Author Topic: Tiny triple expansion steam engine (Read 6809 times)

gbritnell · « **on:** September 01, 2019, 05:03:50 PM »

Gentlemen,
A couple of steam engines have always caught my eye, one being a beam engine the other a triple expansion. I started with the drawings for my Stuart compound launch engine for some basic dimensions and then drew up an engine of my own design. A couple of things came up in the design process and being as I didn't have drawings to work from I went with what I thought would work. The first was that the IP cylinder has it's valve gear inside the crankshaft. Now on a large engine I could see making the eccentrics as a split piece and bolting them together onto the crank but in a smaller engine especially this one the only way I could see to make it was to build the crankshaft in 2 pieces, so I did. The crank segments are keyed together with a tongue and slot. The second was how to bolt the LP-IP cylinder block to the HP cylinder block. I know how the bolting process works but I had to make sure I could assemble the LP-IP block and time the valves them mount the HP cylinder block with regard to mounting on the vertical columns etc. The cylinder bores will be HP .375, IP .625 and LP .875. I took the proportions of the Stuart compound launch and used them as my ratio for obtaining the bores.

crueby · « **Reply #1 on:** September 01, 2019, 05:15:50 PM »

Terrific start on this engine, the crankshaft setup is very clever. Will you put a short sleeve over that area, or I guess the bearings will keep it aligned?

gbritnell · « **Reply #2 on:** September 01, 2019, 05:24:40 PM »

Hi Chris,
The eccentric for the IP cylinder will be over the split so you won't see it but there will also be a bearing on each side so that will keep it in alignment. The opening where the split is is actually for the eccentrics. 3 openings for the rods and 1 for the eccentrics.
gbritnell

b.lindsey · « **Reply #3 on:** September 01, 2019, 09:15:21 PM »

Fantastic, another in the tiny series. Always love those George, will be following along.

Bill

steamer · « **Reply #4 on:** September 01, 2019, 09:17:25 PM »

Beautiful work as usual George! Watching along!

Dave

gbritnell · « **Reply #5 on:** September 04, 2019, 12:49:07 PM »

I started on the cylinder blocks. I decided to make them from iron. This is the same iron as I make my piston rings from, close grained, nice machining. I cut them to size then drilled, bored and reamed. The head bolt holes will be M1.2 x .25. I cut the pockets for the steam ports so when I drill them I have a corner to start from.
gbritnell

Don1966 · « **Reply #6 on:** September 04, 2019, 10:45:59 PM »

Love it George I will Be following!.....

Don

Craig DeShong · « **Reply #7 on:** September 06, 2019, 12:59:36 AM »

I've been wondering what George was "up too" and now we all know. Another great project and I'm looking forward to following along.

toolznthings · « **Reply #8 on:** September 06, 2019, 01:17:26 AM »

Nice looking parts !!

gbritnell · « **Reply #9 on:** September 06, 2019, 04:53:39 PM »

The cylinders are all drilled and the shape rough milled. I'm waiting for some 1mm end mills to finish the porting. The next step will be to set the main cylinder block up and cut the fillet out that the ball mill left by the cylinder mounting bosses. A whole lot of M1.2x.25 tapped holes to do.
gbritnell

crueby · « **Reply #10 on:** September 06, 2019, 05:20:53 PM »

Beautiful!

Roger B · « **Reply #11 on:** September 06, 2019, 05:23:16 PM »

Another splendid piece of miniature engineering to enjoy

gbritnell · « **Reply #12 on:** September 08, 2019, 01:48:30 PM »

I finished filing and sanding the steps on the cylinder block then made the stanchions that hold the cylinders. I tapped all the M1.2x.25 threaded holes so now I can move onto the steam chests and heads.
gbritnell

crueby · « **Reply #13 on:** September 08, 2019, 02:25:13 PM »

What type of valves will it be on each cylinder? Looks like slide on the LP, but what are the other two? Whats the recess on the HP for?

gbritnell · « **Reply #14 on:** September 08, 2019, 03:34:03 PM »

Hi Chris,
They will all be slide valves. The recess is for the studs that mount the HP to the IP.
gbritnell

gbritnell · « **Reply #15 on:** September 10, 2019, 05:03:53 PM »

The upper heads are finished. Builders seem to have one particular job or another that they don't like, mine is drilling scores of holes. I doesn't matter the size I just don't like drilling a lot of holes. I have the steam chests almost done, they just need the gland boss on the bottom shaped. The steam chest covers are also finished. I added a raised boss on the covers to give them a little character.
gbritnell

steamer · « **Reply #16 on:** September 10, 2019, 05:59:12 PM »

Looks awesome George!

I have a full set of drawings for one of the main engines from the USS Ohio BB12. 10000 HP 4 cylinder triple expansion. The top HP cylinder head had (57) 1 3/8 studs holding it on....and that was just the top cylinder head....many more for the receiver connection, lower cylinder head, and frame connections.....I can't imagine drilling holes on that one......

Dave

stevehuckss396 · « **Reply #17 on:** September 10, 2019, 07:02:44 PM »

I feel your pain George. I just recently made a single piece with over 150 holes and all but nine were tapped.

Engine looks nice.

gbritnell · « **Reply #18 on:** September 11, 2019, 05:13:45 PM »

I turned up the lower heads last evening but wasn't in the mood for more drilling so I started on the crosshead guide bar. As is normally the case for parts like this I cut it into a piece of bar stock then use a slitting saw to remove it. All the holes were drilled for the posts and corner radii then the outside radii and around each post hole were stepped off. The part was then separated.
I use an ink marker to highlight the low spots where the cutter mark is then file the high spots until everything blends out.
When everything was filed and finished I set it back up to drill for the crosshead guide mounting holes. The part was then test fitted to the engine.
gbritnell

b.lindsey · « **Reply #19 on:** September 11, 2019, 05:58:09 PM »

Awesome as always George. Another little beautyto watch come to life.

Bill

crueby · « **Reply #20 on:** September 11, 2019, 06:21:06 PM »

Watching along, amazing parts....

Craig DeShong · « **Reply #21 on:** September 13, 2019, 01:34:43 PM »

Following along with the rest of the crowd. Pretty work.

fumopuc · « **Reply #22 on:** September 15, 2019, 07:29:26 AM »

Hi George, nice to see you back in steam.

gbritnell · « **Reply #23 on:** September 18, 2019, 11:47:09 PM »

I'm making good progress on the engine. I have all the machining finished on the lower heads. The crosshead guide plates are done. The connecting rods are started. For the rods I mill up a piece of stock to size, in this case it's .250 x .400. I leave it long for subsequent set-ups. I stand the stock up vertically in the vise using a square, mill the top edge flat, drill and counter drill for the rod bolts then using a slitting saw, cut the cap off. The faces are lightly filed then the cap is bolted on. The part is put back in the vise and the crank throw hole (.156 dia.) is drilled and reamed along with the wrist pin hole (0-80)
The main bearings have all been made and mounted. Only one had to be split for an inside journal. Being that the crank is split all the other bearings just slide in place.
gbritnell

b.lindsey · « **Reply #24 on:** September 19, 2019, 12:13:02 AM »

Great looking parts George. Seems like this one has come together very fast!!

Bill

Dave Otto · « **Reply #25 on:** September 19, 2019, 01:23:51 AM »

Amazing work George!
Enjoying this one; not that I didn't enjoy all the others too.

Dave

crueby · « **Reply #26 on:** September 19, 2019, 02:16:40 AM »

More stunning parts. What do you do for the finish on the brass parts, sanded, polished?

Tonyr · « **Reply #27 on:** September 19, 2019, 05:14:41 PM »

Not only is it impressive work, but the progress is very fast.
How do you find the time.

Tony

gbritnell · « **Reply #28 on:** September 19, 2019, 07:32:21 PM »

Hi Chris,
I just sand with real fine emery cloth, around 400 grit that has already had the tooth worn off it.
Hi Tony,
Well the fact is I'm retired so I can spend a lot of time at the machine.
gbritnell

Craig DeShong · « **Reply #29 on:** September 21, 2019, 12:50:28 AM »

Hi George. I love to follow your projects. Great work on this one too. How do you work on stuff so small?

gbritnell · « **Reply #30 on:** September 26, 2019, 11:45:44 PM »

I almost have the rods finished. I just have to make an arbor to mount them and turn away some of the thickness of the big end leaving a circular boss around the journal.
I started making bolts! Awhile back I said that I really didn't like tapping lots of holes, well the next part of the build is making M1.2 x .25 hex head bolt of all different lengths and I guess that ranks up there with the hole tapping. Just the M1.2 bolts alone count is 84.
I put some of the pieces together just to see what it would look like and to keep my interest while I'm making bolts.
gbritnell
In the bolt picture that dimpled effect is the surface of the paper towel. Just to show the size.

crueby · « **Reply #31 on:** September 27, 2019, 12:18:56 AM »

Very nice! And thats a LOT of bolts to make.

fumopuc · « **Reply #32 on:** September 28, 2019, 07:30:19 AM »

Hi George, that is very nice.
I had to go back to the picture with the one cent or in front of the key board, to understand how tiny it is.

b.lindsey · « **Reply #33 on:** September 29, 2019, 01:28:35 AM »

The family shots are awesome and inspiring. Making all those boots is tedious work no south.

Bill

gbritnell · « **Reply #34 on:** September 30, 2019, 06:12:50 PM »

Finished up the crosshead guide/piston rod pieces with the wrist pin bolts and mounting plates and bolts. Assembled all the pieces to check the fit and everything seems to be good.
I put the quarter in there for comparison. It's .955 diameter, or about 1.00
gbritnell

crueby · « **Reply #35 on:** September 30, 2019, 06:33:44 PM »

Beautiful!

Craig DeShong · « **Reply #36 on:** September 30, 2019, 10:11:34 PM »

Exquisite work George. You’re work is an inspiration for me to continually try to ‘up my game’.

Kim · « **Reply #37 on:** October 01, 2019, 06:11:28 AM »

Wow, George! You do some mighty fine work!
Kim

gbritnell · « **Reply #38 on:** October 02, 2019, 09:22:39 PM »

The final nail biting job to do on the cylinders is to drill the porting. I cleared the mill and set up my sine table with vise. The center hole was drilled with a #0 center drill that has some of the .125 shank ground away. The holes are drilled .039 diameter.

derekwarner · « **Reply #39 on:** October 03, 2019, 12:49:10 AM »

George...beautiful work.......I could be corrected, but re-reading the post thread suggests you have used a Loctited type construction for the crankshaft

We see from the earlier IMG_2090, there will be a very thin path width for the gaskets between the cylinder block & the cylinder covers .....I am guessing approx 3/16" wide max and this includes bolt holes...and that the IP & LP gasket will be one piece ... together the effective gasket width around the ports in the cylinders is extremely thin

Will you use the traditional oiled [envelope thickness [~~0.006"] brown paper for the gaskets?...or have you been tempted to use one of these new fangeled liquid Teflon mediums?

Derek

b.lindsey · « **Reply #40 on:** October 03, 2019, 12:52:09 AM »

Awesome George!! Can't wait to see it running.

Bill

Craig DeShong · « **Reply #41 on:** October 03, 2019, 01:07:59 AM »

Some tedious setup work George. Not much room for error. Thanks for sharing.

gbritnell · « **Reply #42 on:** October 03, 2019, 03:13:09 AM »

To get the crank throws indexed properly I used v-blocks and protractor. I used a drop of Loctite just to hold everything in place and then drilled and pinned everything. The crank throws are turned as one piece, throws and both cheeks. This simplified construction rather than having 6 individual cheeks, 3 crank pins and the main shaft. As far as gaskets I'll probably use tissue paper or just some motorcycle gasket sealant.
gbritnell

derekwarner · « **Reply #43 on:** October 03, 2019, 08:10:03 AM »

Thank you George...I saw one journal pin, but missed the others ............. Derek

gbritnell · « **Reply #44 on:** October 08, 2019, 07:04:46 PM »

Things are moving along steadily. I now have the valve straps, valve clevises, valve rods and valves made. Today I set up to make the reverse quadrants. The radius of the parts fit onto a piece of 2.50 diameter round stock so I set up my rotary table with an old 3 jaw chuck and indicated everything on center. Using my CAD drawing I put all the holes in for the slot corners, part corners and bolt holes.
The parts were sawed off with a 2 inch diameter slitting saw.

b.lindsey · « **Reply #45 on:** October 08, 2019, 07:48:24 PM »

Great set up for doing those George. They certainly should be very nearly identical too.

Bill

gbritnell · « **Reply #46 on:** October 08, 2019, 07:55:45 PM »

Some pictures of the valve straps, valve rods and clevises. The valve rods are threaded into the clevises with 0-80 thread. The valves will be located with 1-72 set screws.

gbritnell · « **Reply #47 on:** October 15, 2019, 12:40:28 AM »

I finished the eccentrics then made the support brackets for the reverse shaft. I had the main bearings mounted with socket head screws which was only temporary so it was time to start making more hex head bolts, this time 1-72. I had started with the drawing for the Stuart compound launch engine but I see as I'm assembling parts that the valve straps are going to hit the crosshead support bracket. They shouldn't but they are so a little modification is in order.

Admiral_dk · « **Reply #48 on:** October 15, 2019, 11:14:20 AM »

Fantastic work George

I have been wondering for some time about what keeps the "bracket" a quarter up the "collums" on this side of the picture ...?... On Jo's much bigger version there are two small grub/set screws on the "inside" ....

tghs · « **Reply #49 on:** October 15, 2019, 12:49:57 PM »

as in the next few months I'll be making 2 piece box links for my navy engine looking at your method gives me hope that I can do as well..

gbritnell · « **Reply #50 on:** October 26, 2019, 07:08:10 PM »

The engine is finished timed and assembled. All that's left to do is the plumbing. I did run across something curious while trying to time the engine. The Stuart drawings for the compound launch describe the eccentrics centerlines as each being 20 degrees above the horizontal centerline or in other words 140 degrees apart. I made the eccentrics to these dimensions but when I tried to time the engine I couldn't come anywhere near to the proper timing. I set my valve for equal travel then adjusted the eccentrics for the proper time in one direction. When I reversed the linkage the valve timing was way off so I did a layout in Cad and came up with 5-1/2 degrees above the centerline or 169 included angle. I made new eccentrics to these dimensions and after disassembling the whole engine to get to the I.P. eccentrics I put everything back together and started over. I set the valve for equal travel then set the timing for forward motion. I then reversed the engine and found that I was off ever so slightly so I split the difference and everything seemed to be fine. Why this occurred I don't know as I built the compound launch to the Stuart dimensions and as I recall it seemed to time fine.
Anyway at this point I'm happy with the timing so here's some pictures before I build the pipework.

gbritnell · « **Reply #51 on:** October 26, 2019, 07:14:51 PM »

Here's the last set of pictures. The last one has an American half dollar (1.20 diameter) sitting next to the engine for a size comparison. The engine turns over freely although a little snug but considering all the joints and moving parts that's to be expected. A little run-in time on the lathe should loosen everything up.

b.lindsey · « **Reply #52 on:** October 26, 2019, 08:07:30 PM »

Another "tiny" beauty George. Can't wait to see it running. Also can't remember the last time I saw a half dollar but hey, it works for scaling purposes

Bill

mike mott · « **Reply #53 on:** October 26, 2019, 08:20:18 PM »

Certainly a handsome engine George.

Mike

scc · « **Reply #54 on:** October 26, 2019, 09:51:27 PM »

Absolutely beautiful work George

I cannot imagine working at this scale

big fingers, tired eyes, etc
Regards Terry

90LX_Notch · « **Reply #55 on:** October 27, 2019, 12:47:42 AM »

George-

Amazing work as always.

-Bob

crueby · « **Reply #56 on:** October 27, 2019, 12:55:23 AM »

Wonderfully done! Even more so once you see the coin!

steamer · « **Reply #57 on:** October 27, 2019, 02:16:13 AM »

There it is....love a nice triple!.....that one is even nicer!....

Dave

Kim · « **Reply #58 on:** October 27, 2019, 04:33:35 AM »

Beautiful, George!
Kim

MJM460 · « **Reply #59 on:** October 27, 2019, 09:10:24 AM »

A beautiful result, and an education looking over your shoulder, thank you.

Now Looking forward to seeing it run.

MJM460

gbritnell · « **Reply #60 on:** October 30, 2019, 10:59:56 PM »

I'm going to call this engine complete. It does run on air but not real well but I guess that's to be expected. When it loosens up a bit more I'll post a video of it. I made the els for the pipework. I turn the piece, drill it then use a ball mill to do the inside at the corner. This gives me stock so that the outside radius won't break through.
Many years ago when I needed small fittings I made this small double V-block fixture. One half of the el is turned then put in the mill and cut off at 45 degrees with a small slitting saw. The piece is them put on the end of a rod and mounted in a V-block. The other piece is mounted then the two pieces brought together leaving a minute gap for the silver solder. I took a picture prior to soldering but it was out of focus so the good picture shows the part after soldering. The radius is then filed and the fitting polished.

gbritnell · « **Reply #61 on:** October 30, 2019, 11:02:11 PM »

Some photos of the finished engine.

crueby · « **Reply #62 on:** October 30, 2019, 11:46:17 PM »

Another real beauty!

I like that method for the elbows, have to give that way a try!

ChuckKey · « **Reply #63 on:** October 31, 2019, 12:35:21 AM »

Very impressive, especially as it has only taken a couple of months, I think. I would be interested to know if applying a vacuum at the exhaust made a difference to the way it runs on air.

Kim · « **Reply #64 on:** October 31, 2019, 05:21:39 AM »

Beautiful work, George, as always!
Kim

john mills · « **Reply #65 on:** October 31, 2019, 08:16:29 AM »

Magnificent looking engine and in such short build time .i wonder if it will run better with a load that gets the pressure up in the high pressure cylinder so that there is some left by the time in expands to the low pressure
cylinder .
John

Admiral_dk · « **Reply #66 on:** October 31, 2019, 11:16:25 AM »

Amazing result George

Beside more running time, I can't think off anything else beside the above suggested Vacuum on the exhaust, that could improve running of an tripple expansion engine on air ....

Johnmcc69 · « **Reply #67 on:** October 31, 2019, 03:21:06 PM »

Absolutely beautiful work George! Really nice (tiny) details.

John

Vixen · « **Reply #68 on:** October 31, 2019, 04:44:24 PM »

Very, very nice Gorge.

If ever I were to build a steam engine, it would be one like this

Mike

Craig DeShong · « **Reply #69 on:** October 31, 2019, 08:07:53 PM »

Interesting way to make elbows. I guess I’m lazy but I just buy the castings.

The Tripple is just gorgeous, your attention to fine detail just makes the model ‘pop’.

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Author Topic: Tiny triple expansion steam engine (Read 6809 times)

toolznthings

ChuckKey