"Tin cans" on the N&W "A" (part II)

[Paul of Covington]

Sorry, I accidently sent picture of "A" without text.

  My question is about the "tin cans" on the front of the N&W "A" above and in front of the front valves.   They seem to be tied in to the steam passage to the valves.    I don't remember seeing anything like them on any other steam engines.  Does anyone know their purpose?

[feltonhill]

They are part of the steam distribution system to the front engine.

 Steam goes through a ball joint just after exiting the side of the boiler.  It then goes through a sliding joint into the steam piping for the front engine.  The "tin cans" are the ends of the sliding joint assembly.  The front engine has a crossover pipe that connects both left and right sides.  It can be seen through the left (right in the photo) front ladder in the 1218 photo The steam pipes to each cylinder exit this crossover pipe and go slightly to the rear and down into the steam chests and valves of each front cylinder.

All this is done to get steam to the front engine while compensating for both the side to side movement in curves and the vertical movement of the track. I believe it is a unique arrangement to N&W.

[Paul of Covington]

  Thank you, feltonhill, for the information.    From all I've read, the N&W people were geniuses at designing steam locomotives.

   I have long been curious about how steam was delivered to and from the forward cylinders on articulated locomotives.   Do you know of a good source of information on details of steam locomotive designs.

[CSSHEGEWISCH]

"Articulated Locomotives", by Lionel Wiener, is a good source of information regarding articulated locomotives of all sorts, including a few types that you may not be aware of.

[Paul_D_North_Jr]

This is another example of where the museum could do a much better job of "interpretation"/ display/ presentation with signs or explanatory diagrams - even just labels.  Even fairly sophisticated railfans might not know such a thing - and certainly not the layperson visitor.  Without that information, it's hard for any visitors to understand and appreciate the thought and technical skill and features of the locomotive - yet isn't that what the museum is there for ?

- Paul North.

[selector]

It would be a fine line to tread between the already overwhelming sensory and cognitive processes that this monster would elicit in even the most casual of observers and technical details that probably only technically-minded people (okay, heavily favouring males) would find interesting.

 

When I go to museums of any kind, I linger and dally, trying to get the most out of the time and experience.  My family members are at my back, shoving.  Such is life.

 

-Crandell

[Paul_D_North_Jr]

OK, fair enough - but I don't see any labels, plaques, or diagrams in the photo above . . .

To the contrary, such aids would likely guide adn enable the casual viewer in utilizing those sensory and cognitive processes that you mention in order to cope with and understand this monster . . . as you - of all the members here - might fully appreciate, to the extent that each observer chooses to take advantage of them.  A lot of this locomotive's nature and characteristics is not at all self-evident ,and hence needs some elucidation to bring it out, as conytrasted with - say, a Tyrannosaurus Rex skeleton on display in a museum.

Yeah, my family usually does the same to me, too.  It's been said that I read every word . . .  

- Paul North. 

[benburch]

Note that they are "cans" rather than just having the minimum amount of piping to the steam chest because when the cylinder demands steam, there would be a pressure drop through the pipes.  The cans provide a volume of steam to expand into the cylinder and minimize the pressure drop.

[selector]

So they are a buffer of sorts?

[BigJim]

The cans provide a volume of steam to expand into the cylinder and minimize the pressure drop.

Not so. If you were to look at how the steam piping is actually routed you will find this statement to be untrue. The cans are mere covers for the ball joint housing underneath, not any type of reservoir.

[samfp1943]

BigJim

The cans provide a volume of steam to expand into the cylinder and minimize the pressure drop.

Not so. If you were to look at how the steam piping is actually routed you will find this statement to be untrue. The cans are mere covers for the ball joint housing underneath, not any type of reservoir.

Thanks, Big Jim!

 "... Not so. If you were to look at how the steam piping is actually routed you will find this statement to be untrue. The cans are mere covers for the ball joint housing underneath, not any type of reservoir..."

        Linked here are a couple of photos of 1218 in the shop in 1999:

http://www.retroweb.com/1218.html  [ The photos are credited to Howard Gregory]

    The right hand photo of # 1218, shows the right front cylinder assembly with much of the surrounding hardware removed.   Backing up Big Jim's explanation of the "Cans".

 This link is to an older photo of 1218 prior to her being dolled up and moved into the Steam excursion program:     http://www.retroweb.com/trains/nw129_m.jpg     [photo courtesy Fred Reburn]

   The "Cans' beig discussed are much more in evidence and appear to look much more 'can-like' and unstreamlined.

[BigJim]

For inquiring minds, follow the link below to find out what is actually hidden under the "Cans";

http://www.nwhs.org/archivesdb/detail.php?ID=23266

[benburch]

Thanks for the correction.  Somebody told me that long ago, and I have carried that wrong information around for approximately 30 years...

[samfp1943]

benburch

Thanks for the correction.  Somebody told me that long ago, and I have carried that wrong information around for approximately 30 years...

Ben:

Sort of the teaching an old dog new tricks sort of theing? 

There are a number of around (This Forum)here that can completely empathise with that! 

[Paul of Covington]

  Thanks, all, for the info and links.    I'll have to explore the NWHS site some more; I think I could spend hours there.

  Regarding the buffer effect, as I understand it, the crossover pipe functions as a very effective buffer, being fed from both sides and feeding both sides, as well as storing a volume of steam to smooth out the pulses.    I can picture a molecule of steam going back and forth in this pipe, never quite making it to either end.

[rrnut282]

samfp1943

        Linked here are a couple of photos of 1218 in the shop in 1999:

http://www.retroweb.com/1218.html  [ The photos are credited to Howard Gregory]

    The right hand photo of # 1218, shows the right front cylinder assembly with much of the surrounding hardware removed.   Backing up Big Jim's explanation of the "Cans".

 This link is to an older photo of 1218 prior to her being dolled up and moved into the Steam excursion program:     http://www.retroweb.com/trains/nw129_m.jpg     [photo courtesy Fred Reburn]

   The "Cans' beig discussed are much more in evidence and appear to look much more 'can-like' and unstreamlined.

In the 2nd photo you linked above there are massive brackets behind the cylinders that partially surround the running gear.  I don't see them in later photos.  What was thier purpose?

[BigJim]

rrnut282

samfp1943:

        Linked here are a couple of photos of 1218 in the shop in 1999:

http://www.retroweb.com/1218.html  [ The photos are credited to Howard Gregory]

    The right hand photo of # 1218, shows the right front cylinder assembly with much of the surrounding hardware removed.   Backing up Big Jim's explanation of the "Cans".

 This link is to an older photo of 1218 prior to her being dolled up and moved into the Steam excursion program:     http://www.retroweb.com/trains/nw129_m.jpg     [photo courtesy Fred Reburn]

   The "Cans' beig discussed are much more in evidence and appear to look much more 'can-like' and unstreamlined.

 

In the 2nd photo you linked above there are massive brackets behind the cylinders that partially surround the running gear.  I don't see them in later photos.  What was thier purpose?

I'm not exactly sure what part you are asking about, but here goes.
The bracket with the semi-circle shape to the inside is the:
1) support for the crosshead guides (attached at the top & bottom of the semi-circle) and
2) support for the valve gear frame (on backside at the top).

If the engine in the photo you are looking at is numbered 1209 or below, then it is equiped with the "Multiple Bearing" crosshead. The crosshead guide attaches to a bracket only at the top of the guide. Therefore you will not see that big semi-circular bracket on those engines.