Author Topic: A small cochran boiler  (Read 18538 times)

Offline Florian Eberhard

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Re: A small cochran boiler
« Reply #135 on: August 23, 2017, 09:03:08 PM »
Hey Roger

Sure - I would say if you wait until the beginning of winter, I should have moved my shop to the new place. (I hope so :P )

I was continuing work on the cochran boiler last weekend. The radiation shield (made from 0.5mm thick stainless steel) has been machined to fit the reversing chamber as exact as possible. To check if it works together with the cover, I took two spacers totgether with douple-sided adhesive tape and sticked the cover and the shield together.
I had to remove some material again but it seems to work. Then I drilled the holes for the stud-threads that will hold the clamps.
And as always when it seems to work pretty nice and you get a little careless, the disaster happens!  :facepalm: :zap:
The drill tip broke off in the boiler shell  :Doh: :facepalm2:

Well - I started research on how to remove a tap and it seems you can use sulphuric acid (I could ged some battery acid) to dissolve the drill redidues.
I haven't done it yeat and will of course test it on something else than the boiler but it should work, since some people use it to remove the residues and oxides from soldering.
I will of course let you know when I was successful.

I contintued with the other 10 holes, cut threads and took some cut-off M1.2 screws to make stays from. I first determined how long they had to be and then cut them to legth on the lathe.
Finally a test assembly with the reversing chamber cover and 10 of 11 clamps looked good and seems to work.

See you with the next update,
Florian



Offline crueby

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Re: A small cochran boiler
« Reply #136 on: August 23, 2017, 10:40:25 PM »
Looking fantastic, very interesting shape to that boiler, almost like Captain Nemo's scuba tank!

 :popcorn:

Offline Florian Eberhard

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Re: A small cochran boiler
« Reply #137 on: September 17, 2017, 01:23:08 PM »
Thanks Chris!

As mentioned in my last post, I had a piece of broken off drill in my boiler. In the meantime i got some sulphuric acid and gave it a try. I positioned the boiler with the whole pointing upwards and then put a drop of acid onto the hole. Then used a needle to get the air out and waited. There was a little bubble of hydrogen gas growing - but rahter slowly. So I heated the boiler up to in about 50C and there we had the bubbles coming out of the hole pretty fast. After half an hour not much happened anymore, so I heated up again and after another 30 minutes i had to replace the acid. Then again, heating up the boiler and with the new acid, the bubbles were produced pretty fast. This whole game was continued for another 2 hours and then when I came back to check, I saw that the tip of the drill was laying on the boiler, right next to the hole. So the bubbles must have lifted it out of the whole. And I must say that worked pretty good! Not the copper,  nor the brass or the silver solder has been attacked by the acid but the drill tip came out without any effort!  :whoohoo: :cartwheel:$

Okay, this also raised my motivation further up an the next step was to make a few spacers for between the reversing chamber cover and radiation shield. And I made two brackets that were used for lifting of the cover on the real cochran boilers.
Those brackets were made from sheet metal, that was bent into an angle first. Then I machined all of the sides in the milling machine, drilled the three holes, machined the beveled side and rounded the corners with a file.

See you next time,
Florian



Online Gas_mantle

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Re: A small cochran boiler
« Reply #138 on: September 17, 2017, 06:20:04 PM »
Looking great Florian  :)

Are you intending to marry up the boiler with a particular engine or is it a general purpose item ?

Offline Florian Eberhard

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Re: A small cochran boiler
« Reply #139 on: September 20, 2017, 09:29:35 PM »
Thanks Peter!
I am not yet sure what I want it to connect with, originally I thought about my little stephenson engine but i will have to figure that out yet.

The Cover and the brackets were riveted together and four holes to connect the radiation shield with the cover were drilled.
I am using rivets to connect those parts and made four spacers from a 3mm dia. brass rod. Riveting was done with my rivet squeezer and once again I am happy that I built it.
Oh and who finds the mistake on the third picture?  :facepalm: Well - its on the inside so I decided to ignore it.
And of course the picture together with the boiler, with all the clamps mounted.

This was another step closer to the finishline. Now there are only 3 major tasks to be completed:
- Handwheels. The ones I made a long time ago came apart because the wood didn't keep its dimensions (which I should have known before). So I am going to make new ones.
- Base plate. I want to make a base plate and then connect it to the base of the boiler using rivets.
- Upper end of the chimney. I want to have some kind of a cap ring or so on the end. I will yet have to find a pleasant form though. (Or have an Idea how to do it)

I did begin with the handwheels 2 weeks ago. First I machined the Handwheel body. Then the wooden collar was made, also in the lathe. And (no pictures) a clamping ring was made too.
The hanwheel is then screwed together with six M0.6 screws.
What you can see on the pictures is the main valve handwheel. There are two more to be done, the one for the blower and the one for the water gauge drain valve - but more about those two next time ;)

Florian
« Last Edit: September 20, 2017, 09:48:20 PM by Florian Eberhard »

Offline crueby

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Re: A small cochran boiler
« Reply #140 on: September 20, 2017, 10:19:56 PM »
Really looking great! Your surface finishes are excellent.


That extra hole jn the inner heat shield? Call it an inspection hole, or a locating hole for the holding jig!  If there was no mistake anywhere, it wouldn't be handmade!   :cheers:


 :popcorn:

Offline Florian Eberhard

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Re: A small cochran boiler
« Reply #141 on: September 21, 2017, 06:08:34 PM »
Your surface finishes are excellent.

Hi Chris

I guess you are talking about the finish of the brass cover?
That is only because the sheet metal had a very good finish from the start. That finish was even improved during the bending process since my bending rolls have an excellent surface finish (ground rolls).
For the end finish, I first reduced any oxides by pickling. Then I threaded the surface with the dremel, using some abrasive fleece in a mandrel (I usually take 3 squares and line them up on the screw). After the fleece, I finish by using some fine grate steel wool. And then you get that finish you can see in those pictures.

Quote
That extra hole jn the inner heat shield?
You got it! Inspection hole sounds good, I like it!  ;D

And here are the other two handwheels:

First I made the wheel bodies, then the clamping rings. Those smaller wheels will have an outer diameter of 12mm over the wooden collar. The wheel body has an outer diameter of 10mm.
The wheel bodies had to be turned around and were rounded on the bottom, just like I did it with the bigger wheel (which has by the way 16mm outer diameter). The wooden collars were cut off and test-fitted to the wheel bodies.
To finish the collar outside, I quickly made an arbour to clamp them on the inside. The rest was then done with a file.
On the last picture, you can see all the valves with wooden handwheel and the old wheels right behind.

So this means I am done with one of 3 points! And I am looking forward to complete the boiler within the next 2-3 weeks. At least so that I can fire it up for the first time!

Cheers Florian
« Last Edit: September 21, 2017, 06:24:45 PM by Florian Eberhard »

Offline crueby

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Re: A small cochran boiler
« Reply #142 on: September 21, 2017, 07:16:50 PM »
Those handwheels are great - the wood really sets them off. What kind of wood did you use? Is there a risk of such a thin rim cracking along the grain lines with heating/cooling/moisture/oil? One thing I have done on small bits on carvings (talons, beaks, etc) was to harden them by soaking in some super-glue.

 :popcorn:

Offline Florian Eberhard

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Re: A small cochran boiler
« Reply #143 on: September 21, 2017, 07:30:39 PM »
Thanks Chris

I don't think that they will crack, boxwood is pretty tough and has a very fine grain.
In addition, i am going to soak those rims with some beeswax. I have done this before and it works pretty well. I usually melt the wax, put the wooden handles in and let it soak for 15 minutes to half an hour.

Florian 


Offline crueby

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Re: A small cochran boiler
« Reply #144 on: September 21, 2017, 07:37:41 PM »
Thanks Chris

I don't think that they will crack, boxwood is pretty tough and has a very fine grain.
In addition, i am going to soak those rims with some beeswax. I have done this before and it works pretty well. I usually melt the wax, put the wooden handles in and let it soak for 15 minutes to half an hour.

Florian
That will give them a great sheen as well.    :ThumbsUp:

Offline Florian Eberhard

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Re: A small cochran boiler
« Reply #145 on: October 08, 2017, 09:18:17 PM »
Good Evening

Well I might need to extend those 2-3 weeks a bit. But I do have some progress to show:

I finally decided against a cap ring on the chimney top. I remembered almost no horizontal boiler which had a cap ring and I also didn't have an Idea about how to design it so it looked good. The solution was this:
I first machined a former and a plug - the plug should support the end of the tube so it doesn't get damaged when pressing the tube onto the former. The chimney tube was cut to lenth before. Then I annealed the tube at one end, applyied some grease and pressed the chimney onto the former.
After using some fleece and steel wool afterwards, the chimney came out pretty nice - and I like how it looks together with the boiler.
-> Another point completed! :)

Cheers Florian

Offline Ye-Ole Steam Dude

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Re: A small cochran boiler
« Reply #146 on: October 08, 2017, 09:27:36 PM »
That looks really nice.

Thomas

Offline Florian Eberhard

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Re: A small cochran boiler
« Reply #147 on: October 30, 2017, 08:17:41 PM »
Thank you Thomas

I have been pretty busy in the shop for the last few weeks, but now its time again to show the progress.
I startet making the base plate. After cutting ouct a piece of 3mm brass sheet metal from a bigger piece - using a hacksaw - I first machined all the sides.
Then I used a chamfer mill to machine a decent chamfer around the upper side. The aluminium plate supports the brass - I first tried without but the surface was not so good due to vibrations.
The next step was cutting off the four edges using a small slitting saw. I first wanted to use the vee block in the vice but that didn't work. So I used the supporting plate from the previous step together with the vee block which was only used to position the base plate.
As i want to rivet the base plate to the boiler base, i had to drill a few holes into that plate. Having drilled the riveting holes before with the rotary table, I chose to do it the same way with these holes. Those holes were also countersunk to allow the rivet head to be completely inside the base plate.
Unfortunately i was not able to use my riveting pliers for those rivets. They were just too close to the base to have any chance getting there. And riveting while holding several things is not very funny and can lead to unwanted marks pretty quick - so I made an anvil to support the rivet. The anvil was made from a M10 bolt (8.8 grade) and then screwed into an aluminium plate to hold it at the right height. The boiler base close to the anvil was slightly lifted from the aluminium plate to ensure the rivet would sit where it should.
Riveting then went pretty easy, I have not been as fast as with the riveting pliers but it only took me about 10 minutes to do all 18 rivets.
The result is perfect - making that fixture definitely payed off!

Florian




Online b.lindsey

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Re: A small cochran boiler
« Reply #148 on: October 30, 2017, 11:01:24 PM »
The end result looks very nice Florian. You should be getting close to completing it now I would think.

Bill

Offline Florian Eberhard

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Re: A small cochran boiler
« Reply #149 on: October 31, 2017, 06:34:08 PM »
Hey Bill

You are right, I am getting very close! (Finally!!  :) )

The firedoor was still loose because I first needed to do the final finish on the boiler.
That included filing away some surplus silversolder. Then I used a dremel abrasive brush (EZ473SA) for the first step. That was followed by some abrasive pad (used on a dremel mandrel) and finally I used some fine grade steel wool. This results in a pretty nice finish, as you can see on the third picture.
I then could also mount the firedoor ring permanently. I filed the firedoor ring hole slighly tapered. After putting the ring onto the firehole tube, I expanded the tube slightly with a piece of plastic and a hammer. That resulted in a pretty good conection, so this is a method I may use again!

Since I didn't plan that kind of boiler base from the beginning on, I had to make a fitting spacer because to be able to mount the blowdown valve. For sealing the fittings, I came up with a new (to me at least!) Idea: I machine a ring that goes over an o-ring. The height of the ring is about 0.8 times the crosssection diameter of the o-ring. Then you simply put the two onto the thread of a fitting and mount it on the boiler. By varying the ring height, you can slightly adjust the fitting position. (For bigger adjustments, you can machine the end face of either the ferrule or of the fitting)

Next up is the boiler feed valve and some pipework aswell.

Cheers Florian
« Last Edit: October 31, 2017, 06:44:06 PM by Florian Eberhard »