Cass 6 Engine Part II
Crankcase, Crankshaft & Bearings
Nelson Riedel, Nelson@NelsonsLocomotive.com
6/24/2004, last updated 04/08/2006

An overview of the engine was provided in Part I.  The details of the lower engine are discussed here.  The starting point is the crankcase castings shown in the following three drawings.  

 

Crankcase: The crankcase is split front to back with the crosshead guide for one cylinder cast with each crankcase half.  The cylinders bolt to the flange on the outer end of the  crosshead guides. The drawings above and on the right show  the crankcase split apart. 

Note that the outside of main casting is not cylindrical; there are flat areas at the top and around the crosshead guides.   
There are slight recesses in the front side near the crosshead guides that provide clearance for the rear side of the rocker arms.   These recesses  necessitate a corresponding narrowing of the inside on the crankcase as shown on the right.  This narrowing in turn requires a thinning of the outer edge of the crankshaft  counterweights.    It seems Heisler packed about all they could in this, their largest engine.      
Engine Mount Bracket: The crankcase has notches on the outer edge that match up with the top and inside of the lower frame bars.   The engine mount brackets fit on the outer and lower side of the frame bars.  Bolts through the bracket into threaded holes in the crankcase clamp the crankcase to the frame bars.  An additional 8 smaller bolts run through the bottom side of the bracket, up through the frame bar and then though the outer edge of the crankcase with nuts on the top.       
This is a drawing of the engine mount bracket.  The two brackets are identical.   The brackets are centered on the crosshead guides.  The right crosshead and the associated bracket are positioned 7" to the rear of the left side.   

Crankshaft: The photo above was taken in the fall of 2003 .  Wish I would have taken measurements then.  On a subsequent trip, the Cass Shop Foreman Artie Barkley pointed out a number of spare Heisler engine parts they have  including the crankshaft pictured on the right.    This crank was great for measurements but was too heavy to reposition for a nice overall photo.   

 

 

The drawing on right describes the bare crankshaft.

 
Counterweights:  There were no spare counterweights so I crawled under the engine and took a few photos and measurements.  The counterweight is 4" wide near the center and then increases to 6" wide further out.  However, near the outer edge it thins again --- to a 2" width.  The 2" wide part is slightly off center toward the front on the front counter weight and toward the back on the back counterweight.    
 This photo of the right side connecting rod shows why the outer part of the counterweight is narrower --- to give clearance for the forked upper end of the  connecting rod.  Photo was taken lying on my back with feet out the right side of the locomotive.   The crankcase is recesses at the front to give clearance for the rocker arm resulting in a narrowing of the crankcase cavity at the front so the front side of the counterweight must also be thinned.  
This drawing shows some of the counterweight dimensions.  The width at the center is 4" matching the crankshaft web width.   The two counterweights are identical.  
Eccentrics: I was lucky again to be shown a spare eccentric set.   The two eccentrics are cast as one part and keyed so there is no adjusting the valve angle.   I didn't attempt to measure the angle between the two halves.   I'll be prepared next time.   
Each eccentric is 4" wide with a half inch wide  - half inch deep recess on each eccentric in the center where the two eccentrics join.  A lip on the eccentric strap rides in the recess to keep the strap from slipping off the eccentric.   
The drawing on the right shows the eccentric dimensions. 

 

The drawing below shows the assembled crankshaft.   This drawing was constructed by pasting together the drawings of the crankshaft, the counterweights, the eccentrics all shown above and the U joint end shown in the U joint and shaft page.      

 

 

 

Main Bearings & Caps:   This photo shows the right side of the front main bearing cap.  There are two large (~2" diameter ) bolts that secure each bearing cap,  The nut for the right side bolt is visible in the lower part of the photo. 

The two set screws are only on the right side of each cap.  I assume the setscrews provide an adjustment to remove any slack in the bearing --- maybe by pushing a wedge. 
This photo shows the left side of the cap.    Note that there are no setscrews on this side.. 

 
This shows the rear of the crankcase with the square head of one of the large bolts that retain the bearing cap.
The drawing on the right shows the overall dimensions of the main bearings.  The outside surface appears to be circular rather than square like the rod bearings.  

The drawing below shows the outside dimensions of the main bearing cap. 

 

 

 

 

 

All the drawings on this page are in the engine drawing files that can be downloaded from the Drawings page.    The upper part of the engine is examined in Part III. 

 

 

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