# A Two Cylinder Steam Engine



## romartin (Feb 2, 2013)

[SIZE=+2]*A TWO CYLINDER VERTICAL STEAM ENGINE*[/SIZE]

*INTRODUCTION*

I have resumed building the steam engine I had started when my encounter with HMEM caused me to embark on a fruitful interlude of tool building during which I learned much and for which I will always be grateful to HMEM and it's members.
This engine is a two cylinder version of the single cylinder steam engine which my brother and I built in 1956/7 when we were kids in the South African town of Eshowe in what was then known as Zululand and is now called Kwazulu. The pic below shows this 50+ year old engine for which no design drawings were ever produced. It was built entirely from scrap metal using our father's old 3.5" screw cutting lathe.







*DESIGN OVERVIEW*

In November of 2011, when planning a two cylinder version of this engine, I decided to develope a design which allowed an option to build a single cylinder version. The two versions have many parts in common. Like the original, all parts are intended to be built from stock metal; no castings are required. Unlike the original engine which used the imperial dimensions and standards then current in South Africa, the new design uses the metric units and standards current in my adopted patria Italy. 

The design was modelled in 3D and construction drawings were extracted from the models. The drawings for all the parts and assemblies for both versions occupy a total of thirteen A4 pages. I will attach each drawings to the post which deals with the parts on it.

Below is a CAD generated image of the overall assembly for each of the versions. To give an idea of the size, the cylinder bores are 22 mm in diameter, the pistons have a 26 mm stroke, while the flywheel has a diameter of 72mm.










From here on I will refer only to the two cylinder version that I'm now building.

The design structures the engine into a number of assemblies. Here are the CAD images of their 3D models.

*Base Assembly*





*Vertical Structure Assembly*





*Shaft Assembly*





*Cylinder Assembly*
Two of these are required.





*Inlet Piping Assembly*





*Exhaust Piping Assembly*





When work got interrupted last year I had completed building the Base Assembly and the Vertical Structure Assembly and all parts of the Shaft Assembly with the exception of the Crank Shaft itself, the Bearings, the Flywheel and the Eccentrics. I had done some initial work on preparing the chunks of steel destined to become the Crank Shaft and the Flywheel.

*WHAT'S NEXT?*

My next posts on this thread will report on these completed parts and assemblies; unfortunately I did not take many photos while doing this work.
Then I'll move on with more detailed reports as the work for completing the engine proceeds.


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## romartin (Feb 3, 2013)

[SIZE=+2]*THE BASE ASSEMBLY*[/SIZE]

*DESIGN CONSIDERATIONS*

The Base Assembly is composed of the Base itself plus the two Bearing Straps with their associated Oil Cups and bolts. The Base itself is fabricated by soldering together subparts made from sheet brass: two Sides from 5mm plate, two Faces, one Top and four Fixing Lugs from 3 mm plate. 

Here are some extracts from the construction drawings, the two PDF files of which are attached to this post.

*Base Side*





*Base Face*





*Base Top*





*BUILD APPROACH*



The key points of the approach chosen for building the Base Assembly were as follows.

Hold the subparts in position for soldering with small M2 brass screws; removing the heads of the screws after soldering.
Before soldering, prepare to final size only those edges of the subparts which are part of a contact to be soldered. Leave excess material on all other edges and reduce them to final size after soldering.
Using a single setup in the milling configuration of my lathe to perform final machining of the cut outs in the Top, of the tapped holes in the Top for the eight Pillars of the Vertical Structure, and of the tapped holes in the Sides for the Bearing Strap bolts. This is to ensure high precision in their relative positions and alignment.
Prepare the Bearing Straps and their Bolts first, and then use a single lathe setup to machine the split holes for both the Bearings with the two Bearing Straps held in place on the Base with their own bolts. This is to ensure perfect alignment of the two Bearings. In this lathe setup, the Machine Vice holding the Base is mounted directly on the flat upper surface of the lathe's cross slide.
*PHOTOS*

Using the Filing Guide to make the rounded profile of the Fixing Lugs.





The subparts of the Base ready for soldering.





The assembled subparts of the Base in the oven for soldering.





The Base Assembly Parts





The finished Base Assembly.





*WHAT'S NEXT?*

The next post will report on the building of the Vertical Structure Assembly. 

View attachment Base1 Assembly 1of1.pdf


View attachment Base2 Assembly 1of1.pdf


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## canadianhorsepower (Feb 3, 2013)

nice work thanks for the drawing
Thm:


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## romartin (Feb 4, 2013)

[SIZE=+2]*THE VERTICAL STRUCTURE ASSEMBLY*[/SIZE]

*DESIGN CONSIDERATIONS*

The Vertical Assembly is composed of two groups of 4 pillars which screw into the Base and together support at their top ends a horizontal platform on which the pair of Cylinder Assemblies will be mounted. Below the Platform, the rear two pillars of each group also support a subassembly for guiding and constraining the vertical oscillation of the Small End.

Here are some extracts from the construction drawings, the two PDF files of which are attached to this post.

*Platform*





*Slide Upper Support*





*Slide Lower Support*





*Piston Slide*





*BUILD APPROACH*




The making of the parts of the Vertical Structure Assembly did not present particular difficulties. Some points of the approach chosen were as follows.

Use a single milling setup of the lathe to perform final machining of all the holes in the Platform. This ensures precision in their relative positions and alignment.
For each of the Slide Supports, use a single milling setup of the lathe for boring and tapping all the holes. This ensures precision in their relative positions and alignment.
*PHOTOS*

The parts of the Vertical Assembly.





The Vertical Assembly. A temporary bolt is holding each of the Slides up against the lower face of the platform.





The Vertical Assembly mounted on the Base Assembly.





*WHAT'S NEXT?*

The next post will report on the parts of the Shaft Assembly which were completed last winter. 

View attachment Vertical Structure1 Assembly 1of1.pdf


View attachment Vertical Structure2 Assembly 1of1.pdf


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## romartin (Feb 5, 2013)

[SIZE=+2]*THE SHAFT ASSEMBLY - 1. Conrod and Eccrod Units*[/SIZE]

*DESIGN CONSIDERATIONS*



The Shaft Assembly is composed of:

the Crank Shaft itself,
the Flywheel,
the two Eccentrics,
the two Bearings,
the two Connecting Rod Units with their Big and Small Ends,
the two Eccentic Rod Units with their Eccentric Straps and Links.
The three PDF files with the construction drawongs of these parts are attached to this post. However reporting on their builds will require several posts. 

This post reports on the Connecting Rod Unit and the Eccentric Rod Unit which were completed last winter and for which I do not have photos of the build process.

Here are some extracts from the construction drawings. 

*Connecting Rod Big End*





*Connecting Rod Small End*





*Eccentric Rod Straps*





*Eccentric Rod Link*





*BUILD APPROACH*

The making of the parts of the Connecting Rod Unit and the Eccentric Rod Unit was fairly straight foreward but required care owing to their small size. 

The approach for making the Big Ends may be of interest. First the M2 bolts and nuts for holding the upper and lower straps together were made from 5mm bar mild steel stock. Then both Big Ends were done together with a single chunk of 18mm bronze bar. At a certain point the lower halves of the straps were cut away from the bronze chunk, and the contact surfaces of both upper and lower straps were milled flat. The lower halves were then fixed with the bolts back onto the upper halves which were still part of the bronze chunk, thus allowing final turning of the 7mm bores and their outer faces.

A similar approach was followed for the Eccentric Straps.

*PHOTOS*

The Connecting Rod Unit. One Unit is assembled and one is shown as disassembled parts.





The Eccentric Rod Unit. One Unit is assembled and one is shown as disassembled parts.





*WHAT'S NEXT?*

The next post will report on the building of the Bearings and the Crank Shaft. 

View attachment Shaft1 Assembly 1of2.pdf


View attachment Shaft1 Assembly 2of2.pdf


View attachment Shaft2 Assembly 1of1.pdf


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## aarggh (Feb 6, 2013)

Loving this build Ian! Thanks for putting the files and pics up for everyone, very generous.

cheers, Ian (yes, another one!)


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## romartin (Feb 6, 2013)

That you Luc and Aarggh! I'm enjoying doing it!


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## romartin (Feb 6, 2013)

[SIZE=+2]*THE SHAFT ASSEMBLY - 2 Bearings and Crank Shaft*[/SIZE]

This post reports on the recently completed building of the Bearings and the Crank Shaft. These parts are part of the Shaft Assembly, the three construction drawings of which were attached to the previous post. Making the Crank Shaft has been by far the biggest challenge so far! 

Here are some extracts from the construction drawings. 

*Crank Shaft Bearing*









*Crank Shaft*









*BUILD APPROACH*


The key aspects of the approach chosen for the Crank Shaft and its bearings were as follows.

Make the Bearings before the Crank Shaft, finishing their bores with a 7mm reamer. Then fir the crank shaft to the bearings.
Machine the Crank Shaft from the solid. This approach was decided after some trials to test the feasibility of building it up from separately prepared disks and bars. My attempt to silver solder the trial pieces of steel failed - the steel oxidised before reaching the fusion temperature of the solder. I suspect that this may be due to the presence of lead in the steel.
Facilitate precision in the positions of the crank pins relative to the center of the shaft via two narrow flats milled along the length of the solid bar. These flats were used twice:
posioning the solid bar in the Machine Vice for drilling the center holes for machining the crank pins;
positioning the Crank Shaft in the Machine Vice for milling the profile of the cutouts in the crank disks.

Attempt to avoid where possible the need to transmit torque to the point being turned through the finished crank pins. In other words attempt to orient the part so that the section to be turned was near to the dog or chuck.
*BUILD LOG*

*The Bearings*

The Bearings were turned together from 18mm phosphor bronze bar. Their bores were finshed to size with a 7mm reamer.





*Preparing the Crank Shaft Chunk*

Intial machining from bar stock produced a steel cylinder of diameter 38mm (2mm oversize) and length 127.5mm (final size) with the two shallow flats milled along most of the length and with three center holes at each end - one at the center and one on the axis of ecah crank pin. This cylinder also had eight shallow grooves around it to mark the edges of the four crank disks. I regret that I have no photos of this machining nor of it's product.

*Machining the Crank Pins*

Following removal of a modest amount of metal from all sections of the shaft with the exception of the disks themselves, I started the long task of making the two crank pins. The following three photo show the machining of the second crank pin. The shaft is mounted between centers along the axis of the pin and therefore turns with a marked eccentricity. 


To reach into the depth of the crank the cutting edge of the tools had to project almost 30mm from the front face of their tool holders. The whole job was done with the spindle turning at 63 rpm. The 6mm space between the inner faces of the crank disks was gradually deepened in a series of nearly 30 "steps" each of which deepened the slot by 1mm. Each step consisted of three substeps:

Use a small threading tool to make a V sided slot 1mm deep and aboy 3 mm wide at the center of the slot.
Use a left shouldered knife tool to widen the slot up to the disk on the left of the slot. This was done in four passes of 0.25mm each.
Use a right shouldered knife tool to widen the slot up to the disk on the right of the slot. Again this was done in four passes of 0.25mm each.
Every ten or so steps, the inner faces of the disks being formed were faced off using the appropriate knife tool. This process was of course repeated at the end. The final step was special in that the cuts were very light with frequent checks for fit with the bore of the corresponding Big End.

Each of these steps took about 20 minutes. Thus the turning of each crank pin took around 10 hours. Interestingly, this 10 hour process required almost 100 tool changes! Without my new QCTP it would have been very tiresome!














The following photo shows the three tools used during this process. They were resharpened frequently. Note that the holders of the knife tools hold the tool with a small horizontal angle (1 degree). This enabled me to do all the tool swapping without having to adjsut the angle of the QCTP itself.





*Rough turning the sections of shaft*

Once the two Crank Pins were completed there was no further need for their center holes and so the excess material from the shaft sections could be removed. Almost all of this metal (of which there was a surprising amount) was removed by holding the work firmly in the 3-jaw chuck near to where the material was being removed. For the two end sections, the thin disk left in the jaws of the chuck was cut away with a hacksaw. For the middle section, the chuck jaws were holding the work by one of the pairs of crank disks.














Here is the crank shaft at the end of this rough removal of material. The shaft sections are still oversize by about 1mm and, having been turned in the chuck and not between centers, are not perfectly concentric with the center holes. The crank disks are still too thick by about 0.5mm. Note too that the diameter of the crank disks is still 2mm oversize and that the flats in correspondance with the crank pins are still there.






*Milling the crank disk cutouts*

This process was done with the lathe in its milling configuration, using a 12mm end mill in the 3-jaw chuck. The work was done with four different setups, one for each side of each pair of crank disks. The flats on the rims of the crank disks were used to ensure that the orientation of the disk being machined was correct. The curved section of the profile was machined in a series of small steps: X was increased by 0.1mm (just under 0.004") and Z was decreased by the appropriate amount to follow the 8mm radius. The resulting stepped surface was then smoothed carefully by hand with a small flat file.

The attached pdf file shows the Excel page with the detailed instructions I had with me in the shop while doing the job.










*Final turning of the disk rims and the sections of shaft*

At this point I could finally mount the crank shaft between centers for the finishing cuts on all the cylindrical surfaces along the main axis ie the three shaft sections and rims of the four disks. No particular issues here except to take light cuts (max 0.25mm) with sharp tools, and to avoid squeezing the shaft tightly between the centers - just tight enough to have no side movement. Notice the rubber band holding the dog to the driving pin of the faceplate.






*Finished Crank Shaft*

The photos show the finished crank shaft first on its own and then mounted in the Bearings on the Base Assembly.










*WHAT'S NEXT?*
The next part on my plate is the Flywheel. 

View attachment CrankDiscCutouts.pdf


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## romartin (Feb 9, 2013)

[SIZE=+2]*THE SHAFT ASSEMBLY - 3 Flywheel*[/SIZE]

This post reports on the build of the Flywheel and the associated fixing screw. They are part of the Shaft Assembly, the three construction drawings of which were attached to the first post about the Shaft Assembly.

Here are some extracts from the construction drawings. 










*BUILD APPROACH*


The key aspects of the approach chosen for the Flywheel were as follows.

Machine the flywheel from a single 18mm slice cut from a 75mm bar of AVP (Pb) steel.
Hold the slice in the 3-jaw chuck to machine one face and the bore.
Then use a custom mandrel to hold the slice via the bore to machine the other face and the rim.
If necessary, make a custom extension for the 3mm first and second taps to allow use of the tap guide. Then drill and tap the fixing screw hole through the boss by holding the flywheel in the machine vice directly bolted to the upper face of the cross slide, using the bore through the boss to ensure that the axis of the bore is at the same height as the axis of the lathe spindle.
Make the grub screw in brass to avoid damage to the Crank Shaft.
*BUILD LOG*

*Rough Machining*

This photo shows a moment of the process of the initial rough machining the slice. First the raw slice was neld in the 3-jaw chuck by the outer surface of the rim to rough machine the exposed face including the boss, the 3mm recess and the rim edge, leaving an excess of less than 0.5mm.






Then the slice was reversed in the chuck, this time holding it by the inner surface of the rim. In this setup the outer surface of the rim and the second face, including the 3mm recess, the boss and the rim edge were rough machined again leaving about 0.5mm of excess.
Here is the slice at the end of the rough machining. At this point the slice is ready for finish machining.






*Finish Machining*

Holding the Flywheel in the 3-jaw chuck by the outer surface of the rim, the exposed face was finish machined to final size. Then an initial 6.5mm hole drilled through the boss was bored to final size with very light cuts until a smooth fit with no wobble on the Crank Shaft was achieved.






Next a custom mandrel was fashioned on the end of piece of 12mm steel rod held in the 3-jaw chuck.






Without removing the mandrel from the chuck, the flywheel was mounted on it with the unfinished face exposed so that it, and the outer surface of the rim could be finish machined to final size.






*Drilling and Tapping the hole for the Fixing Screw*

Before starting the job I made a jig to increase the length of the shank of the 3mm taps.






Then the flywheel was mounted in the machine vice which was itself mounted directly on the upper face of the lathe's cross slide. The height of the flywheel was positioned with the help of the tail stock center. 






The 10 degree angle for the Machine Vice was set with the help of a carpenters angle guage. Then, after milling a small flat on the boss and starting with a center drill, the hole for the Fixing Screw was dilled and tapped.










*Making the Fixing Screw*

The Fixing Screw was machined from a short scrap of 6mm brass rod. The photo shows the final step of cutting the screwdriver slot in the head using the slotting saw I have built for my QCTP.






*Finished Flywheel*

The photo shows the finished flywheel with its brass Fixing Screw.






*WHAT'S NEXT?*

The next parts on my plate are the last ones to complete the Shaft Assembly, namely the two Eccentrics and their grubscrews.


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## canadianhorsepower (Feb 9, 2013)

Nice work thanks again for the drawing.

one question why did you go 90 degree instead of 180 for crank pin


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## romartin (Feb 9, 2013)

Thank you Luc. 
Your question. Since the cylinders are double acting (ie live steam pushes the pistons on their up strokes and on their down strokes), the 90 degree angle between the cranks ensures that the engine will start itself whatever the angle of the crank shaft and that it has no dead spots. Furthermore the power is more evenly transmitted to the crank shaft because when one piston is at the top (or the bottom) and is therefore doing no useful pushing, the other one is in midstroke and is therefore doing its maximum useful pushing.


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## romartin (Feb 11, 2013)

I gave a quick answer to Luc's question in my previous post but the old grey wheels continued turning! I'm refering to the advantage of the 90 degree angle between the cranks of evening out the transfer of energy from the steam to the crank shaft. I came up with a simple, and approximate model.

The torque on the crank shaft poduced by a single piston as it move from TDC to BDC (Top/Bottom Dead center) will roughly follow the first half of a sine wave - ie it will start at 0, rise to a maximum value (say 1) when the crank is at 90 degrees and then fall back to zero. The same curve will then be followed again on the upstroke from BDC to YDC. The overall curve for a complete 360 degree cycle therefore looks like a two humped camel or a rectified sinewave. Not surprisingly, the repetition period of this waveform is 180 degress.

The torque on the crank shaft from a two cylinder engine with the cranks at 180 degrees will be simply twice that of the single cyllnder i.e. it will start at zero, rise to 2 when the crank shaft is at 90 degrees, fall back to 0 at 180 degrees, rise again to 2 at 370 degress and fall back to zero at 360 degrees. The repetition period remains 180 degrees.

When the cranks are placed at 90 degrees with respect to each other, the analysis is a bit more complex. We have to add one of these repeating camels to itself shifted to the right by 90 degrees. A sinewave shifted by 90 degrees is a cosine wave. So the resulting waveform is the sum of a rectified sine and a rectified cosine. The resulting wave is a hump which starts at 1, rises to a peak of 1.41 (square root of 2) at 45 degrees, then falls back to 1 at 90 degrees and then repeats itself another three times to complete a full 360 degree cycle. The shape of the hump is the middle half of a sine wave (i.e. from 45 degrees to 135 degrees).

So the smoothing effect on the torque applied to the Crank Shaft derives from two effects:

Smaller Excursion: the amplitude of the torque varies between 1 and 1.414 instead of from 0 to 2
Higher Frequency: the repetition frequency of the torque waveform is doubled from 2 per cycle to 4 per cycle
 
Math
Trig formula: sin(A+B) = sinAcosB + CosAsinB
With B = 45 degrees so that cosB = sinB = 1/sqroot(2)
and so we get sinA + cosA = sqroot(2)sin(A+45)


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## romartin (Feb 13, 2013)

[SIZE=+2]*THE SHAFT ASSEMBLY - 4 Eccentrics*[/SIZE]

This post reports on the build of the two Eccentrics and their associated fixing grubscrews. They are the last remaining parts of the Shaft Assembly, the three construction drawings of which were attached to the first post about the Shaft Assembly. At the end, the present post also shows the Shaft Assembly put together from all its parts, and the Shaft Assembly integrated with the Base Assembly and the Vertical Structure Assembly.

*DESIGN CONSIDERATIONS*

Here are some extracts of the Eccentric from the construction drawings.











There are differences with respect to the drawings attached to the earlier post; they derive from my decision to increase the diameter of the grubscrews from M2 to M3:

the diameter of the bosses is increased from 12 mm to 14 mm.
the width of the bosses is increased from 4 mm to 5 mm.
the grubscrews are threaded M3 with an overall length 5.5 mm.
*BUILD APPROACH*


The key aspects of the approach chosen for the Eccentrics were as follows.

Machine the Eccentrics together from a single length of 20mm AVP steel bar stock.
Hold the bar in the 3-jaw chuck to machine the external (ie eccentric) profile including the 1mm wide slots, checking the fit with the corresonding Eccentric Straps.
Mount the bar in the 4 jaw chuck using the dial indicator to check that the center of external profile is offset from the lathe axis by exactly 2mm. Use this setup to machine the 14mm diameter bosses and the 7mm diameter bores of both eccentrics.
With the bar still in the 4-jaw, use the electric drill in its cross slide holder to drill and tap the cross holes for the fixing screws.
Make the two grub screws in brass to avoid damage to the Crank Shaft.
*BUILD LOG*

Here is the bar with a 26mm length turned to the finished size of 18mm.





These pics show the bar with the first of the two 1mm grooves and then with the two Eccentric Straps mounted in place to check their fits. The grooves were made with a special bit ground on the end of a 2 x 8 parting tool. During this process I discovered that the protruding lip in one of the Straps was a bit wider than 1 mm. I took the easy way out of widening the groove of one of Eccentrics. 









Below you see a stage of the setting up of the bar in the 4-jaw chuck with the help of two small chuck keys and my Dial Indicator mounted on the QCTP. (This is one of the tricks I learned from an HMEM member.) I need two small keys because the handle of the chuck's main key is too long to turn except when inserted into the topmost tooth.





The boss of the first Eccentric has been turned to its final 14 mm diameter and the boring of the 7 mm hole is in progress. Boring started after drilling with a center drill, a 3mm drill and a 6.5 mm drill.





The next pic shows the setup for drilling the hole for the grubscrew of the first Eccentric. The electric drill is held by it's neck in a holder which I made at least 14 years ago and which bolts onto the upper surface of the lathe's cross slide. Unfortunately my plan to use this setup also for tapping with my usual tap guide proved impratical; there was insufficient space available even with the cross slide fully wound back. I decided to do the tapping of the holes later using my lathe's milling setup and using the holes to position the Eccentrics in the Machine Vice.





Below you see the first Eccentric being parted off with a freshly sharpened 2mm parting tool under power feed.





This is the milling setup for tapping the holes for the M3 grubscrews using my usual tapping guide.





Below you see the two finished Eccentrics with their brass grubscrews.





*COMPLETED SHAFT ASSEMBLY*

At this point I had completed all the parts of the Shaft Assembly, so I could assemble it for a snap. Here it is. The fit of the parts is still a bit tight.





I could not resist the temptation to integrate the three finished assemblies. Here is a pic of the new Shaft Assembly integrated with the Base Assembly and the Vertical Structure Assembly.





*WHAT'S NEXT?*

My next objective is to make the two Cylinder Assemblies. I still have to choose the approach and get some of the material.


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## Gerry Sweetland (Feb 13, 2013)

What a wonderful way to show and document your build!  I wish I could express myself so eloquently.
I have been building Elmer's #11 and have been taking photos as I go thinking that I may post a build log.  I was thinking that I would supply solid models and or drawings too (even G code if it would be useful to others), then I stumble on to your excellent build log.
Thank you for the inspiration and looking forward to the rest of your build.
Gerry


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## romartin (Feb 14, 2013)

Thank you Gerry!


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## romartin (Feb 15, 2013)

[SIZE=+2]*THE CYLINDER ASSEMBLY - 1. Introduction*[/SIZE]
*INTRODUCTION*

This post contains some preliminary considerations on the design of the Cylinder Assembly. The three construction drawings are attached to this post. Here are some extracts of the Cylinder Assembly from these drawings, showing viewS of the 3-D CAD model. The first one shows a front and a rear view of the Assembly, showing the various units and parts of which it is assembled. I use the term _unit_ to mean a part which is assembled in a non-reversable manner (like soldering or glueing) from simpler parts. 






The image below shows a section though the Cylinder Assembly in the XZ plane at Y = 0, clearly showing the Piston, the Slide Valve, and the passages for the steam linking the Steam Chest with the cylinder and the Exhaust. 






For people who have not yet met this Slide Valve, here is a brief description of the way it works. 
The first point worth noting is that it is the pressure of the steam in the Steam Chest which keeps the Slide Valve pressed up against the flat surface of the Cylinder Face. 
The Slide Valve makes a vertical oscillation which it receives from the associated Eccentric on the Crank Shaft. This vertical motion of the Slide Valve alternately exposes one end of the cylinder to the live steam in the Steam Chest while, via the hollow in the face sliding on the Cylinder Face, connecting the other end of the Cylinder to the Exhaust outlet. In the above image, the Piston is shown in it's highest position. Since the Eccentric which moves the valve is fixed to the Shaft at 90 degrees with respect to the crank pin which moves the Piston, the Slide Valve is in the middle of it's oscillation and is moving downward. In this position it is blocking both the upper and the lower steam ports on the Cylinder Face. The downward movement of the Slide Valve will progressively expose the upper steam port to the live steam in the Steam Chest and connect the lower port to the exhaust outlet. When the Piston is in the middle of it's downward movement, the Slide Valve will be at the bottom of its movement with the upper steam port fully exposed to the live steam and the lower steam port fully connected to the Exhaust. The Piston continues it's downward movement but the Slide Valve starts moving upward so that when the Piston reaches the bottom of it's excursion, the Slide Valve is again in the middle of its excursion and is therefore agin blocking both steam ports. And so on....

*DESIGN CONSIDERATIONS*

*Symmetries*



I had an initial objective that the Cylinder Assembly for the single cylinder engine and the two Cylinder Assemblies for the double cylinder engine all have the same design. Note however that in the two cylinder version of the engine the two cylinder assemblies are not identical; they are mirror reflections of each other because while the steam chest is on the left of one and on the right on the other, they both have the inlet and exhaust nippls to the rear. So the design objective became that the component parts of the Cylinder Assembly have certain symmetries so that the two mirror reflections can be assembled from the same set of parts. What symmetries are required?

Cylinder Unit: The threaded bolt holes in the upper and lower rims of the Cylinder must line up with the holes in the Platform when the Cylinder Unit is rotated 180 degrees about a vertical axis and when it is rotated 180 degrees about a horizontal axis parallel to the crank shaft. The first symmetry ensures that the Cylinder Unit can be mounted with the Steam Chest to the left or to the right. The second symetry ensures that the exhaust nipple can be at the rear or in front.
the Steam Chest: The left half and the right half of the Steam Chest must be mirror reflections of each other. This symmetry ensures that the Steam Chest can be to the right or to the left of the Cylinder and that, in both cases, it can be oriented so that inlet nipple is at the rear or at the front.
In my first stab at the cylinder design the cylinder flanges were fixed with five equally spaces bolts as did the original engine made over 50 years ago. But I had to change this to be six equally spaced bolts in order to satify the symmetry requirement.

In practical terms, these requirements for symmetries imply a need for special attention to precision when making the parts. For example for a Cylinder Unit to allow either of the cylinder ends to be at the bottom means that both ends must be perfectly square to the cylinder bore.

*Steam Passages*



The two steam passages linking the Steam Chest to the top and bottom of the cylinder are each composed of three sections:

A horizontal slot, called a steam port, with a height of 2mm, milled right through the Cylinder Face.
A vertical slot 3mm wide milled into the outside of the cylinder wall.
A horizontal hole drilled from the end of the vertical slot right through the cylinder wall.
All three sections of the passages are machined before the Cylinder, the Cylinder face and the Exhaust Nipple are soldered together to form the Cylinder Unit.

*Bolting of Cylinder Assy to Platform*

In the two 3D views one can see that the bolts holding the lower flange to the cylinder aappear to be too long. This is because the same bolts pass through six matching holes in the Platform part of the Vertical Assembly. The rearmost of the six bolts is even longer than the others; this is because it also passes through the Slide Upper Support to hold it up against the lower face of the Platform.
A consequence of this choice of bolting is that it is the tapped bolt holes in the cylinder walls which determine the angle in the horizontal plane of the cylinder relative to the Platform. It is therefore important that these holes be precisely positioned.

*WHAT'S NEXT?*

For me, the most challenging part of the Cylinder Assembly seems to be the Cylinder Unit both because of the precision required and because I'm always a bit nervous when there is silver soldering to be done. However before starting this adventure I shall put a somewhat irksome chore behind me, namely making the 20 M2 bolts required for each Cylinder Assembly! 

View attachment Cylinder Assembly 1of3.pdf


View attachment Cylinder Assembly 2of3.pdf


View attachment Cylinder Assembly 3of3.pdf


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## lennardhme (Feb 15, 2013)

Great series. looking forward to more.
many thanks.


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## Swifty (Feb 15, 2013)

Amazing job Ian, just goes to show what can be produced using only a lathe with a milling attachment.

Paul.


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## romartin (Feb 16, 2013)

Thank you Lennardhme and Paul.


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## romartin (Feb 16, 2013)

Hey Gerry have you started posting a build log of your Elmer #11?


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## Gerry Sweetland (Feb 16, 2013)

romartin said:


> Hey Gerry have you started posting a build log of your Elmer #11?



No, not yet.  I am planing on making the cylinders today, taking some photos as I go.  I have the base, crankcase and engine foot made.  I will maybe start it this afternoon after getting my ducks in a row to begin the log.  Upload photos, begin working on the text, etc.  I would like to create the text in word then copy to the forum in segments as I go I think.

So far your build looks amazing.  Looking forward to your progress on the cylinders. 

Gerry


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## romartin (Feb 23, 2013)

[SIZE=+2]*THE CYLINDER ASSEMBLY - 2. Making all the Bolts*[/SIZE]

*INTRODUCTION*

In my previous post I referred to making the set of bolts for the two cylinders as an "irksome chore". This is perhaps a bit unfair in the sense that it becomes so because there are 40 of the darn things and not because the steps required for each bolt are boring. It would be equally or even more irksome to make 40 cylinders or 40 flywheels! So on reflection I think that the process of converting over 70cm of 5mm steel bar into 40 M2 bolts may hold some interest for some members and so will report it in this post like any other step in the build of my engine.

*DESIGN CONSIDERATIONS*

For both asthetic and practical reasons these 40 screws are identical except for a single parameter namely the length of the shank (L) as shown in the drawing extracts below.










So the bolts are all have 2mm diameter shanks threaded for a length of 5.5mm of which only 4mm of thread are intended to enter into the corresponding threaded hole. The bolts all have the same head which is a hexagon with 4mm across the flats (F) and with a circular base, height 0.5mm, of diameter 4.62mm (V) which is the distance between opposite vertices of the hexagon obtained from the formula V = F / cos(30).


The 20 bolts required for each of the two Cylinder Assemblies are listed below:

6 bolts with L = 7mm for fixing the Cylinder Top Cover to the Cylinder Unit.
5 bolts with L = 10mm and 1 bolt with L = 15mm for fixing the Cylinder Bottom Cover and the Cylinder Unit itself to the Vertical Structure.
8 bolts with L = 19mm for fixing the Steam Chest Cover and the Steam Chest to the Cyinder Unit.
*BUILD APPROACH*

The bolts were machined from a 5mm diameter bar of mild steel. I was not able to discover the composition of this steel but judging from the way it behaved during machining I would guess that is lead free and with a carbon content of around 0.3%.

The process I use to make nuts and bolts is of course influenced by the tools I have. If I were making a single bolt then the basic sequence of steps I would use for making it would be more or less to make the shank, prepare a cylinder for the head, cut the bolt off the bar and then hold the bolt by the shank to make its head.


Here is this process described in more detail.
Make the shank and prepare the cylinder for the head
Hold the raw bar in the chuck with about L + 6 mm protruding from the jaws.
Use a knife tool to face off the end.
Use a knife tool to turn the first 7mm of the shank to the final diameter of about 0.02 mm under 2mm.
Thread the first 5.5mm of the shank holding the M2 die in some sort of tailstock die guide.
For bolts with shanks longer than 7 mm, use a knife tool to complete turning the shanks in one or two sections not longer that 6mm. This is necessary to avoid excessive flexing of the rather thin shank even when the tool is sharp.
Use the knife tool to turn to a diameter of 4.62 mm a cylinder 4.5mm long for the head.
Manually cut the screw off the bar leaving the head section with a length of at least 3.5mm.

Make the head
Gently hold the bolt in the 3-jaw by the shank with the head cylinder pressed up against the jaws.
Face off the end so that the head has the required finished length of 3mm.
Make the flats of the hexagon with a hand file, using my File Guide [thread]19573[/thread]and using the lathe's Gear Train to position the angle of the lathe spindle.
Use a metric threading tool to turn the 30 degree bevel on the edge at the end of the head.


So, on this basis, what is a good process for making 40 bolts? I had to choose between two alternatives.

Make the bolts one by one, doing for each the above process. With this option I would do a lot of setting up and measuring to ensure that all the bolts turn out with the correct dimensions.
Do each setup once only and for each apply the corresponding step of the process to all 40 bolts. With this option I would do a lot of bolt mounting and dismounting but, with proper use of a carriage stop, I would do the setting up and most of the measuring only once.

I plumped for the second approach. So I applied each of the following four steps to all 40 bolts.
For each bolt, make the shank, prepare the head cylinder, cut the bolt off the bar. During this process the Knife tool was sharpened after every three bolts.
For each bolt, face off the end of the head using the carriage stop to ensure that all heads have the same length.
For each bolt file the flats of the hexagon section of the head, again using the carriage stop to ensure that the circular bases all have the same length.
For all bolts machine the 30 degree bevel again using the carriage stop to ensure that all bevels have the same depth.
There was a problem in this approach owing to the fact that my 3-jaw self centering chuck cannot grip diameters below 3mm and so cannot grip the 2mm shanks of the bolts. To make a single bolt I would solve this problem simply by holding a smaller chuck in the 3-jaw. But this is inappropriate when using the same setup for many bolts because the teeth of this smaller chuck dont close in a plane orthogonal to the axis; when closing the chuck, its teeth move foreward along the axis as well as closing towards the axis. This would have made the use of the carriage stop inaccurate for the last three steps of the process. So I solved the problem by making a small mild steel split sleeve which has a 2mm bore, a 3.4mm external diameter and is 5mm long. The big chuck squeezes the sleeve which in turn squeezes the bolt shank. It is important that the external diameter of the sleeve is a good bit less that the diameter of the head base, and so I could still press the head bases up against the chuck jaws to ensure the correct position of the bolt along the lathe axis. It worked fine.

*BUILD LOG*

This is the carriage stop which came with the lathe when I bought it and is worth it's weight in gold! Some day I'm going to make a second one to use on the other side of the carriage for when I'm machining rightwards towards a shoulder.





*Step 1: Shank and Head Cylinder*

Here is a bit of 5mm raw bar sticking out of the chuck ready to make a bolt with a 19mm shank.





Here is the first 7mm of shank turned to a diameter of 1.98mm.





Here is this first 7mm of shank being threaded M2 with a tailstock guide for the die. 





Here is this first 7mm of shank with about 5,5mm of M2 thread. 





Here is the bolt with a further 6mm of shank and then with the completed shank with a total length of 19mm.









Here are all 40 bolts at the end of this first step.





*Step 2: Face Off the Head*

The next three photos show the small sleeve with a 7mm bolt next to it, the bolt inserted into the sleeve and finally the bolt held in chuck via the sleeve.













Here are all 40 bolts at the end of the second step ie with the heads faced off to the final length of 3mm.





*Step 3: File the Hexagon Section of the Head*

The next two photos show the setup with the Filing Guide for filing the flats of the hexagon sections of the heads and the way I use the lathe's gear train to index the angular position of the spindle. The train is set up to multiply by 4 and the final white gear in the train has 60 teeth. Hence for each full revolution of the lathe spindle 240 teeth pass the horizontal indexing rod held uin the block of wood. So to rotate the spindle by one sixth of a rotation I must let 40 teeth go past the index rod. With the help of the pencil marks at every tenth tooth of the gear it's a piece of cake!
Note that the carriage stop is in position to ensure that the limit to leftwise horizontal motion of the file is always at the same distance from the chuck jaws.









Here is a single bolt with the hexagonal section of its head filed.





Here are all 40 bolts at the end of the third step ie with the heads faced off to the final length.





*Step 4: Bevel the Edge of the Head Section of the Head*

This photo shows the setup for beveling the Egge of he Hex Section. The carriage stop is in position to ensure that the limit to leftwise motion of the tool is always at the same distance from the chuck jaws.





And here finally are all 40 bolts finally finished.





Total shop time for the job was roughly 20 hours: an average of 30 minutes per bolt. Something tells me that there must be a quicker way!

*WHAT'S NEXT?*

Now I can start of the two Cylinder Units. After all my recent handling of steel I'm looking foreward to machining brass.


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## Chriske (Feb 23, 2013)

Hi,

Thanks for the drawings, Nice thread btw.
Would it be possible to convert the complete assembly to stp or step format and post it on the forum please.
I like to walk through. An inside view is always very impressive...

I think this engine will be a candidate for a school project next year. 

Thanks in advance.

Chris


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## romartin (Feb 24, 2013)

Hello Chris,
I would like to oblige but you'll have to help me. I didn't know of the stp format but Google sorted that out. Unfortunately 
my CAD software uses dwg format and doesn't include the stp format amoung its SaveAs or Export formats. With Google I failed to find a dwg to stp converter. Can you point me in the right direction?


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## Chriske (Feb 24, 2013)

Ian,

STEP format is the most widely used data exchange form
It is possible your CAD software does not allow to convert to stp or step format.
But seeing your 3D images I thought you were using one of the latest CAD software.
The older versions of AutoCAD (for instance) does not allow to export to stp or step.

See also : http://www.fileinfo.com/extension/stp

Thanks,

Chris


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## Gerry Sweetland (Feb 24, 2013)

Hi Ian,
That's pretty cool how you use your change gears to help you index your head.  I like your file jig too.
Gerry


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## TorontoBuilder (Feb 24, 2013)

romartin said:


> Total shop time for the job was roughly 20 hours: an average of 30 minutes per bolt. Something tells me that there must be a quicker way!



Hi Ian,

My compliments on the very fine build thread. This serves as an example of how to write a build thread. 

Well laid out, copiously illustrated with clear sharp photos, and complete the plans. I particularly appreciate that your laid out the build process without skipping any critical processes or omitting photos to save time. This ensures that novices such as myself can complete the same build with little difficulty. No matter if it is now or 3 years from now when you may not be around to answer questions. 

If you can get a stp file I too would appreciate it.

finally, I am not sure the size of the bolts you made, but wouldn't it help if they were machined from hex rod of the appropriate size saving the need for the indexing and filing?


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## romartin (Feb 25, 2013)

Gerry, Chris and Torontobuilder. Thank you all for your generous compliments.

Chris. You are right, my CAD SW is over five years old; I have been putting off upgrading because I didn't feel the need for it and to avoid the inevitable and usually unreasonable investment of time required! Now I have a reason to upgrade so I will move a CAD update at least onto my table if not directly onto my plate!

Torontobuilder. Yes starting from hex would save about 10 minutes per screw. Back in the 50s in South Africa I once ordered mild steel hex rod from the UK to make the bolts for steam engines. Delivery took six weeks by sea! Now, here in Rome I have found hex rod in brass and stainless steel but not in mild steel. It is available from the UK in both imperial and metric sizes in 12 inch lengths at a certain price. But I decided to make the bolts from round bar because I wanted that round base below the hex section both aethetically and to protect the brass surfaces under the heads from being scratched by the socket spanner.


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## Chriske (Feb 25, 2013)

Ian,

Off topic ....

Depending on how often you'll need 3D CAD software I would advice learning it.  Once you master it you'll gain *lots* of time
There are a few free version to be found out there.

I must admit, for me making all these drawings for the projects I'm building is part of the fun. Addicted is the correct word here I think...

Chris


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## rodw (Feb 25, 2013)

romartin said:


> Torontobuilder. Yes starting from hex would save about 10 minutes per screw.



I wondered how much time a collet block would have saved you when I first read this thread. Only because I found out I can get a 5c collet spindle for my lathe, so have been considering investing in a set of blocks for jobs like this where I wanted a hex head on some round stock. I was not sure if you would hold the screw in the collet or screw it into some round stock held by a collet given the small size.


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## romartin (Feb 25, 2013)

Chris


> Depending on how often you'll need 3D CAD software I would advice learning it. Once you master it you'll gain *lots* of time
> There are a few free version to be found out there.
> I must admit, for me making all these drawings for the projects I'm building is part of the fun. Addicted is the correct word here I think


I have been using 3D CAD software for many years now and thoroughly agree that the effort to learn 3D modelling and the extraction of 2D drawings from the 3D model is more than worth while both for the time it saves when building and because it is fun! What I was trying to say in my reply to you was that, in my experience, the effort to install and learn an _upgrade_ to this or any other software tool often seems unreasonable.


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## romartin (Feb 25, 2013)

Hi RodW.


> I wondered how much time a collet block would have saved you when I first read this thread.


I dont have collets on my lathe and have been meaning to look for some and of course, to weigh the cost. However in the case of my screws I dont see why I would have saved time with respect to using a 3-jaw self-centering chuck. In my mind collets contribute accuracy rather than speed.



> I was not sure if you would hold the screw in the collet or screw it into some round stock held by a collet given the small size.


I think that some sort of sleeve, made in a material softer than the bolts, is advisable to protect both shank and thread of the bolt from the very hard jaws of a chuck or collet. I decided not to thread the sleeve both because I wanted the same sleeve to work for bolts of different lengths and because, especially for the longer bolts, I didn't like the idea of the spindle torque being transmitted from the thread to the head via the entire length of the bolt's slim shank. I preferred to make a short sleeve which squeezed the bolt's shank right up next to the head.


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## TorontoBuilder (Feb 25, 2013)

romartin said:


> ... I decided to make the bolts from round bar because I wanted that round base below the hex section both aethetically and to protect the brass surfaces under the heads from being scratched by the socket spanner.




Ah, I see the logic, I didn't notice the flange on your bolt heads and hadn't yet read about that in the details. 

I can appreciate the desire to add those little details... time is of little consequence when compared to getting all the details right on a showpiece. That and the process is much of the enjoyment so whats a few extra hours.

Myself, if I build this to actually steam then I'd use hex and washers... just to get to the actual steaming quicker. But it is good to see hwo other people think when designing and building.


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## Gedeon Spilett (Feb 25, 2013)

Hi,
in the post #16 you write 
" Since the Eccentric which moves the valve is fixed to the Shaft at 90 degrees with respect to the crank pin which moves the Piston,..."
but it is usually not so, you have to add some lap on the valve and advance the setting of the eccentric accordingly, to allow steam expansion and greatly improve running with steam.

I have read the whole built, wow, amazing thread, you do not spare your work, and very elegant design too, many thanks for sharing. 

Zephyrin


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## mnay (Feb 25, 2013)

One of the most detailed build logs I have seen.  Beautiful drawings and complete descriptions.
Thanks for sharing your ideas and your work with us.
Mike


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## romartin (Feb 26, 2013)

Hi Zephyrin.

Yes indeed! Thank you very much for this stimulus and for your compliments. As stated in it's preamble, the paragraph you mention wanted to be a brief explanation of the Slide Valve for folk meeting it for the first time. However I should have mentioned the theme of efficiency which you have touched. So here goes, once again for the same audience and again trying comunicate principles and issues. I'm still trying to be brief but the subject is not that simple.

As you say, one can improve the performance efficiency under live steam by adjusting both the dimension of steam ports and/or slide valve and the angle of the eccentric. The objective is to reduce the fraction of the cycle for which live steam is connected to the piston from the full half cycle (0 to 180 degrees) to somewhat less (e.g. 0 to 90) so that for the rest of the half cycle the push is coming from the expansion of the steam already in the cylinder. At the end of the stroke the steam pressure will have fallen and so less energy will be thrown away through the exhaust port. In our example, if the live steam pressure is 5 atmospheres above atmpspheric (=6 absolute) then, at the end of the stroke, the pressure will have halved to roughly 3 atmospheres absolute (= 2 atmospheres above atmospheric).

One would like to keep the exhaust connection open from 180 degrees to 360 degrees. However, with a single Eccentric moving a single Slide Valve which moves across fixed Steam Ports, the angle of maximum opening of the exhaust connection must necessarily be 180 degrees from the angle of maximum opening of the live steam connection. These two connections can have different durations but their centers must be diametrically opposite. So if we insist that the live steam be admitted to the cylinder from 0 to 90 degrees (center 45 degrees) then the center of the exhaust connection must be 225 degrees which seems embarassing because if the connection were to open at 180 degrees then it would close at 270 degrees ie 90 degrees too early. 

In practice however this is less embarassing than it may seem at first sight, because once the exhaust connection opens, the pressure in the cylinder falls rapidly to atmospheric pressure (assuming that the used steam exhausts into the atmosphere). The premature closing of the exhaust connection results in a back pressure building up in the cylinder which, in our example, would be of the order of one atmosphere above atmospheric when the piston gets to 360 degrees. 

One can seek a better compromise by trying to move the angle of maximum connection nearer to the 90 degrees we started from. So instead of opening the inlet from 0 to 90 we could open it from 20 to 90 remembering that at the top of its stroke the piston is not able to transfer torque to the crank shaft very well. This moves the inlet axis center foreward by 10 to 55 degrees and so the exhaust axis center moves foreward to 235 and hence the exhaust could still open at 180 but would close at 290 instead of 270.

How do we adjust the Valve System to be more efficient? 

Firstly the angle of the Eccentric must be set so that the throw of the eccentric is vertical at the two points of maximum connection. In our example, if we wish the maximum input connection to the top of the cylinder to occur when the crank pin is at 55 degrees then at that point the eccentric must be at 180 degrees ie at 125 degrees ahead of the crank pin. This is 35 degrees ahead of the 90 degree position for the inefficient valve system.

Secondly we must modify the Sllde Valve itself to reduce the fraction of the cycle for which the connections are open. In our example we want the live steam connections to be open for only 70 degrees and the exhaust connection to be open for only 110 degrees. Thus a) the height of the valve must be increased so that the upper (lower) Steam Port begins to be exposed to the live steam only when the Eccentric axis reaches 125 + 20 = 145 (325) degrees. Secondly we must reduce the height of the cavity in the Valve so that the upper (lower) Exhaust Connection begins to open only when the eccentric axis reaches 125 + 180 = 305 (125).

Easy! Mmmmmmm!

A final thought - with a given steam pressure and a given engine, introduction of a higher efficiency valve system will actually reduce the useful work delivered but it will reduce the consumption of steam by even more i.e. it will have improved the efficiency. Put another way, getting a certain amount of work efficiently from a given steam supply requires a bigger engine than would be required if we dont bother about efficiency. Steam ships, which had to carry their fuel with them, carried the quest for efficieny much further with very big engines which uesd the exhaust steam from a first small cylinder as the inlet steam for a second medium sized cylinder the exhaust steam from which was used yet again as input steam to a large cylinder. These engines were relatively very efficient but of course had very poor power/weight ratios.

I have already written more than is wise at my age and ask forgiveness for any clangers which may be present. Perhaps it would have been wiser to leave this discussion to a real engine designer or, even better, to a designer of real engines but alas I fear there aren't any left!


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## romartin (Feb 26, 2013)

Hi Mike and thank you!


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## ConductorX (Feb 26, 2013)

romartin:  It is a beautiful engine and your craftsmanship is superb.  

I assume that since you are also posting detailed drawings we are allowed to copy your design and build our own engine if we wish?

Thanks for your time and detailed posts.


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## romartin (Feb 26, 2013)

Hi ConductorX. Thank you for your compliment. Yes of course you may use this design, or parts thereof, to build your own. That is what our forum is all about! If you should do so, then I hope you will post a build log.


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## GKNIPP (Feb 26, 2013)

Romartin, I was wondering if I missed the PDF drawings for the eccentrics and flywheel?  Maybe I scrolled right past them?

Thank you.

Greg


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## rodw (Feb 26, 2013)

romartin said:


> Hi RodW.
> 
> I dont have collets on my lathe and have been meaning to look for some and of course, to weigh the cost. However in the case of my screws I dont see why I would have saved time with respect to using a 3-jaw self-centering chuck. In my mind collets contribute accuracy rather than speed.



The collet block I was thinking of is a hexagonal block that holds a collet in the centre so you would not use the collet in the lathe chuck. Then you can just fix the 6 sided block, rotating it to mill each side, with an appropriate back stop to keep position but then maybe you don't have a mill? But it might work milling on the lathe perhaps? That's why I said I wasn't sure if it would help. The block kits themselves are not that expensive, about $30 in the US which of course becomes $90 in the Southern Hemisphere!

I often make parts in batches of 100-200 and am always looking for ways to make it easier but my parts are nowhere near as complex as yours and I was amazed by your resourcefulness to get the detail right!


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## romartin (Feb 26, 2013)

GKNIPP said:
			
		

> I was wondering if I missed the PDF drawings for the eccentrics and flywheel? Maybe I scrolled right past them?


Hi Greg. The three PDFs for all the parts of the Shaft Assembly are attached to the first post which talks about the Shaft Assembly i.e. Post #5 which is on Page #1 of the thread.


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## romartin (Feb 26, 2013)

RodW said:
			
		

> The collet block I was thinking of is a hexagonal block that holds a collet in the centre so you would not use the collet in the lathe chuck.


RodW, Thank you for this suggestion. I didn't know about Collet Blocks and will bear them in mind from now on. Using one to mill (in my lathe) the flats of the hexagons of my bolts would probably have saved a bit of time with respect to hand filing them.


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## GKNIPP (Feb 26, 2013)

Thanks a million.  I'm just blind.

Greg


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## romartin (Mar 7, 2013)

[SIZE=+2]*THE CYLINDER ASSEMBLY - 3. Cylinder Unit - 1*[/SIZE]

This post reports on the building of the three sub-parts of which each of the Cylinder Units is composed. The following post will cover the soldering of these parts and the finish machining of the soldered Cylinder Units.
The drawings of all the parts of the Cylinder Units are attached to the first post on the Cylinder Assembly.

*DESIGN CONSIDERATIONS*

The Cylinder Units are built by silver soldering three brass parts namely a Cylinder Tube, a Cylinder Face, and an Exhaust Nipple. Most aspects of the design have been mentioned in the introductory post to the Cylinder Assembly and so I will not repeat them here. 

With respect to the design shown on the drawings, I decided one change. The steam channels linking the live Steam Ports to the holes through the cylinder walls will be milled into the curved arc of the Cylinder Face and not into the wall of the Cylinders. The reason for this change is to facilitate the flow of molten silver solder, bearing in mind that the position for soldering will have the Cylinder Tubes lying horizontally with the Cylinder Faces resting on top of them. 

Here are some extracts from the updated drawings.
















*BUILD APPROACH*

*Overall Criteria*


There were three important criteria for the formulation of the approach to the build.
_Do as much final machining as possible after soldering._

More precisely, try to limit the finish machining before soldering to surfaces which are going to be in contact for soldering. However there are surfaces which are not contact surfaces to be soldered but which would be very difficult to machine after soldering. In the case of the Cylinder Unit this is true of:
those portions of external wall of the Cylinder Tube wall which are not in contact with the Cylinder Face;
the front and rear faces of the Cylinder Face;
the threaded portion of the Exhaust Nipple;
the steam passages milled into the rear surface of the Cylinder Face.
Thus the surfaces to be finished machined after soldering are:
Cylinder Tube: the bore and the upper and lower faces to the covers
Cylinder Face: The Face itself and the upper and lower edges
For all these surfaces the preliminary machining in preparation for soldering must leave excees material (roughly 0.5mm) to be removed after soldering.
_Limit the oxidization of surfaces to be soldered both by reducing as much as possible the elapsed time between preparing the surfaces and actually doing the soldering and by keeping the parts in plstic bags during the waiting time_
Brass surfaces oxidize and the solder does not take to the oxide layer. So for surfaces which are not to easy to brush up before soldering, it is important to minimize the oxidation by limiting the waiting time and/or the oxygen before soldering.
_The three parts to be soldered must be held in position firmly during soldering._
Remember that for silver soldering the fit between contact surfaces must be neither too tight nor too loose; silver solder requires a bit of space (a few thou) but not too much to work it's capilary magic. The Exhaust Nipples can be made to hold themselves in the holes of the Cylnder Face by making one or two small bumps on their surfaces with a punch. Holding the Cylinder Face and the Cylinder Tube together in the right position needs a bit more ingenuity; I decided to use a sacrificial 2mm brass bolt which passes through the Cylinder Face in what later will become the exhaust port and which screws into a shallow (3mm) threaded hole in the Cylinder Tube wall (which will be 3.5mm thick after finish machining).
*Preparing the Cylinder Face*

The only difficult part to prepare for soldering is the Cylinder Face, because it requires final machining of it's stepped curved surface which makes contact with the outer surface of the Cylinder Tube wall. After considering various alternatives I decided to use a boring bar between centers and to mount the Cylinder Face on the upper surface of the cross slide not below the boring bar as I have done on other occasions but behind the boring bar so that the center line of the Cylinder face is at the same height as the lathe's axis. To do this I used a robust 90 deg angle plate on which I mounted a pair of brass "jaws" and a small brass End Stop. The upper edge of the lower jaw is at exactly the right height (ie 11 mm lower than the lathe's spindle axis). The upper jaw has three 6mm grubscrews to hold the Cylinder Face in place during machining (with a piece of protecting brass between the screws and the work piece).







This arrangement gives me big advantages:

I can use the boring bar itself to ensure that the face of the angle plate is parallel to the lathe's splindle axis. Knowing the radius of the boring bar (10mm) I can then set the zero of the cross slide index dial.
I can then use the face of the angle plate to adjust the radius of the arc described by the cutter. For example the smaller arc has a radius of 14.5mm; so I set the angle plate to be at 4.5mm from the boring bar and then adjust the cutter to just touch without marking the angle plate.
I can use the movement and index dial of the cross slide to vary and control the distance of the Cylinder Face from the cutter, both for setting the depth of cut and for doing the final cut with the axis of the Cylinder Face curves exactly coinciding with the spindle axis of the lathe.
To check the radii of the two outer sections (radius 15.5mm) and the single inner section (radius 14.5mm), I plan to prepare from scrap brass rod two short cylinders with appropriate diameters. 
The two outer sections can be prepared using the same tool and without altering its radius setting simply by reversing the boring bar between the centers (i.e the head end becomes the tailstock end and vice versa) and then making the lathe spindle rotate backwards. This is perfectly safe on my lathe because the working interface of the lathe spindle is a bayonet and not a thread.

*BUILD LOG*

*Exhaust Nipples - non contact surfaces*

First I prepared the non contact surfaces of the nipples. While at it I made four because the live steam nipples are the same. The contact surfaces will be machined nearer to soldering time...





*Cylinder Faces*
Then I started the pre-soldering machining of the Cylinder faces. The two rectangular blocks shown in the image below were recovered by milling away the excess from two pieces from the 25mm brass rod. The width (22mm) is final size but the thickness (10.55mm) and the height (36mm) have at least 1.5mm of excess material.

For both thickness and height one of the two faces is chosen as the reference face and the excess material on it is taken to be exactly 0.5mm. Bearing this in mind the exhaust passage and the 6mm hole to receive the Exhaust Nipple were positioned and drilled.





Now it was time to use the jig for making the arcs. Here is the boring bar being used to set up the jig with the face of the angle plate parallel to the lathe axis.





This phote shows the first Cylinder Face with the central arc (radius 14.5mm) finished so that the outer face of the Cylinder Face (ie the face of the angle plate) at exactly 20.5mm from the lathe axis. (The extra 0.5mm will be removed after soldering).





Before proceeding with the outer arcs of the first cylinder, I made the central arc of the second Cylinder face. 

These central arcs were the easy ones; the outer arcs require more attention! With no Cylinder face in the jig, the boring bar cutter was adjusted to have a radius of 15.5 mm and the lathe's carriage stop was moved to the right of the carriage and set so that rightward movement of the carriage would be blocked when the cutter edge was exactly 32.5mm from the End Stop of the jig. The first Cylinder face was then mounted with the reference end up against the End Stop. In this position the right end outer arc was machined again making sure that the last cut was with the face of the angle plate at 20.5mm from the lathe axis. The next two photos show the setup (note the carraige stop) and the result (with the boring bar out of the way). 









I then removed the first Cylinder Face from the jig and repeated the operation for the second one.

To do the left end outer arcs the secong Cylinder Face was removed from the jig, the carriage stop was restored to the usual side of the carriage and, without altering the setting of the cutter, the dog was moved to the opposite end of the boring bar which was in consequence reversed ie its cutting edge was on the right and had to move downwards to do the cutting. The carriage stop was set so that leftward movement of the carriage would be blocked when the cutter's edge was 4.5 mm from the End Stop of the jig. The first Cylinder face was then remounted in the jig again with its reference end up against the jig's end stop. In this position the right end outer arc was machined again making sure that the last cut was with the face of the angle plate at 20.5mm from the lathe axis. The phote shows the setup with the cutter in this upside down position. 





Then the same again for the other Cylinder Face. Here you see the two Cylinder Faces at this stage of the game. Before soldering they still need a bit of milling but that will wait until it can be done with the same milling lathe setup as the Cylinders.





*Turning the Cylinder Tubes*

The Cylinder Tubes are machined from two bits of 32mm brass rod; I cut these bits long enough so that I can also make the upper and lower flanges for the cylinders. The first step was to face off the end and then drill and bore to a depth of 39mm a hole of diameter 21mm (i.e. 1 mm less than the final diameter of the cylinder bores. 









Then the outer diameter of the Cylinder Tube rims was machined to final size (diameter 31mm). This are a contact surfaces for soldereing so one must remember to avoid touching them.





The lathe carriage stop was then set so that leftward movement of the carriage would be blocked with the tool cutting edge at 32.5mm from the face. To make this measurement I use the index dial of the compound slide. Then the machining was done with the knife tool gradually increasing the depth of cut as the carriage advanced. After four passes with a maximum cut depth of 0.25mm I had the result shown in the next pic: a shallow cone starting near the right end and ending about 6mm short of the position defined by the carriage stop. These last 6mm have their final diameter of 29mm.





The job was then completed in a similar fashion using a right shouldered knife tool with the carriage stop on the right of the carruage up to a shoulder 4.5mm to the left of the cylinder end. Here is the result; the Cylinder Tube on it's own and then the Cylinder Tube with a Cylinder Face perched on top of it.









The final turning step was of course to part the Cylinder Tube off for an over length of about 37mm i.e. about 0.5mm of excess material at each end. 





I then did all this over again for the second Cylinder Tube. Before soldering both Cylinder Tubes still require machining with the lathe in it's milling configuration.

*Finishing the Exhaust Nipples*

Before converting my lathe to it's milling configuration I made the two sacrificial bolts and finished the turning of the Exhaust Nipples. To do this I held them by their threads using a suitable hex nut as shown in the pic below.





*Making holes in the Cylinder Tube walls*

Here you see the shallow hole for the sacrificial bolt being tapped.





The next pic shows a Cylinder Tube being set up at an angle of 70 degrees from the lathe axis, in preparation for drilling the steam hole through the cylinder wall.





The next three pics show the milling of a small flat, the spot drilling and the final drilling of the steam hole.













*Making holes in the Cylinder Faces*

The Cylinder Faces have a 2mm hole at the center of the inner arc and two 3mm width steam channels to connect the steam ports to the holes through the Cylinder Tube walls. 









*Sub-parts ready for soldering*

The pic below shows the three sub-psrts and scrificial bolt for each of the two Cylinder Units.





*WHAT'S NEXT?*
The next post will report of the work needed to complete the two Cylinder Units namely the silver soldering and then the final machining. As I mentioned before I'm always a bit nervous when there is silver soldering to be done, particularly when the parts being soldered are not small....


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## romartin (Mar 16, 2013)

[SIZE=+2]*THE CYLINDER ASSEMBLY - 3. Cylinder Unit - 2*[/SIZE]

This post reports on the soldering and finish machining of the soldered Cylinder Units.
The drawings of all the parts of the Cylinder Units are attached to the first post on the Cylinder Assembly.

*BUILD LOG*

*Silver Soldering*

This first pic shows the "oven" and the propane torch with the biggest of the three nozzles. The oven is an open trough made of some sort of heat resistant building material (not asbestos!). From the same material I prepared a V perch for one Cylinder Unit.





Below is a closeup showing two short pieces of silver solder in each of the two steam passages of the Cylinder Face.





This is the solder which will flow into the curved gap between the Cylinder face and the wall of the Cylinder Tube. I also prepared a suitable "invitation" depression at both ends of the Cylinder Tube so that I could touch the silver solder rod at those points to fill the gap between the contact surfaces around the rims. The join between the Nipple and the Cylinder Face edge already presents an adequate "invitation" and so needs no special peparation.

Before uniting the three sub-parts I mixed the plux powder with a small amount of deionized water to make a smooth thick white paste and spread this liberally on all the contact surfaces. The Exhaust Nipple is held in place on the Cylinder face with the help of small bump made with a center punch on it's 6mm spigot. The Cylinder Face is held against the Cylinder Tube with the sacrificial screw. All the visible lines of contact between the parts were then liberally covered with flux paste. Here is a pic of the first victim ready for roasting.





I have no pics of the actual soldering process which, for me, is too tense and fast to admit such fun. In my very limited experience of silver soldering it is important to do the job quickly. This means having mentally rehersed the process first, it means applying abundant heat, it means not expecting the anti-oxidizing efficiency of the flux to last for more than a few seconds! For an experts advice on silver soldering I point you to Chris Heapy's Workshop Techniques:
http://www.astronomiainumbria.org/a...ca/easyweb.easynet.co.uk/_chrish/techindx.htm

As a matter of fact my first attempt failed. By the time I got around to touching the solder to the invitation on the second end, the flux was dead and the solder simply didn't want to know. The next pic shows the victim after pickling in battery acid and washing in abundant flowing water. I think you can see the unsoldered gap between the Cylinder Tube and the Cylinder face.





Making a new set of subparts took me a couple of days. The second time around the soldering of both Cylinder Units went well. I put more flux on the exposed surfaces all around the lines of contact, I used more heat right from the beginning, and I had the sequence of process steps much clearer in my mind.

The next pic shows one of these Cylinder Units after a preliminary cleaning with fine emery paper.





At this point the two Cylinder Units were ready for finish machining.

*Finish Machining*



There were five separate setups, in the order listed below. Each setup was applied to both Cylinder Units before proceeding to the next setup.
Face off the top end of the Cylinder.
Face off the bottom end of the Cylinder and bore the Cylinder to its final diameter of 22mm.
Mill the Port face, mill the steam ports, drill and tap M2 the 8 bolt holes.
Make the 6 threaded holes in Cylinder's top end.
Make the 6 threaded holes in Cylinder's bottom end.
*Cylinder ends and bore*

I'm sorry but I forgot to take snaps during the first two steps. I used the three jaw chuck and used my dial Indicator to check the absense of wobble.

Before starting I made a decision to allocate one of the units to be on the left (flywheel end) and the other to be on the right and made suitable distinguishing punch markings just below the two exhaust nipples. I was then careful for each Cylinder Unit to machine it's bore in the same setup used to face off it's the bottom end. 

*Valve Face*

For the third and subsequent steps, the lathe is in it's milling configuration. Here the Cylinder Units are held vertically in the vice with emery paper protecting the cylinder ends. All positioning of the part for milling was done using the index dials of the cross slide and the vertical slide (being careful to feed always in the same direction when making the final approach to a new position). The zero setting of these dials was done by detecting the reference edges of the Cylinder Face (bottom and front) with the help of a length of 5mm stainless steel held in the 3-jaw chuck. This system probably gives me a certain systematic error (ie common to all positions) but does give a relatively high precision when moving from one position to the next.

To mill the Valve Face, I used a 12mm end mill and made two vertical passes with an overlap of 0.5mm at the center.





The next three pics show the milling of the ports and the result. The 2mm end mill I used has a depth limit of 4mm which was just enough but which wouldn't have been enough if I hadn't decided, for other reasons, to mill the hidden steam passages into the Cylinder Face and not the Cylinder Tube wall!













The pic below shows a moment during the tapping of the eight holes for the bolts which will fix the Steam Chest and it's cover to the Cylinder Unit.





*Tapped holes in Cylinder Ends*

For making the six tapped holes in each end of each Cylinder Unit, I again used the lathe's milling configuration. This time the Cylinder Units were mounted horizontally with the Valve Face at the bottom (protected and raised to clear the Exhaust Nipple) and with a small brass V block at the top.

The pics below show the setting up using a face plate to ensure that the Cylinder End was square to the lathe's spindle axis, and using the 5mm rod in the 3-jaw chuck to do the zero setting of the Y and z slide index dials with the Cylinder bore as the reference. I chose the center of the bore as the origin ie Y = Z = 0.









Once the setup was complete the positioning for each of the holes was done in the same way as for the Valve Face. The six holes lie equidistant around a circle of radius 13.5mm. The table below gives the values of Y and Z for each of the holes.
Y=-13.50 Z=0
Y=+13.50 Z-0
Y=-06,75 Z=-11.69
Y=+06,75 Z=-11.69
Y=-06,75 Z=+11.69
Y=+06,75 Z=+11.69

The next two pics show the spot drilling and the tapping of one of the holes.









*Finish Machined Cylinder Units*

Here finally is a snap of the two finish machined Cylinder Units. To complete them the Valve faces and the bores must be lapped but I will do this later.





*WHAT'S NEXT?*

As I'm anxious to mount these Cylinder Units in position and check the alignment of the whole I have decided to do the Cylinder Flanges and the Piston gear next.


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## romartin (Mar 19, 2013)

[SIZE=+2]*THE CYLINDER ASSEMBLY - 4. Cylinder Covers*[/SIZE]

This post reports on the making of the top and bottom Cylinder Covers which I will call Flanges in this post. The drawings of all the parts of the Cylinder Units are attached to the first post on the Cylinder Assembly.

Here are some extracts from the drawings showing the Plan and Front 2D views of the flanges.















*BUILD APPROACH*




Three aspecta of the build approach are worth mentioning.
I decided to make the 6 bolt holes around the rims of the flanges using my lathe's milling configuration in the same way as I had done for the corresponding tapped holes on the cylinders. To do this the flanges have to have enough spare material to be able to grip them in the machine vice. For this reason I started making each pair of flanges (top + bottom) from a single chuck of 32mm brass rod. In fact these two chucks were the leftovers from the chunks from which the cylinders were made. With this in mind, the steps for making the flanges were as given below.
Using the 3-jaw chuck, machine on one end of a chunk the rim and the cylinder interface of the top flange, including the 8mm recess for the Piston Nut.
Reverse the chunk in the chuck and machine the rim and the cylinder interface of the bottom flange, including the 5mm hole for the piston rod.
Same again for the other chunk for the second pair of flanges.
Convert to milling configuration and drill the set of 6 holes in both ends of both chunks.
Sperate the two flanges in each pair. In fact I used a hacksaw as I didn't fancy trying such a long parting operation on the lathe.
Convert back to lathe configuration for machining the other faces

For the bottom flanges it is very important that the locating disk on the cylinder interface, the hole for the piston rod, the 10mm spigot which fits the 10mm hole in the Platform, and the M10x1 thread on this spigot all be perfectly concentric. Getting perfect concentricity for features on opposite sides of a turned part rquires a bit of care. I decided to machine the side with the 10mm spigot and it's thread with the flange mounted on a custom mandrel with a closely fitting 5mm spigot through the hole for the piston rod and a nice fat shoulder to keep the flange square up against the face of the locating disk.
For both the top and the bottom flanges the position of the flange is determined not by the fixing bolts but by the fit of the 0.5mm thick locating disk which enters into the cylinder bore. For this reason I decided to give the bolt holes in the flanges a diameter of 2.25mm instead of the nominal 2mm shown on the drawings. (The situation is similar to fitting a new back plate onto a chuck; the bolt holes through the back plate should be oversize so that the bolts dont interfere with the positioning of the back plate; their job is simply to hold the chuck firmly onto the back plate.)
*BUILD LOG*

This first snap shows the two chunks each with two flanges of which the cylinder interface and the outer rim has been machined. The material between the two rims was left with a diameter slighly larger than that of the flanges. 





The next pic shows one of the pairs mounted in the machine vice for drilling the 6 bolt holes. The Y and Z zero setting was done by detecting the horizontal and vertical edges of the locating disk of the flange. The technique for positioning the flange to get the 6 holes in the right place was described in the previous post.





Here then are the two pairs with the cylinder interfaces and bolt holes for all four flanges. The pairs are now ready for separating into separate flanges. The groove around the girth of the chunks is there to help me keep the hacksaw straight.





The machining of the upper faces of the top flanges was done holding them by the rim in the 3-jaw chuck with the help of a custom spacing washer made from white PVC as shown in the pic below.





Here is a snap of the two finished top flanges.





Finishing the bottom flanges was more complex. First the outer faces of both bottom flanges were faced off to the final overall height (10.5mm including the locating disk).





Then, from a bit of scrap mild steel bar, I made the custom mandrel with a nice fat shoulder (20mm diameter), a 5mm spigot 9mm long and a M4 thread 5 mm long. This mandrel remained in the chuck until the machining of both bottom flanges was finished.





The next two snaps show respectively the machining and the threading of the outer face of one of the two bottom flanges mounted on this custom mandrel.









Here then is a pic of the two finished bottom flanges.





At this point of course (thankful for having prepared all the bolts first!) I could not resist mounting the Cylinder Units and the Flanges onto the Platform to check the fits and to get a first glimpse of what my steam engine would look like. During this process I discovered that I had boobed the position of two of the twelve bolt holes in the Platform - these two holes were about 0.25mm away from their correct positions. I corrected this with about half an hours work with a small rat-tailed hand file. One day I may decide to make a new Platform and recover from this one a Platform for the single cylinder version of the engine design. Here is a pic of the engine after these assembly operations.





*WHAT'S NEXT?*

The next job is to lap the bores of the cylinders and then make the two sets of Piston gear.


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## romartin (Mar 23, 2013)

[SIZE=+2]*THE CYLINDER ASSEMBLY - 5. Lapping Bores and Making Piston Gear*[/SIZE]

This post reports on lapping the Cylinder bores and making the Piston gear. The drawings of all the parts of the Cylinder Units are attached to the first post on the Cylinder Assembly.

*LAPPING THE CYLINDER BORES*

From experiments with a temporary brass piston about 15mm in length I determined that the two cylinder bores were not only almost perfectly parallel but also of the same size to within 0.02mm. I decided to make use a single lap for both. 

The lap was turned from a bar of aluminium which started life with a diameter of 35mm bar but which had already been used to make a lap for a cylinder of somewhat larger bore diameter. This time I used one end of this bar to make a shorter lap a bit over twice the length of the cylinders. 

The target diameter for the lap was 0.04 less than the diameter of the smaller bore. However before making the final cut I make eight equi-spaced horizontal grooves along the length using a metric threading tool mounted horizontally in a tool holder and moving the lathe carriage by hand. These scores had a final depth of about 0.5mm. To control their spacing around the diameter I used my usual technique for indexing angles of the spindle using the screw cutting gear train as shown in previous posts. 

Once the lap was made I cleaned the lathe, removed the tailstock, and positioned the carriage as far to the right as possible. The "grinding paste" I used was a very liquid mix of parafin and very fine pomice powder sold for polishing both stone (like marble) and metals. I also kept a supply of parafin handy for keeping the lap moist with the help of an old toothbrush.
As I had anticipated, the actual lapping process was quite quick. I started turning the lap by hand until the cylinder being lapped moved easily over the entire length of the lap. At that point I put a glove on my right hand to hold the cylinder, applied plenty of parafin, positioned the cylinder in the middle of the lap and turned on the lathe (250rpm) for the final polishing, being careful to keep the entire length of cylinder on the lap until I had turned off the lathe motor. No problems. Here are some pictures.

Making the grooves down the length of the lap





The lap ready for use





A cylinder bore after lapping





*MAKING THE PISTON NUTS*

Here is an extract from the drawings.





It is important that the threaded hole through the nut be perfectly square with the flat face which will press down onto the Piston. Simirlar precision for the rim and for the hex spigot on the other side are not required. For this reason I used the first setup in the 3-jaw chuck to face off the bottoms and drill and thread the holes of both nuts. Then the machining of the rims and the spigot on the upper sides was done using a threaded M3 mandrel which I already had in my draw of such goodies. Here are some pictures.

Machining the upper face to form the spigot.





Filing the hexagon onto the spigot.





The finished Piston Nuts.





*MAKING THE PISTONS*

Here are two extracts from the drawings.











Care is rquired when making the Pistons both because perfect concentricity and squareness is required for almost all its surfaces and becuase the Piston cannot be held by the external diameter once this has been turned to it's final diameter. I mulled over the best approach and finally decided the following sequence.
Setup 1
Grip a suitable chunk of brass rod in the 3-jaw chuck with at least 20mm protruding 9ie enough for both Pistons. Turn the outer diameter to 22.5mm (i.e. about 0.5mm oversize with respect to the Cylinder bores) for a length of 20mm.
Drill and ream a 3mm hole down the center for a depth of 20mm
Face off the end and then cut or part off a slice of length a bit over 8mm.
Face off again and then cut or part off a similar slice for the second Piston.

Setup 2
Mount one of these Pistons in the 3-jaw chuck using a spacer between it and the chuck face to ensure that the turned face is parallel to the chuck face.
Face off to reach the final Piston height of 8mm
Bore the recess for the Piston Nut

Setup 3
Same again for the other Piston

Setup 4
Use the 3-jaw chuck to make a custom mandrel with a fat shoulder and a partially threaded 3mm spigot like that on the upper extremity of the Piston Rod. The shoulder should be at least 36mm from the chuck jaws to allow the Piston to be tried down the full length of the cylinder. Do not remove this mandrel from the chuck until both pistons are finished.
Mount a Piston on the mandrel and finish machine its outer diameter to be a close sliding fit in the bore of one of the Cylinders.
Same again for the other Piston with the bore of the other Cylinder.

Here are some pics showing the application of this approach.

Machining the bottom face and the hole for the Piston Rod.





Plunging a 6mm end mill to start the recess.





Boring the recess to final size.





The custom mandrel for turning the outer diameter.





The finished Pistons.





*MAKING THE PISTON RODS*

Here are some extracts from the drawings.









The key issue for making the Piston Rods is that one wants to use precision ground 5mm stainless steel rod but this makes it more difficult to ensure perfect concentricity of the threaded spigots at the end with the rod itself. The answer is to use the 4jaw chuck, a dial indicator and sufficient patience to mount the rod perfectly concentric with the lathe axis. Once this is done the amchining is simple. This process must be repeated for each end of each rod.

Here is a pic of a rod being setup in the 4-jaw chuck.





*MAKING THE PISTON ROD GLANDS*

Here are some extracts from the drawings.









As can be seen, I decided a change with respect to the design shown in the original drawings because I have realized that it would be practically impossible to get a spanner anywhere near these glands let alone use it to adjust them. So instead of the glands having a hexagonal section they will be round (diameter 15mm) with ten 2mm holes equispaced along radii in the horizontal plane. This will allow the glands to be adjusted by inserting a 2mm lever into a hole. The shank of an old 2mm drill will make a good lever.

The hole for the piston rod and the M10x1 internal thread must be perfectly concentric and so will be machined in the same setup. 

Here are some snaps of the build.
Boring the hole for the M10x1 thread.





Machine threading.





Setup for drilling the ten radial holes using my electric drill fixed to the cross slide and indexing the angle of the lathe spindle with the gear train.





Spot drilling for one of the radial holes. The spot drilling was of course followed by drilling to a depth of 4mm with a normal 2mm drill.





Here are the finished glands.





*TRIAL ASSEMBLY*

Now having all the pieces I could try assembling the piston gear and integrating them with the rest of the engine. The first step was to mount the Piston gear with the cylinders and the bottom flanges onto the Platform and check the fits and alignments. I then added the Piston Slide and their suppports. The snap below shows the result at this stage. 





The fits seemed ok to me - i.e. a bit tight but without spots whch were tighter than others. I proceeded to mount this group on the top of the eight pillars and then connect the Small Ends of the Connecting Rods to the Piston Slides by inserting the pivot bolts. Here is a pic of the result.





Again the fits seemed ok and so I consider this phase satisfactorily concluded.

*WHAT'S NEXT?*

There is still quite a bit of work to do to finish the engine. The Steam Chests and Valve gear have to be made as do the Input and Exhaust Piping Assemblies. The engine also needs a solid and not too narrow wooden base. Then all parts need a bit of finishing. I love the interplay of natural metal colours and so am inclined not to paint anything.

Next on my plate is to make the two Steam Chest Units and their Covers. This means more silver soldering...


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## romartin (Apr 9, 2013)

[SIZE=+2]*THE CYLINDER ASSEMBLY - 6. Steam Chest Units and Covers*[/SIZE]

This post reports on making the two Steam Chests and their covers. The drawings of all the parts of the Cylinder Assembly are attached to the first post on the Cylinder Assembly.

*STEAM CHEST UNIT*

Here are some extracts from the drawings.










*Build Approach*

The Steam Chest Unit is composed of three brass sub-parts silver soldered together. These parts are the Steam Chest itself, the Inlet Nipple and the Valve Rod Guide. While making the latter two are straight foreward turning tasks, the Steam Chest is quite a complex shape. Clearly most of the work would be done in the milling configuration - however the M8x1 internal thread for the Valve Rod Gland would have to be screw cut in the normal configuration with the work in the 4-jaw chuck. 



I decided to use more of the 25mm diameter brass rod I had already acquired to make the Cylinder Face. The Build Plan for the Steam Chests was therefore clear.

Use the 3-jaw chuck to face off two bits of this bar to have a finished length of exactly 38mm.
Convert the lathe to its milling configuration with the machine vice oriented to close vertically.
Reduce these round bars to rectangular blocks with the required 22m x 12mm section by flycutting the four sides after careful setting up to ensure squareness.
For each Steam Chest in turn:
Mill the central cavity 10mm x 24mm) using first an 8mm end mill and then a 5mm end mill on the four corners.
Drill the eight 2mm bolt holes using the X (cross slide) and Z (vertical slide) index dials to position the work precisely for each hole.
Drill the 6mm x 3 hole at the top of one side for the boss of the Inlet Nipple.
Position the work at an appropriate angle and then drilling the 3mm hole from the above hole into the central cavity.
Drill the 5mm hole through the top for the Valve Rod Guide
Drill a 3mm hole through the bottom along the axis of the Valve Rod. Later, this hole would hold a custom jig to help center the work in the 4-jaw chuck for doing the M10x1 screw cutting.
[/;ist]
Convert the lathe back to normal configuration.
Make a custom jig with an M3 spigot to go through the hole for the Gland and a boss of diameter 10mm to facilitate use of a Dial Indicator to center the Steam Chest in the 4-jaw chuck.
For each Steam Chest in turn:
With the custom jig in the 3mm hole, center the work in the 4-jaw chuck.
Drill and bore the hole to a diameter of 7mm for a depth of 4.5mm.
Screw cut the hole M8x1

*Build Log*

These three photos show the process of fly cutting the four sides of one of the 25mm bars to produce a block with a section of 22mm x 12mm. The second photo shows the use of a faec plate to ensure that the axis of the bar is perpendicular to the lathe's splindle axis. To produce flat surfaces, I prefer flycutting to milling with an endmill for two reasons: firstly I get a much better surface finish and secondly I can sharpen the flycutter toolbit but I cant sharpen endmills!














Here are the finished blocks; sorry the photo is rather blurred.






The following pics show milling the central cavity and drilling the six bolt holes.










Here are the two Steam Chests at this stage.





And here they are with the lateral holes for the Valve Rod Guide, The Inlet Nipple and, at the bottom, the custom jig.





The next three photos show the custom jig itself, the jig being used with the Dial Indicator to center a Steam Chest in the four jaw for crew cutting the thread for the Valve Rod Gland, and the finished Steam Chests ready for soldering.













The following rather blurred pic shows the two Valve Rod Guides ready for soldering. I didn't snap the Inlet Nipples because they're identical to the Exhaust Nipples soldered to the Cylinder Units.





Here you see one of the Steam Chests lying in the "oven" about to be silver soldered. The solder for the Valve Rod Guide was applied from insode the cavity to avoid messing the visible outside surfaces. The soldering of both Steam Chests went off without a hitch.





Here are two photos showing the Steam Chests after pickling and after a clean up with fine emery cloth.









*STEAM CHEST COVERS*

Here are some extracts from the drawings.









*Build Approach*

I decided to fabricate thee Covers dirsctly from 3mm brass plate. The machining of the edges and the recess on the ouetr face as well as the drilling of the eight bolt holes would all be done usibg the milling configuration of my lathe.

*Build Log*

After rough cutting two rectangles of brass plate with about 1mm of excess on both width and length, for each I first machined the four edges to make two 22mm x 36mm rectangles. To ensure squareness of the angles, before tightening the jaws of the machine vice, I gently press an already machined edge (after deburring!) up against the shank of a 2.5mm drill held reversed in the 3-jaw chuck.

Then for each Cover in turn I mounted it in the machine vice with its faces normal to the lathe's spindle axis for drilling the bolt holes and milling the shallow decorative recess in the outer face, as shown in the following two pics.









With the machining finished I then gave the facial and lateral surfaces a quick polish with fine emery paper. Here then is a snap of the finished Steam Chest Covers.





*WHAT'S NEXT?*

The next course on my plate is to make two sets of Valve Gear namely the Slide Valve, the Valve Rod, the Slide Valve Pusher and it's Fixing Screw.


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## romartin (Apr 14, 2013)

[SIZE=+2]*THE CYLINDER ASSEMBLY - 7. Valve Gear*[/SIZE]


This post reports on making the two sets of Valve Gear. Each set is composed of:

Valve Rod,
Valve Rod Link,
Valve Rod Gland,
Slide Valve,
Valve Pusher and it's Fixing Screw.
The drawings of all the parts of the Cylinder Assembly are attached to the first post on the Cylinder Assembly.

*VALVE ROD*

The Valve Rods are made of stainless steel. I decided to make them from precision ground 3mm rod. The hole down the axis with a lateral vent hole at 11mm from the top is to avoid back pressure when the rod moves in the blind hole of the Valve Rod Guide at the top of the Steam Chest. Here is an extract from the drawings.






I used the 3-jaw chuck to hold the rods both for drilling the hole down the axis and making the M2 thread at the other end. Drilling a fine hole in stainles steel requires a good quality drill and a bit of care and a bit of time. I drilled the lateral vent by punching a center pop and then using the drill press with the rod held in a small machine vice. I could have used the lathe but the vertical configuration of the drill press allows me to see better what I'm doing.
Here is a pic of the finished valve rods.






*VALVE ROD LINKS*

The Valve Rod Links are part of the articulated joint between the Valve Rod and the Eccentric Rod. A 2mm bolt and nut joins each Valve Rod Link to the corresponding Eccentric Link on the end of it's Eccentric Rod. The Valve Rod Links themselves are made from brass. Here are two extracts from the drawings.










The links were made using the milling configuration of the lathe with the exception of the rounded collars which were turned holding the links on a short M2 Mandrel. Sorry I have no pics of the build process; here is a shot of the two finished Eccentric Links and the two mild steel M2 bolts and nuts which join them to the Eccentric Links.






*VALVE ROD GLAND*

These glands prevent the live steam from hissing out of the Steam Chest through the gap around the rod. I changed the design a bit with respect to the original drawings by introducing a hexagon section at the end to facilitate adjustment of the gland.

Here are some extracts from the new drawings.






The glands were made from 10mm phosphor bronze rod. For a gland it is important that the hole for the valve rod and the thread be perfectly concentric - they must therefore be made in the same setup. I then made the hexagon by holding the gland in a threaded hexagon nut (which was itself held in the 3-jaw chuck) and using my file guide and the lathe gear train for indexing the angular position for each of the six flats. Here is a photo.






*SLIDE VALVE*

Inspite of their finicky size the slide valves have a fairly complex shape to be produced with my lathe in it's milling configuration. With respect to the original drawing there is a small change - the depth of the vertical (3mm) slot is reduced from 6mm to 5mm. I did this because 5mm is sufficisnt to clear the Valve Rod and the 3mm end mill I have has a depth limit of 5mm!

Here are two extracts from the new drawings.










First I made two rectangular brass blocks by milling away the excess from two bits of scrap brass.






Then I milled the bevels to produce the sloping sides. The angle of the slope can be derived from the drawings - it is arc tan(1/6). To set the block at the appropriate angle in the machine vice I used a carpenters angle guide as shown in the following snap.






The next step was to mill the crossed slots. The block was mounted on its side in the machine vice - first I made the 5mm slot (moving the cross slide)and then the 3mm slot using the vertical slide.

*Doing the job*





*Result*





The final step was to mill the recess which form the bridge between a cylinder port and the exhaust port.






Here are the two finished Slide Valves.






*VALVE PUSHER AND IT'S FIXING SCREW*

Other finicky customers! For them as well a minor design change: the pusher has been lengthened by 0.3mm so that the head of the Fixing Screw seats fully onto the 3mm recess on the top of the Valve Pusher. 

Here are some extracts from the drawings.










I decided to make the two pushers at opposite ends of a bit of 5m x 5mm square rod. This was to facitate the last step of the machining which was to cut the slot down the middle so that the fixing screw would squeeze the two halves of the pusher and thereby grip onto the valve rod.
Since I didn't have any 5x5 rod I first produced it by milling away the excess from a bit of scrap brass. Then I drilled the 3mm holes from side to side. Rotating the bar 90 deg in the vice I then drilled the holes for the Fixing Screw - first at the diameter appropriate for a M2 tap and then, for half the depth (2.5mm) at a diameter of 2mm. At this point I could tap the bottom halves with an M2 tap held in my usual tapping guide.

This snap shows the bar at this stage of the game. 






At this point I converted the lathe back to it's normal configuration, mounted the 4-jaw chuck and used my Dial Indicator to center the bar in the chuck.






Then, with the chuck oriented with the 3mm hole horizontal, I used my QCTP mounted manual slitting saw to cut the slot (slit?)






Once the two slots were cut, I separated the two Pushers and faced of the cut ends again holding the work in the 4-jaw chuck. 
The two Fixing Screws were turned from 3mm brass rod stock. The slits in the heads were made with the Slitting Guide shown above. Here is a pic of the two finished Valve Pushers with their Fixing Screws.






*ASSEMBLED ENGINE WITH VALVE GEAR*

As usual, at this point I could not resist the temptation to assemble all the existing parts of my engine. This time I even made the gaskets to seal the contact faces of both the Cylinder Covers and the Steam Chests and their Covers. I made the gaskets from a fairly heavy white paper. To make the holes I used the cover as a template with the paper pressed against it, first pricking each hole with a sharp pointed tool and then pushing a twist drill of the nominal hole diameter straight through with no twisting movement. This made technique produced fairly clean round holes of the right size. Here are pics of the gaskets.










Hear is the engine with the new Valve Gear and of course the Eccentrics and their Straps which have been patiently awaiting this moment for several months now.






*WHAT'S NEXT?*

My next task is to make a wooden Base and the Inlet and Exhaust Manifolds which provide the two cylinders with common inlet and exhaust nipples. And then to see whether it will run on compressed air.


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## Lawijt (Apr 14, 2013)

What a job....I can only dream about that. But a question....Why you build a steam engine??? Why you don't build a nice V8 with a blower??? If I see this , you can build anything!!!
Thanks for all that beautifull pictures , tekst & drawnings.

Greetings from Belgium

Barry


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## romartin (Apr 14, 2013)

Hi Barry!
Thank you for your kind words.
I think I build steam engines because for me they have something noble and magic which stimulates my imagination in a way that no IC engine has ever done. I remember being sad about 60 years ago when I realized that those magnificent steam locomotives I so loved were being replaced by electric trains tapping energy from an overhead wire. Not to mention being thoroughly dismayed and upset when the electric ones were replaced by smelly diesel beasts.
As a young engineering student I did a two month stage in the maintenance shop of a major coal fuelled electric power station with enormous boilers furnishing superheated steam to a shining row of turbines each coupled to its dynamo. In that place too I would clamber about on narrow ladders and gangways soaking up the sights and odours and sounds that spoke gently of immense power kept under tight control.  
So I got hooked as a kid and I'm still at it! I know it's not a very good reason but there it is...


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## romartin (Apr 25, 2013)

[SIZE=+2]*THE PIPING ASSEMBLIES*[/SIZE]

This post reports on making the Inlet and Exhaust Manifolds which provide this two cylinder engine with a single input connector and a single exhaust connector.

The working drawing for these manifolds are attached to this post. Here are two extracts showing the manifolds.










*DESIGN CONSIDERATIONS*

The design has been simplified with respect to the model images shown in the opening post of the thread. Each manifold is now composed of a Tee, an Elbow, a Pipe connecting the Tee to the Elbow, and two Male Collars each with a Nut to connect the Tee and the Elbow to one of the nipples on the engine cylinder assemblies. The connection interface of the nipple on the Tee is identical to the connection interface of the nipples on the engine cylinders. The four joints Male Collar - Elbow, Tube - Elbow, Tube - Tee and Male Collar - Tee are all silver soldered.

The only difference between the Inlet Manifold and the Outlet Manifold is the length of the Tube. 

*BUILD APPROACH*


Two aspects of the build approach are worth mentioning.

I intended to fashion the rounded edges of the Elbow and Tee using my File Guide. This requires that the part to be filed be mounted in the lathe chuck with the axis of the curve along the lathe spindle axis. The curves concentric with the Tube presented no problem; they can be filed with the setup used to turn the bore which receive the Tube. However on the Elbow, the curve concentric with the Male Collar requires a special setup using a custom mandrel screwed temporarily to the Elbow along the axis of the Male Collar. Once the curve has been filed, then the hole to receive the Male Collar can be machined to its final size.
The Manifolds are rigid; they have little flexibility to tolerate poor alignment between the axes of their Male Collars and the axes of the mating nipples on the Cylinders. This implies an important requirement that the parts of the Manifolds must be firmly held in the right relative positions during the soldering process. To ensure this for each Manifold I made a custom jig consisting of a brass bar with two nipples having the same relative positions as those on the Cylinders. The position on the bar of one of the nipples of the jig coud be adjusted before tightening is fixing nut, and the correct distance between the nipples of the jig was ensured by fixing the jig itself to the engine using two short threaded sleeves each of which engaged the threads on both an engine nipple and a jig nipple. In this setup, the nut holding the adjustable nipple on the jig was tightened.
*BUILD LOG*

*Male Collars and Nuts*

Making the Male Collars and the Nuts is fairly straight foreward turning. To make the internal M10x1 threads of the nuts, I choose to turn them on the lathe without using the motor i.e. to turn the lathe spindle by hand. This ensures that a fully dimensioned thread reaches right the bottom of the nut; something a die cannot do. I use a bit of sticky tape of the rim of the chuck to indicate the exact angle at which to stop turning the spindle and the bottom of the thread.
Here is a rather dark pic of the turning of the 45deg taper on a Male Collar, followed by a snap of the finished Male Collars and Nuts.










*Elbows and Tees*

I decided to make the Elbows and Tees from 10x10 square brass stock of which I had a short but sufficient piece. This required using my 4-jaw chuck and going through the process of getting the bar to run true using the technique with the Dial Indicator and two small chuck keys. I'm getting better and quicker at doing this now and am beginning to appreciate that, when necessary, I can get a part to run more truely using the 4-jaw than it does with the 3-jaw self centerer.
The first step was to machine the Pipe interface end and file the curve concentric with the pipe for both Elbows and both Tees. Here is a pic of the setup for filing the curves, followed by a pic of the four parts at the end of this step.











The lathe was then converted temporarily to it's Milling Configuration, and the Elbows were prepared to accept the Custom Mandrel by making a M4 thread along the Male Collar Axis for a depth of 6mm. 

Here is a pic of the Custom Mandrel (which I already had from some previous exercise), followed by a pic of the curve concentric with the Collar being filed on one of the Elbows.










And here is a snap of the two Elbows after this filing.






At this point, with the lathe once again in Milling Configuration, the holes for the Male Collars were finalised. Then back to Turning Configuration to machine the M10 nipples of the two Tees, again using the 4-jaw chuck. For the external M10 threads I used motor power. Here is a pic of the finished Tees.






*Soldering*

Here is a picture of the Custom Jig for the Inlet Manifold.






This snap shows the Inlet Manifold fixed to the Jig lying in the oven ready for soldering. All contact surfaces, including the internal ones, were cleaned with fine emery paper and then covered with flux paste. Naturally I avoided allowing any flux to reach the Nuts and the position of the Jig ensures that molten flux will run down onto the Elbow or Tee and not up onto the Nut.






The soldering went off without problems. Here is a pic showing the two manifolds after a short pickle in battery acid and and a good wash in abundant water.






I then cleaned the manifolds using fine emery paper and mounted them on the engine. The trouble taken to make the custom jigs seems to have been worth it, the Nuts of both Manifolds screw easily with no binding onto the mating nipples on the engine. This final snap shows a back view of the Engine with the mounted Manifolds.






*WHAT'S NEXT?*

Apart from needing a wooden Base for stability, the engine is now complete and ready for testing on compressed air. 

View attachment Piping2 Assemblies 1of1.pdf


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## wulyum (Apr 25, 2013)

What a great project and very well presented. Many thanks
Wulyum


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## romartin (Apr 25, 2013)

Thank you Wulyum; glad you like it. I've enjoyed making it and am dying to see it running which could be in the next few days.
Bye the way, I couldn't find the customary introductory post about you in the Welcome section of the forum. Have you posted one?


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## romartin (Apr 27, 2013)

[SIZE=+2]*SEEING IT RUNNING*[/SIZE]

This post reports on first test runs of the completed steam engine. It is now screwed to a simple base of varnished wood. Attached to this post are the last two working drawings which show the models of the integrated engines respectively with one cylinder and with two cylinders.
Here are four snaps of the finished engine.

*Front*





*Front Right*





*Back*





*Back Right*





*FIRST TESTS*

The testing was done with compressed air and was all over quite quickly. First I removed the Inlet and Exhaust Manifolds and made the engine run with only one cylinder connected to the compressed air line; the other cylinder was therefore a small load. In this way I checked the correct timing and functioning of the valve. Then the same again for the other cylinder. Then I remounted the Manifolds and was finally able to see and hear my engine running as recorded by the following rather clumsy video. Towards the end this video tries to demonstrate the self-starting property of the engine conferred by the 90 degree angle between the cranks. 

http://s1061.photobucket.com/user/romartin1/media/VerticalEngine/EngineRunning_zps2a36bfeb.mp4.html

*UPDATES TO DRAWINGS*


I have updated all the drawings to reflect the engine as built. Rather than create new places for these updated drawings I preferred to replace the old versions in the posts to which they were attached. The list below indicates where to find these new versions of the drawings. 

Base1 Assembly 10f1.pdf - Post #2 on Page #1
Base2 Assembly 10f1.pdf - Post #2 on Page #1
Vertical Structure1 Assembly 1of1.pdf - Post #4 on Page #1
Vertical Structure2 Assembly 1of1.pdf - Post #4 on Page #1
Shaft1 Assembly 1of2.pdf - Post #5 on Page #1
Shaft1 Assembly 2of2.pdf - Post #5 on Page #1
Shaft2 Assembly 1of1.pdf - Post #5 on Page #1
Cylinder Assembly 1of3.pdf - Post #16 on Page #2
Cylinder Assembly 2of3.pdf - Post #16 on Page #2
Cylinder Assembly 3of3.pdf - Post #16 on Page #2
Piping2 Assemblies 1of1.pdf - Post #53 on Page #6
Overall1 Assembly 1of1.pdf - This post
Overall2 Assembly 1of1.pdf - This post
*CONCLUSION*

Well that's it! I have enjoyed this experience of keeping a public log of the build as it progressed and would like to thank all those folk who have followed this trail and have provided me with much stimulus and encouragement. 

View attachment Overall1 Assembly 1of1.pdf


View attachment Overall2 Assembly 1of1.pdf


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