Author Topic: A small cochran boiler  (Read 33635 times)

Offline Florian Eberhard

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A small cochran boiler
« on: January 19, 2016, 08:51:26 PM »
Good Evening to everyone!

I thought i'd write something about that little cochran boiler, I started long time ago. (and never finished up to now)
For those of you who don't know what a cochrane boiler is, i have attached a sectional drawing of one.
The boiler was started in 2008 and the first part was one of the plates that holds the flues, which is being formed with a hammer, after bending it twice into a "U" shape.
The according form was made from wood which has been first machined to a cylinder and then had some material removed to bring it into the required shape.
The first plate is completed - next to the boiler tube which has an outer diameter of 60mm.
You can see the beginning of the forming process in the picture where the u-shaped copper sheet is being held by a wooden spacer and a screw clamp.
The wooden form turned out handy to drill the flue holes into the tube plates. The tubes were cut by saw and then machined to get a smooth end. Tube dimension is 6mm outer diameter and 0.5mm wall thickness. After finishing the tubes, I have put together the tubes and the tube plates to see if it was going to work how it should. And it did!  :D

Have a nice evening and see you next time,
Florian
« Last Edit: June 05, 2017, 09:49:31 AM by Florian Eberhard »

Offline Robert Hornby

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Re: A small cochran boiler
« Reply #1 on: January 19, 2016, 10:51:15 PM »
Very nice work indeed there Florian, I will be following closely.

Robert
Age and treachery will always overcome youth and skill

Offline oil mac

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Re: A small cochran boiler
« Reply #2 on: January 20, 2016, 12:07:53 AM »

 Florian,
             Absolutely superb workmanship & genius on overcoming a very difficult task, Also glad to see someone building a model of a Scottish boiler which was widely used

Offline sbwhart

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Re: A small cochran boiler
« Reply #3 on: January 20, 2016, 06:40:45 AM »
That's an interesting project Florian, its got my interest keep the progress reports coming please.

Stew
A little bit of clearance never got in the way

Offline Steamer5

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Re: A small cochran boiler
« Reply #4 on: January 20, 2016, 07:54:58 AM »
Hi Florian,
 Nice project! Watching & enjoying! Can't wait to see how you do the "Ogee" ring around the firebox

Cheers Kerrin
Get excited and make something!

Offline Roger B

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Re: A small cochran boiler
« Reply #5 on: January 20, 2016, 09:44:54 AM »
Hi Florian, glad to see you back in the workshop  :ThumbsUp: I'll be following along  :wine1:
Best regards

Roger

Offline 10KPete

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Re: A small cochran boiler
« Reply #6 on: January 20, 2016, 11:16:45 AM »
A most interesting boiler design. I'd not seen it before your post so had to go 'look it up'.

Keep it coming, I will be right here following along! 

 :cheers:

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline Florian Eberhard

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Re: A small cochran boiler
« Reply #7 on: January 21, 2016, 05:48:21 PM »
Hello Again

Thanks for the comments, the special design of that  boiler is what made it that interesting for me!
Back to boilermaking:
The next part was that ring I suppose Kerrin means whith "Ogee" Ring. It starts as a copper sheet disk as shown on the first picture. The round piece of brass is just used to clamp it as close to the edge as possible. On the second picture, you can see it while annealing it. It looks almost finished but the progress is always getting smaller.
After I finished forming, I did cut a hole into the ring to fit it onto a piece of tube. That tube is going to be part of the firebox.
Then the test if it still fits the boiler shell.
After that, I started cutting the openings into the boiler shell where the firetube plates are going to be located. As I was just using hand tools to work on the shell, I started by drilling lots of small holes. Then I made two cuts with the hacksaw to remove that piece of the shell. To get that opening into its shape, I used some files and again the hacksaw to complete it.
The top of the firebox will be a spherical copper dome that I found at an austrian onlineshop.

Cheers Florian
« Last Edit: June 29, 2017, 09:06:42 PM by Florian Eberhard »

Offline zeeprogrammer

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Re: A small cochran boiler
« Reply #8 on: January 21, 2016, 10:06:46 PM »
Following along Florian.
This is very interesting.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Online b.lindsey

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Re: A small cochran boiler
« Reply #9 on: January 22, 2016, 12:34:26 AM »
Very different and interesting design Florian. I am watching with interest. Nice work thus far on it too!

Bill


Offline Don1966

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Re: A small cochran boiler
« Reply #10 on: January 22, 2016, 12:50:05 AM »
Beautiful work going on in this thread and I will be following your progress....... :ThumbsUp:


Don

Offline Steamer5

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Re: A small cochran boiler
« Reply #11 on: January 22, 2016, 04:21:46 AM »
Hi Florian,
  Yes that the Ogee ring! Learnt about them when I did my steam tickets last century !
Yours is a neat way round the double compound curve that must have required considerable talent to get right.
 The guy that we had as an inspector at the place I worked knew all about them & they were one of his favorite items to check! We didn't have any.....seems they were used in small place like dry cleaners around here.

Cheers Kerrin
Get excited and make something!

Offline Florian Eberhard

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Re: A small cochran boiler
« Reply #12 on: January 23, 2016, 09:31:58 PM »
Yours is a neat way round the double compound curve that must have required considerable talent to get right.

Or just some good Ideas how to make it  ;) (Although it would have been quite difficult in this size!)
However, I can really imagine that these were critical on the "real" boilers as corrosion ususally is worst where two parts are being conected.
Especially this "Ogee" Ring (Where does that Name come from??)  forms a small gap getting narrower until where the ring is riveted together with the boiler shell.

I also bought a dome to use as a top of the boiler. To connect it with the boiler, i machined a step on the shell and also into the shpere.
The fit is machined so that the dome fits onto the boiler by using slight force. The intention was to avoid it moving around when soldering.
The two firebox plates will be held by copper wire for soldering. After soldering, I will just file away the wire that sticks out until it is flush to the shell.
Holding the firebox dome to machine an opening into it was quite difficult. I then tried to place it on top of a wooden rod and that actually worked pretty well for drilling. The hole for the smoke tube was also machined into the smoketube plate of the reversing chamber.
Then a mockup assembly of how the firebox, the connection and the smoketube-plate will look like in the boiler. Finally the part-soldered firebox witht he firing hole tube fitted to its side.
« Last Edit: June 29, 2017, 09:24:01 PM by Florian Eberhard »

Offline vcutajar

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Re: A small cochran boiler
« Reply #13 on: January 23, 2016, 09:44:37 PM »
Quietly following along.  Enjoying and very educational the way you do things.  Thanks.

Vince

Offline fumopuc

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Re: A small cochran boiler
« Reply #14 on: January 24, 2016, 06:41:58 AM »
Hi Florian, a very nice build report of this extraordinary boiler concept. Waiting for the next steps.
Kind Regards
Achim