That weird-looking fabricated truck used on some FM-GE "Erie-built" units: maybe it's not so weird after all. I think it is, in its mechanical principles, very similar to the (Martin Blomberg designed) A1Atruck used on EMD's E-series passenger locomotives.
Looking at photos, the Erie-built truck shows swing hangers with elliptical springs in the same positions as the E-unit truck: I'm guessing that subsystem is similar in design principle. (The functional equivalent in the drop-equalizer trucks used in other Erie-builts-- and Alco passenger units-- is hidden from view.) This subsystem is concerned with "secondary" suspension: suspension of the bolsers and carbody from the truck frames.
The "primary" suspension system-- how the truck frame is suspended on the axles-- is what looks unfamiliar. On the drop equalizer trucks, the equalizing levers are the drop equalizers, the prominently visible bars that dip down below axle level between the axles. On the EMD truck (this from the description of the trucks in Jim Boyd's "Passenger Alcos" book) are ABOVE the axles, and hidden from view within the frame casting. I think what we see in the fabricated Erie-built truck is probably functionally equivalent to this, with the difference that the equalizing levers (the bars with the straight bottoms and curved tops that connect the axle-boxes) are displayed on the outside face of the truck frame: an arrangement which may have seemed more natural with a truck fabricated from flat plates than it would have with EMD's cast truck frame.
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At least some of the Victorian Railways B-class EMDs ("AA-7": double ended F-unit carbody on SD running gear, among the first EMD six-motor units and one of the early Australian mainline diesels) were delivered with fabricated (welded) truck frames-- it was anticipated at the time, and in fact happened, that these would be prone to cracking after a few years (they were replaced with cast frames when the locomotives were several years old). Did GE anticipate any comparable problem with its fabricated truck frames? And did any of the Erie-built units last long enough for problems to appear?
Looking at photos, the Erie-built truck shows swing hangers with elliptical springs in the same positions as the E-unit truck: I'm guessing that subsystem is similar in design principle. (The functional equivalent in the drop-equalizer trucks used in other Erie-builts-- and Alco passenger units-- is hidden from view.) This subsystem is concerned with "secondary" suspension: suspension of the bolsers and carbody from the truck frames.
The "primary" suspension system-- how the truck frame is suspended on the axles-- is what looks unfamiliar. On the drop equalizer trucks, the equalizing levers are the drop equalizers, the prominently visible bars that dip down below axle level between the axles. On the EMD truck (this from the description of the trucks in Jim Boyd's "Passenger Alcos" book) are ABOVE the axles, and hidden from view within the frame casting. I think what we see in the fabricated Erie-built truck is probably functionally equivalent to this, with the difference that the equalizing levers (the bars with the straight bottoms and curved tops that connect the axle-boxes) are displayed on the outside face of the truck frame: an arrangement which may have seemed more natural with a truck fabricated from flat plates than it would have with EMD's cast truck frame.
...
At least some of the Victorian Railways B-class EMDs ("AA-7": double ended F-unit carbody on SD running gear, among the first EMD six-motor units and one of the early Australian mainline diesels) were delivered with fabricated (welded) truck frames-- it was anticipated at the time, and in fact happened, that these would be prone to cracking after a few years (they were replaced with cast frames when the locomotives were several years old). Did GE anticipate any comparable problem with its fabricated truck frames? And did any of the Erie-built units last long enough for problems to appear?