Cass 6 Main Frame I
Nelson Riedel, Nelson@NelsonsLocomotive.com
6/24/2004, last updated 04/08/2006

Note:  The initial plan was to present the Cass 6 Frame on one webpage.  However, after taking more photos and measurements I decided to provide a frame overview and details on the sides in Part I and  describe the remaining details in Parts II & III

The Heisler (excepting the early production) used a unique frame side members each made of two square steel bars with stiffening plates.   This frame was called the "Diamond Frame".   The next photo shows the left side of Cass 6 with the cab removed.  The lower bar bends down between the trucks, probably to lower the position of the engine.  The lower bar is symmetrical with the  truck centerlines.   The upper bar is not symmetrical with the trucks; on the front truck it starts to bend up in front of the rear wheels.   On the rear truck, the bar starts to bend up at the same point the lower bar starts to bend down.    

The next photo shows a closer view of the engine attachment to the frame.

 The next photo shows the front sill.  The sill arrangement is similar to that of the Shays ----- except that the frame sides are symmetrical to the locomotive centerline. 

Front Sill: The side view of the front sill.  Note that the lower frame bar ends at the sill and the upper bar extends about 2/3  the way across the top of the sill.

Rear Sill:  The photo below shows the rear sill which is a casting.  Note the unusual shape of the link to the tender.  The droop is necessary to make the tender level.  That chamber in the rear of the coal bunker is empty; it may provide access to the pin retaining the coupler link.

This shows a side view of the locomotive rear sill.  The ends of the casting are rounded and the polling recess part of the casting.   This photo and the first two were taken in the spring of 2003 just after the new boiler had been installed.   The other photos were taken in June 2004 after the overhaul had been finished and everything painted.
This photo shows the front stiffing plate.   All the stiffening plates are 1/2" thick.
This shows the rear stiffening plates.  Note that double plates are used here.   The holes were made  with a touch.   I initially speculated that the holes were for cooling.  Mike Getscher emailed suggesting that the holes were made to peen  over the ends of stay bolts that were replaced during a boiler refurbishing.    On the next trip I looked and found that the holes lined up exactly with the stay bolts.  I meant to ask the Cass Shop foreman about it but got side tracked.   This is a new boiler so the stay bolt locations must exactly match the old boiler.   A frame drawing in Kline's The Heisler Locomotive  seems to show cast plates with vertical slots the entire height ---- maybe to access the stay bolts.

The drawing above shows the Cass 6 frame side and the drawing below shows side with the plates and sills  

These drawings provide the critical measurements needed to lay out the relationship between the frame sides, boiler and engine.  Additional frame details are provided in Parts II & III.

All the Cass 6 main  frame drawings are combined into the single file that can be downloaded from the Drawings page.