Author Topic: Tiny triple expansion steam engine  (Read 1306 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.

Online 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
Talent unshared is talent wasted.

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
Talent unshared is talent wasted.

Online 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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Online 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
Talent unshared is talent wasted.