over fire jets. WAS External reducing valves

Thu Feb 21 14:18:41 EST 2019

Bud, Thanks very much for forwarding Gordon’s research. Now we know for sure.

And it confirms what Jim Stapleton of Northernmost VA shared with the list earlier.

“I believe the canisters on the outside are mufflers to reduce the extremely loud sound of the air being pulled into the firebox.”

Nice work all.   John Garner

From: NW Mailing List [mailto:nw-mailing-list at nwhs.org] 
Sent: Thursday, February 21, 2019 8:53 AM
To: NW Mailing List <nw-mailing-list at nwhs.org>
Subject: Re: over fire jets. WAS External reducing valves

John,

I think Gordon Hamilton found the answer about the use of rock wool in the canister.  I am below copying his email to me:

“Bud,

I have found the following references to the need for silencers on the over-fire jets:

UNCLE SAM'S LOCOMOTIVES - The USRA and the Nation's Railroads, Eugene L. Huddleston, 2002, p. 113 (available online on Google Books)

"It was true that on the PRR and most other roads having the devices [over-fire air jets], getting the fireman to use them was the biggest obstacle to their success....One good reason for not turning them on was that they were very noisy.  This problem was eventually partially solved by applying mufflers at the inlet into the firebox where the fine but powerful steam jet 'sucked' in the air."

1947 LOCOMOTIVE CYCLOPEDIA, pp. 426, 427

Several over-fire jet designs are shown with "T-Z Smoke Nozzle Silencer" heading.  The "acoustic material" is identified as "fiberglass or rockwool," and encircles a "hardware cloth" core.

So, I think we can safely say that the "cans" are silencers,

Gordon”

My thanks to Gordon for researching this question.

Bud Jeffries

From: NW Mailing List 

Sent: Wednesday, February 13, 2019 10:02 PM

To: nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org>  

Subject: RE: over fire jets. WAS External reducing valves

Jim, That sounds reasonable to me. The rock-wool shown in the drawing could act as a sound damper.  Thanks for your input.  John Garner,  Newport VA

From: NW Mailing List [mailto:nw-mailing-list at nwhs.org] 
Sent: Wednesday, February 13, 2019 2:13 PM
To: NW Mailing List <nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org> >
Subject: Re: over fire jets. WAS External reducing valves

I believe the canisters on the outside are mufflers to reduce the extremely loud sound of the air being pulled into the firebox. 

Jim Stapleton 

Northernmost VA

On Feb 13, 2019, at 11:41, NW Mailing List <nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org> > wrote:

John, don’t know, but I doubt it.  What if a little dust was injected into the firebox, it was just sucked up the stack along with cinders and all.  Bud

From: NW Mailing List 

Sent: Tuesday, February 12, 2019 8:25 PM

To: nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org>  

Subject: RE: External reducing valves

Thanks Bud. Most helpful. Do you happen to know if the ‘cans’ hanging below each nozzle on the side of the firebox (S1a for example) were air intake filters?   John Garner

From: NW Mailing List [mailto:nw-mailing-list at nwhs.org] 
Sent: Tuesday, February 12, 2019 6:51 PM
To: NW Mailing List <nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org> >
Subject: Re: External reducing valves

John,

The jets were controlled from the cab.  The position of the jets were along the firebox side and were staggered so that a jet on one side was not exactly opposite the other side.  I don’t know about being adjustable, but they did use a steam nozzle that drew air in through an orifice using the venturi (spelling?) effect.  N&W only used overfire air jets on yard engines and if the exhaust and draft was heavy the jets would be off, and if the engine was halted or working with the light exhaust and draft, the engineer could turn the jets to get more complete combustion.

Hope this helps,

Bud Jeffries

From: NW Mailing List 

Sent: Tuesday, February 12, 2019 12:19 PM

To: nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org>  

Subject: RE: External reducing valves

Bud,  Can you briefly explain the operation of these jets? Were they automatic or controlled by crew? Was air flow adjustable or just on/off? Was steam used as the power source to achieve the necessary air flow?     Thanks,   John Garner

From: NW Mailing List [mailto:nw-mailing-list at nwhs.org] 
Sent: Tuesday, February 12, 2019 10:29 AM
To: NW Mailing List <nw-mailing-list at nwhs.org <mailto:nw-mailing-list at nwhs.org> >
Subject: Re: External reducing valves

N&W tested the use of overfire air jets for road service in 1944 with 2151.  With heavy exhaust creating very good draft in road service, the railway found that the jets gave no appreciable benefit.  Overfire air jets did find favor for use on locomotives in yard service where draft was much more sporadic and often not heavy.

Bud Jeffries

From: NW Mailing List 

Sent: Monday, February 11, 2019 4:54 PM

To: NW Mailing List 

Subject: Re: External reducing valves

Speed didn’t have anything to do with the use of overfire air jets.  Rio Grande had some big Baldwin 4-6-6-4s with overfire jets.

Their function was to kill smoke by introducing air over the fire to more thoroughly burn the fuel.  The first tests of them on the N&W were on a Z-1a (1352) and a W-2 0-8-0 (if I recall correctly the 680).  The tests were done at Bluefield Yard; the catenary was in full view.  There are at least two N&W photographs of the test.  I don’t know the date, but it was before the electrification was done away with.

Ed King

From: NW Mailing List via NW-Mailing-List 

Sent: Monday, February 11, 2019 3:02 PM

To: NW Mailing List 

Cc: NW Mailing List 

Subject: Re: External reducing valves

While on N&W steam : Most all the 0-8-0 switchers had over the fire air jets-- I'm guessing to aid in keeping a hot fire because of their slow mundane work vs the faster road locos had speed to help in firing. Is that the only reason for the jets ?  Ron Hash

  _____  

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