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Gas-fired LaMont boiler

Posted: Sun Jun 23, 2019 9:11 pm
by Steam Captain
Since many things have changed and not by a small part by having read lots of threads here about boilers, I've decided to abandon the solid-fired Benson boiler idea.

It does seem possible to have the
kind of boiler I described in my thread here:


but I decided for a non-solid fuel burner. After studying lot's of material, the boiler should be/do/have:
  • A watertube boiler.
  • An easily quantifiable means to regulate the burner. Thus, solid fuel is excluded (not talking about dust firing as it seems to be an undiscovered country for the small scale)
  • A focus on radiation HS.
  • A convection HS tube bundle.
  • An economizer.
  • A superheater before or even behind the convection HS.
  • An air preheater
  • A steam separator.
  • A single, but redundant feed water pump.
I always have the feeling to write too much, but I hope this will be interesting for others, too. Especially since gasoline is much more volatile than a piece of oak, I want to adress why I chose gasoline. I use gas blowtorches for my hobbies for around 10 years. I silver-brazed my first boiler, a scotch model boiler, with a gasoline blowtorch. For me, it simply was attractive to work with machinery, that is not used so much anymore. It went so far, that I built a blowtorch-fired "paint can" forge.

Here is the link. It is in german, though. But the pictures possess all the crucial information of the text: ... l%F6tlampe

The step from a blowlamp forge to a blowlamp boiler was naturally just a small step for me.

The boiler will be defined by the N-shaped travel path of the combustion gasses. The left bar of the N will be the burning chamber with the water wall acting as a radiation HS. 4 burners will create jet-flames looking upwards. The idea behind it is to elongate the flame with this means. Each 2nd tube on the top side will be cranked out to allow for the passage of the combustion gasses.
A sheet metal bow will lead the gasses to the middle bar of the N, where the superheater, the convection evap and the eco bundles will be in.
The last bar of the N will house the air preheater.

I am building a water-walled burning chamber from copper tubes. I thought of using unmodified blowlamps just placed in a sort of rack besides the boiler and let the burner nozzle stick inside the boiler. But I want to have a vertical flame and blowtorches don't always work with the burner nozzle looking right up or down due to the liquid part of the gasoline getting too close to the burner and cooling it too much.

I'll use brake pipes and nozzles from spraying guns or similiar tools for the burner.(I read someone on this forum used a paintbrush pistol as a burner) - Maybe it is even worth a separate thread.

Today, I have thrown together a crude, wooden negative to wrap the copper tube around. This will be the water wall enclosing the burning chamber.


The corners are smoothened with a drawknife to attain a bending radius of 22mm for the 6mm(1/4") copper pipe. This is more or less the minimum bending radius without any fill-ins. The round wooden blocks on top are the place holders for the burner nozzles and will be clamped or screwn on to crank the tubes around for the burner nozzles.


The picture above shows a successful test bend.


As you can see at the test coiling, the burning chamber will be elongated to have enough space for the jet flames to develop. One short side already shows a cranked tube for the burner. The tubes of the opposite side will be alternating in hight to create space between each of them for the gasses to leave the burning chamber. I'll show in another post what I mean.


The picture above shows the first complete turn. Hidden is the completed bending of the feed end.


The photo above shows a wooden block I use to hold the coil in place. Using 2 of these blocks and 2 clamps works just right. While the last, finished segment before a bent to make is clamped down like this, the bent is carefully made by hand or a small piece of soft wood with a groove in it. To conclude a bend, the following length of tube is clamped with the second clamp and the first one can be removed to be used after the following bending. This way, I will continue until I reach the end.

Re: Gas-fired LaMont boiler

Posted: Mon Jun 24, 2019 4:57 pm
by RNoe
Keep posting your ideas and progress.
I am interested watching your evolution of thinking.

Caution: Consider using liquid fuels that will not produce heavy vapor that can collect in the bottom of the boat and then flash explode!
This eliminates gasoline and propane.
I am choosing to fire my boiler with oil instead. #2 stove = diesel oil (minus the local road taxes). Higher flash point is much safer.

Re: Gas-fired LaMont boiler

Posted: Mon Jun 24, 2019 6:54 pm
by Steam Captain
Hey. Thank you for your response. This test boiler is not yet intended for a use in a boat. It is all an experimental phase for the real deal later on. the boiler is just to have test runs on my opposed-piston steam engine project. If everything works out as planned, I'd like to be the first one to have a 6-cylinder opposed-piston marine steam engine in my boat. But I'd probably go for a wood-fired boiler as the boat boiler.

I am not yet at the point of deciding the specific boiler I want to use, as other things have to be cleared out first - having an own workshop for a boat/ a hull to design a boiler for.

I appreciate your motivational words👋

I am planing to bend more piping tomorrow to have at least one cranked burner nozzle opening finished. I actually didn't realize how much time it takes to bend 6mm copper tubing without folding it.

Building the radiation HS

Posted: Tue Jun 25, 2019 8:30 pm
by Steam Captain
After a couple of hours in my workshop, I only managed to coil almost 5 further rounds. I don't know if I am too careful bending the tube. But at least I now feel relatively safe avoiding any tube collapse.

Unfortunately, my phone died in the workshop & thus, I can not show the results. But it already showed, that I will definitely use 2 more clamps. Pulling on the tube seems to raise the probability of collapsed tubes I noticed at the test bend. While applying some axial force along the tube towards the bend to be made seems to well avoid any mishaps.

What I noticed working the tube around the negative is, that The tubes might loosen somewhat while working on the other side. So to attain the best results, I will permanently clamp wooden blocks over the finished tube coils to keep it as stiff as possible. That combined with clamping a tube all around while bending makes a great, although time-consuming, work process.

At the end all will be held together with small mini suspenders brazed onto the tubes. This will also later create part of the skeleton holding all the boiler parts in place.

I also thought about a plan B in case a bend ruins the entire work - In that case, I will just cut that specific part out and continue with a new tube, connecting everything back together with brake pipe fittings and period. More to come.

Re: Gas-fired LaMont boiler

Posted: Wed Jun 26, 2019 1:55 am
by barts
When I wound the 1/2" (~13 mm) tubing for Otter's boiler, I filled the tubes w/ sand. For very small tubes, you might want to consider Cerro bend or other very low melting point (below 100 C) metal alloys to prevent tube collapse.

- Bart

Bending with sand/low melting point metal

Posted: Wed Jun 26, 2019 7:47 am
by Steam Captain
Sand sounds fine to me, but wouldn't the poured metal leave a coating inside, like being plated?

Re: Gas-fired LaMont boiler

Posted: Fri Jun 28, 2019 4:16 am
by Steam Captain
i deleted this post due to being illogical.

Re: Gas-fired LaMont boiler

Posted: Sat Jun 29, 2019 5:01 pm
by cyberbadger
I thought this website on a Lamont Boiler made in 2001 might be helpful....


link to LaMont boiler test run

Posted: Sun Jun 30, 2019 7:12 pm
by Steam Captain
Hey Cyberbadger,

Many thanks for the link. Although I've dug it up some time ago, it still is a very informative test protocol. There is a lot of data providing for a nearly exhaustive test run of their LaMont boiler. Unfortunately, we don't see many sources like this one. Thanks for the input👋

Cranked tubes to allow gas passage

Posted: Mon Jul 01, 2019 7:35 pm
by Steam Captain

Above I described the short side opposite of the burners will be cranked alternatingly (is that even the terminus technicus?) to allow for the combustion gasses to pass through, exiting the burning chamber.

Below is a photo of how it looks like in real life:


The copper tubes still are a little rough and unevenly bent. I'll care for that after the coiling of the HS has been finished.

The tubes are just small enough to be bent without any fillings. I followed the formula for bending copper tubes without any special tools, which kept bending easy enough, though time-consuming due to me trying to be very careful.

I am rather satisfied with the parallelness of the tubes. If only the cranks at the burner openings would look so even.