Heisler Boiler Construction III
Nelson Riedel, Nelson@NelsonsLocomotive.com
2/26/2010, last updated 02/27/2010

This page describes the remaining parts associated with the boiler and smoke box including:

  • Smoke Box Front

  • Blower & Nozzle

  • Petticoat

  • Cylinder to Saddle Exhaust Pipe

  • Safety Valves 

  • Boiler Water Input Globe Valve and Check Valve

  • Blow Down Valve 

Smoke Box Front:   The material for the smoke box front was a 8" X 1.5" cast iron disk obtained form McMaster-Carr.   It was turned to match the design drawing.  The hinges and dogs will be added later. (I'm too anxious to get steam up --- those details can be added next winter.)        

Blower & Nozzle: The blower and nozzle were also made per the design drawings except that the input line was changed from 1/4" OD tube to 3/16" OD tube.    The base plate is a scrap of the tube used for the smoke box.  The base is much wider than absolutely necessary so that the two attachment screws can be accessed easily.   The blower line feeds through the smoke box wall via the angled 3/16" tube to female 1/8" NPT fitting  on the inside to a straight 3/16" tube to 1/8" male NPT fitting on the outside.       This photo also shows the screws that attach the smoke box to the saddle.  Most of those holes were drilled from the bottom up using the saddle as a pattern.   Those holes that couldn't be drilled that way were marked using the holes in the saddle as a template. 

Petticoat:  When it came time to make the petticoat, standard pipe fittings were found to be a close match to the required dimensions.  The photo above is from the  boiler side of the smoke box showing the fittings.  The notch is the lower left of the smoke box permits the smoke box to slide past the feed water heater input fitting. 

The 2" to 1-1/4" reducing coupling and a 4" long 1-1/4" nipple combination were used for the petticoat.  McMaster-Carr has drawings and CAD files for most plumbing fittings on their website.  The drawing on the right was made by combining two CAD files downloaded from McMaster-Carr.  
This photo shows the bottom of the petticoat where most of the hub on the coupling was turned off and the inside smoothed. 

Note that the petticoat is supported by a bracket attached to the smoke box front.  The original plan was to support the petticoat with a bracket to each side the smoke box.   This arrangement turned out to be simpler and has the advantage that the petticoat is removed with the smoke box front.  The bracket is made from a scrap piece of 3" channel.  
Things are really tight in the smoke box.   When I first tried to push the smoke box front into position with the petticoat attached a small interference between the top hub of the coupling and the lower compression fitting on the pipe from the throttle to the superheater input pipe was found. The photo shows how a bit of grinding solved the interference.



Exhaust Pipe: The last piece of the Blower- Blast Nozzle function is the exhaust pipe from the cylinder to the saddle.  The left side pipe is pictured above.   The pipe is 3/4" OD tube (5/8" pipe).    The end that fits into the engine exhaust manifold requires a custom fitting.  

This is that custom fitting at the cylinder end.  The brass elbow is for 3/8" NPT threaded pipe and was drilled out to 3/4"   The brass piece with the O-Rings was made from  1" diameter brass bar stock; the shoulder next to the elbow was left at 1" diameter.  Both ends were turned to 3/4" diameter and the grove made for #018 Viton O-Rings (7/8" OD-3/4" ID).  The WROT copper fitting is a street elbow.  All these pieces were silver soldered together.   The screw was made with a piece of 6-32 threaded stainless rod and and stainless nut silver soldered on the end.   
The flange on this end was made at the same time as the saddle.  A short piece  of the 3/4" OD tube was silver soldered inside the flange.   The pipes were then fitted to the saddle and to the cylinder and the ends that fit into the elbow marked and cut to the correct length.    The three pieces were assembled and the ends attached to the saddle and to the cylinder.  Once everything was found to fit correctly the elbow was soldered while the ends were still secured using 400 degree soft solder.

 The blower and feed water inputs are noted on this photo.        
Safety Valves:  The safety valves pictured on the right fit in 1/4" NPT holes in the steam dome top.   These particular valves are used in hydraulic service.  The setting is sensitive to the torque used to tighten the valve so Teflon tape is used and the  valves tighten until just snug. 
The safeties relieve to the sides so the the defectors show here were fabricated from aluminum bar stock.  They are 1-3/16" OD, 15/16" ID and 1-3/8" high.  The height may be a little excessive; if so, they can be cut down later.      
Blow Down Valve:  The blow down valve connects to the middle front of the outside of the firebox, just above the mud ring as shown on the right.  The elbow and nipple are off-the-shelf  1/8" NPT fittings.  That is a  compact high-pressure brass ball valve, 1/8" NPT female X male, lever handle  from McMaster-Carr (#4112T13).  A 1/8" nipple will be added to the output side to get the discharge beyond the side of the frame.

Water Input Valve and Check Valve:  The photo above shows the boiler water input valve and check valve near the front of MRSR91.   This input  is fed from the left side injector.  


This shows the water input valve and check valve on the model.   The input on the model will be from an electric pump located under the oil tank rather than from an injector.   The input pipe will run along the top of the walkway into the front of the cab.  More detained information will be provided in the Water Plumbing section.

 This wraps up the description of the construction of the boiler fittings.    


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