Re: June 1968 - no spark arrestors...the straight scoop.
| April 19, 2012 12:26PM |
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As built, the 480's and 490's had Master Mechanic Front ends in the smoke box. This arrangement utilized a rather high exhaust nozzle. Plates in the smokebox directed the gasses (smoke, cinders, etc.) under a table plate that sat across the smokebox at the height of the nozzle (about mid-smokebox height), forward and through a screen that was angled downward across the front of the smokebox. The gasses then moved to the rear of the smokebox through the petticoat pipe and up the stack. The screen caught the big cinders and also broke them into smaller sizes.
All the ng engines had this set up.
The screen would get plugged eventually and a large pile of cinders would accumulate in the smokebox right behind the door. The smokebox had to opened up periodicly to clean out the cinders.
As good a design as it was, it did allow come good sized cinders to come up the stack. The Grande fought this with a cinder bonnet on top of the stack.
In 1940-42 the 480's and 490's were fitted with "cyclone" front ends. This design uses a low exhaust nozzle, with a low table plate that is inline with the bottom row of flues. A round "cyclone" device which looks like a squirrel cage blower sits on the table plate around the nozzle. The petticoat pipe extends from the base of the stack to the top of the cyclone. Plates above the cyclone direct the the exhaust down and through the cyclone. The cyclone has plates (vanes) arranged around it so as to create a swirling effect to the exhaust. The idea is the cinders get swirled around in the smokebox, get broken up by the vanes into small particles, and shot out the stack.
The cyclone front end is pretty much self cleaning and the only time you need to open up the smokebox is during annual inspections. It is also more efficent in that the gasses have less contortions to go through to go up the stack to make the draft, so a larger exhaust nozzle can be used. In the master mechanic front end the gasses come out of the flues, down under the table plate, up through the screen, then back down under the edge of the petticote pipe where the exhaust nozzle launches it up the stack. All this changing of direction requires more velocity up the stack the keep the gasses moving fast enough to create a draft. To do this, a smaller exhaust nozzle is used. In the cyclone front end, the gasses come out of the tubes (the gases from the top rows of tubes are deflected downward by a baffle plate on top of the cyclone), and into the swirlling mass of turbulance created by the the vanes of the cyclone and the exhaust steam going up the stack. The gases swirl around and go straight up the stack with less resistance. With less resistance, you don't need as much velocity up the stack and a larger exhaust nozzle can be used. The larger the nozzle the less back pressure you have in cylinders, and the freer the engine runs.
The end result was the cyclone front ends did a very efficient job of breaking up the big cinders and snuffing up the hot ones to the point that the D&RGW found the cinder bonnets redundant. The result is if you find a pic of a 480-90 with a cinder bonnet it dates from before 1940-42.
Anytime you put a screen in the exhaust path, you slow the exhaust down and decrease efficiency. The Ridgway spart arrestors used a double screen, which did a real number on the steaming qualities of the engines. If you cut down the ability to steam, you have to fire the engine harder to make up for it. This results in more coal being used, which creates more cinders, which makes for more fire danger. It's a losing proposition. In the early 1990's I had a couple of D&S fireman work occasionally for me in Chama. They told me that our engines steamed much better that the D&S engines with the Ridgway Spark Arrestors.
To us fans of the joyious music a steam locomotive makes at work, the master mechanic front end makes the best sound. Listen to a Mudhen or a 470 at work and you hear a loud sharp percussive exhaust, where as a 480-90 has a softer less forced sound. This is because of the smaller nozzles in the mudhens and 470's. The Mudhens and 470's throw much bigger and more plentiful cinders too - even with a cinder bonnet.
My guess is the cyclone front ends were only applied to the 480-90's because there was not enough room in the smoke box of the smaller engines
to accomodate the cyclone device.
When the C&TS started in 1970, the did not use cinder bonnets. Even back then I noticed that the 480's did not throw the quanity of cinders the 470's did in Durango. Cinder bonnets did not make an appearance until 1974 or so.
In 1988 we did an experiment and ran most of the summer "bonnetless". The results were no more fires than we had before, and the engines steamed noticably better. Making smoke for a photorun took real work.
When the leaves fell from the aspens in the fall we were forced to put them back on because the fires we did start with out the bonnets in place were much further from the track. With bonnet in place the hot cinders would bounce around in the screen, fall out the side on to the running board and bounce off onto the ground next to the track where the fire patrol could deal with them.
In my opinion, cinder bonnets on cyclone front end engines are a good political move, but not much more.
A "bonnetless" 488 and 489 make a runby at Coxo for the Rocky Mountain RR Club's 50th Anniversary Special in June 1988. I was firing 489 and it took a LOT of coal to get 489 to smoke like this. Note that 488's fireman wasn't quite as ambitous.
All the ng engines had this set up.
The screen would get plugged eventually and a large pile of cinders would accumulate in the smokebox right behind the door. The smokebox had to opened up periodicly to clean out the cinders.
As good a design as it was, it did allow come good sized cinders to come up the stack. The Grande fought this with a cinder bonnet on top of the stack.
In 1940-42 the 480's and 490's were fitted with "cyclone" front ends. This design uses a low exhaust nozzle, with a low table plate that is inline with the bottom row of flues. A round "cyclone" device which looks like a squirrel cage blower sits on the table plate around the nozzle. The petticoat pipe extends from the base of the stack to the top of the cyclone. Plates above the cyclone direct the the exhaust down and through the cyclone. The cyclone has plates (vanes) arranged around it so as to create a swirling effect to the exhaust. The idea is the cinders get swirled around in the smokebox, get broken up by the vanes into small particles, and shot out the stack.
The cyclone front end is pretty much self cleaning and the only time you need to open up the smokebox is during annual inspections. It is also more efficent in that the gasses have less contortions to go through to go up the stack to make the draft, so a larger exhaust nozzle can be used. In the master mechanic front end the gasses come out of the flues, down under the table plate, up through the screen, then back down under the edge of the petticote pipe where the exhaust nozzle launches it up the stack. All this changing of direction requires more velocity up the stack the keep the gasses moving fast enough to create a draft. To do this, a smaller exhaust nozzle is used. In the cyclone front end, the gasses come out of the tubes (the gases from the top rows of tubes are deflected downward by a baffle plate on top of the cyclone), and into the swirlling mass of turbulance created by the the vanes of the cyclone and the exhaust steam going up the stack. The gases swirl around and go straight up the stack with less resistance. With less resistance, you don't need as much velocity up the stack and a larger exhaust nozzle can be used. The larger the nozzle the less back pressure you have in cylinders, and the freer the engine runs.
The end result was the cyclone front ends did a very efficient job of breaking up the big cinders and snuffing up the hot ones to the point that the D&RGW found the cinder bonnets redundant. The result is if you find a pic of a 480-90 with a cinder bonnet it dates from before 1940-42.
Anytime you put a screen in the exhaust path, you slow the exhaust down and decrease efficiency. The Ridgway spart arrestors used a double screen, which did a real number on the steaming qualities of the engines. If you cut down the ability to steam, you have to fire the engine harder to make up for it. This results in more coal being used, which creates more cinders, which makes for more fire danger. It's a losing proposition. In the early 1990's I had a couple of D&S fireman work occasionally for me in Chama. They told me that our engines steamed much better that the D&S engines with the Ridgway Spark Arrestors.
To us fans of the joyious music a steam locomotive makes at work, the master mechanic front end makes the best sound. Listen to a Mudhen or a 470 at work and you hear a loud sharp percussive exhaust, where as a 480-90 has a softer less forced sound. This is because of the smaller nozzles in the mudhens and 470's. The Mudhens and 470's throw much bigger and more plentiful cinders too - even with a cinder bonnet.
My guess is the cyclone front ends were only applied to the 480-90's because there was not enough room in the smoke box of the smaller engines
to accomodate the cyclone device.
When the C&TS started in 1970, the did not use cinder bonnets. Even back then I noticed that the 480's did not throw the quanity of cinders the 470's did in Durango. Cinder bonnets did not make an appearance until 1974 or so.
In 1988 we did an experiment and ran most of the summer "bonnetless". The results were no more fires than we had before, and the engines steamed noticably better. Making smoke for a photorun took real work.
When the leaves fell from the aspens in the fall we were forced to put them back on because the fires we did start with out the bonnets in place were much further from the track. With bonnet in place the hot cinders would bounce around in the screen, fall out the side on to the running board and bounce off onto the ground next to the track where the fire patrol could deal with them.
In my opinion, cinder bonnets on cyclone front end engines are a good political move, but not much more.
A "bonnetless" 488 and 489 make a runby at Coxo for the Rocky Mountain RR Club's 50th Anniversary Special in June 1988. I was firing 489 and it took a LOT of coal to get 489 to smoke like this. Note that 488's fireman wasn't quite as ambitous.
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488 stops for water at Los Pinos tank on closing day Oct. 1979. Photo courtesy Don Richter
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