So far what I found is that a simple screen is good for keeping out leaves and dropped coins but not so much for finer particles. The problem is that once a particle is blocked, it totally obstructs the mesh that blocked it. To filter medium-fine sand, say 1000 microns (0.040 in), we’d need about an 18 mesh screen with a 0.017 dia wire, and that configuration has an open area of 48% Without going through the calculations, it would only take about 1½ cc of sand to obstruct enough of the screen to begin restricting flow.
What this all comes down to is that it looks like if you really want to filter what goes through your Webers, we need to figure out a way to get a dome of foam under the wire hemisphere and keep it there. If coins and such are all you’re worried about, then I think a fairly inexpensive solution is possible, and I’m checking into some industrial filters that may work with just a little modification.
If anyone wants to go through the calculations themselves, some helpful information is listed below. Let me know if you’ve got an idea on the foam dome.
John
Woven wire mesh info
http://www.ron-vik.com/plaintwilled.aspx
surface area of a hemisphere = π/2 • d²
1” = 25,400 microns
sand = 100-10,000 microns
hair 500 microns
1000 microns = 0.040”
18 mesh = about 50% -70% open area, approx. 1000 micron opening
60 mm trumpet, the area for a hemisphere sitting on top is 5,656 sq mm.
38 mm choke cross section area = 1,134 sq mm
