Double-Acting Twin Beam Engine Build

[crueby]

Got a start on an engine that I've been wanting to build for a while - a twin-beam double-acting steam engine, in a larger size to allow for more ornate style. I had done a Stuart Half-Beam kit years ago, think that got me going on this style.

Below are some sketches that I drew up to work out the general arrangement and to see what cylinder size would fit my lathe/mill setup (sherline). After finding some nice bar stock at Yarde Metals drop zone (good prices, small selection since it is off-cuts), I settled on a 1" bore, 2" stroke, 12" beam arrangement. These sketches are just the starting point, details may well change as it goes, and will be making detail drawings to post as each part is done.

Build will start with the cylinder assembly....

 

[crueby]

First up on the build, making the end caps for the cylinders. Started with a length of 1.25" brass (C360) in the 4-jaw chuck. Having learned the hard way about getting bolt holes to line up in parts, I am setting up the mill for drilling with the chuck on the rotary table to do the drilling for the perimeter bolts, and locking down the cross slide table until all the end caps, cylinders, and base plates are made, so that I can be sure that the holes will all line up (much easier than redoing the setup multiple times!).

The stock was centered up in the 4-jaw, and the end faced off for the bottom cap. Then moved the chuck and stock over to the mill to drill the 5 bolt holes (#43 drill), each one 72 degrees farther around than the last - rotary table makes this setup so easy - first centered the table, then offset the table 0.550" to put the center of the drill in the middle of the cylinder wall, and locked down the table for the rest of the operations. Then, drilled each hole and advanced the rotary table 72 degrees.

Moved the chuck back to the lathe to part the cap off, 0.150" thick. Repeated for second bottom cap (leaving stock in chuck for all this saved having to recenter each time too).

Next up were the two top caps, which have the packing gland recess in them. Faced off the end, and machined in the recess around the outer edge (leaving a 0.835 diameter, 0.150" tall protrusion). Took that to the mill for a set of 5 bolt holes just like the bottom caps. Came back to the lathe, and bored a 0.250 center hole for the piston rod, then with a small boring bar widened that out to 0.500, 0.200 deep for the packing gland. With that all done, parted off.

There is still some work to be done on the top caps to bore/tap holes for the packing gland, but that will be done later, since it requires moving the rotary table, and I dont want to do that till after the cylinders are made.

Wish I could put the commentary between the photos - anyone know a way to do that while still using the HMEM photo upload service?

 

[crueby]

Next up is to make the cylinders - Started with a longer piece of 1.25" brass (finished length will be 2.5"), centered it up and faced off one end. Moved chuck to the rotary table on the mill, still set up in same place from making the end caps, and drilled #50 holes in the perimeter, 0.200 deep, 72 degrees apart, and tapped those holes with a 2-56 bottoming tap.

At this point, was ready to re-chuck it in the 4-jaw with the other end out. However, to make sure that there would be enough room to bore through the brass without crashing into the chuck (since the bore would be larger than the center hole in the chuck), I put in a set of 2-56 cap screws in the cylinder first. That left enough gap for the end of the boring bar to come out of the stock but not touch the chuck face.

After recentering, faced off the end and turned it back to the final 2.5" length. Then, back to the mill. At this point, it was important to get the bolt holes in the second end to line up with the first end, since a flat will be milled in the side of the cylinder to make a mounting place for the valve assembly, and the flat will span the gap between two of the bolt holes. So, using a square I transferred the location of one of the holes to the other end, and used that position as the starting point for drilling. Since it would have been a pain to get that mark to the zero position on the rotary table, I just rotated the table till the mark lined up under the drill, and read off that angle. Turned out to be 32 degrees, so did the rest of the drilling at 32+(72 * hole_nbr) increments.

Then, back to the lathe, bored a 3/8" starter hole, and was ready for the boring part - boring out the center. Since my larger boring bar would not fit in the starter hole, began boring with a small bar, then switched up to the larger one after a few passes. Lots of swarf later (had to vacuum out the bore every couple passes since the chips would build up in the long cavity), the final passes were done with a series of light cuts to leave a smooth finish that only needed a little polishing. All done - except this is a twin beam, so had to do all that again for second cylinder!

One last item to use the rotary table position for - drilled/countersunk a set of holes in a pair aluminum plates that will be used as base plates to mount the cylinders plus the valve cranks later on. For now, just drilled for the holes to mate up with the bottom end caps.

Next up - milling for the valve chest.....

 

[crueby]

Okay, ready for the next step, milling in the flats and mounting the base for the steam chest. In a casting set, this would all have been done as one piece, but since this build is from bar stock, the base for the steam chest is being added on.

The cylinders were clamped in the mill table vise, checking to make sure the top was parallel to the travel of the cutter, and then a 5/8" wide flat was milled in with a fly cutter. I like the finish that the fly cutter leaves better than using an end mill, use it whenever I can.



Then, a piece of 3/4" x 3/8" flat bar stock, rough cut slightly longer than the cylinders, was clamped in place and soldered in place, making sure that the flux/solder flowed all the way through the joint since the steam passages will be passing through this area later and leaks would be a problem.



Then, back to the mill for a light pass to trim the end of the bar down flush with the top of the cylinder - important to get the piece properly aligned/vertical so the final face matches the top of the cylinder for a good seal with the end caps.



The cylinders look plain at this point - later on I will be milling in some ribs and recesses to dress them up. First though, I think the next step will be to make the packing glands and fit them to the top caps....

 

[romartin]

Hi Crueby! I shall be following your build with relish. So far it looks great.
I'm curious to know what solder you used for joining the steam chest base to the cylinder?

 

[crueby]

Hi Romartin - For soldering these two parts, I used Tix silver solder, made for jewelry work - it has a low melting point, so it is no good for anything near flame, but it has very high strength and it flows deep through tightly fitting joints. The flux for it is corrosive if left on the metal, so you have to flush it with water afterwards. It is available from most jewelry tool suppliers, and some model catalogs. Bit pricey, but it does not take much at all to do a large joint. Again, not for use on any parts that will be near direct flame, like a boiler or IC engine, but since I mainly run on air that is not a problem for me. I started using it on ship model fittings, since it works so well on small parts, wicking itself into the joints and leaving little on the surface. Highly recommend using thier flux with it, been using same small bottle for years and years.

 

[weez]

Wish I could put the commentary between the photos - anyone know a way to do that while still using the HMEM photo upload service?

After uploading images you can click on the arrow next to the attachments icon (paperclip). This will bring up a box with the uploaded images listed. Clicking on one will place the image where the cursor is currently located -shown as . It took me awhile to figure this out too. I do think it makes for better posts when there is text by each picture instead of one big lump of text followed by a bunch of pictures.

 

[crueby]

After uploading images you can click on the arrow next to the attachments icon (paperclip). This will bring up a box with the uploaded images listed. Clicking on one will place the image where the cursor is currently located -shown as . It took me awhile to figure this out too. I do think it makes for better posts when there is text by each picture instead of one big lump of text followed by a bunch of pictures.
View attachment 67959

Excellent - Thanks much!! I'll do that from now on.

We have the technology, just dont know how to use it!

 

[crueby]

Excellent - Thanks much!! I'll do that from now on.

We have the technology, just dont know how to use it!

It let me go back and edit the 3rd post to try putting the pictures inline - great, thanks for the tip!!!

 

[Herbiev]

Looking really great. Love the clear pics

 

[crueby]

Got the packing glands made and fitted to the top caps. I changed my mind on the bolt holes for the glands, had originally drawn it as having 5 to match the cap-to-cylinder bolts, but decided to go with two instead, to make it easier to align. I am thinking it will float the alignment on the piston rod this way - that is how I did it on other engines and seemed to work fine there.
So, I updated the drawings for the caps/glands (and fixed/added a couple missing dimensions too), here is that new version:


For the glands, turned a short length of brass rod down to 0.835 and center drilled it 1/4" for the piston rod:


and then turned down the shoulder on both ends to 0.50 diameter, 0.225 deep to fit the top caps:


Then, moved the chuck over to the mill, set it for 0.325" from the center of the piece, and drilled a pair of #43 holes through, 180 degrees off from each other.



Leaving the rotary table locked in that position, went back to the lathe and parted off the two glands, leaving the rims at 0.125" thick. Then, using the same position on the mill, drilled matching #50 holes in the top caps, 0.200 deep and tapped them for 2-56 screws.


The finished top caps/glands:


Next thing to be done is to drill the steam inlet/exhaust passages in the steam chest bases. After that will most likely mill some ribs into the outside of the cylinders to make them look more like cast pieces - they are a bit too plain as they are...

 

[weez]

Excellent - Thanks much!! I'll do that from now on.

We have the technology, just dont know how to use it!

You're welcome, glad I could help. Great start to this engine. I will be following along.

 

[lennardhme]

Looks a good project - will follow also.
Nice pics, thanks.

 

[crueby]

The outside of the cylinders were looking too bland, so went back and milled in some recesses to dress them up, looks more like castings with ribs now.

To start, set up the rotary table tipped up to horizontal, and chucked up the cylinder, using one of the top caps on a live center to steady it, with the packing gland side in since the larger hole on the outside was too big for the center. Marked off the locations for the ribs, and set the mill to take a 0.080" cut with the cross-slide back:


Then, ran the cross-slide forward till the mill was centered, and used the rotary table to turn the piece to make cuts in one direction, feeding the table side to side between cuts till one full window was milled out:


That process was repeated for the rest of the windows:


Same sequence for the other cylinder:


And then started sanding/polishing them to get rid of the end mill marks. There must be a way to mill like this without getting the tool marks showing each pass - anyone?


After that, ready for what is always a nerve-wracking sequence for me - drilling the steam passages through from the cylinder to the chest. Lots of double-checking angles and measurements to make sure that things will line up. This is one place where the tilting table comes in real handy, much easier to tweak the angle than trying to do it in the vice.

Started with drilling in the exhaust/inlet ports while still horizontal, these holes just go halfway into the base plate:


After that, drilled from the side of the plate to make the exhaust passage - this hole meets the center one in the base plate:


Then two holes to the side of that one, drilled/tapped 2-56 to give a place to bolt on the exhaust flange. I like to have a seperate fitting to bolt on the exhaust pipe, makes it easier to install/remove when needed than if it was screwed directly into the base plate.


Then ran the table back up to around 5 degrees, and sighted in from there till the holes would line up. Then milled a small recess from the edge of the cylinder back to where the passage will start:


And center drilled for the start of the passage in that new flat:


And drilled down from there till it met the inlet port (lined up!)


That finished off the major work on the cylinders themselves, other than making mounting the steam chest and valve....

 

[crueby]

Time to build the steam chests for this engine. First, refined the original drawing for the cylinder/chest:



Frist step was to drill/tap the mounting holes for the steam chest into the base plate on the side of the cylinder. These are 2-56 tapped holes, 0.200 deep, positioned to center the steam chest opening on the steam inlet/exhaust passages:



Then, squared up a 2" length of 3/8" x 3/4" brass bar stock, set it 0.125" from one edge, and started boring for the valve rod. This is a set of 3 concentric holes, starting with a 3/16" dia. shallow hole for the packing gland, then a 1/8" dia. hole for the valve rod, then a 5/64" hole at the end for the narrow end of the valve rod (which narrows down once for the valve nut threads, then again past the threads to fit into the guide hole at the far end of the valve chest. I've found it easiest to get the holes to line up to start with the largest diameter, and work down. So, started with the 3/16" hole, 0.150 deep:





Then, without moving the table, drilled a 1/8" hole down 1.5" deep, which is where the opening in the valve chest ends - the larger drill resists drifting more than the smaller one, so went as deep as possible with the 1/8" drill:



Then, finished up with the 5/64" drill - had to have as much as possible sticking out to reach that deep (actually had intended on using a smaller drill size originally, but that drill would not reach).



After that, moved the table to each side by 0.175 and drilled for the packing gland mount holes, #50, 0.200 deep. These are tapped 2-56. These holes fall just inside the mount holes for the valve chest, which are to be drilled next.





Turned the valve chest on its side, and laid out and drilled the 6 #43 holes for the mounting bolts. Also did matching holes in the valve chest cover while I was at it:



Here are those parts all test fitted. Took some 2-56 bolts and cut the heads off to make the mounting studs, which will be loctited in later on. Hex nuts will be used to close it up. Using studs rather than bolts makes it easier later on to pull off the valve chest cover to time the valves, without letting the chest fall out of position.





Last step on the chest is to mill out the opening in the center. After drawing it in place per the plan, used a drill to hog out the majority of the metal in the opening....


Then came back with a mill to open it up in a series of narrow passes:


The finished part:


And in place on the cylinder:


Only parts remaining on the chest are to drill the steam inlet and mill some recesses in the cover, and to make the packing gland itself. Not a bad day's play in the shop! (happily retired, lots more time to play!)

 

[crueby]

On to more parts of the steam chest. To start, did the recesses in the cover plate, and drilled the steam inlet hole:



both plates done, ready for sanding/polishing later...


Made the valve packing glands from some short lengths of brass square. Drilled the 1/8" hole for the valve rod,



Then the #43 clearance holes for the 2-56 mount bolts either side of the valve rod, 0.175" from the valve rod center to match the holes in the valve chest:


Then chucked the piece up on the lathe to turn down to the outside of the valve rod hole, leaving a T-shaped piece:


After that, just a matter of some time with a file to taper the ends and round the corners:


Here is how the parts are looking so far:


Next up was to make the valve rods themselves, starting with a length of 1/8" steel rod. I left them a bit long for now, till I work out the linkage details. Started by turning down the narrow end, that will ride in the bottom hole of the valve chest:


Then threading the middle section where it will have an adjusting nut to hold the valve itself. Originally was going to make this a 5-40 thread, but realized I did not have a die for that (have 5-40 tap, wonder why I never got the die too? Oh well), so switched it to 5BA, which is very close, and have a tap/die set for that. Used a tailstock die holder I made recently - amazing how much easier that tool makes threading long lengths without wandering!


Here is how it looks in place:


While in threading mode, turned down shoulders on both ends of lengths of 1/4" steel rod for the piston rods, for mounting the pistons on one end and the clevis on the other. These shoulders were turned down to 0.1875" dia. and are 3/8" long.


The shoulders were threaded 3/16-40:


Same done for second rod for other cylinder. Funny perspective from the camera - these two rods are really the same length...

 

[crueby]

Up to making the steam valve sliders. Started with a length of steel bar long enough to make both sliders - easier to hold two steady for most of the work then cut them apart later. Started out by spot drilling the depth for the end mill - the set I have is not center cutting:


Then started in with the end mill, making the slot on one of the valves:


Then thr other:


Turned the valve piece over, and started milling in the posts (guess its really milling away everthing BUT the posts?) that will hold the adjusting nut. Started by making the outside edge cuts in one direction,


Going deeper over a few passes....


Down to the final depth:


Then switched to a 1/8" end mill (same diameter as the valve rod) and started making the lengthwise cuts down the center:


Also taking several passes down to same final depth:


Then started making the final cuts to make the slot to hold the adjusting nut on one valve:


And on the other:


Final steps on the valves were to make a light pass with the fly cutter to narrow down the pieces to final width and then to cut them apart.


Here is how it looks so far:


Then, made the adjusting nut from a scrap of 1/8" thick brass...


And putting it all together:


Later on, when I decide the design of the valve linkage, the upper ends of the valve rods will be trimmed to length and fitted out as needed.


Almost done with the cylinder assemblies - just the pistons to go!

 

[crueby]

Time to make the pistons. Started with chunks of 1" steel rod, centered up in the four-jaw very carefully, and faced down both sides to final thickness:


and then center drilled #20 and tapped 3/16-40 to match the piston rods


The piston rods were screwed on and held with high-strength loctite, then rechucked the piston rod in the lathe, and again got it all centered carefully. On some previous engines I just used the 3-jaw chuck at this stage, and wound up with pistons that were not quite concentric with the piston rods, causing all sorts of grief. Hope I learned that lesson permanantly!


Then the nervewracking part - turning down the outside of the piston, sneaking up on the final dimension to match the cylinder bore:


Once a snug fit was acheived, moved the piston out, applied some diamond lapping paste (had that on hand for final honing of chisels) along with a little bit of oil, and lapped the piston to the bore. Started out hand-turning the spindle to spread the paste and to make sure it would not grab, then ran the lathe at very slow speed, moving the cylinder back and forth till I felt same resistance all the way up and down....


Cleaned off all the paste/oil again, put on a little new oil, and did a quick compression check - with the bottom cap on the cylinder, dropping in the piston I could hear it pushing air out the port. If I covered the bottom port, the piston would just sit there, then slide down when I uncovered the port. Should be a good fit! Very happy with how this one is coming along...

 

[Davewild]

Lovely work Crueby, I have the same machines, however you have some tooling I don't recognize, where did you get the boring bar? It looks much longer than the stock Sherline, I have been trying to find a longer boring bar to no avail!!!

Regards

Dave

 

[crueby]

Lovely work Crueby, I have the same machines, however you have some tooling I don't recognize, where did you get the boring bar? It looks much longer than the stock Sherline, I have been trying to find a longer boring bar to no avail!!!

Regards

Dave

Hi Dave,

I got that boring bar and a couple other items from a friend in my archery league that was a retired machinist. It has C.M.C. USA on the side. It is a very nice bar, quite rigid, and takes only a small hole to start boring in. Not sure where to get one, have seen simaler ones in catalogs like McMaster-Carr, Enco, Graingers, usually for a steep price - tough to find a smaller diameter one.

The quick-change tool rest I bought from A2Z Corp - they make a bunch of aftermarket Sherline parts (also got the longer z-axis column for my sherline mill). Really like the quick change setup - have a number of the tool holders that I leave set up with left/right/center cutters, cutoff bar, and boring bar. Nice thing is that the height adjustment stays with the tool holder, so no need to reset the height every time. The one thing I did on there rest was re-mill the bottom surface - they sent it fairly rough, so it would not stay in place, kept rocking/turning under pressure. In their instructions it said to put a piece of paper underneath to prevent that - instead, I remilled the bottom flat, with a slight hollow in the middle, so it would grip properly around the edge when tightened down.
I also got a set of larger-shank tool holders that take replaceable inserts to use with them. Very handy.

Another real handy item are the welders parallel clamps - they are Kant-Twist clamps, in the two smaller sizes. Come in real handy for holding multiple parts together to place into the vice. Grip really well, dont twist parts out of alignment when tightening, and also have a groove on one side of the block that let you grip round stock.

Some of the other items, like the tailstock die holder, are home made - got info on that one from others in the forum, very handy. If you dont want to cut morse tapers, you can get blanks in alum. or steel from places like LatheCity.

Chris