Author Topic: 3 inch boiler build  (Read 20693 times)

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #255 on: January 08, 2019, 10:55:46 PM »
My multifuel adventures continue.

This evening I tested the Trangia inside the cast iron housing which features a few posts above. It was tested under very similar conditions to the open structure I tried last night, i.e. indoors, same burner height, similar amount of water in boiler. Last night with the open structure it took 50 minutes from cold before the safety valve blew off. This evening with the cast iron housing an hour and a quarter in and still nowhere near. There was also an acrid smell - not overpowering but unpleasant. I'm not sure if this came from poorly combusted alcohol or from the plasticky paint inside the housing, but I gave up the ghost and turned off the heat. So, even though I thought that the housing was plenty open enough, clearly it wasn't, so I'll use the open structure if and when I fire the boiler with the Trangia in the future. I guess this could be an option for indoor use.

Zephyrin had it nailed - of course  :)

Meanwhile, look what landed in my back yard today:



Hitherto I have resisted gas, but I took some good advice and decided to cut myself some slack and keep my options open. When I saw how furiously this bad girl burns when you open up the throttle, I realised why it's a popular option. Doesn't look like raising steam will be a problem   :Mad:

Mods have already begun on the gas burner. I know each situation is different, but any advice on the optimum distance between this standard size burner and the bottom end plate of a 3 inch boiler will be welcome...

gary

Offline MJM460

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Re: 3 inch boiler build
« Reply #256 on: January 09, 2019, 06:10:19 AM »
Hi Gary, still following along.  Sorry I have been a bit quiet the last few days.

A few comments to bring me up to date with my thoughts and observations.

The point about heat conduction to the plinth from the trangia burner might be important.  Meths has to warm to 93 deg before it boils to make the vapour that issues in blue tongues from the holes around the rim.  Heat loss through the base might limit the amount of meths that could be evaporated.  A disk of cork or ply, or replacing the Al plinth with a wood block would be worth a try.

I see two issues in the air flow, getting enough air to mix with the fuel and then getting the combustion gases to flow through the boiler flue tubes.  It looks like you have plenty of air flow to the burner, but your boiler flue tubes present a very small flow area compared with the intended use of this burner where the combustion gases flow up the outside of a pot around the full circumference.  This might be why you are needing tome spassisted draft to get enough flow through the tubes.

I expect you might get more heatfrom the gas burner, definitely worth a try, but may still have the same issues getting enough hot gas flow through the tubes.  Again some draft assist might be required.

I donít know if those safety valves arrive preset, but I suspect you have to check them before relying on them.  I tend to be suspicious of very small pressure gauge calibration.  A couple of things you can do to get an idea of accuracy.  First, I assume you did manage to lift the valve using pliers or similar to make sure it was not stuck when it arrived.

First, make a replacement filler plug for the boiler that will accept a thermocouple, called a thermowell.  The hole for the thermocouple is blind so does not leak pressure.  I will try and attach a picture to show you the idea.  Then standard steam tables tell you the pressure corresponding to the temperature.

Depending on the safety valve design, you may be able to use a thin rod to lift the valve and use a digital scale to measure the force at which the valve just starts to lift.  Then measure the diameter of the hole which forms the steam passage, it might correspond to a standard drill size.  The set pressure can then be calculated from the force and area.  Mind you there are a few inaccuracies in this method, not easy to tell just when the valve starts to lift, so a bit of inaccuracy there, and measuring small holes is subject to some error.  It is probably reamed so testing with the shank of some drills will give a reasonable idea if it is a standard size.  Again not sufficiently accurate for a boiler inspector, but should be able to tell the difference between 45 psi and 70 psi.

Best is comparing it with an accurate gauge by a club boiler inspector, first cold on air, then checked hot in a steaming test.

All the best for the continuing experimentation.

MJM460

The more I learn, the more I find that I still have to learn!

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #257 on: January 09, 2019, 07:01:30 AM »
Hi MJM460 -

Thank you for your continued input.

I'll try insulating the bottom of the Trangia as you suggest, though whether it will make enough of a difference remains to be seen. Someone else has suggested that a burner with wicks might be a better option for this application, so more experimentation to follow it seems...  :)

I'm hoping that I won't need assisted draught with the gas (or that if I do it'll just be a little bit of steam blower) but I'll find out when I try it. The gas burner seems pretty powerful. I am a newbie at this though, so may be underestimating the issues...

I'm not too worried about the safety valve question at present. I always test it with pliers before firing the boiler (a habit from my childhood days with a Mamod). My guess is that the main culprit for inaccuracy is the gauge but as you say that's unverifiable without another testing method. The boiler doesn't have a filler plug - it has a hand pump and check valve, so I wouldn't be able to install a thermocouple in the way you suggest. For now, I'm content to know that the safety valve works, which it does.

Cheers,

gary

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #258 on: January 13, 2019, 11:46:03 PM »
I tried the boiler on my gas burner for the first time. I removed the pot stand from the stove burner and set the latter up temporarily on some bits of round stock. Way more powerful than the meths was, as expected - it blew off the safety valve in 15 minutes and I'm pretty sure it would have been much quicker than that if I had turned the flame up higher. It maintained a steady jet of steam from the steam out valve, and I noticed that when I opened the steam blower just to try it, it pulled the flame up into the tubes quite dramatically. However, I think I gave it too much blower as the whole thing went a bit out of control and started to splutter water, at which point I turned off the gas and let it cool down. Overall, though, looking good, and the colour of those flames is to die for:



Meanwhile, in preparation for my next try with coal, I bought this after a fellow forum member kindly drew my attention to it:



It's a quality little piece of British engineering from the 1970's - a cooling fan for some piece of equipment on a plane, possibly military. It appears they are quite often used as blowers. It has the kind of motor which doesn't reverse direction when the polarity of the wires is changed round, so the suction tube has to cover the fan rather than connect to the nozzle. Fortunately I had a copper plumbing reducer which wedges pretty snugly between the three housing screws. Here it is jury-rigged; I think a bit of metallic tape and/or heatproof sealant will suffice to see it working:



Having been given feedback that my last firebox for coal was too wide and not sealed enough, I got started on making a leaner, tighter one:



I am now by no means certain that this boiler - which is 3 inches in diameter with only five tubes - will run on coal (or wood or charcoal). In fact I'd say it's touch and go. But it's worth one more try...
 
Meanwhile - as I want to end up with a few options for firing - I'm waiting for a couple of things to arrive which will further my adventures with liquid fuel...    :)

Offline Gas_mantle

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Re: 3 inch boiler build
« Reply #259 on: January 14, 2019, 12:01:50 PM »
That blower looks to be robust piece of kit and ought to improve your chance of coal firing  :)

I wouldn't bother about sealing it to the copper reducer for now, it doesn't need to be a tight seal. Depending on its original purpose you may even need to reduce the speed if it is sucking your coal up the tubes  :Lol:

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #260 on: January 14, 2019, 04:36:20 PM »
Peter -

I knew you wouldn't recommend anything less!   ;)

Not sealing the reducer is fine by me. One less job to do. It was pure luck that it wedged neatly between the screws.

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #261 on: January 14, 2019, 10:56:38 PM »
This evening I decided to actually try running the boiler rather than just heat it up and gaze at it in stupified awe while it did its thing.

Using the gas burner, I took it up to 50 psi on the gauge. I had the gas turned up a bit higher than last night and it took me 10 minutes to reach 50.

I then opened the steam takeoff valve a bit, resulting in a steady jet of steam which made a narrow strip of paper which I held in front of it flap. The pressure stayed at 50 until I opened the takeoff a bit more, at which point it dropped a little, but it was easy to get it back up again just by restricting the steam out a bit and/or turning up the gas. I went on like this for 20 minutes, with the pressure between 40 and 50 most of the time. At one point it dropped to 30 psi, but that was mainly due to inattention on my part I think. I pumped in more cold water several times and the system recovered quite quickly from that.

That said, the gas was turned up full for most of it, but this didn't seem to do any harm other than to use more gas...

When I get to lagging the boiler it can only get better...

After 20 minutes, I decided to have a fiddle with the steam blower. I was amazed at the dramatic effect it had even with the gas turned up full. The gauge went up fast, and looking up into the bottom of the boiler I could see the flame being sucked up the tubes. I think the blower on this boiler might be useful even with gas.


I'm tempted to be pleased with this, but the one thing I do not yet know is whether or not that jet of steam will drive an engine.

There's only one way to find out...

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #262 on: January 18, 2019, 11:43:39 PM »
While waiting for a couple of items to arrive, I made a start on installling the DRO on my mill in preparation for starting on my first engine (which day draws constantly closer). Fixing the display with its bracket to a convenient storage unit made me feel good, and it looks pretty:





Unfortunately, though, it is attached to the mill's axes by nothing at all as yet and so remains decorative for the moment. That said, I did make a start on making the mounting brackets for the glass scales.

 Those of you who have been following this thread will know that the Lixada camping stove gas burner seemed to raise steam with the boiler quite effectively. While I will  continue to use gas as an option, I am nevertheless in pursuit of a couple of funky alternatives. I received two contenders in the post today:



In the green corner we have an eight-wick kerosene stove from China. It has a catalytic converter/secondary combustion chamber/whatever you want to call it. Although it is not a pressurised unit it vapourises the kerosene and generates a fiendish amount of heat. Unfortunately I took no photos. I did shoot some video but that comes later. It cost less than a tenner, including shipping.

In the blue corner we have a pressurised kerosene stove all the way from India. £22.99 including P&P.  It took me a couple of goes to get the hang of it. For those of you who are unfamiliar with these things, it's like an old-school Primus stove - the burner needs to be preheated. In this case I filled the 'spirit trough' (hidden in photo by frame of stove) with methylated spirits and ignited it, thereby pre-heating the vapourising tubes and allowing the kerosene burner to kick in under pressure:



This resulted in a seriously hot flame which rivals the gas burner and which I suspect will raise steam effectively:



Assuming these two bad boys raise steam, they will be hacked and modified as final alternative heat sources for the boiler, which will be fun and allow for some creativity. However, I will wait until I try them on the boiler before chopping them up so that if they don't work they can always be used as stoves or repurposed for something else in the future. Either way, no great loss at the price.

Trials with each of these under the boiler soon.

Meanwhile, talking of stoves, be stunned by this guy's amazing skills:


gary

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #263 on: January 20, 2019, 11:26:17 PM »
So, this evening I tested the two kerosene stoves:

First



then



The blue Indian pressurising stove emerged as the winner. It's fierce, and almost up there with gas I'd say. It had the gauge up to 50 psi in 12 minutes and the safety valve blowing off in 15. It might do better yet with a bit of burner/boiler distance adjustment. It's also great fun to use and looks fabulous  :Mad:  :)

In contrast, the green 8-wicker didn't even have the needle off the peg in 15 minutes. It's a nice stove of a kind I haven't seen before, and it burns with a very hot flame but a flame of the wrong size and shape. Some fiddling with heights would help, but not enough I reckon. The steam blower made a considerable difference, pulling that soft flame into a neat cone which pushed the pressure up fairly quickly, but this revealed another problem: when the safety valve blew off the flame went out. Not sure why, but it did. That's a problem with this stove because the burner assembly is such that either it or the boiler would have to be removed to relight it. The pressurising one is much easier to relight because the burner is accessible.

It will be very pleasant to use the 8-wick stove to cook a pot of couscous on the patio in France in the Summertime as the barbecue sizzles.

So... thus far the promising contenders are the gas burner and the blue kerosene stove. The square pot stand on the stove will be cut off. I intend to use these two heat sources interchangeably. The idea is to have them both set at the same height so that they can be set in position without doing anything to the boiler. I also aim to make a cool-looking boiler stand and burner supports. However, the proof of the pudding will be in testing the setup out on an engine, so I'd better get on and start building one.

Whether or not the boiler will run on coal assisted by the electric blower remains to be seen, and I intend to have a second go at making a firebox for it. I may do this in parallel with building my first engine, which I shall start once I have the DRO fitted to the mill.


Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #264 on: January 22, 2019, 12:57:21 PM »
The youtube version of the above post:

<a href="http://www.youtube.com/watch?v=5E_qofAb01Q" target="_blank">http://www.youtube.com/watch?v=5E_qofAb01Q</a>


Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #265 on: February 10, 2019, 10:50:05 PM »
There is still quite a bit to do before I can call the boiler finished, but I have decided to pause on it here in order to build an engine so that I can make sure that the boiler will actually run one! That's what it's all about, after all...

I'm just about to start a new thread on the build of the engine, basic and simple as it will be given it's my first effort. When that is done, assuming all goes well with tests, I'll return to the boiler and this thread.

Meanwhile, I have installed the DRO on the y axis of my mill, and am waiting for some parts to arrive so that I can start the x-axis. Here's a video on that - off topic, but no harm I guess:

<a href="http://www.youtube.com/watch?v=kYhjgh9H50c" target="_blank">http://www.youtube.com/watch?v=kYhjgh9H50c</a>


Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #266 on: April 01, 2019, 10:15:49 AM »
Finally and at last, I can definitively say that the Indian pressurizing kerosene stove stove has the oomph to get the boiler to run an engine:

<a href="http://www.youtube.com/watch?v=FN4fvsMWZL8" target="_blank">http://www.youtube.com/watch?v=FN4fvsMWZL8</a>

 :cartwheel:

Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #267 on: April 01, 2019, 10:48:29 PM »
Starting to hack the kerosene pressure stove to make it into a (hopefully) beautiful burner   :)


Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #268 on: April 08, 2019, 11:13:11 PM »
With the cooking pot frame removed, it all starts to look a bit less cumbresome.

I plan to repaint the whole assembly, and got started with the paint stripper this evening, but I ran out of it. Well, I didn't, but I thought I had, only to discover another tin on the shelf just as I was packing up. The end of the tube furthest from the tank was soldered to the frame by the manufacturer. It was a poor join which broke away under very little force, leaving a hole near the end of the tube. I fixed this by cutting the piece with the hole off the end of the tube, then boring out a small piece of round brass bar to make a cap which I silver soldered on to the end of the tube. Removing the square frame has made the assembly less stable than it was, so I am in the process of machining and attaching a piece of aluminium angle which will secure the tank to the eventual base board:



The piece of aluminium angle will be given some decorative holes along its length:


Offline gary.a.ayres

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Re: 3 inch boiler build
« Reply #269 on: April 09, 2019, 11:09:03 PM »
So... I got the rest of the paint off the tank, primed it and sprayed it with dark grey Rust-o-leum 'Painter's Touch' spray paint (which I have always found to be very good when I have used it). The support bracket was drilled with various holes both functional and decorative, and I also added a rail which contributes little structurally but makes the whole thing look more finished, given that I couldn't remove the legs that it is fixed to due to the risk of disrupting the existing silver soldering. This will eventually be fixed to a baseplate along with the other elements in the plant, though it will be interchangeable with other burners. I'm quite pleased with the look, though the photo leaves a bit to be desired - it was taken with my new video camera which I only got today and haven't found my way around yet.