[AT] OT - Old Chimney Question

charlie hill chill8 at cox.net
Fri Oct 22 16:52:26 PDT 2004


Larry,

I have a bag house dust collector that is powered by a 6 hp electric motor 
turning a blower about 30" dia. at 1800 rpm.   A few years back I needed to 
suck the dust out of a confined space so I hooked 100' length of 6" diameter 
corrugated plastic pipe to the inlet and routed the pipe into the confined 
area.  It worked ok but that thing put off a howl that must have had every 
dog with in 5 miles crying.
It sounded like an approaching space ship from an Orson Wells from an 
episode of the twilight zone.  WOoWOoWOoWOoWOoWOo

Charlie


----- Original Message ----- 
From: "Larry D. Goss" <rlgoss at evansville.net>
To: "'Antique tractor email discussion group'" 
<at at lists.antique-tractor.com>
Sent: Friday, October 22, 2004 11:25 AM
Subject: RE: [AT] OT - Old Chimney Question


> Even with the blowers, precipitators, bag houses, and everything else
> that modern stacks have to have on them, they whistle.  And air currents
> are really hard to predict.  If it wasn't so, meteorologists would have
> better reputations, and HVAC systems wouldn't have to be balanced after
> installation.  I have yet to see an industrial stack that was "detuned"
> to the point that the plume didn't wave when the wind is blowing.
>
> BTW- Just to remind you where I'm coming from on some of this ramble, I
> tune and repair pianos and organs as a sideline interest.  A number of
> years ago, I put together a dog and pony show called "Strings, Bells,
> Horns, and Whistles".  In it, I demonstrated in junior high schools the
> fundamental methods for generating musical tones as a background for the
> band and orchestra instruments that we have.  One of the demos I gave
> the kids was to put the end of a corrugated toilet water supply pipe in
> my mouth and blow bugle calls on it.  You don't even have to pucker and
> buzz your lips to make it work.
>
> Larry
>
>
> -----Original Message-----
> From: at-bounces at lists.antique-tractor.com
> [mailto:at-bounces at lists.antique-tractor.com] On Behalf Of charlie hill
> Sent: Friday, October 22, 2004 7:21 AM
> To: Antique tractor email discussion group
> Subject: Re: [AT] OT - Old Chimney Question
>
> Larry,
>
> Boilers and industrial stacks sometimes have ID blowers.  I wonder if
> that
> would work to correct a problem on a chimney.   I guess it wouldn't be a
>
> good solution.  I'm just wondering if it would work.
>
> Charlie
> ----- Original Message ----- 
> From: "Larry D. Goss" <rlgoss at evansville.net>
> To: "'Antique tractor email discussion group'"
> <at at lists.antique-tractor.com>
> Sent: Thursday, October 21, 2004 9:21 PM
> Subject: RE: [AT] OT - Old Chimney Question
>
>
>> Super heat and a "rip roaring fire" can make a marginal chimney work,
>> but a well designed chimney doesn't need that.  Ever.
>>
>> Chimneys do indeed have a back draft.  Even the pressurized ones in
>> power plants act like super-sized pop bottles and "whistle".  The
>> frequency is so low that you can't hear it, but a monometer placed
>> almost anywhere inside a flue will show cyclical variations in air
>> pressure as the wind blows by. If you've ever watched the plume off a
>> stack from any distance, you'll notice that it appears to wave up and
>> down as it leaves the chimney.  If you pay attention to any one small
>> section of the plume, you'll notice that it proceeds in a straight
> line
>> as soon as it leaves the chimney top.  The waviness of the plume is an
>> optical illusion based on the fact that the pressure inside the stack
> is
>> constantly fluctuating and the smoke leaves at a different vertical
>> speed depending on the internal pressure.  Under some conditions the
>> column of air heading out the stack will not just change its upward
>> speed, but it will actually reverse as the chimney "whistles."  That's
>> when you get smoke inside the house.  A smoke shelf (smoke chamber)
>> helps because it effectively makes the chimney into a "stopped flute"
>> much the same as the organ pipe of the same name.  But making sure the
>> top of the chimney is clear of the pressure fluctuations caused by the
>> wind passing over the surface of your roof is also helpful for exactly
>> the same reason as the fact that the pitot tube on an airplane wing is
>> never mounted close to the wing surface.
>>
>> This is more about chimneys than anyone probably wants to read, but
> the
>> bottom line is that chimney design is not guesswork.  You can predict
>> ahead of time what certain changes in a flue will make.  And, yes you
>> can successfully have more than one heat source feeding into the same
>> flue and have all of them draw correctly regardless of which ones
> happen
>> to be working.  There are guidelines to be followed for that.  I don't
>> know exactly where to turn for the complete instructions I remember
>> seeing when I was a kid, but Better Homes and Gardens is one of the
>> sources we used at that time.  Their "Back To Basics" book came out a
>> generation or so later and it gives some of the fundamentals, but
> there
>> is a more comprehensive source somewhere.
>>
>> Larry
>>
>>
>> -----Original Message-----
>> From: at-bounces at lists.antique-tractor.com
>> [mailto:at-bounces at lists.antique-tractor.com] On Behalf Of
>> DAVIESW739 at aol.com
>> Sent: Thursday, October 21, 2004 6:13 PM
>> To: at at lists.antique-tractor.com
>> Subject: Re: [AT] OT - Old Chimney Question
>>
>> Heat is what causes the chimney to draw if you don't get it hot enough
>> it
>> won't work.  A small stove in a large chimney just won't do the job.
>> Also
>> always start out with a good rip roaring fire to heat the chimney then
>> cut it  back
>> this will get things started and the smoke will go up not down.  A
>> longer
>> chimney won't work if you don't have enough heat to get it  working.
>>
>> When I put my stove in my house in southern Oregon I had a 10 in  1
>> pitch and
>> the expert said that I needed to get the chimney up high enough so
> that
>> the
>> wind wouldn't curl around and come back down the chimney, I wonder
>> where he
>> learned that bunch of BS from. We had 80 mph winds up on that hill I
>> don't
>> think they could curl around and blow back on themselves. Now if the
>> wall  was
>> straight up that would be another matter.
>>
>> The main thing is to match the size of the chimney to the amount or
> size
>> of
>> the stove to get proper heat rise from it. A good stove shop should
> have
>> the
>> details for what you need.
>>
>> Walt Davies
>> Cooper Hollow Farm
>> Monmouth,  OR 97361
>> 503 623-0460
>>
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