Statistical Dave wrote:
"Summary from Guy's post, questions to follow:
Type D required for New cars - 1918"
On, and after November 1, 1920
"For Type D cars post 1937, any idea of the rate of replacement with Type E?
Obviously as a percentage of the total fleet it could not exceed the
percentage of pre 1933 built cars, less post 1937 rebuilds... but would most
older cars equipped with Type D couplers retained them to scrapping?"
It would be speculative, but I would think a larger percentage of cars built new, and not rebuilt, with type "D" couplers were still equipped with them when scrapped. Think of (just) the thousands of x29 cars. A complete Type "E" coupler was $31.o5 in 1938, and $107.85 by 1952. So, I would guess that numerous knuckles and parts were replaced prior to fully replacing the thousands of Type "D" couplers. The statistics of such conversions were not required by the AAR, thus individual railroad statistics would be the only source. Would they have bothered? I doubt it, but it may have been so.
"Does anyone know the "strength" of Type D relative to Type E?"
Summary of the American Railway Association tests, circa 1930:
The result of the two groups of tests show that the "E" couplers average 40,000 lbs. greater in ultimate strength, 15,000 lbs. greater in yield point, and had about 20% less permanent set at 250,000 lbs. All of the "D" couplers developed a secondary failure through the upper front face at the notch provided to facilitate lock assembly, a point where many failures occur in service. In the case of the "E" coupler, no failures developed through the face proper, all occurring at the juncture of the guard arm and face. The elimination of the notch in the front face and the reinforcement of the face walls, combined with the greater resilience of the guard arm account for the improvement of the "E" coupler indicated by this group of tests.