Re: home brew hydro rants: wedgwire, bears, nozzles and too much water

 
Do you know the shape? Maybe you could make a wooden form and bend
some scrap stainless sheet metal over it, which will be easier than
making the curved louvers on my cat con heat shield. Aluminum might
even work, the curve adds a lot of strength. Use painted mild steel or
rebar for the supports and make them easy to replace. Aircraft Spruce
sells tubing formed to airfoil shapes for bracing struts. You could
try partially flattened aluminum tubing or electrical conduit.


If you rethread them, straight o-ring joints the same size and pitch
as pipe thread are much easier to cut on a lathe unless it has a taper
attachment. Look at the "swivel" fittings on hydraulic hose, which fit
standard pipe ends that have been countersunk on the end for the
sealing surface. Another common example is the screw-in heater
elements for electric water heaters.

Pipe from 1" to 2" uses 11-1/2 threads per inch which many lathes
can't cut. If the pressures are low you could cheat it to 12.

jw

 

Yeah thats an idea.  Aluminum.  I've never seen a screen like this in
real life .. just drawings and pictures.  I doubt I could bend stainless
over a form to the precision needed.  Have a look at
http://www.coandaintakes.com/how_coandas_work.html

You can see its just a triangle like wedge of wire bonded to a frame, but
with very precice gaps.

Have a look at http://www.coandaintakes.com/Profile_wire.html   that shows
the basic shape with some demensions.

I've heard that these are used to separate solids in sewage treatment
plants and in large fish friendly municipal water systems.  Be cool to
find some place that was upgrading and had their old stuff lying around.

And you'd think that they could be made out of high density plastic --
but I guess there isn't a lot of people out there who need them, so
demand isn't all that high.  

Maybe i'll get some quotes.  Last time I tried to buy one was when steel
prices were insane.  Maybe the prices have dropped enough to justify  --
or maybe someone has a dropped order and some extra lying around.





cool thanks.  Yeah I'll just have to bring the nozzles down to my buddies
shop and screw around.  Just another thing to do -- was really hoping I
could just screw them in and get testing with them.  So it goes!

 

|
|
| >>
| >> I've been looking at using a wedgewire screen to make a reliable
| >> intake system. Ain't easy stuff to get, wedgewire screens.
| >>
| >> But its not easy stuff to come accross .. and having someone make
you
| >> a stainless steel one isn't cheap at all. So still hunting me one
of
| >> tho
| > se
| >> magic screens but not lay out a grand for it.
| >
| > Do you know the shape? Maybe you could make a wooden form and bend
| > some scrap stainless sheet metal over it, which will be easier than
| > making the curved louvers on my cat con heat shield. Aluminum might
| > even work, the curve adds a lot of strength. Use painted mild steel
or
| > rebar for the supports and make them easy to replace. Aircraft
Spruce
| > sells tubing formed to airfoil shapes for bracing struts. You could
| > try partially flattened aluminum tubing or electrical conduit.
|
| Yeah thats an idea.  Aluminum.  I've never seen a screen like this in
| real life .. just drawings and pictures.  I doubt I could bend
stainless
| over a form to the precision needed.  Have a look at
| http://www.coandaintakes.com/how_coandas_work.html
|
| You can see its just a triangle like wedge of wire bonded to a frame,
but
| with very precice gaps.
|
| Have a look at http://www.coandaintakes.com/Profile_wire.html   that
shows
| the basic shape with some demensions.
|
| I've heard that these are used to separate solids in sewage treatment
| plants and in large fish friendly municipal water systems.  Be cool to
| find some place that was upgrading and had their old stuff lying
around.
|
| And you'd think that they could be made out of high density plastic --
| but I guess there isn't a lot of people out there who need them, so
| demand isn't all that high.


What about Brass sheet, braze into a triangle. Then braze onto the
support.
You can cut brass easily or have someone do it for you.
Plus it'll last longer than Aluminum.

Cheers
 

 @news.motzarella.org:


Yeah I ended up just ordering one.  Prices are less than half of what
they were last year.  $200 delivered for 26"x 26" with 1mm gap.  I could
easily spend that much time and effort screwing around trying to make
one.  Plus this is stainless so it should last forever

I'll let y'all know if they actually work worth a crap

thanks

-zachary

 z wrote:

I looked through your links and understand how this screen is supposed to
work, but it seems it would only work on a spillway or weir outlet.  I don't
see how you could use any water stored behind a dam, as the only water doing
into the penstock is a portion of the water going over the weir.

I still don't understand how the collection box underneath it will stay
flooded and not let air get entrained into the penstock when the water flow
over the weir drops off in dry times.  If the collection box doesn't stay
flooded, it seems like you'd have problems.

I don't recall how large your dam/water supply is, but a foot wide weir
screen might be made from wood.  You could cut some foot long 3/4 inch by 2
inch stock lengthwise on the diagonal so you have 3/4 x 2 triangular shaped
pieces.  Arrange them like slats in a window shutter sort of design with all
the leading edges facing upstream and raised up slightly from the back edge
of the upstream piece.  Sort of like a large cheese grater..  I don't think
the angle of 'attack' is too critical, maybe 7-10 degrees is enough ??

Of course the gap formed by the leading edge of one row and the back edge of
the upstream row will determine the maximum debris size that can get
through.  It would seem that silt and flat debris like leaves would slip
right in.  Not sure this is the sort of thing you want.

And you'll only capture a portion of the water that goes over the weir,
perhaps a steeper 'cut' angle for the leading edge will capture more, up to
a point.

daestrom