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

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

Jay:

In theory, there is no reason the silicon chimney won't work, as most of the surface area is actually in the fins inside
the circumference, and not the outside diameter at all. The minimal additional area you get by having a looser fit
chimney is likely marginal.

However, at a hundred bucks, I can certainly see a dozen other ways to get a chimney in place for a LOT less money, and
nearly as neatly as well. Hell, even an aluminum sleeve closed with a couple of pop rivets, though far from
aesthetically optimum, will keep the tube nice and cool (given the same blower capacity) and for only a couple of bucks,
tops... There are times to spend outrageous sums of money and this isn't necessarily one of them (at least for my
budget, anyway).

Of course, if I were actually building a 5 kW capable linear, I probably would have far more money than sense,
particularly if you expect it would be used on the CB Band, and even on the Ham Bands (at least in the US) it is so far
into illegal territory that you'd probably not give a damn in the first place. Therefore, the cost of the silicon
chimney is probably a mere pittance, compared to eventual costs of defending the eventual litigation from running such a
linear... [sigh]

Oh, wouldn't it be nice to have so much disposable cash as to not really care the consequences....

--Rick



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

Rick Frazier wrote:

Jay:

In theory, there is no reason the silicon chimney won't work, as most of the surface area is actually in the fins inside
the circumference, and not the outside diameter at all. The minimal additional area you get by having a looser fit
chimney is likely marginal.

However, at a hundred bucks, I can certainly see a dozen other ways to get a chimney in place for a LOT less money, and
nearly as neatly as well. Hell, even an aluminum sleeve closed with a couple of pop rivets, though far from
aesthetically optimum, will keep the tube nice and cool (given the same blower capacity) and for only a couple of bucks,
tops... There are times to spend outrageous sums of money and this isn't necessarily one of them (at least for my
budget, anyway).

Of course, if I were actually building a 5 kW capable linear, I probably would have far more money than sense,
particularly if you expect it would be used on the CB Band, and even on the Ham Bands (at least in the US) it is so far
into illegal territory that you'd probably not give a damn in the first place. Therefore, the cost of the silicon
chimney is probably a mere pittance, compared to eventual costs of defending the eventual litigation from running such a
linear... [sigh]

Oh, wouldn't it be nice to have so much disposable cash as to not really care the consequences....

--Rick



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



Hello Rick:

I was wondering if the .050 inch gap around the plate was there to allow
a second orifice to relive back pressure and add some more cooling.

Maybe this is a good question to a Eimac engineer.

I have heard amp builders say they want the gap there.

Jay in the Mojave

Rick Frazier wrote:
: In theory, there is no reason the silicon chimney won't work,
: as most of the surface area is actually in the fins inside
: the circumference, and not the outside diameter at all. The
: minimal additional area you get by having a looser fit
: chimney is likely marginal.

The Silicon Chimney is considered the current technology and
is just fine for the application.

: However, at a hundred bucks, I can certainly see a dozen
: other ways to get a chimney in place for a LOT less money,
: and nearly as neatly as well.

You could make it yourself and save quite a bit of money,
McMaster sells the material.

: Hell, even an aluminum sleeve closed with a couple of pop
: rivets, though far from aesthetically optimum, will keep
: the tube nice and cool (given the same blower capacity)
: and for only a couple of bucks, tops...

An aluminum chimney would be very bad news and a potential
source of serious trouble.

: There are times to spend outrageous sums of money and this
: isn't necessarily one of them (at least for my budget, anyway).

You burn one serious tube up over being cheap on the chimney
or blower, you'll only do it once. It's an expensive mistake
to be a cheapskate.

: Of course, if I were actually building a 5 kW capable linear, I
: probably would have far more money than sense,

The 4cx5000 will do an easy 9kw with the proper power supply.

: particularly if you expect it would be used on the CB Band,

regardless of where it's used.

: and even on the Ham Bands (at least in the US) it is so far
: into illegal territory that you'd probably not give a damn in
: the first place. Therefore, the cost of the silicon chimney
: is probably a mere pittance, compared to eventual costs of
: defending the eventual litigation from running such a linear...
: [sigh]

It not a problem to own and operate such a linear in the proper
application. It is a problem when you run it over the max legal
power allowed. For 100% RTTY Duty Cycle, the mentioned amplifier
would be a legal limit cruiser in amateur service.

: Oh, wouldn't it be nice to have so much disposable cash as
: to not really care the consequences....
: --Rick

Get off the decafe Rick, there are more than a few tetrode
with handles amplifiers found on the amateur bands every day...
running legal power...

cheers,
skipp

ps: Time for a cheap plug for the yahoo rf amplifiers group:

http://groups.yahoo.com/group/rfamplifiers/

Skipp jumps in wrote:

Rick Frazier wrote:

: In theory, there is no reason the silicon chimney won't work,
: as most of the surface area is actually in the fins inside
: the circumference, and not the outside diameter at all. The
: minimal additional area you get by having a looser fit
: chimney is likely marginal.

The Silicon Chimney is considered the current technology and
is just fine for the application.

: However, at a hundred bucks, I can certainly see a dozen
: other ways to get a chimney in place for a LOT less money,
: and nearly as neatly as well.

You could make it yourself and save quite a bit of money,
McMaster sells the material.

: Hell, even an aluminum sleeve closed with a couple of pop
: rivets, though far from aesthetically optimum, will keep
: the tube nice and cool (given the same blower capacity)
: and for only a couple of bucks, tops...

An aluminum chimney would be very bad news and a potential
source of serious trouble.

: There are times to spend outrageous sums of money and this
: isn't necessarily one of them (at least for my budget, anyway).

You burn one serious tube up over being cheap on the chimney
or blower, you'll only do it once. It's an expensive mistake
to be a cheapskate.

: Of course, if I were actually building a 5 kW capable linear, I
: probably would have far more money than sense,

The 4cx5000 will do an easy 9kw with the proper power supply.

: particularly if you expect it would be used on the CB Band,

regardless of where it's used.

: and even on the Ham Bands (at least in the US) it is so far
: into illegal territory that you'd probably not give a damn in
: the first place. Therefore, the cost of the silicon chimney
: is probably a mere pittance, compared to eventual costs of
: defending the eventual litigation from running such a linear...
: [sigh]

It not a problem to own and operate such a linear in the proper
application. It is a problem when you run it over the max legal
power allowed. For 100% RTTY Duty Cycle, the mentioned amplifier
would be a legal limit cruiser in amateur service.

: Oh, wouldn't it be nice to have so much disposable cash as
: to not really care the consequences....
: --Rick

Get off the decafe Rick, there are more than a few tetrode
with handles amplifiers found on the amateur bands every day...
running legal power...

cheers,
skipp

ps: Time for a cheap plug for the yahoo rf amplifiers group:

http://groups.yahoo.com/group/rfamplifiers/



Hello Skipp:

Hope all is well with you and your family.

All good info here.

The old guy down the road has beautiful duel 4CX1500 Linear Amplifier.
He has problems seeing, and believes the amp is used conservatively on
the ham bands. He believes the Bird wattmeter slug he is using is a 1500
watt slug, in reality its a 2500 watt slug that gets slammed to the peg.
I didn't say anything to him about it.

Besides whats a few dB amongst friends....... Hehehehehee

Shamful plug:
http://groups.yahoo.com/group/rfamplifiers/

Jay in the Great Mojave Desert, ....just down the road ah ways from the
fillin station.