Vertical Boiler Fittings

Webb tried this on the LNWR. When he found ice forming on the bit under the fire he realised he was wasting his time.

If you run it with the burner flat out and the safety valve blowing merrily and measure how much water you have to pump in to keep the level constant for a time, you know how much steam it is making and so how big an engine it will run. Allow a big margin for losses!

I would expect the twisted shim down the tubes t help, they are quite big for their length and so hot gas can get up the middle without ever touching the sides. Don't go mad, start with half a turn and it then try increasing the twist to see if it gets better.

More blower means you can burn more gas, but eventually you can have too much and have excess air which cools it all down again. Another set of experiments, but when you have enough air to be able to have the gas full on seems like a good place to stop.

Duncan - thanks for this.

I will try the twisted shim trick, as it may help but can be taken out again if it doesn't.

That, combined with lagging the boiler, might add up to a significant improvement. However, I'm feeling quite optimistic at this point about its performance on gas. I also still have another couple of firing methods to explore using liquid fuel as well as redesigning the firebox and using a blower to try coal again. How successful these will be remains to be seen, but even if this thing only runs on gas it will not be a disaster.

Rather than get too involved in measuring its output and consumption, I now plan to start with the 12 mm oscillator (which will be my first engine) as soon as I have fitted the DRO to my mill, and see how the boiler performs with that under various conditions. Proof of the pudding! If it runs easily I'll go on to make a bigger engine.

I agree, but considering the boiler as a machine for converting water to steam it might pay to keep an eye on its limits.

You don't want an inadequate source of heat because that won't raise steam. That's been the problem so far.

On the other hand you don't want excessive heat either. Apart from being wasteful (which probably doesn't matter in this case), it risks overheating the boiler's structure, softening it and in the worst case melting solder or popping the boiler itself. It could ruin the boiler and damage your good self.

Consider what would happen if you used an oxy-acetylene torch as the burner. A gas torch that can cut steel underwater would make short work of a copper boiler's metalwork!

The boiler translates heat at high temperature to useful steam heat at a much lower temperature. As most flame temperatures are high enough to melt copper, it's important that water inside the boiler keeps the structure cool. The water has two jobs - as well as raising steam, it's crucial to keeping the boiler cool. A boiler will go badly wrong if the water inside fails to keep its structure inside safe limits (below say 250C). One cause of locomotive boiler explosions is letting the water level fall below the firebox: with nothing keeping it cool the temperature of the metal under the flame rises rapidly, softens and then bursts. Nasty.

Forcing extra heat into the boiler is OK provided it doesn't cause excessive temperatures. It's far from OK if the extra heat causes any part of the structure to get too hot, and internal overheating may not be obvious. By analogy, you can hold one end of foot length of copper wire in your hand while melting the other in a Bunsen flame. The wire melts because it can't conduct heat away fast enough to keep the temperature from rising locally.

I favour trying insulation first. You might need more heat as well, but I'd try that second. As it's a pressure vessel, albeit a small one, keep a close watch for danger signs.

Keep us posted - I'm intrigued to know more.

Dave

Dave -

Again very salient. I appreciate your alerting me to the danger of overheating.

Just to be clear - I'm planning to investigate fuels other than gas not because I think they would give more heat, but because I'd like to have options - as much for aesthetic reasons as anything.

The 'Lixada' camping gas burner certainly seems to deliver enough heat. Whether it delivers enough to risk damaging the boiler (assuming it hasn't boiled dry) I do not know, but yes - it would seem sensible to moderate the flame when possible.

To me, this points to insulating the boiler (as you suggest), trying the twisted shim trick, keeping the gas flame a bit lower and ensuring that the water level is topped up.

It also occurs to me that using a bit of steam blower might help, as it pulls the flame up the tubes rather than just letting it fry the bottom end cap, on the basis that this may allow a similar level of heat transfer with the burner turned down lower (i.e. a better distribution, requiring less heat). Any thoughts on this point would be appreciated.

The boiler has now been fired to steam-raising pressures somewhere in the region of eight times. However, I do not wish to tempt providence, and shall keep an eye on these factors and on the condition of the boiler in general as you suggest.

Will definitely keep updating the thread.

Cheers,

gary

Edited By gary.a.ayres on 15/01/2019 13:22:43

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 filed 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:

Edited By gary.a.ayres on 19/01/2019 00:28:46

Edited By gary.a.ayres on 19/01/2019 00:30:11

Edited By gary.a.ayres on 19/01/2019 00:30:59

Edited By gary.a.ayres on 19/01/2019 00:51:44

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

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.

Edited By gary.a.ayres on 20/01/2019 23:40:46

The youtube version of the above post:

I'm sure someone proved that laminar flow was impossible in 'our' sizes of boiler tube and steam flow rates.

Neil

Certainly if there is a scrunched up bit of metal stuck in the tube to negotiate...

Here is a video which features the boiler running a small oscillator which I just completed (my first engine). The engine leaks a fair amount of steam so could benefit from a bit of fettling, and the whole setup needs to be developed, but at least I now know it works!

Edited By gary.a.ayres on 21/03/2019 06:59:36

And now... the first test of the kerosene pressure stove with an engine:

Edited By gary.a.ayres on 01/04/2019 10:20:45

The customisaation of the kerosene stove starts here:

Some progress with the kerosene burner:

Kerosene burner assembly and tank completed:

It might have been a good idea to pause there, but no - I had to go and order this:

https://www.amazon.co.uk/dp/B00JQ2DG4A/ref=pe_3187911_185740111_TE_item

It's a multifuel pressure stove which will run on a variety of fuels, including (according to one reviewer) meths if the hole is enlarged in one of the spare burners. Couldn't resist it, even if just for comparison to the Indian pressure stove, though hopefully it will prove to be a good companion or alternative to it. And I think it will look great with the orange paint removed from that bottle and the aluminium polished up...

Edited By gary.a.ayres on 24/04/2019 23:53:06

Here is the multifuel stove in action. I took the pot stand legs off, and - following a suggestion I read online - drilled out the nozzle to 1.0 mm to run on alcohol. The picture shows it burning vapourised 'alcool a bruler' denatured alcohol from France. I haven't tried it with the boiler yet but early indications are good...

Just to say that I have changed my screen name as I'm starting up a business in an unrelated field and want to avoid overlap/confusion. Arthur is my middle name.

I tested the multifuel burner on alcohol with the boiler and small oscillator:

The engine ran, but not brilliantly and not for very long. That said, it was quite a windy day and the camping windshield you can see in the photo could only offer so much protection.

My fuel tests are nearing their end. At this point I can say vapourised kerosene definitely, gas definitely and vapourised alcohol maybe. I have decided to forget about coal until I make or buy a bigger boiler. The next step is to complete the boiler with a finished stand and proper mounts for the gas and alcohol burners, then to insulate the boiler. I don't think the system can be properly evaluated until the boiler is insulated.

After some time out dealing with other things, I got back into the shop and made a stand for the boiler:

Off on holiday for three weeks, but aim to start insulating the boiler when I get back.

I have now begun the process of insulating the boiler. The ceramic fibre sheet was cut to size and holes marked using a cardboard template. It was then secured to the boiler barrel with thin copper wire:

The plan is to cover this with an outer shell made of thin aluminium sheet.

Edited By gary arthur on 18/08/2019 16:25:09