Saturday, June 6, 2009


I cut the base for the precipitator complex.  The prototype at Bethlehem Steel that I am modeling, has twin units and is connected to both A and B furnace.  There is also a pipe connection that allows waste gas from other furnaces to be run through these units.  All in all it makes for some very complicated piping.  (See Precipitator Part 1 for a photo of the prototype)   
Most of this piping is being made from poplar or maple dowels, with some Plastruct tubing being used.  I prefer the wood for two reasons - yellow wood glue if used right will for a virtually unbreakable bond, and also with the various different transitions from one sized pipe to another I can put the dowel in the lathe and turn the transition in place.  Plastruct does make transitions, but they don't always match the prototype practices.    In some cases at Bethlehem I have a transition from a 1" diameter dowel to a 3/8" inch diameter.    
The piping for the precipitators all connects to one of two large diameter mains - I used 1.125" doweling for these mains or manifolds.  Off of these mains will be four intakes and four outtakes.  The intakes each split in two so there are technically 8 intakes I guess.     There are 8 google valves controlling these in and out takes, which I will be modeling shortly.  I used 3/4" dowels to stub out these pipes, just to where the google valves will attach.   The clean gas main transitions down to 7/8" and will continue toward the A-Furnace stoves.  There is also a 1" connector that connects with the clean gas main and jumps over the precipitators and the dirty gas main.  At Bethlehem the practice was to use tubing as pipe supports in places - this is represented by the 3/8" dowels.    The dirty gas main tees off to a main run that will head toward the other furnaces as well as another 1" run that will connect with B-Furnace - this run heads directly toward the A-Furnace cast house and then along the cast house wall and through the gas washer framework.   I have stubbed part of this in to where there will be another google valve.  
A note on cutting and drilling these dowels - I use a power miter saw to cut most of these pieces and I drill out for the connecting pipes using forstner bits in a drill press.  The most important thing in cutting and drilling these pieces is to have a reference lines on the dowels every 90 degrees.  This is so you can have your connecting pipes enter and leave and exact 90 degrees and when you are assembling a pipe bend you can keep the pieces aligned properly.   To mark the dowels I use a trick that I learned years ago building model rockets - you use the stop mold on a door jamb to draw a straight line down the side of a dowel - just put the dowel against the jamb and the stop and then use a mechanical pencil to draw a nice sharp line along the edge of the stop.  Now that you have your one line - cut a piece of paper to wrap around the pipe - mark the overlap exactly and using that mark fold the paper twice - this will give you equal marks at 90 degree intervals - now go back to the door jamb and draw the lines.   Use these lines to drill your holes - in this case some of the dowels had holes on three different sides.   When you cut or put the dowel in the drill press use the lines to make sure the piece is perfectly level by measuring up to the line half the diameter of the dowel.   When you glue up a turn, use the lines to align the pieces.     
In the pictures you can see the rough connections - these will all still be sanded and filled if needed and the wood will be sealed and sanded.  In the end you shouldn't be able to tell if you are looking at plastic or wood.

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