Heisler Engine Construction Part I
Crankshaft, Pistons, Heads & Eccentrics

Nelson Riedel, Nelson@NelsonsLocomotive.com
4/20'/2006, last updated
09/15/2009

These parts were machined in 2006 while waiting for the investment cast parts to be produced.  As documented elsewhere, the investment casting effort fell through and these parts set for over three years.  The engine has now been successfully built.  The page was updated to show some minor chages and include the current number for these parts.

Crankshaft - HM100:  The design information for the crankshaft is in Engine Design I.   The webs are made from 5/8" X 1.25" steel bar stock.  The closest size available locally was 5/8" X 1.5".  Two pieces were cut a little extra long and silver soldered together.  The sides of the combination were then milled to achieve the 1.25" width.  One end was also squared.  The block was then mounted in the vise on the mill and the mill indexing used to locate and drill the two 3/4" holes.  Photo shows the webs after the holes were drilled.

The holes turned out to be a bit oversize. In hindsight I should have drilled them 1/32" undersize and then used an adjustable reamer to bring the holes to the desired size.

 

The next step was to silver solder the pieces of drill rod to the webs. The rod for the crank was cut extra long.  The main shaft rod was cut to correct length and the ends turned to 5/8" per the drawing before soldering the webs.

The slightly oversize web holes made it difficult for the solder to flow into joints.  Ideally, there should be about 0.002 clearance.  The gap was maybe 0.005" or slightly greater.  The crankshaft was etched and the soldering operation repeated several times until satisfactory joints were achieved. 

Next,  1/4" holes (drilled undersize and reamed) were cross drilled through the webs and drill rod. Pins of 1/4" drill rod were put in the holes.  The pins were cut about 1/16" long and the excess on each end flattened with a hammer to retain the pins.   

 

The next step was to mount the main shaft in the lathe chuck and turn the excess length of the crank shaft from the front and back sides of the web. The radius and grooves were then turned on the end of the webs. 

The part of the main shaft between the webs was then sawed off and the inside of the webs smoothed.

The final step was to use an end mill to cut the keyways in the shaft.  The photo shows the completed  crankshaft.

This shows the main bearings fitted to the crankshaft.  Thrust bearings are shown on the outer ends of the man bearings.  The initial plan was to use these thrust bearings to give  a finished appearance.   However, after i=the engine has been constructed its obvious thta these bearings wouldn't be visible and a waste.

Eccentrics: The design information for the eccentrics is also in Engine Design I. The eccentrics are 1.75" OD X 1/2" thick disks. The only steel rod I had close to the required size was a length of 2" OD 303 stainless, so stainless it was. I turned down about 1.25" of the end of the rod to 1.75" and turned the end smooth.  I then drilled a 3/32" hole 1" deep in the end of the rod about 1/2" from the edge.  A 9/16" disk was then sawed off the end of the rod.  The saw cut was then turned smooth on the end of the rod and a second 9/16' disk sawed off the rod.

The disks were then chucked and the sides with the saw cuts turned to achieve the required 1/2" thickness. 

The disks were then stacked on top of each other and a roll pin driven in that 3/32" hole.  The disks were then mounted in the four-jaw chuck with about 1/4" sticking out beyond the jaws.  A dial indicator was  positioned against the part sticking out and the jaws adjusted such that the total throw was 5/8".  The indicator was also used to locate the extremes and  small marks were scribed on the face at the extreme positions. The photo shows using the dial indicator to position the disks in the chuck..

A 5/8" hole was drilled and then bored to the required 3/4" diameter.    

 

The template shown on the right was made to position the keyway relative the extreme positions.  Unfortunately, I subtracted 25 degrees from 90 degrees and got the 55 degrees shown in the image.  When I tried to time the valves I found the valves opened about 10 degrees too early (DAH!).  I remade the eccentrics using the technique shown only using a 65 degree angle.
A line was scribed on the face of the top disk connecting the extreme position marks .  The shaft hole was cut in the template.  Part of the template along the extreme line was cut way so that the template could be aligned with the line scribed on the front of the top disk.  The template was then glued to the disk. The broach bushing was inserted through the hole in the template to help position the template. 

After the glue set, the end of the broach was inserted in the slot in the busing and the bushing was rotated such that the broach was over the parallel lines on the template.  The bushing was then clamped to the disks to keep it from moving as shown in the photo. The broach was then removed from the slot and a press used to broach the keyway in both disks at the same time.

After the keyways were broached, the disks were separated and the recess turned on the one edge.  (Be sure to check the drawings or photo to get the recess on the correct side.)  Note that the two eccentrics are identical. 
The eccentrics are mounted such that the recesses of both eccentrics are next to the seam between the two eccentrics.

The key fixes the radial position of the eccentrics.  The setscrews (not shown on these eccentrics) hold the eccentric lateral position. 

Cylinder Heads - HM110 & HM111, Packing Gland HM112: The heads and piston rod rod packing glad were the next parts machined. The design information for the heads and gland is at  Engine Design III. The heads were turned from a short length of 3" diameter 12L14 steel purchased online from ASAP Source. The 12L14 contains a small amount of lead to make machining easier.  I turned the cylinder side of the head, cut off the thin piece with the band saw and then mounted the 2.125" shoulder in the lathe chuck and finished the other side. 

Drilling the head bolts on the 2.625' bolt circle can be a challenge.  This time I turned a short piece of aluminum rod to fit in the packing hole of one of the lower heads. It is retained by a 10-32 bolt through the rod.  The other end of the rod was mounted in a 5C collet in a collet fixture centered on the rotary table as shown in the photo on the right.   That collet fixture is essential fixed to the rotary table ---- an easy way to mount things to the rotary table and have them centered.  The holes were marked with a center drill and the head was then  removed from the fixture and holes drilled through on the drill press.  This head was then used as a pattern to drill the holes in the other three heads.   The heads will be used as patterns to drill the holes in the cylinders and crosshead guides.   

The photo above shows the finished heads: the upper heads on the left and the lower heads in the middle.  The packing glands shown on the right were turned from 1.75" diameter bronze rod that will also be used for the crossheads.

Piston Rod HM121 & Crosshead-HM122: The design information for the piston, rod and crosshead  is in Engine Design V.  The rod is made from 5/16" diameter stainless steel stock.  The Crosshead is fabricated from 1.75" diameter bronze bearing stock.

The first step was to thread the ends of the HM121 piston rod.  I was concerned that the threads be straight so that the rod would be on the axis of the piston and crosshead.  I turned the threads to about 90% of the required depth and then ran a die (held in tailstock) to finish the threads.  I used a collet chuck for this operation to get the rod centered  accurately and to avoid marring the rod surface.

The crossheads were done next.  A suitable length of stock was chucked in the lathe and the shoulder on the end finished and the center hole drilled and tapped.  The rod was threaded into the crosshead using high temperature Loctite (#672) to secure the joint.  After the Loctite set a 1/16 hole was cross drilled through the shoulder and rod and a roll pin inserted to also secure the rod.  The pin will serve as a reminder to not remove the rod from the crosshead. 

The rod was then chucked in the lathe and the crosshead turned to the correct diameter, the end finished and the hole for the 4-40 setscrew in the end was drilled and tapped.  I used a collet chuck for this operation to center the rod as accurately as possible and make sure the rod wasn't scratched.     

The photo shows the crosshead and rod after this operation.

The next step was to mill 3/8" off each side leaving a 1" thickness.

The hole for the rod pin bearing was drilled after the sides were milled.  This hole is a little tricky since it intersects the hole drilled for the rod.  Bronze tends to grab the drill and everything flies if it isn't firmly secured.  I secured the crosshead in a large drill press vise (using strips of aluminum between the crosshead and the jaws).  A  3/16" hole was drilled first followed by a dull 3/8" drill.  The hole was then reamed 1/64" at a time until the required 7/16"  diameter was achieved. The resulting hole is round and perpendicular to the rod axis.

The last step was to mill the slots in the sides of the crosshead.   The photo shows the finished crossheads and rods.

Main Piston-HM120:  Brass, bonze or stainless steel can be used for the piston.   I decided to use 3" diameter bronze bearing stock for the piston too.   An entire piston except for the upper end was machined on the end of the rod.  A cutoff tool was used to make the grooves for the rings. The stepped center hole was bored rather than drilled to make sure it was centered.  The center hole was tapped using the tailstock to hold the tap.  The piston was then sawed off the rod (band saw) and the piston chucked so the upper end could be turned smooth.    The final step was to drill the two holes for the piston wrench.

The photo above shows the finished pistons, a set of rings and the piston wrench.  The wrench has a pair of pins (10-32 screws) that fit in the holes in the upper end of the piston.  The 1" diameter hole through the wrench allows a deep socket to be used on the locking nut.   The process will be to install the crosshead and rod through the crankcase and the piston through the upper end of the cylinder.  A ring compressor will help get the rings inside the cylinder. A rod can be inserted through the hole in the crosshead to keep it from turning.  The piston wrench can then be used to screw the piston onto the rod.  The jam nut can then be fitted to the end of the rod and a socket used to tighten it while the piston wrench keeps the piston from turning.     

The assembled pistons-rods-crossheads are shown in photo above.  Fabricating these parts was easier than expected.

 

Valve Heads HM117 & HM118: The finished valve heads are shown on the right.  The heads were fabricated from 2" diameter 12L14 steel rod using the same techniques as for the cylinder heads.  These heads are described in Engine Design IV.

The packing gland was fabricated from a 5/16" compression to 1/8" NPT fitting. The fitting was modified by cutting off the pipe thread end and a brass plug silver soldered inside.  The fitting was chucked in the lathe and the hex part of the body  turned to 0.400" diameter a distance of 1/4" from the end.  The body was then silver soldered into a 13/32" hole in the lower head.  The head was then chucked, the protruding part of the fitting shortened to 5/16" and the inside step bored to match the drawing.   A plug was silver soldered in the closed end of the nut and the plug then drilled/reamed 13/64".   

Valve Piston HM114 & Rod HM115:  The valve piston was turned from 1.75" bronze bearing stock.  This stock is ~1/32" oversize so it is big enough for the 1.75" valve piston.  The bar was chucked in the lathe and the valve was turned on the protruding end. The photo shows the parting tool used to make the piston ring grooves. The compound slide was used to position these grooves precisely.  The groove position and groove width are the critical parts of the valve piston.   
The next step was to make the recess between the ring groove pairs as shown in the photo.   The bevel on the end was also machined at this time.  The valve was then sawed off the stock using a band saw.  Next, the valve was chucked and the remaining end finished.  The last step was to drill/bore the center and the recesses in the ends. 

The photo above shows the finished valves with rings and valve rods.  A short piece of 3/8" brass hex stock was silver soldered to the stainless steel valve rod serves as the stop at the bottom of the valve.  A lock nut will be used at the top end.  Stainless steel washers will be used at each end of the valve. The lock nut will be tightened just enough to remove most the slack but still allow the rod to move side to side to match the rocker arm motion.  The lower end of the stem will be cut to length and threaded after the valve linkage has been assembled so the correct length can be determined.  

 

 

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