Author Topic: 3 inch boiler build  (Read 19352 times)

Offline zeeprogrammer

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Re: 3 inch boiler build
« Reply #15 on: July 12, 2018, 10:15:00 PM »
I smell another thread getting started on torches and soldering.
I have the PMR #1 vertical boiler kit and what I'm being led to believe is my MAPP torch (similar but similar bigger to my propane torch used to make Crme Brle) won't do the job.



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Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #16 on: July 12, 2018, 10:35:05 PM »
I bought a Seivert propane torch specially for my boiler (though no doubt it will see other uses, and maybe even other boilers). It's kinda the industry standard for such things I believe, at least in the UK. The amount of heat it pumps out scares me. When I first used it I totally underestimated how fierce it would be so I didn't use enough insulation and  actually set my workbench on fire when I was soldering the boiler!  It was literally in flames... and on the shelf above, plastic containers melted and it was raining their content of stainless steel cap head screws in my workshop for a bit until I wised up (a little bit)  :Mad:

It was reasonably cheap to buy online and a small bottle of propane doesn't cost the earth either, but of course as you note Peter every single thing one acquires creates yet another storage issue.

I also have a small portable oxy/mapp kit which is great for a localised high-temp heat, and I have silver soldered steel pulley components together with it in the past. Used in tandem, the Seivert can produce a good overall silver soldering heat and the oxy/mapp can put a localised cherry on the cake. A very hot cherry indeed.

But tbh Peter (and Carl) if I were you I would think about biting the bullet and if possible getting a Seivert or similar big propane blaster despite the storage issue, as I do think that even a 3 inch boiler could be a misery with an under-powered torch.

By which I mean even more of a misery than it can be with an adequately powered one...  ;)

Offline zeeprogrammer

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Re: 3 inch boiler build
« Reply #17 on: July 12, 2018, 11:57:35 PM »
Ah. I hadn't realized this is your thread Gary. I hope I'm not taking it on a tangent.

I just know so little about such things. To me...propane is propane. But it seems the type of 'torch?', 'blaster?' ... the thingie that puts out the flame...is more critical. No?

So using the same old propane tank, gotten from the local gas station, is fine but the 'torch' makes the difference?

I do know there are other fuels...but again, I don't know anything about them.

I'm interested in this because 1) as I said I have that PMR #1 boiler but 2) my dream since I was a kid was to build a working loco (like Kozo's stuff).

Fire, in whatever form, scares the 'crap' out of me but I know I have to learn about it.

Again...might be worth another thread. At some point I'll start one.
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
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Zee-Another Thread Trasher.

Online crueby

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Re: 3 inch boiler build
« Reply #18 on: July 13, 2018, 12:59:12 AM »
Yup Zee, the torch makes a huge difference. Nice thing on the Sievert handles (if you get the right series) is that it takes a range of nozzles. Smallest nozzle is a few dozen btu, biggest is a few thousand! I bought a range of them for the different jobs, boiler needs the biggy, piping the baby one. Runs off their regulator on a 20 pound propane grill tank.

Offline Jasonb

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Re: 3 inch boiler build
« Reply #19 on: July 13, 2018, 07:36:14 AM »
It all comes down to the rating of the burner not how hot the particular gas burns, even a Sievert with a small burner won't do a boiler, for small ones something around the 7kw rating would do and double that on a big boiler .

Size wise a suitable burner at 7.7kw is 28mm across so Zee's kitchen one may just be a touch too small.

Also make sure you use a High Pressure regulator, a camping or BBQ with generally be low pressure, for these large burners you need a 4bar regulator to get enough gas through them.

Offline Zephyrin

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Re: 3 inch boiler build
« Reply #20 on: July 13, 2018, 08:58:41 AM »
You have to dremelize these awful blobs of silver solder and start again...the little rotary oval mill with diamond shaped tooth works great for that !
absolute clean metal, pink copper and golden silver solder, degreasing with acetone, don't put fingers, good flux in a large area around the point of interest, and a fast heating up to the required temp to see the solder flowing all around the tube by capillarity, you can't miss that, if the solder melt in ball there is something wrong again.
You also may found 55% Ag silver solder, that melt at a lower temp than the usual 40%.

as said above, a propane bottle, 4bar regulator, a torch 500g/hour;

and yes, the heat output is tremendous, as is the return of heat by the bricks or ceramic blanket, you cannot use the little bits of brazing rod...wear gloves, even for a very short session, which should last for about 5 to 10 min.

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #21 on: July 13, 2018, 10:08:21 AM »
Hi guys, and thanks for all your thoughts.

@Carl - no worries! Doesn't feel like a tangent to me, and if it is then it's a useful one. Sorry, the term 'blaster' isn't the correct one - it was just me being poetic.  :)

The others have rightly pointed out that it's the spec of the torch and regulator that are the important factors. Here is the very torch that I bought - 28mm diameter, 7.7 kw, regulator 0 - 4 bar:

https://gasproducts.co.uk/gas-blow-torches/sievert-gas-blow-torch-kits/sievert-general-purpose-gas-blow-torch-kit.html


@ Zephyrin - thank you. You are a star.

 I have already 'dremelized' (great word  :)) the majority of the blobs off, but am still left with a fair amount of silver solder albeit much tidier than it was. Do you think it would be an idea to dremelize all of it off down to the bare copper? I can post a picture of it in its present state if that would help.
One of my problems - as Stuart points out further back in the thread - is that I flared the end of the tube so probably have no room between tube and plate for the silver solder to flow into. I'm now thinking that if I took off as much of the silver solder as possible I could then take a sharp-ended dremel burr and cut a tiny circular channel round where the tube joins the plate. The channel obviously would not go all the way through the metal but would hopefully act as a kind of seat to keep the silver solder where it is needed. This would not be capillary action but it might be better than nothing.
Just an idea... any opinions would be appreciated.

Finally (and I may as well say it now), this particular join is a pain in the neck, but - as far as I can see - the rest of the boiler is not too bad for a first effort, so I am in no way going to give up on it. My plan is to persist with the repair. However, I'm thinking that if I keep trying to fix it and still fail after several attempts it might be better to cut my losses and remove and replace the tube. Tug has mentioned this option in my previous thread. If I am driven to that, I'm wondering if drilling into the mouth of the tube from each end might be the way to go, possibly using progressively larger drills until I'm up to diameter. I believe that this method is sometimes used. In theory it should then be relatively easy to drop in a new tube (and not flare the end this time!).

Will be grateful for any thoughts on any of the above.

gary

Offline Jasonb

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Re: 3 inch boiler build
« Reply #22 on: July 13, 2018, 11:28:05 AM »
As your tube has already been thinned by your attempts to expand it I would be a bit worried about trying to get back to bare copper as you will remove some of the already weakend tube end in the process.

If you later decide to remove the tube then have a look at  Ramon's "wide awake" thread were he starts to discuss the boiler to see how to mechanically take a boiler apart and end up with usable bits. If you do go for drilling out then I would mill the end off flush with the tubeplate and then use the head/table feed of the mill to lower a slot drill into the tube as a drill bit is likely to snatch.

http://www.modelenginemaker.com/index.php/topic,2851.0.html

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #23 on: July 13, 2018, 12:58:19 PM »
Jason -

On the first point - yep, that makes sense.

Second point - thanks for the info. Am hoping I won't need to go that far, but will certainly bear in mind your tips if I do, and will look at Ramon's thread anyway.

Cheers,

gary

Offline Gas_mantle

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Re: 3 inch boiler build
« Reply #24 on: July 13, 2018, 01:49:57 PM »
Gary, just as a matter of interest can you remember what gauge of copper you used ? I realise that isn't anything to do with the problem you are having but I'd like to compare what you used with the materials I have  :)

Offline Stuart

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Re: 3 inch boiler build
« Reply #25 on: July 13, 2018, 02:31:11 PM »
Now I am getting very concerned

To build a boiler ( exclude the brass mamod type ) you have only two options

1. Build it to a published plan by a know designer
2. Do the required stress calculations for the working pressure and from that select the correct gauge of a known copper , also the size and spacing of any stays that the calculations require

If you are a member of a club consult you boiler inspector

I assume both these boilers are for private use and no members of the public will be nearby
In that case you will not need a boiler certificate but if third parties are involved then it need to be inspected and insured

Now copper boilers fitted with well made and sized safety valves seldom fail cin a atastrophic maner  but its you hide . The point was made to me many years ago think about driving a 3 1/2 inch or 5 inch loco that boiler backhead is not far from the crown 💎

To sate a point a bit of 15mm copper water pipe looks ok it stands 80psi all day internal pressure , but external crush pressure in an annealed state after you have had it red hot is another matter

Sorry for the doom and gloom but I for one would not like to read of a member having a mishap


And finally no I will not do the calculations for boiler construction in copper/silver soldered model boiler

Steel boilers are a very different kettle of fish you should be a coded welder to make them


A disclaimer I have made 4 3 1/3 g and 6 5g loco boilers from plans but my last three I had professionally built due to the size and cost of the copper and silver solder
My aim is for a accurate part with a good finish

Offline Jo

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Re: 3 inch boiler build
« Reply #26 on: July 13, 2018, 02:46:03 PM »
Good points Stuart.

Lets go back to basics: Gary who designed this boiler?

Jo
Usus est optimum magister

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #27 on: July 13, 2018, 03:08:12 PM »
@ Jo - the boiler is based on a design by Stan Bray, scaled up from 2" to 3" with all dimensions of tubes etc as close as I could get to x1.5 in the materials available.
The original is in this book:
https://www.amazon.co.uk/Making-Simple-Model-Steam-Engines/dp/1861267738/ref=asap_bc?ie=UTF8

@ Stuart - Just to be clear, I am only building one boiler, not two.
Thank you for voicing your various concerns, but I am already aware of many of the points you make. For example, I have already bushed the boiler for a 45 psi safety valve, I haven't used ordinary plumber's pipe, and I know that a boiler needs to be inspected and passed before it can be used in public (I am trying to build it to a spec that might pass an inspection. If it doesn't, then it will be for my use only)....
Also, I hope you don't mind me pointing out that I have never asked you to do any calculations for me. I feel I have to make this clear because there's a line in your post that could be taken to imply that I have.

@ Peter - all of the copper for the boiler was purchased from model engineering suppliers to the required specifications  :).
I can't remember the dimensions and gauges off the top of my head but willl look them up over the weekend when I have more time, post them in this thread, and let you know.

 :ThumbsUp:

gary

Online crueby

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Re: 3 inch boiler build
« Reply #28 on: July 13, 2018, 03:11:23 PM »
It all comes down to the rating of the burner not how hot the particular gas burns, even a Sievert with a small burner won't do a boiler, for small ones something around the 7kw rating would do and double that on a big boiler .

Size wise a suitable burner at 7.7kw is 28mm across so Zee's kitchen one may just be a touch too small.

Also make sure you use a High Pressure regulator, a camping or BBQ with generally be low pressure, for these large burners you need a 4bar regulator to get enough gas through them.
I agree on the regulator, well worth it to get the one Seivert supplies fir the torches.

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #29 on: July 13, 2018, 03:23:52 PM »
Quote
I agree on the regulator, well worth it to get the one Seivert supplies fir the torches.

 :ThumbsUp: