Tuesday, April 22, 2014

What To Do When Canadian Tire No Longer Stocks The Part??

World Hancock 24-M-L-46 Air Motor Reverser Lever Missing
Cab Restoration CPR 4-6-4 Royal Hudson #2858 
At Canada Science & Technology Museum

A project of Bytown Railway Society's "Dirty Hands Club"

Bytown Railway Society's "Dirty Hands Club" has been restoring the cab of CPR 4-6-4 Royal Hudson #2858 at the Canada Science & Technology Museum in memory of long-time and founding member, Duncan Dufresne.  The DHC has encountered many challenges in this project, not the least of which is missing parts, parts that have rusted or corroded, or parts that no longer function.  

When parts are no longer available from commercial sources, they have to be made from scratch.  The parts can be made from standard metal bar stock using a metal lathe and a Bridgeport milling machine, or in the case of the Air motor reverser lever, cast in silicon bronze using the "lost-wax" method.  

This is but one small chapter in that restoration. 

Step 1 - Find an original.  Take Measurements.  Take Photos.  
Photos & Measurements From #2850 At Canadian Railway Museum "Exporail"

Photos of Air Motor Reverser Lever On CPR 4-6-4 #2850 at Canadian Railway Museum "Exporail"
Step 2 - Make A Wooden Pattern
There are 16 pieces of wood in this pattern. 
Wooden Pattern of Air Motor Reverser Lever Before Painting
Step 3 - Make RTV Rubber Molds From The Wooden Pattern
Making The Second Half of RTV Rubber Molds
Step 4 - Make Wax Patterns From RTV Rubber Molds For "Lost Wax" Casting
Wax Patterns Being Made.  Adding Sprues, Gates & Risers.  The Completed "Lost Wax" Tree - Ready For Ceramic Slurry.
Step 5 - Prepare Wax Patterns For Casting
Coat the "Lost Wax" tree in a slurry of ceramic shell and silica sand.  Allow the slurry to air-dry.  Repeat 8-10 times.
Fire the ceramic shell at 1700F for 30 minutes to melt out the wax and to create a ceramic mold. 
Ready For Baking.  Wax Being Melted & Shell Being Fired.  Ceramic Mold Ready For Pouring Bronze
Step 6 - Melt & Pour Bronze
Melting The Bronze - 2200F.  Pouring Molten Bronze Into Ceramic Molds
The wooden pattern was made by "Jedi Master" Ross Robinson and "Master Caster"  Bob Moore from measurements taken by John Bryant and Andy Cameron at the Canadian Railway Museum, "Railexpo", at St Constant, QC.  RTV rubber molds and wax patterns were made by Bob Moore.  Bronze castings, ceramic shells, and wax trees were made by Bronze Sculptor Dale Dunning and Ryan.   

Step 7 - Straight Out Of The Mold, Ready For Finishing
Ready For Finishing
Step 8 - Machined, Fitted, & Installed
Machined, Fitted & Installed
From Start To Finish

The "Dirty Hands Club" (a very, very informal crowd) gathers most Wednesday and Saturday mornings at the Canada Science & Tech Museum to work on the #2858 project and in the restoration of its fleet of operating rolling stock.  You can find them right in the back of the Museum complex in Building #2495.  Just follow the train tracks. 

Some Other Bronze Castings With Their RTV Rubber Molds

Bob Moore

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