I'm thinking of building a campfire-powered "flame licker" atmospheric
engine to produce around 75 watts. Anyone ever build one and have some
advice about size, rpm, seals, valves, governing (you know, hold my hand
during the whole process)?
Campfire powered engine... sounds interesting.
What does an engine like that consist of? What do you do with it?
btw, Still waiting for you guys to start using my free classified section,
make it to be huge. Check it out, it's a nice classified ads website.
Suggestions are welcomed.
Your web search results will probably yield more if you try hot-air
engine or stirling engine, which I believe are the same thing tou are
referring to. There are a good number of sites which would be helpful,
you'll just have to sift a bit to get rid of the firms pushing
overpriced vaporware, and the occasional overpriced thing you can
Ecnerwal wrote in
I've looked at a lot of sites, but in general they are showing off tiny
model engines. Any sites which have larger engines are either bragging
about their engines or are some company trying to sell alternative energy.
I was hoping I could get a few pointers from someone who has built a
By the way, the campfire power would be a flue coming from just over the
fire to the intake valve of the engine.
Those engines would not work very long over a campfire!!!! They are
designed to run on clean burning fuel such as alcohol or some such. The
ash from the fire would soon stop the engine from running. They have
very little power as well. Try a stirling engine. They were used in
yesteryear to pump water using a "campfire"(wood fire) for heat.
If you can pressurize the working fluid, you can get much more power
out of a smaller engine. If you use Helium or Hydrogen as the working
fluid, the power goes up dramatically over air. At 800 PSI, and a 600 C
delta-T, you can get 2 Hp out of a 50 CC displacement Stirling engine
with a regenerator (steel wool can be used for that). I'm still researching
seals that can be run dry at modest temperatures to avoid coking of the
lube oil. Then, I'd use a split crank fitted with sealed ball bearings for
both mains and rod-end bearings. I'm thinking that seals made from Teflon
should work in such an engine.
James Askew wrote in
Never thought too hard about the ash. Good point. I'll look into Stirling
power. Based on a couple of spreadsheets I saw I might need something as
big as 500cc turning at about 1000 rpm.
Just last weekend I was at Barnsley Gardens in Adairsville, GA, and in the
really old house they have, the fireplace/furnace they had there had some
sort of fan in the flue that turned axles that different things could be
attached to. The plaque they had next to it said that Henry Ford tried to
buy the furnace from the family. I don't know what they used it for, or if
this helps you any, but I thought it was pretty interesting. This obviously
wasn't a high rpm machine, but I guess it shows its possibly to do something
with a wood flame.
Standard Christmas decoration on my Grandparents' table for Christmas
dinner was a chiming set of angels that rotated by the heat off of a set
of small candles rising up through a propeller. Not a lot of recoverable
energy, but enough.
The original poster might do well to have a look at the likes of the
Rider Ericson Stirling cycle engines. These were able to provide
reliable, if limited output in a package that would not blow up in the
face of the unskilled operator, as was the danger of boiler steam. They
have a real advantage, for the survival or boondocks operator, that they
do not rely on any high prescision seals or pressurised crankcases, such
as the current lot of high output Stirlings require. Pretty
straightforward design, anyway.
If the output is to provide electricity, what about a thermocouple set?
Soon after Dean Kamen introduced the Segway vehicle he was on 60 Minutes
ore 20/20 showing a new design of Stirling engine powered generator. You
might check his website for more info. The market for this was rural
areas that burn wood for fuel to cook and stay warm.
He may may have some updates.
As I inderstand, an Atmospheric engine is one which the steam is blown
into the cylinder and then followed by the admission of water. The
cool water causes the steam to condense and the vacuum created,
relative to the atmosphere, is what drives the piston of these
engines. Are we all thinking about the same thing? --Doozer in
The definition of atmospheric engine encompasses far more than the
steam engine you describe.
An atmospheric engine is one that uses atmospheric pressure to push
the piston. Therefore, there must be some way of lowering the
pressure in the cylinder to less than atmospheric. It can be done by
condensing steam, as you describe, or it can be done by cooling off
The earliest internal combustion engines were atmospheric engines.
It seems odd, now, but it took a radical change in thinking to use
steam pressure and/or internal combustion pressure, instead of the
atmosphere, to move an engine's power piston.
Lyle Cummins' book "Internal Fire" covers this in depth.