Question for MR. KING: N&W Ashcroft Duplex Gauge

NW Mailing List nw-mailing-list at
Sat Mar 5 17:47:46 EST 2016

Abram – I would defer to Louis Newton for a good answer to this.  

I believe that the Mallets would be the only engines using this gauge, because the others did not have receiver pipes (the conduit from the high-pressure exhaust to the low-pressure intake) but they all had steam chest pressure gauges.  This gauge pointing to a value more than 300 pounds sort of stretches the credulity, since nothing would be higher than full boiler pressure of 300 pounds.

But that’s just off the top of my head; Louis can probably give better information.


From: NW Mailing List 
Sent: Saturday, March 05, 2016 5:07 PM
To: NW Mailing List 
Subject: Question for MR. KING: N&W Ashcroft Duplex Gauge

Mr. King:

The N&W's bigger engines were fitted with an 8.25" dia Ashcroft duplex gauge which was mounted about eye-level to the Engineman, to the right of the air gauges, and just to the left of his line of forward vision. These gauges had a red hand and a black hand, which somehow gave information about the status of the steam distribution system.

I have attached three photographs. One is a front view of the gauge. The other two photographs show the two 5/8" dia buttons which were sweated onto the bottom of the case at the point where the piping threads in. These buttons were lettered "Steam Chest" and "Receiver Pipe" with lettering dies.

I can understand how Steam Chest pressure would be meaningful to the Engineman, but I do not understand how Receiver Pipe pressure would be useful information to him.

Do you remember what the N&W called these duplex gauges as applied to the bigger engines, and can you give a description of their operation?

You can see, in the photographs, where I have the red and black hands staked. Can you suggest any more realistic hand settings for this gauge, which is now only on "static display" ?


-- abram burnett


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