MRSR 91 Superheater
 Nelson Riedel, Nelson@NelsonsLocomotive.com
10/05/2004, last updated 10/13/2004

The two major features of the Heisler West Coast Special are the piston valves and the superheater.   The superheater is described in this page..

Steam Lines: The steam lines on the earlier Heisler run from the back of the steam dome to the upper edge of the steam chests.  With the superheater, the steam lines run from the upper rear of the smoke box to the front of the cylinder castings. This photo shows the right side elbow at the smoke box feeding into an insulated pipe that leads to the right cylinder.  The small tubing is an oil feed that connects to a check valve that is attached to the elbow. The left side  has an identical configuration. The plate directly below the smoke stack is the Superheater tag.  
Superheater Tag ........ 
Snifter Valve: The ~ 1" pipe coming out the top of the large steam feed elbow was a puzzle at first but then I guessed it went to a shared snifter valve.  The curved pipe that follows the smoke box surface is the air pump exhaust that runs along the top of the smoke box and then vertically just behind  the smokestack.   The ~1" pipe out the top of the elbow connects to an identical pipe on the other side.  There is a tee at the middle of this connection that in turn connects to the check valve on top of the smoke box  That's the check valve under the front edge of the disk in the photo.  The other end of the  check valve is connected via the tee to the vertical part of the air pump exhaust.  The check valve provides the snifter valve function serving both sides.   That disk is a puzzle ------  maybe the crew uses it to warm their pizza. 
Petticoat:  I took some photos of the inside of the smoke box to show the superheater tubes.  The petticoat is right in the middle.   Note that there is a gap between the top of the petticoat tube and the bottom of the smokestack.  

The bent tubes to the rear of the petticoat are the superheater tubes.
Exhaust Nozzle:  The exhaust nozzle sets on the smoke box saddle via a hole cut in the bottom of the smoke box.   That is probably the blower pipe on the right side.
Superheater Tubes:  The superheater tubes are U-shaped and run from a manifold at the top of the smoke box down and then take a 90 degree turn and go into large boiler tubes.  I didn't think to look into the firebox end of those tubes to see if I could tell how far back the superheater tubes run before they double back.  The two ends of each superheater tube are held to the manifold by brackets,  bolts and Tee nuts in a slot in the manifold. 
The next set of photos are of a smaller 70 ton Heisler.   The petticoat and all tubes have been removed exposing the manifold and tube sheet.  There are a total of 10 large boiler tubes for 10 superheater tubes.   The output pipes to the cylinders come off each end of the manifold.  The throttle valve is in the steam dome.  A pipe from the throttle valve feeds the back side of the manifold.   
I took this photo of the underside of the manifold in hopes of determining the routing within the manifold.   No luck on that point.  It's my guess that the 10 superheater tubes are in parallel.  
This photo was taken through one of the holes in the front tube sheet.   The pipe is the feed pipe from the throttle valve to the superheater manifold.  The steam dome cover was off letting sunlight illuminate the elbow and flanges at the back end of the pipe.  The upper flange is part of the throttle valve.  The two rods on the upper right are stays for the front tube sheet.   There is a similar set on the other side.

 

The current plan is to model a much simpler (and less effective) superheater.    One possibility is to merely make a couple loops of the steam feed lines in the rear part of the smoke box. 

 

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