Heisler Engine Construction Part III
Cylinders, Bushings & Exhaust Manifolds

Nelson Riedel, Nelson@NelsonsLocomotive.com
9/14/2009, last updated 09/15/2009

We had record cold last year here in central Ohio.  (Since temperatures have been in a downturn the last decade while CO2 levels have increased I see that political correct term is no longer "global warming", it is now "climate change"   That was a good move since the climate has changed constantly since the earth was born, they can't be wrong.)   The photo above was taken from the shop window.  Those guys drilled holes through the foot thick ice to drop their lines.  I walked out one day and had a chat.  They weren't catching anything --- but seemed to be enjoying an inner warmth from some 100 proof and also relishing the escape from their partners.   Fortunately, I have a shop for my escape. 

 I had recently given up hope on doing investment castings for the cylinders.  One alternative was to get a one foot  length of 4 1/2" diameter cast iron bar stock and try to machine cylinders that resemble castings.  It turned out to go really well and I now wonder why I considered castings for those parts. 

Cylinders HM107 & HM108: The cylinders are described in the  Engine Design III  page.  The first step was to saw the really heavy iron bar to the correct length for each cylinder ( the length of the bar matches the width of the cylinder ~5.25" for the left cylinder ~6.25" for the right cylinder.  Photo shows the small band saw  doing the job slowly but seemingly with little effort.
The next step was to saw slabs off the sides to bring the shape closer to a rectangle. 
The next step was to use the lathe to square the sides as shown on the right.


Cast iron is my favorite metal to machine --- it doesn't grab the tools and leaves few burrs.  However, it is really dirty.  The chips and dust must be vacuumed up frequently to minimize the mess.   (Also, I've learnt to not mention I'm machining iron to the wife.)


The next step was to saw off the four corners as the first step in rounding the sides.
This is the setup used to mill the corners round.  Note the spacers under the cylinder to lift it off the rotary table so that the edge next to the table could be machined.  The fist cuts were taken by fixing the rotation and moving the milling table left to right.   Small cuts were taken ~ 0.05" .  This went really well and fairly quickly. 
Once the basic shape was achieve, the cuts were taken while rotating the cylinder under the mill as shown on the right. 
After the milling was done the ends were smoothed on the  belt sander to get rid of the cutter marks.   That is the left cylinder shown in the photo.  Both cylinders made it to this point in one winter day that included three meals, many snacks, some TV and a nap. 
The next day it was back to the lathe to bore the cylinder holes.   The 4-jaw chuck takes a few minutes to set up with the dial indicator but works really well.  The holes were first drill using a sequence of drills up to 1.25; which is the largest drill I have.   Much really black dust and a big pile of chips accumulated, but really nice holes.  
The photo at right shows the cylinder back on the rotary table to mill the steam passages in the sides of the cylinder holes.  Note that the holes for the heads and observation ports have been drilled and tapped.  Also a slot has been milled out for the exhaust manifold. 

The woodruff cutter is cutting the recess for the exhaust from the valve bushing.   

This is another view of cutting that exhaust passage.  These passages are made with cores in the prototype cylinders so they are don't need to be very precise.  This operation turned out to be much easier than anticipated.
This shows all the passages in the two cylinders. 
Another view of the steam passages in the cylinders.  

The cylinders were bored and the passages machined on the second day.  

Exhaust Manifolds HM118 & HM119:  The manifolds are described in the Engine Design IV page.  These were made on the same two days as the cylinders.

 The manifolds were fabricated from  from 1 1/4" square aluminum bar stock in the the following sequence:

  1. Hole for exhaust output drilled
  2. Screw attachment holes drilled from bottom
  3. Recess in bottom milled out
  4. Excess sawed off top
  5. Flat part of top smoothed on mill.
  6. The rounded sides of the hump were made using the mill as shown on the right
  7. The attachment holes counter bored for SHCS.
This shows the finished manifolds. 

If I was to do the manifolds again I'd probably use cast iron.  

Main Cylinder Bushings HM109 & Valve Bushing HM113:  The main cylinder bushing is described in Engine Design III and the Valve Bushing is described in Engine Design IV.

The bushings are turned from 1.5" (valve) and 2.5" (main cylinder) diameter cast iron rods.  The end and the OD of the first bushing is turned on the end of the rod and then the bushing is sawed off and the process repeated for the second bushing.  The photo shows turning a valve bushing OD.

The sawed end of the bushing is then turned to the correct length.  Next, the inside is drilled and then bored to the correct ID.  The photo shows boring a valve bushing.
After all four bushings were finished to the correct length, OD & ID, the 3 jaw chuck was moved from the lathe to the rotary table on the mill.

This photo show milling the ports near the end of a main cylinder bushing.  The rotary table is used to position the cylinder for the slot and the mill table is moved left to make the cut.

Note that the cuts are made from the inside on the main cylinder bushing.  After the slots were milled, they were widened on the outside using a rotary tool.



The rotary table is positioned so that the axis is horizontal to make the ports on the valve cylinder.  The exhaust ports are simple holes.  The holes were first spotted with a center drill and then a drill was used to make the hole as shown in the photo.
Groves for the main passage ports were turned on the lathe.  It is important to make these ports as accurate as possible.    These holes were drilled with the center drill --- a drill that doesn't wander much.  The holes were then squared up with a file.  The critical part it to make the top and bottom of the holes line up with sides of the groove.    Even though the ports were drilled from the outside, there were essentially no burrs on the inside.  
This shows the finished bushings.


 The finished cylinders, bushings and exhaust manifolds are shown above.   The bushings have not been installed permanently at this time---- note that the ports on the main cylinder are orientated toward the outside rather than the middle.  

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