I'm just beginning to understand why the turners seem so enthusiastic.
It's not wood, but it came out right the first time!
Photos at bottom of page.
Next up: learning to braze with an oxy-acetylene torch...
Much like soldering. Distribute the heat where it needs go and the (fluxxed)
braze will flow nicely Don't tough the tip to the work! ; )
In my (limited) experience, the faster you get it done, within reason, the
better it will look. Incidentally, in one related experiment I did, I
noticed the heat caused the the garage floor to disintegrate. That happened
30 years ago, but I suspect garage floors haven't changed that much! :)
Probably you already know all this, but I enjoyed writing about it. Have
I've watched a number of YouTube videos, and it does look much like
soldering. My plan was to hold the long tube vertical in my vise and
braze the brass fitting into place - then, before it could cool, stack
on the short tube and braze that to the top of the brass fitting. Then,
after everything had cooled to room temperature, add the cap to the top
of the short tube and braze that in place.
Actually, I hardly know anything at all about what I'm doing - and AFAIK
no one has ever built a pump engine like this before. It's a great
adventure. If it works as expected, the next version will be solar
powered with an operating temperature ~1000°F.
The shop floor will remain safe for a little while longer. :)
Thanks for the speed advice - and for the warning about concrete!
The melting point of brass is about 1700 degrees and that of stell is about
2700 degrees (see
That makes your brazing problem much more delicate, I think, than the ones I
You will use a brass brazing rod of course, and I'm sure you will practice
with the material
before you apply the heat to your good one. Alot like me and my M&T
joints..! : )
I'm planning to do my practice after the fact. My SO's grandson's
father-in-law has offered to let me watch while he demonstrates how it's
I'll take along a second set of parts so that I can build a second
engine under his supervision.
I figure that all except one of 'em will be beautiful. ;-)
A fluidyne is a Stirling cycle (heat) engine whose only moving parts are
a gas and a fluid. Previous fluidynes were configured with three
vertical water columns, and one of these provides an alternating
pressure - typically higher than atmospheric for half of the cycle and
lower than atmospheric for the other half of the cycle.
The short answer is that they alternately suck and blow.
Yuppers. Any source of heat will do, but I like solar heat because it's
really, really inexpensive. Stirling engines operate on a temperature
differential between a "hot head" and a "cold head".
Stirling cycle engines also operate in reverse. If you apply mechanical
energy instead of heat, they operate as heat pumps and one part of the
engine will get cold while another gets hot.
If you visit http://www.iedu.com/DeSoto/Projects/Stirling/ and click on
the globe image, you can see photos and videos of some of these things
working (and sometimes not working).
The in-line fluidyne is my attempt to eliminate two of the three water
columns and most of the plumbing to make the engine easier and less
expensive to build, and substantially more efficient in operation. My
goal is an engine that performs the conversion from heat energy to
mechanical energy with better than 50% efficiency...
I understand the heating part of it, but what provides the cooling?
Increasing pressure should just heat things up further (if I remember
how Superman turned coal into diamonds), right?
BTW, that parabolic mirror is impressive!
The cold head is air cooled - so heat is dissipated by convection and
The temperature, pressure, and volume behavior is described at "Modeling
fluidyne behavior"; and pressure is relieved by displacing water
(increasing the volume occupied by the air).
Thanks - it works fairly well. The next one will have the mirror turned
90° so that the trough will be ~88" wide and only 48" long - which will
allow using the 48" focal tube as the hot head of the engine and should
boost the input temperature to somewhere around 1100°F.
It's the HF 7x10 (identical to same size from Griz, etc)
If you're thinking of buying a small lathe and can afford to spend just
a little bit more (I couldn't), this 7x14 looks like a better buy:
There are a number of suppliers of the 7x14 (sometimes referred to as the
7x12 - it depends on the method of measurement) and they are sourced from
two manufacturers in China, Seig and Real Bull. There are also a lot of
tweaks and improvements that can be made. A good site to check out is:
Also it's well worth signing up to the minilathe mailing list:
Warning! Tool fever affects those involved with machine tools at least as
much as it affects woodworkers :-)
Yes there is a great feeling of euphoria when you turn your first piece -
and the second piece, and.....
There's also the realisation that you can now do a lot of things you couldn't
do before but wanted to. All sorts of things in an around the
home/workshop/garage where you think "I can solve this problem by just
turning up one of 'these'"
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