper for the model.  Where can I buy the proper nuts?  All of the studs are US threads, 4-40, 6-32, 8-32, 10-32.

Thanks in advance for any replies.
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Johnlanark

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #26 on: October 28, 2012, 03:42:14 PM »

Hi Fred - I have to say I agree about the socket head screws! Why not make your own nuts? Thread both ends of a piece of round bar; put two nuts on each end; lock them so that the flats on the outer two are parallel; clamp to your milling machine table on two parallels under these outer nuts; mill across at each flat to make a length of hex bar the dimension that you want. Cut off waste. In the lathe, drill, tap and part off nuts. Or turn down to make bolts. John
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fredrosse

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #27 on: October 29, 2012, 12:46:51 AM »

John. making the nuts did occur to me, although I would have to get a "round tuit", and that has become very hard to find these days!  I do hope that they are available, even at $1USD each they would be a bargain compared to the time I would have to spend making them.
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admin

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Re: Building a Small Vertical Double Acting Engine from Castings
« Reply #28 on: October 29, 2012, 01:09:15 AM »

Socket head cap screws on this engine are considered by some an "abomination", and I am beginning to agree.  I would like to replace all of the cap screws with proper studs and hex head nuts.  

The problem is that the hex nuts I find are somewhat out of proportion for the model, generally having the hex wrench flats a larger dimension than would be proper for the model.  Where can I buy the proper nuts?  All of the studs are US threads, 4-40, 6-32, 8-32, 10-32.

Thanks in advance for any replies.

Fred-

The cap screws actually look very good on the engine, but just "out of period".
Some folks are into the "period" look (myself, just to see how authentic I can make a model look), and some are not.

I bought a number of sizes of small bolts.
They are very nice bolts.

Bolts can be made from hex stock.
I will post some photos of what I have, and can send you some if you would like them.

I think I ordered a bag of a number of various sizes and lengths, but they should be somewhat easy to make from hex stock.

« Last Edit: August 01, 2017, 10:00:02 AM by admin »
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