Seek Drawing/Dimensions of Steam Compressor

[mmagliaro]

Regarding the ever-common Westinghouse cross-compound compressor ....



Just how big is the real thing?  How wide, and how tall?
Does anybody have a measured drawing?  Or has anyone ever actually measured
the darn thing when visiting a steam locomotive?
I ask because I ordered some N Scale brass detail parts from Precision Scale Co (yes, they make some),
and the compressor looks big to me.  It is noticeably larger than the casting on the side of a Kato Mikado.
It doesn't look so big that it could be HO, however.

I hesitate to use the casting if it really is oversized.

Thanks.

[DKS]

This site appears to have some drawings: http://www.nelsonslocomotive.com/Heisler/Brakes/DesCompressor/DesCompressorI/DesCompressorI.htm

[Chris333]

There is the steam cyclopedia. I'm sure they come in different sizes, like 6.5 or 8".

[mmagliaro]

I checked the steam cyclopedia, but it doesn't have any actual dimensions of the thing that I can see.
There is discussion of how it works.

DKS, thank you.  That site is where I swiped the photo I posted (it is in the ICS steam loco training book series,
and I own the original books with that photo in them).   You are right.   On that page there is one drawing with dimensions
and they are fuzzy, but I think the 8-1/2" compressor is about 29" wide based on those numbers.  Thanks.

Will measure the casting now...

[Kisatchie]

Will measure the casting now...

Hmm... hurry! the suspense
is unbearable...

[Chris333]

I checked the steam cyclopedia, but it doesn't have any actual dimensions of the thing that I can see.

I was thinking about each drawing, they are all HO scale I believe.

[mmagliaro]

The Kato one measure .182" = 29.12"

The Precision Scale brass one is .215"  = 34.4"

MUST EAT WORDS!  I found a clearer version of the drawing that DKS referred to.   A number I thought was a "10"
is actually a "13" (the drawing on the website was fuzzy!)
So the width is 10-1/2 + 13-3/4 + 7-1/4  = 31.5

This Kato is about 2.4" too small and Precision is 3" too big.    Both are mighty close.

So.... Kato appears to have it right, and Precision appears to have blown it.  Precision specifically
lists this part as an "8-1/2" version, too, so there's no possibility that it was supposed to be a different version.

5 scale inches is normally very slight in N.  But this is a little detail part, so the oversized one really looks
big and bulky.   Very disappointing.

[Chris333]

Don't forget RLW for air pump castings.

[robert3985]

Max,

What size pumps were on the prototype you're modeling?  UP FEF-3 833 is on display at the Ogden Union Station about 15 miles from my place (not a big distance in Utah) and has dual Westinghouse 8-1/2" Cross Compound Pumps on its pilot.  I would be more than happy to take a tape measure and camera down to do some measurements for you tomorrow if your engine has the same size pumps.

The last engines built by/for the U.P. had many parts in common, so the Big Boys, late Challengers and FEF-3's had the same size pumps, all located on their pilots.

I have been thinking about ordering the Precision Scale Westinghouse Cross Compound 8-1/2" Pumps for superdetailing my Athearn Big Boys, Challengers and de-skirted Kato GS's, so I'd be interested too to see if the Precision Scale part is the right size.

I'll check here in the morning for your answer.

[mmagliaro]

Max,

What size pumps were on the prototype you're modeling?  UP FEF-3 833 is on display at the Ogden Union Station about 15 miles from my place (not a big distance in Utah) and has dual Westinghouse 8-1/2" Cross Compound Pumps on its pilot.  I would be more than happy to take a tape measure and camera down to do some measurements for you tomorrow if your engine has the same size pumps.

The last engines built by/for the U.P. had many parts in common, so the Big Boys, late Challengers and FEF-3's had the same size pumps, all located on their pilots.

I have been thinking about ordering the Precision Scale Westinghouse Cross Compound 8-1/2" Pumps for superdetailing my Athearn Big Boys, Challengers and de-skirted Kato GS's, so I'd be interested too to see if the Precision Scale part is the right size.

I'll check here in the morning for your answer.

Thanks, Robert.   Unfortunately, I have no idea what size the pump is on this engine.  Details on SP&S steam locos are very scarce.  I have a few photos, and a few scans of the original erecting drawings of the GN engine that this
engine really was.  But none of that tells me exactly what type of pump this is.   The engine was operating in the late 1940s and early 1950s, so that era might indicate the 8-1/2, since I glean from reading an on-line Westinghouse manual that this was a very common size.    That same manual also indicates a 10-1/2, but looking at a picture of it, I know my prototype isn't that.

Sorry I don't have any more info.   If you get a measurement, that might be helpful, but after looking at prototype
photos, and some photos of the HO brass import version, I am convinced that the Precision scale casting is
way too big.   It is somewhat oversized in width, and very oversized in height and overall bulk.  So I am going to nip
the casting off a spare Kato Mikado shell and use that, as it is very elegant and delicately cast.  The plastic one
is better than the Precision brass one, to be honest.   Those Precision castings are very old, and it looks to me like
well-made modern plastic beats them.

[PGE_Modeller]

Max,

The drawing on page 786 of the 1925 Locomotive Cyclopedia gives an overall height of 53 1/2" and an overall depth of 17 7/8".  The cross-section drawing does not give an overall width but scaling from the dimensions that are provided gives a width of slightly over 33 5/8" not including the air strainer which attaches by a 90 degree bent pipe to the back of the compressor just above the low pressure air cylinder.

Cheers,

[mmagliaro]

Wow, Greg.   33-5/8"w and 53-1/2 high.   That's very good to know.
And that means that the Precision Scale part is darn close.

Well, now, scaling off the actual prototype photo I posted at the beginning of my SP&S project
thread, the compressor is 0.59 as tall as the driver that is directly beneath it.  So although the photo is at an angle,
I think I can scale pretty well from that.

0.59 x 73" = 43"

Since yours is 53-1/2, I guess the only logical thing to conclude is that the compressor on this engine is
not an 8-1/2 Westinghouse cross-compound.  Whatever it is, 10" is a lot of difference, 25%, and even scaling
from a photo, it would be closer than that.

That's why the Precision one looks so oversized for my model.   So... I will use the Kato one because it is more in proportion
with the prototype photo, but lesson learned.   

THANK YOU to everyone who provided sources and measurements for this.   I wish there was a "library" of some sort in railwire
to save things like this.