THE EMD 567 SERIES TWO-CYCLE UNIFLOW ENGINE, AN INSPIRATION: PART 2

…although we could talk a little two-cycle design, we spoke with a very heavy four-cycle accent. We did believe we could understand what a two-cycle engine was trying to tell us, so with the optimism of youth we barged into the design that ultimately turned out to be the 567.

E.W. Kettering, Chief Engineer, EMD

The 567 Series Engine

In the mid 1930’s, EMD realized that the Winton 201 Series engine was not going to be sufficient to meet railroad demands as it wasn’t powerful or reliable enough.  They discovered that fixing the problems of the 201 would require an entirely new engine and thus they decided to start with a clean sheet of paper.  On one side they listed everything they got right with the 201.  On the other side they listed all the failures.  Their plan was deceptively simple:  Fix the failures, keep what they got right and build a more powerful engine that would better use the space within the carbody of a locomotive.

Unlike the 201, an early emphasis was placed on design for manufacturability to increase interchangeablity, tooling commonality and productivity.  As an example, all 567 engines use the same oil pump design.  The only difference is the length of the gear teeth.  An unintended benefit of this emphasis on interchangeability is that almost all parts of the engine, including revised designs, are interchangeable between engine serial numbers.

As with the 8-201, research began with a test engine studying cylinder liners, porting and pistons.  The pistons required substantial development to further refine the crown cooling system begun with the 201.  EMD found that traditional asymmetrical pistons with the pin bore though the wall of the piston caused substantial heat-induced stresses.  These stresses resulted in ring belt cracking due to the temperature gradient between the crown and ring belt.

567 test engine

EMD’s first 2-567 test engine.  Illustration Credit:  “History and Development of the 567 Series General Motors Locomotive Engine”  Page 18

Their solution to the temperature gradient problem was the “trunnion piston”.  The piston pin is installed though a trunnion, which is in turn a slip fit in the piston crown.  The trunnion is secured to the bottom of the piston by a snap ring.  This elegant solution solved not only the ring belt cracking problem by reducing the temperature gradient across the piston, but also allows the whole piston to rotate, potentially distributing skirt and ring wear more evenly.

piston temps

Winton and early EMD pistons suffered greatly from ring sticking due to high ring belt temperatures. This was solved by the EMD “heat dam” piston but presented a new challenge: The high temperature gradient caused the ring belt to separate from the piston crown.  Illustration Credit:  “History and Development of the 567 Series General Motors Locomotive Engine”  Page 25.

Another discovery during development of the 567 Series worth noting is that, like many two-cycle engines, the 201 series suffered piston and liner scuffing around the cylinder ports.  This can sometimes be due to the reduced contact area between the liner and the piston rings, resulting in metal to metal contact, ring breakage and eventual failure of the liner in the port strut contact area.

However, during testing of a 567 Series engine it was discovered that the cylinder liner operates at a much lower temperature around the intake ports.  This naturally causes a straight-bored cylinder to contract in the area of the intake ports, in the same way tightening your belt constricts your gut!

Liner Temps

This illustration, taken from “History and Development of the 567 Series General Motors Locomotive Engine” shows the temperature gradient across the cylinder liner in the area of the intake ports.  Illustration Credit:  “History and Development of the 567 Series General Motors Locomotive Engine”  Page 37

EMD’s solution?  Rather than bore a taper in the cylinder, as is commonly done on air-cooled aircraft engines, they decided to relieve the port area about .014″ on diameter.  This solved the piston and liner scuffing problem.

Liner Relief

An illustration from the EMD 645 series Engine Maintenance Manual, showing a cross-section of the liner and the location of liner diametral relief.

Numerous other improvements in injectors, crankcase structure, rod and rod bearing design, exhaust valves and valve bridges and other components resulted in what became the 567 Series.  At 567 cubic inches displacement per cylinder and a rated power of 1,750 HP in the later models at a piston speed of 2,100 FPM, the 567 is the engine that “Dieselized” American railroads.

567

An early 567 Series engine, note the square hand hole covers. Later 567’s and modern EMD engines have round hand hole covers.  Illustration Credit:  “History and Development of the 567 Series General Motors Locomotive Engine”  Page 64

While railroad history isn’t the purpose of this blog, it’s worth noting the enormous effect EMD’s engines have had on American railroad operations.  The 567 Series was installed in the EMD “E Series”, “FT Series” and the exceptionally popular “GP Series” locomotives, among others.

While the GP locomotives are by far the most popular, it’s an almost forgotten FT unit, GM-103, that is the most historically important.  Powered by four 1,350HP 567A engines, it was an EMD mainline freight demonstrator.  Freight, not passengers, are the bread and butter of American railroads and it was FT-103 that sold some American railroads completely on the diesel and forced the rest to follow.

FT103

Half of GM FT-103 repainted in it’s orginal demonstrator colors at the 1989 EMD open house in LaGrange, IL. Photo Credit: Unknown

FT-103

AT&SF #115, a complete four-unit GM FT. Photo Credit: Jack Delano / Wikipedia

Dick Dilworth, Chief Engineer of EMD at the time, tells it best.  After hearing that a railroad executive, undoubtedly William Jeffers of the Union Pacific Railroad, had talked down to one of EMD’s salesmen about the capability of their FT-103, he got on the phone:

“I hear you’ve been taking advantage of one of our men.  I’d like to make a prediction.  If you’ll put our four-unit freight locomotive alongside your Big Boy on that hill out in Utah, we’ll push your Big Boy so far back into Lionel’s window with the rest of the toys that no one will ever talk about it again.”

Today, EMD locomotives powered by the same basic engine architecture pioneered in the 1930’s pull heavier trains than five UP Big Boys ever could over “that hill” (The Wasatch Grade).

FT-103 now resides under cover at the Museum of Transportation in St. Louis, MO alongside many of the steam locomotives it helped push back into Lionel’s window.  The technology it brought to the railroad lives on and relatively unchanged from it’s original form.

emdft

Me in the head unit of FT-103 with it’s 567A engine.

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