by Allen Hazen
Dynamic brakes on the F-3 (and F-2, I think) had a pair of longitudinal vents on the roof, and no visible fan. (I assume there was a fan somewhere inside: I note that another well-known locomotive builder has typically had dynamic brakes with internal cooling fans...)
On the F-7, the d.b. fan was a 36inch fan, similar to the four radiator fans.
On the F-9, this was replaced by a 48" fan: supposedly a spotting mark to distinguish F-7 from F-9, but actually late F-7 were built with 48" fans.
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Q 1: Any further complications to the d.b. style/model correlation? In particular, were any late F-3 (F-5) built with F-7 style d.b. (Supposedly the main differences between F-3 and F-7 were electrical; F-5 were F-3 built with F-7 traction motors: the change in t.m., in other words, preceded the introduction of the other "mainly electrical" changes.)
Q 2: the dynamic brakes on all these models were installed in the same location, in a roof "hatch" in front of the engine. In theory it would have been possible, then, to remove the d.b. from one of these F-units and replace it with one of another type. Was this ever done? (The CRI&P late in existence acquired, from the Union Pacific, a bunch of "F-9" units that looked, from the side, like F-3, because they had in fact originally been built as F-3 and then (while still under UP proprietorship, been re-built to F-9 standards... and the rebuilding didn't include such cosmetic touches as stainless steel vent grids along the sides. I would assume that the rebuilding DID include installation of F-9 style d.b., but (Q 2a) am I right on this? and (Q 2b) does anyone know of other F-3 (or F-2) that later had d.b. with visible roof fans installed, or of F-7 originally built with 36" d.b. fans which were later upgraded with later style d.b.?
On the F-7, the d.b. fan was a 36inch fan, similar to the four radiator fans.
On the F-9, this was replaced by a 48" fan: supposedly a spotting mark to distinguish F-7 from F-9, but actually late F-7 were built with 48" fans.
--
Q 1: Any further complications to the d.b. style/model correlation? In particular, were any late F-3 (F-5) built with F-7 style d.b. (Supposedly the main differences between F-3 and F-7 were electrical; F-5 were F-3 built with F-7 traction motors: the change in t.m., in other words, preceded the introduction of the other "mainly electrical" changes.)
Q 2: the dynamic brakes on all these models were installed in the same location, in a roof "hatch" in front of the engine. In theory it would have been possible, then, to remove the d.b. from one of these F-units and replace it with one of another type. Was this ever done? (The CRI&P late in existence acquired, from the Union Pacific, a bunch of "F-9" units that looked, from the side, like F-3, because they had in fact originally been built as F-3 and then (while still under UP proprietorship, been re-built to F-9 standards... and the rebuilding didn't include such cosmetic touches as stainless steel vent grids along the sides. I would assume that the rebuilding DID include installation of F-9 style d.b., but (Q 2a) am I right on this? and (Q 2b) does anyone know of other F-3 (or F-2) that later had d.b. with visible roof fans installed, or of F-7 originally built with 36" d.b. fans which were later upgraded with later style d.b.?