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     Projects ... A3 Switcher    Cylinders 8/31/2010

This page covers the machining of the Cylinders ... Section 14.0 pages 84 - 92


Lots of stuff in this section ... 14 different pieces totaling 26 machined parts most have critical alignment requirements. The cylinder is the most complex piece ... several surfaces, mounting holes and ports that have to be drill at a particular angle and depth. Not to mention the round cylindrical surface that has to be hand shaped. Then there's the Tee using the 4 jaw chuck ... that one also took a lot of time and careful alignments.

There are 2 issues with this section which needs to be looked at and then you decide your course of action:

The 4 Cylinder mounting holes I moved 1/64" so that the Cylinder sits lower on the frame. (see fig14-3, pg 85).

The Rear Cylinder Head dimensions don't add up for the side view (fig 17-21 pg 89). I made the bushing hole deeper, which required that the Piston Rod Bushing be also changed.

The Discover Live Steam forum has some discussion on the Cylinder location.


Each picture below is a thumbnail so it can be enlarged to get a better view ... back arrow to return.

 
932 Bronze from On Line Metals this will really add some serious weight to the frame.
  1st mill cuts ... this stuff cuts real nice.
 
Now that I have the basic outline ... marked the areas so I knew exactly where to cut.

  Boring for the piston. Needs to be between .875 and .876, so a plug gauge is used frequently.
 
An action shot ...   I did a layout as a check but I really used the DRO for the cutting the steam ports. That's a Carbide 1/8" endmill.

 
I didn't want to ding the smooth surface of the bore so I made an aluminum insert.   One of the steam passages ... must be very careful on the depth, too deep and you will be remaking the part. I used the mill stop so that the drill would not get pulled in.
 
Here I used a indexer, C collect and adjustable mandrel to remove most of the material on the cylindrical surface. Able to get within .008 of the final dimension. Then went to the lathe to finalize the surface, saved a lot of time.   Same setup Kozo suggest ... the parting tool is just to the right. The results fabulous ... very smooth surface. Only needed to remove about .008" or about 2 passes.
 
I wasted a lot of material machining the Rear Cylinder Heads. That big gap on the left was required because my cutting tool is wide. The cut off blade will not give me a straight cut.
  Milling the Steam Chest
 
Finishing up the Tee ... this was a lot easier then I thought it would be ... no problems.
  Aligned the mill head ... then installed the Exhaust Deflector and drilled the mounting holes. Repeated for the Steam Inlet Deflector.

 
Drilling jig for the Exhaust Deflector radius ... the drill by itself would deflect too much without extra material to hold it in place. Did same for the Steam Inlet Deflector.
  Almost done ... installed on the frame.
 
Top View   Bottom View
 
Now things are getting to look pretty nice ...

  Interesting insides ....
  I haven't finished the Cylinder section yet ... still have the 3 covers, drain cock holes ... will do those when machining the Cylinders Cock (section 19) and a few nuts & bolts.

Although Kozo doesn't feel it is necessary to hone the cylinder walls ... I'm thinking since I'm using O-Rings rather than Graphite Fiber I will be honing. In his New Shay he uses an O-Ring and hones the cylinder. So I think there is a message there.


Moving on to the Pistons and Crosshead ...

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