CN 9900's

New "Draper Taper" CN 9900's were operating on CN freights in late-January and early-February, 1986. On January 30, 1986 at 1435 CN 9901-9900-9525 were heading west, just west of Ernestown at Bath (top three photos). 

Confusingly known alternatively as SD50AF and/or SD60F's (class GF-638a in CN nomenclature, GMDD order C448) these four locomotives were considered demonstrator SD60F units with the then-new 710 prime mover instead of the 645 used on the SD50-series. Their GMDD builder's plates were stamped SD50AF. 

Think of them as SD50 on the outside, SD60 on the inside! The rest of the class, built as GMDD order C480, were sixty SD60F's numbered 5504-5563. These first four have number boards and triangularly-arranged class lights above the front cab windows. The others built beginning in February of 1989 had nose-mounted number boards and linear class lights. CN's SD60F's with their microprocessor-improved reliability were in class GF-638b and GF638c, (CN's 5400-series SD50F's were in classes GF-636a and GF-636b). CN's motive power department's model number is shown as SD50AF/SD60F:

The four 9900's were renumbered into the 5500 series circa 1988, thereby displacing earlier 5500's into the 7500-series, faster than Archimedes' bathtub!

On March 11, 1986, CN 9903-9900-5282 are working hard leading CN No 397 west through the S-curve at Mi 183 Kingston Sub:

Railfans love to hypothesize about these units. Some have suggested that while numbered as 9900's, the four units were actually on lease from GMDD before being later absorbed and renumbered as CN 5500's. Were they experimental, test-bed prototypes, pre-production locomotives or demonstrators, various terms used to described them? 

CN 5500-5501 went to the DMV&W; 5502-5503 were sold for scrapping by K&K Recycling. The rest of this class of units was retired by CN circa 2017. Pastorally-posed GMDD builder's photo image of CN 9900: 

Lots o' links:

• Kaslo shells in HO and later, Aurora locomotives.
• David Othen memories.

Running extra...

This is Feb24 OOF (One-Off February) fifth and last Post OO5. You may have noticed that each post during the month centred on an event or a piece of equipment that was unique, happened only once, or was a one-off, too. Now it's Leap Day, February 29th - that too is too unique! You'll also note something unique and unusual that every blog post title in this OOF has in common, too. If you think you know what that thing is that's too unique and too unusual, you might be a prize-winner! Simply reply with your guess, in five or fewer words, via email to mile179kingston@yahoo.ca or comment on this post. The contest closed March 2 at 2:22 p.m. The winner will be randomly chosen from all entries received and announced in the next post. Thanks for playing!