When did railroads begin adding “taconite extensions” to ore cars?

[BurlingtonNorthern]

Thanks in part to help I received on this forum, I recently discovered that all of Burlington Northern’s U-27 “Lake Superior” type ore cars had extensions welded to the top of them in order to allow them to carry a greater quantity of taconite, an iron product which is lighter then the ore they were originally designed to carry.

(The extensions are the yellow lips present on the tops of each of the cars in the included images.)

Similar modifications seem to have been made to ore hoppers on other railroads as well.

Do any of you know when the railroads began making these modifications to their ore hoppers. Better yet, since the extensions seems to have been added to Burlington Northern’s fleet of ore hoppers before the 1970 merger, would any of you know when these extensions were added to the ore hopper fleets of the Northern Pacific and the Great Northern, the two railroads from which Burlington Northern acquired most of its ore hoppers.

I am currently adding these extensions to my current fleet of ore hoppers and was merely curious.

 

[UP2CSX]

It was sometime in the early 60's. I served as a deckhand on an ore boat in the summer of 1964, saling between Duluth and Cleveland. The Missabe Line had most of their ore cars with extensions at that time although some trains still had them as-built. I assume the Missabe was adding extensions to all the existing cars at that time and the GN and NP were probably doing the same. Our dock was served exlusively by the Missabe Line so I can't say for sure but ideas like that usually took hold at about the same time.

 

[jrbernier]

Minnesota Taconite Ore Cars

The Minnesota Taconite Admendment was passed in 1963. This changed property taxes on mining and jump started taconite production in the state.
Taconite production methods had been developed and a state tax law change was put into effect in about 1941. This was part of the WWII 'war effort'. At least one taconite plant(Reserve Mining) was started up, but the incentives for investing in taconite would not come about until HF116 was passed in 1963.
GN and DM&IR ore cars with pellet extensions followed. The taconite pellets are not has heavy as raw ore, and the small ore cars 'cube out' too fast. The pellet extensions allow a full 70-75 ton loading of the cars.

Jim