F-unit d.b. retrofitting

[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.
--
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.?

[Engineer Spike]

I'm sorry that I can't give you a 100% definitive answer. It seems like models from F2 up kept the general same design. It might have very well been easy to remove the hatch of a F#, and apply one with the external fans from a later model. As we have discussed before, it seems like EMD was very flexible with how a customer could specify how much original content could be included in a rebuilt unit. Good examples are wrecked units which might have F# guts, but a F9 body. There were other examples like the GN GP9 order with 1350hp of the traded FT. If the newer dynamic brake arrangement produced higher capacity, then it would be well worthwhile to change it. If there was no or little benefit, then what difference wold it have made?

[Pneudyne]

Take a look here: https://utahrails.net/articles/up-f-units.php.

About half-way down the page, under the heading “Conversions to F7s” is this:

“Between 1952 and 1954 the 1400 class F3s that weren't reassigned in to the Northwest in 1950 were converted internally to F7s by the railroad's own shop forces. While other shops may have done some of the work, most of the conversion project was done at the new Salt Lake Shops. The conversion consisted of installing a 567BC engine in place of the original 567B engine, and updating the electrical components. Many of the F3s also received the F7-type of dynamic braking with the 36-inch diameter cooling fan. A retired railroad electrician from the Salt Lake shop has said that most of the upgrade program of the dynamic braking components was done in the railroad's Pocatello, Idaho shops during 1951.”

Evidently the conversion from the F3 type dynamic brake unit (with four horizontal-shaft fans) to the F7 type (with one vertical shaft fan) was feasible and it was done.

Cheers,

[Pneudyne]

Further down the same web page is:

“All of the 84 units in the 500-class F9s (41 F9As and 43 F9Bs) were completely remanufactured by EMD at La Grange, from the same number of F3s that remained in both the 1500 and the 1550 classes. This total excluded the four units that had already been retired and rebuilt in 1952 as F7s after the November 1951 wreck at Orchard, Idaho.

"The rebuilding work included replacing the 567B or BC engine with a 567C engine. All new electrical gear was installed, including new D22 generators and new D47 traction motors. The units were considered by both the railroad and EMD to be F9 locomotives, albeit in remanufactured F3 carbodies. The only external indication of the F9 internal components was the 48-inch dynamic brake cooling fan on top and a rearrangement of the carbody panels to the F9 configuration of a louver set ahead of the first porthole. The class was assigned to the Northwestern District and the operating department tried to keep them from going either south of Ogden, Utah, or east of Green River, Wyoming.”

So the F9 48-inch fan dynamic brake unit was also retrofitted to the F3 structure. One could extrapolate from there to assume that retrofitting the F9 dynamic brake unit to the F7, in place of the original 36-inch fan unit, was reasonably possible.

Cheers,

[Allen Hazen]

Thanks, Pneudyne!
I remembered reading somewhere (maybe a Preston Cook article) that the "modular" design of the post-war (F2 and later) F-units made this possible, but didn't (still don't, except for your posts!) remember any reports of it actually being done. (Except for the Union Pacific's F3 --> F9 rebuilding: at least some of these units went to the Rock Island, I think during the time when the U.P. was attempting to merge with the C.R.I.&P. and obviously wanted to keep the weaker railroad alive, and they are mentioned in a book on Rock Island diesels(*). Some photos in the book show them looking very much like F3, complete with "chicken wire" on the grills at the top of the carboy walls: one is taken from a low enough angle to show the d.b. fan on the roof. Another is taken from a similar angle... but of a unit which had had its d.b. fan removed! C.R.I.&P. didn't have many mountain grades, and U.S. railroads with non-mountain routes were very slow to appreciate the benefits of dynamic brakes. The Rock Island bought its U25B and U28B locomotives without d.b., and probably looked on d.b. as a needless waste of maintenance money on its F9!)
--
Louis A. Marre, Rock Island Diessel Locomotives 19301980" (Railfax (= publisher of "Extra 2200 South"), 1982).

[Pneudyne]

The attached page from an EMD brochure briefly delineates the change in dynamic braking system from the F3 to the F7, with a claimed 23% increase in capacity.

EMD F7 & E8 p.06.jpg (361.53 KiB) Viewed 2452 times

Re the delayed adoption of dynamic braking by “flatland” railroads, in part this may have been because earlier dynamic braking systems on diesel-electric locomotives were less suitable for use as slowing brakes than as holding brakes on the grades. However, as brake capacity increased over time and the peak effort speed moved downwards, dynamic braking systems gained utility as slowing brakes, and then with the extended range facility, as near-stopping brakes. Too, set-up time might have been an impediment to DB use for relatively short periods of time. For example, British Rail found that crews were reluctant to use the rheostatic (dynamic) braking fitted to some of its earlier AC electric locomotives, so it went to an early form of blended braking, using an electromechanical “transducer”.


Cheers,

[Allen Hazen]

Thanks again!
---Nice touch that the optional dynamic brake for the E-8 was a unit interchangeable with those used on F-7. (But not, when you think about it, all that surprising. How many customers wanted d.b. equipped passenger units? And they are both four-motor types. So... savings on engineering (and warehouse shelving for the spare parts business) by using a common "module".)

[swissrailfan]

As to the chicken wire on F3/7 the early F7 had chicken wire then was changed to the Farr louvered screens/grills I think mid production of the F7. Many F3/7's were retrofitted with the Farr screens/grills. There is no reason why the DB"S on F3/7's cannot be interchanged they are mounted in the roof as removable panels. So newer DB"s could be installed if desired.

[SSW921]

According to a Don Dover F unit article in Extra 2200 the screen covering/"chicken wire" lasted until July 1948. This was most of the way through the Phase III production of F3s.

As for dynamic brake swaps, I've seen photos of Santa Fe passenger Fs with the wrong dynamic brake hatch.

Ed in Kentucky