Author Topic: Tiny triple expansion steam engine  (Read 1303 times)

Offline gbritnell

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Tiny triple expansion steam engine
« 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.
Talent unshared is talent wasted.

Offline crueby

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Re: Tiny triple expansion steam engine
« 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?




 :popcorn: :popcorn: :popcorn:

Offline gbritnell

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Re: Tiny triple expansion steam engine
« 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
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Online b.lindsey

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Re: Tiny triple expansion steam engine
« 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

Offline steamer

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Re: Tiny triple expansion steam engine
« Reply #4 on: September 01, 2019, 09:17:25 PM »
Beautiful work as usual George!    Watching along! :popcorn:

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline gbritnell

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Re: Tiny triple expansion steam engine
« 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
Talent unshared is talent wasted.

Offline Don1966

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Re: Tiny triple expansion steam engine
« Reply #6 on: September 04, 2019, 10:45:59 PM »
Love it George I will Be following!..... :ThumbsUp:


 :cheers:
Don

Offline Craig DeShong

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Re: Tiny triple expansion steam engine
« 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. 
Craig

Offline toolznthings

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Re: Tiny triple expansion steam engine
« Reply #8 on: September 06, 2019, 01:17:26 AM »
Nice looking parts !!
Thanks for the visit !
Brian

Offline gbritnell

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Re: Tiny triple expansion steam engine
« 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
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Offline crueby

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Re: Tiny triple expansion steam engine
« Reply #10 on: September 06, 2019, 05:20:53 PM »
Beautiful!

Offline Roger B

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Re: Tiny triple expansion steam engine
« Reply #11 on: September 06, 2019, 05:23:16 PM »
Another splendid piece of miniature engineering to enjoy  :praise2:  :praise2:  :wine1:
Best regards

Roger

Offline gbritnell

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Re: Tiny triple expansion steam engine
« 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
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Offline crueby

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Re: Tiny triple expansion steam engine
« 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?


Offline gbritnell

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Re: Tiny triple expansion steam engine
« 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
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Offline gbritnell

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Re: Tiny triple expansion steam engine
« 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
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Offline steamer

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Re: Tiny triple expansion steam engine
« Reply #16 on: September 10, 2019, 05:59:12 PM »
Looks awesome George!   

 :lolb:  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
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline stevehuckss396

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Re: Tiny triple expansion steam engine
« 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.
Do not be like the cat who wanted a fish but was afraid to get his paws wet.

Offline gbritnell

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Re: Tiny triple expansion steam engine
« 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
Talent unshared is talent wasted.

Online b.lindsey

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Re: Tiny triple expansion steam engine
« Reply #19 on: September 11, 2019, 05:58:09 PM »
Awesome as always George. Another little beautyto watch come to life.

Bill

Offline crueby

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Re: Tiny triple expansion steam engine
« Reply #20 on: September 11, 2019, 06:21:06 PM »
Watching along, amazing parts....

Offline Craig DeShong

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Re: Tiny triple expansion steam engine
« Reply #21 on: September 13, 2019, 01:34:43 PM »
Following along with the rest of the crowd.  Pretty work.
Craig

Offline fumopuc

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Re: Tiny triple expansion steam engine
« Reply #22 on: September 15, 2019, 07:29:26 AM »
Hi George, nice to see you back in steam.
Kind Regards
Achim

Offline gbritnell

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Re: Tiny triple expansion steam engine
« 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
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Online b.lindsey

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Re: Tiny triple expansion steam engine
« Reply #24 on: September 19, 2019, 12:13:02 AM »
Great looking parts George. Seems like this one has come together very fast!!

Bill

Offline Dave Otto

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Re: Tiny triple expansion steam engine
« 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

Offline crueby

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Re: Tiny triple expansion steam engine
« 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?   :popcorn: :popcorn: :popcorn:

Offline Tonyr

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Re: Tiny triple expansion steam engine
« 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

Offline gbritnell

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Re: Tiny triple expansion steam engine
« 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
Talent unshared is talent wasted.

Offline Craig DeShong

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Re: Tiny triple expansion steam engine
« Reply #29 on: Today at 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? 
Craig