Harry Cupper’s Steam Engine of the Week: Happy Mothers day! Caitlin’s Class the B&O P-7d!

By | May 11, 2015


In celebration of Mother’s Day this week Harry Cupper will take a look with us at a locomotive type whose streamlining was designed by a mother. Ms. Olive Wetzel Dennis, an “engineer of service” who was the first woman member of the American Railway Engineering Association. The P-7d should be well known in the Thomas fandom as Caitlin’s likeness which thunders up to the Ulstead at high-speed.


Three of these beautiful streamliners were built for luxury passenger service the B&O offered between Cincinnati, Ohio and Baltimore, Maryland. The “engineer-girl” invented and held the patent for the Dennis ventilator, which was in the windows of the passenger cars and could be controlled by passengers. It was a major advancement in the air-conditioning of coaches. She also brought to the finger-tips of passengers on these trains controls over overhead lighting and the reclining seats. Ms. Dennis also created stain resistant fabrics for use in passenger coaches.


Ms. Dennis made sure the coaches pulled by the P-7d’s were put through overhauls as good as the engines after every trip. P-7d’s would each pull 10 coaches including a baggage car, an onboard coffee shop like a mobile Starbucks, three luxury coaches, a dining car with stainless steel appliances worthy of cooking only the finest meals (like french fried potatoes!) and two or three more coaches where regular Joes were jammed into about 60 people each.


Enough about the coaches! Back to the engines. The P-7d’s were as elaborately painted as Caitlin is. They had hemispherical smokebox caps, front end shrouding, parallelogram striping and were painted bando blue and yellow. They were fitted with all the best appliances and gear like all Timken rolling bearings on all axles and in the side rods (similar to N&W 611) and Worthington feedwater heaters.


These were such fine locomotives the B&O could run two trains with just three engines available, but the locomotives had to be swapped about half way through their journey in West Virginia. With a P-7a pulling the train, you could expect to arrive in 12 and a half hours in Cincinnati. Unfortunately, the good looks could not save these engines. Eventually, the streamlining was removed and all three engines met torch in 1951.

How Caitlin survives which road number she was remains a mystery. =)

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