Posted by Jim Wilkins on April 18, 2010, 1:19 pm
They are part of the sunflower family with many small flowers per
stalk, instead of one big one.
They are fibrous, a proxy to test for clogging, and always available
cheap in the grocery store.
"I'm not looking to redo a metal-shop (other
than a small drill-press and welder) but rather cad the design and
farm out to have parts cuts and I may do the final welding. "
I'm wary of inventors who do that because I don't want to become an
unpaid creditor. The project I worked on last year was funded by GM
and still we were nervous.
When building machinery there is always the decision to build or buy
each part. In my experience it's better to outsource parts when you
are sure of the design and fabricate them yourself when you aren't, so
you can make changes. For instance you might find that you want to
spirally groove the rolls rather than perforating them (easier to
clean), or make them slightly different sizes to give a shearing
action if they are geared together, or add supporting rollers in the
center because they deflect. Or something breaks. Your machine shop
has a two week backlog and you need it done NOW before the crop
An example of the problem of clever people who lack hands-on
experience is the inventor who special-ordered expensive 2.000" thrust
bearings to go on a shaft made of 2" water pipe, which is actually
2-3/8" in diameter. I steered him toward a place that rebuilds
hydraulic cylinders and might have some 2.000" rod left over, and
quietly slipped away. The last time I looked his web site was gone.
Posted by Morris Dovey on April 18, 2010, 3:15 pm
On 4/18/2010 8:19 AM, Jim Wilkins wrote:
I wonder how many (tens of thousands of) times that, or something very
similar, has happened...
...I was in Menards yesterday (Saturday) to get copper pipe and a couple
of fittings for my most recent fluidyne effort - and the guys in the
plumbing section were chuckling because I'd brought along my calipers so
as to not make that very same mistake. :)
This not knowing what isn't known makes getting "out of the box" riskier
than a lot of folks realize until suddenly they find they've wasted the
resources they needed to finish the job.
The quiet voice of experience is an important asset to everyone doing
anything they've never done before.
DeSoto, Iowa USA
Posted by Jim Wilkins on April 18, 2010, 4:11 pm
I am nominally an electronic technician and taught myself machine shop
practice because most electrical and a surprising percentage of
mechanical engineers don't know what's available or how things are
made, and make bad and costly assumptions based on their understanding
of today's technology when pipe standards for example actually evolved
from much earlier needs and limitations.
The tricky part is explaining tactfully and respectfully to Dr So-and-
so (a Yale ME professor) that he could use Pem studs which he'd never
heard of instead of his complicated scheme to mount more electronics
inside his robot. I'm not too good at explanations and often have to
make a demonstration sample at home to establish credibility.
Posted by Curbie on April 18, 2010, 7:10 pm
I started a search on DIY parabolic troughs when we last talked and
this guy seems far above the rest, he considered whether condition and
different purposes in his design which seems fairly complete.
You ever seen this guy's stuff before???
DIY construction manual
His support math and design concept
Posted by Morris Dovey on April 18, 2010, 8:22 pm
On 4/18/2010 2:10 PM, Curbie wrote:
I have. He occasionally posts to alt.solar.thermal. His real forte is
analytical geometry (which is a bit like saying that a Ferrari is
"sporty") and if you haven't seen his graphics work, it's worth taking
some time to browse through the links at
I've promised myself that if I ever visit southern France, I /will/ look
him up. :)
DeSoto, Iowa USA