Tandem Compound Poppet Valve Steam Engine Build, ala Cedge

[cedge]

The shop is now hospitable again and I'm back in gear for this season's first build project. I'm hoping to stretch things enough to do a couple of different builds, but time will tell.

I've spent the day turning out cylinders, so I'll share a bit of what was accomplished today.

I started out by cutting and cleaning up 3 pieces of junk yard brass that turned out to be some really sweet 360 free machining metal. I turned and faced the pieces to get rid of the bumps and warts and then drilled them to within 1/16 inch  of the finished bores. Since one of the engines.....(yeah, there will be two when I'm finished) is a compound arrangement, the two bores will be .6250 and .750 inches.

I then broke out the HSS boring bar and got serious. In the photo below, you'll notice a lighter area just  inside the bore, indicated by the red arrow.



This is a trick that Zeusrekining (Tim) taught me on my last project. Rather than blindly boring the whole length of the cylinder from the start, I bored about 1/4 inch in and used a "go/no go" gauge to get a close running fit. This particular cylinder is a 3/4 inch bore so I used a 3/4 inch slug for testing.



This left the rest of the bore untouched and the lip of the step up was easy to see while using the boring bar. The diminishing step up served as a visual indication for when things began getting close and resulted in a dead on .750 bore when the last pass was made. Nice tip, Tim...thanks.

Once the bores were done, it was time for the fun stuff to begin. Those of you who saw the recent 3D image, already know these cylinders will be contoured in a number of places. I'm nowhere near Gbritnell's level, but Ive definitely learned that I enjoy an engine with somewhat fewer hard edges.

The process began with a bit of marking up which was done on the lathe using a digital caliper that has had one tine shortened. This made easy work of locating the various elements I'd need to turn.



For those who haven;t seen this trick, the long tine gives you a means to indicate from an edge while the shorter tine marks the metal. This mark out was done with the lathe turning slowly. The long tine was held against the end of the work piece and adjusted to the needed dimensions for each mark. This also trick works well when working on the mill. (just remember it's an inside measurement so you cut TO the line)

The first cuts were made using a parting tool. It was used to make sure the corners were clean and square.  This also took the worry out of aggressively removing the remaining metal between features. The flanges were filed on the lathe  to round them. as were the rounded contours that flow from one flange tot he next.



The photo below shows the "before and after" of the process. You'll note things get a little close near the chuck. You'll want to give your undivided attention to filing this close to the spinning jaws. I use small needle files for this work and stand away from the chuck as much as possible.



Here is today's harvest after a bit of polishing has been started. The heavy bases will stay attached for some of the upcoming mill work ans then the cylinders will be transfered to mandrels for some further lathe work. Two of these will be used on the compound engine while the third will become a single cylinder version. Stay tuned.... lots of things to do before these are ready to run.



Things got a little delayed this week as I needed to clean about 20 engines for the first showing of the season. Saturday was spent with a few machining friends, 50 plus engines , loads of warm springtime sunshine and a great crowd of friendly onlookers. I'll have to say I didn't really miss being in the shop....(grin).

Today I got back to things and made a bit of progress with the cylinders.

The photo below shows one of the cylinders after it's first trip to the mill. I machined flats on all 3 bases to give me a proper datum point for the first few modifications. This trick proved to be a life saver on my last project and has since been adopted as a regular thing.



This flat face, along with the substantial "base" gave me plenty of meat to grip while working with a lot of overhang in the vice. It also helped me assure that all the cuts would be square and at 180° in relationship to each other. The flat does require a bit more use of the wiggler when things are repositioned, but it is a lot easier than many methods I've seen.




I chose to use a 5/8 inch end mill cutting to 0.100 in depth so that the hole would have a slight wall along the outside edges. I accepted that the holes would be slightly oversized and made up for it by turning the valve bases to a press fit in order to match the holes.

 

The valve base was then soldered into place using the 3/16 inch hole that was drilled in each piece. These holes will also be used as indexing points in later proce3dure. By soldering from the inside, there was less overflow to clean up on the outside. Since these pieces will see very little pressure, I chose to use a silver bearing solder for convenience.



The work pieces were then taken back to the mill to even up the surfaces of the valve bases. This surface now becomes the new datum point for future operations such as drilling and tapping the ends of the cylinders. After a bit clean up and removing the heavy base, the cylinders look less like candle sticks and more like parts of a steam engine.



Finally got back to the shop after a small lapse in motivation. I've managed to get a little done, so the break was not a total loss.

The cylinders have now been drilled for the steam ports. Patience and an easy touch got the #43 holes deep enough to match up with the larger 3/16 holes coming in from the valve bases.



The 3/16 holes were drilled last to avoid the chance of breaking a drill while entering another hole from the side.

If you recall, I mentioned the valve bases became the new datum point in a previous comment. This is where they came in quite handy. Locating the various holes in relation to each other became as easy as you could ask. A simple flip of the work piece was all that was required to get perfect alignments. These indexing points still have a couple of functions to serve before they too will be replaced.



The cylinders will require a total of 5 gland nuts and two different sizes since one cylinder on the tandem uses two different diameters cylinders. Here is one of them show early in the turning phase. You can see the markup / caliper trick was used here as well as the cut off tool for heavy metal removal to depth. (keep practicing with the cutting off... its a very handy skill)




Here the photo shows one of the glands, threaded at 3/8 x 32 tpi. The piston rod will be 3/16 inch dia. so there will be plenty of room for the graphite string packing to fit in the wells. The gl;ands will be concealed by the spool, also shown in the photo. This will serve to connect the two cylinders.



Here you can see the gland as it fits the collar. The 1/16 lip was left to give added support to the piston rod and to aid in positioning the gland in the end of the cylinder.



I still have glands to make, but here is how the combination of parts will fit together. I'm currently awaiting an order from www.microfasterners.com before I begin drilling and tapping the nearly 50 holes required to fit ti all together. Hopefully that project will begin tomorrow.



Welcome aboard.....
Steve

[chuck foster]

steve    wow!

chuck 

[Brass_Machine]

 

Steve, this a great start. Gonna settle in for this one.  Gonna love the ride.

Eric

[cedge]

Thanks guys....
I'm hoping this one will be fun. I'm trying to remember to document the small tricks as I use them, but I keep getting int the build and forgetting to shoot pictures....LOL.

Steve

[cedge]

Today was no time to be impatient. I took on the drilling and tapping of 48 holes for the 2-56 head studs. Since the last thing I wanted was a busted drill or tap, I took several precautions.

The Chinese DRO system really paid its way, by making several things easier. The "hole circle" mode was used to keep things uniform as the holes were first center drilled. This makes sure the drilled hole can't wander, as the "pre-drilling" acts as a guide to keep it running true. I know.... we all do it, but some of this is meant for the new guys....(grin)



Since there isn't much room for error, I went a wee bit overboard with the DRO, shooting for .00005 on the read outs. No.... it isn't required, but the heads and glands have to fit quite close to true concentricity, so it was just one of those precautions I just mentioned. At 5 decimal points of accuracy, it should all work out fine.




After being center drilled, the holes were drilled using a #49 drill instead of the #50 which the books recommend. The blind holes are 5/16 inches deep and had to be tapped to depth. By using the #49 drill the chances of damage to the tap was reduced. Marv Klotzs  was the source of this tool saving tip in a previous discussion of tapping on this board.




Tapping was also done using the DRO to make sure the tap was in perfect alignment with the holes. While it might strike some as being overkill, it took very extra little time and it made a tricky job much easier to accomplish. Notice, the tap guide is being used.  Hey MA!!.... 48 cleanly tapped holes and no busted tools!!!




Here are the three cylinders with the holes.... posed with a coke can to give a better feel for scale of things. When you look at the alignment of the valve bases, you'll see a few of the reasons I value that cheap Chinese DRO.




Family will be priority one, this weekend and into the first part of the coming week.  I won't be getting much shop time. I'll post more when I've gotten back in the shop and to work again.

Steve

[Stilldrillin]

Hi Steve,

Lovely to see you`re back to it again. 

I`m on board, and enjoying the ride already..... 

Good luck! 

David D

[shoey51]

will try to keep onboard for this one

[cedge]

Hang around. the fun has just begun....the more the merrier. Nothing to report tonight, other than one road weary Cedge.  We spent the day wandering the back roads of the mountains of gerogia and North Carolina today. A tad over 300 miles of twists and turns on narrow winding roads. Lots of beautiful scenery but my A$$ hurts too much to sleep right now.....LOL

Steve

[cedge]

Not a lot of photos tonight, since it's all been drilling and tapping tiny holes. Not much entertainment value, but it sure makes assembly much easier. Here is the first test fitting of the cylinders, glands and head. I'll be fitting the pistons and rod next so I can begin measuring the elevation needed to mount the assembly. Still need to make the glands for the 3rd cylinder but needed a break from making tiny holes.

The file is there to compensate for the 1/8 inch difference in the diameter of  the two cylinders.

Steve


 

[Bernd]

Nice Steve. Had to put on my sun glasses to view that pic. 

Bernd

[cedge]

Tonight's installment deals with working oneself out of painted corners. Once in a while, I wind up realizing I've removed the part from its base too early and no longer have a way to mount it back in the lathe for one more needed operation. It can leave you scratching your head and muttering things the kiddies shouldn't hear.

That wasn't the case in this particular instance, as I chose to make the cut off early, rather than risk life and limb by working right up against the spinning chuck with a hand file. I knew I'd have to revisit the problem, but since I already had newly established indexing surfaces for the milling and drilling requirements, I took it in stride.  I have Philp Duclos to thank for the solution. (I'm really beginning to like this guy)

A short chapters in one of his Shop Wisdom books shared a down and dirty, easy to make, quick release mandrel that can be made on the fly, for just such situations. His tip was to turn a shaft to a close running fit, notch it with a shallow cut and place a small round dowel in the slot as a locking pin. This pin has to sit about .002 lower than the overall diameter of the shaft.





A gentle twist of the work piece in the counter (anti) clockwise direction will lock the cylinder on the shaft and hold it for turning operations, as long as you don't try to make too heavy cuts. The lathe will actually tighten the work piece as you work. When finished, a gentle twist in the clockwise direction will unlock the work piece and allow it to easily slide off the shaft.



This trick allowed me to finish rounding off the bead on the cylinder end and to clean up the flange surface where I'd had to restart the cut off and missed the original cut by a few thousandths. Since this prevented the glad from seating seamlessly, it had to go. As I said before.... easy, quick and one of those down and dirty little tricks that can save your bacon.....eh?

Okay.... I'll admit to miscalculations when I make them, but this one was more of a midstream design change that had to be compensated for. The spacer that goes between cylinders had to be remade after I decide to have hex heads on the gland nuts, instead of recessing them. This meant the first one was suddenly short by a full 1/4 inch. No sweat, but it did add to the number of already very plentiful holes to be drilled. 

I popped the new one into the mill, drilled the first 8 holes. Since these holes are critical to alignment, I decided not to drill on through and risk the drill point wandering off on its own.  So how would one flip a round part and match up the holes in the same locations as the ones on the other flange? Nope.... I couldn't leave a flat spot on this piece so another means of indexing was needed.

I've already turned the pistons and the piston rod was simply a piece of 3/16 drill rod, so I placed the piston in the cylinder, slid the gland in place along with the spacer. I then bolted them in place using four 2-56 hexhead screws. Before I tightened things down I moved the gland around a bit to find the point where there was least friction on the piston. (more on this in a minute). Once all was free, I tightened the bolts and put the whole assembly in the mill. The photo below shows it awaiting wiggling to center the quill before drilling the 8 holes.



As you can see, having the flat indexing points is proving to be invaluable to this project. They have made the hole placements painless if no less boring....LOL They will remain until the cylinder section is ready to bolt to the engine base, which is not that far away at this point.

I mentioned "moving the gland around" up above. Since the glands serve as the "head" for these cylinders, they are critical to the overall alignment of the pistons and piston rod. This engine will have to almost perfectly align at 6 separate points and still remain low friction if it is to run at all. Since the glands are "trapped" by the spacer assembly and the cross head guide, they were made with slightly over sized holes to allow them to "float" a few thousandths while being aligned. They will be locked into position once the other components are installed and locked down. This will take some of the sweat out of being "close" but "not quite there" as things progress.

Steve

[shoey51]

I just love the way you go about things Steve. great work there and great problem solving
 

[sbwhart]

Thats a real neat trick with the little dowel drive Steve that ones filed away in the memory banks.

Real nice work 

Stew

[Stilldrillin]

Love the "camlock" drive idea Steve!     

David D

[cedge]

Finally, I got to stop drilling holes for a bit. Still more to drill, but I finally got to do something that felt like progress....(grin).

The collar that joins the two cylinders also houses the gland nuts, which in the real world, would need to be accessible for maintenance purposes, so I decide to give this little engine a port hole.

The spacer was bolted up to the cylinder and placed in the mill vice for drilling.  I wanted a 9/16 inch hole which would have a "collar" around the opening. After drilling to 1/2 inch, I switched to a 9/16 inch end mill to finish the opening.



A small piece of scrap box brass was then turned to a light press fit and fitted into the spacer's new opening, using a small arbor to hold it in alignment. Since the quill was already centered from the previous operation, things went quite smoothly as I used the quill to seat the cross piece.



The Spacer was then removed from the cylinder for soldering. You'll note the cross piece has a light groove cut into it. This was done to allow the solder to flow more easily. The other "trick" is less obvious. By choosing the 9/16 inch measurement, the cross drilled hole was about 1/16 of an inch larger than the bore of the spacer. This gave me a solid piece within the bore to accept solder, assuring that the piece is not going to get knocked off anytime in the future.



Once the solder cooled, the spacer was once put back in the mill to remove a bit of the new metal. Since the next operation will be to turn the piece using the cam locking mandrel, I didn't want to put a lot of stress on the tool with extended interrupted cutting. I like the mandrel idea, but it's too new to have my full faith and trust quite yet.



Once the cylinder was put back on the lathe, the spacer needed a several different operations performed. First off it was a wee bit out of alignment, so I broke out my hand alignment wheel. I slightly loosened the four 2-56 hex bolts, turned on the lathe and then ran the wheel into the side of the spacer. This nudged the spacer into alignment so I could tighten the bolts to hold it there.

Once the alignment was done, the cross piece was center drilled and then drilled to 3/8 inch, so a small HSS boring bar could be brought into play. Light cuts were the order of the day until the cut began to get close to the bore size. At this point I once again employed the little wheel tool, just to make sure all was well before making the finishing pass within the bore. The results are such that you can't see where the joints are anymore... even with the new metal transecting the bore at two places.



The cross piece was turned down to match the cylinder contour and then put back in the mill for opening of the port hole to 1/2 inch.  A bit of deburring and some filing later, the port holes are looking like a good addition to the project.



Steve

[Bernd]

Beautiful work as always Steve.     

Picked up on the aligment tool. Neat. Will have to remember that.

Bernd

[cedge]

Bernd...
Thanks for the encouragment.

That little wheel is worth several times its own weight in chocolate....LOL.  It hates wobble. When I remount a work piece in the chuck, it often wobbles when the lathe starts up. By running the wheel up against the work piece, it nudges it back into axial alignment. You can nudge form the side or it can do its job by running against the end of the work piece. Very handy.

In the sad saga of the Cam Gear disaster in the Victorian build, I managed to nearly destroy a gear that had many hours of work in it. A stupid mistake on my part had the gear twisted to about a 20° angle to its axis. After the dust settled and my heart began beating again, the wheel tool was applied to remove the damage. I ran the wheel against the "end" of the piece to get it turning straight, then I nudged the rim back into concentricity from the side.


This wheel tool is made of a simple round on a shaft. My next one will probably be made with a bearing.

Steve

[Brass_Machine]

Nice work Steve. I read the post from back to front... was looking at the port hole asking myself how you did it. Glad I got my answer. Nice job!

Eric

[Rob.Wilson]

  WOW  very nice Steve 

Rob

[cedge]

Tonight is going to be a bit photo heavy, so bear with me. These engines have a longer than usual cross head guides. Each of them will have long openings , similar to the one I put in the spacer section. Building them has proven to be a bit frustrating as I managed to make the same mistake, not once, but twice, resulting in the openings being rotated about 8.5 degrees off plumb. That is what happens when you are using hex bar and forget which face you used to index in the vise... nuff said.....@#$&%*!! Simple solution.... use round stock with one flat spot....LOL.

The first successful cross head guide is shown below, after it was turned, faced and then milled. The opening was drilled and milled to 9/16 just as the spacer was made. The elongated part of the cut was done using an end mill in small steps that were milled through, top to bottom in small bites. This procedure will be shown, in a few moments.



Once things were deburred and some file work was completed, a pair of small 9/16 rounds were turned and drilled with a 3/16 hole. The reason for the hole is for an easy alignment later in the process. The rounds were left slightly over sized, perhaps .002 so they would fit snuggly in their respective radii.



The space between them now needed to be filled, but the piece had to fit around the rounds snuggly.as well. This was accomplished by carefully milling a piece of 3/4 square stock 9/32 deep with a 9/16 end mill and then using it to bore through the square for the other arc. The piece was then milled down to fit the gap.






Once this were fitted properly, a session of soldering was next on the agenda. I even took time to use a pencil lead around the areas where I didn't want solder to puddle and stick. Solder won't adhere to pencil or even smoked metal, making for less clean up.



The work piece was left to cool and then moved back to the lathe to turn down the new metal. This also let me inspect the solder joints which proved to need a little additional work. Once a couple of solderless joints were addressed, it was time to see how the windows were going to turn out. This is the step where those two 3/16 holes in the end pieces proved their worth. By putting a 3/16 dowel pin in the chuck, I was able to easily center on the holes and align everything for the next step. Note the pencil lead can still be seen in this photo.



After centering the quill with the dowel pin, the next step was to bore a couple of 7/16 holes to begin opening up the window ports. Then the end mill was used to "nibble" out the remaining metal a bit a time. Run it all the way through and then advance it a few thousandths until you remove the unwanted metal. Then you want to make a quick pass back along the opening to clean things up.



Once the milling operation was finished, it was back to the lathe to  make the bore round once more. First step was to use the half inch end mill to get everything back to the original bore dimension. I then widened the first 1/2 inch using a boring bar until the 9/16 end mill would just barely sip into the opening. It's no fun trying to use a boring bar in an interrupted cut. Just trust me on this...(grin). The missed alignment of the port wasn't the only headache this adventure produced. The end mill made a nice substitute and soon had the bore where it needed to be.



There is still a bit to do to the piece, like adding a pair of ribs which will need to be soldered in place, but the next one should be a breeze after feeling my way through this one. The little single cylinder has become somewhat of a test bed as I work through the ins and outs of some of the parts. I only hope it won't suffer from all the abuse, when things are completed.



Steve

[Stilldrillin]

Steve,

It`s early morning here...... Not had me breakfast, yet......

I`m sitting here with a bemused/ mystified/ admiring expression......

As usual...... I don`t know what you are up to/ where you`re going..... But. I appreciate the way you do everything you do....



Keep on doing it...... 

David D

[shoey51]

I agree with what david said

[chuck foster]

steve, i just got to say thanks for this build and write up 

as you know it is going to be a while before i can get out to my shop and make some chip's.so i'm going to get my "modeling fix" through your build and every one elses.

thanks a million steve  (and see that thumb has no rivets) 

chuck 

[Darren]

Steve, I do marvel at your fine work .....

[Bernd]

Steve,

If you hadn't shown that series of sequences to make that window I won't have been able to sleep the next few nights. I'd be laying awake wondering, "How did he do that".

Great work on those fine details that make a model stand out from the others. Sure you and Kozo Hiraoka aren't related? 

Bernd