On Sun, 22 Jan 2006 05:52:42 -0800, Jay in the Mojave
wrote:

+Hello All:
+
+Look at this e-bay auction for high temp Chimney's. Pictured is a
+3CX5000 Tube. Yeah I know only a driver, hehehehe
+
+But I thought that the Chemney needed to have a .050 inch clearance
+between the ID (inside diameter of the Chemney) and the OD (outside
+diameter of the tubes plate. Allowing air to flow over the outside of
+the tubes plate OD surface. Or is it ok to use such "Silicon Rubber
+Chemneys" forcing all the cooling air thru the tubes inner plate cooling
+fins?????
+
+http://cgi.ebay.com/4CX5000-YC156-Si...cmd ZViewItem
+
+I have seen these Chemneys on production model amplifiers.
+
+Jay in the Mojave
******

The silicon rubber chimneys actually slide over the tube and do not
require clearance. You do have to make sure that the blower fan and
pressurized lower cavity can handle the extra back pressure.

The inner fins provide more surface area for cooling than the outer
surface of the tube alone. So it is fine to force as much air through
the fins as possible. There is a point of diminishing returns though.
Only so much air can flow through the tube fin area. After that, the
excess intake air will increase back pressure on the fan as it
collects in the bottom chasis.


james