Aerodynamics

typesix wrote:Budd built RDC-9s with about 1/2 the horsepower of a RDC-1 or 2 because less horsepower was required for the trailing cars since the first car broke the air. The SPV had two noses, a blunt one for 100 mph gearing and a more aerodynamic nose for 120mph gearing. Automobiles at 50 mph spend almost 1/2 required horsepower to overcome drag.

What possible advantage would a blunt nose provide on a train geared for 100 mph when a more aerodynamic nose was deemed appropriate for 120 mph gearing?

MudLake wrote:

typesix wrote:Budd built RDC-9s with about 1/2 the horsepower of a RDC-1 or 2 because less horsepower was required for the trailing cars since the first car broke the air. The SPV had two noses, a blunt one for 100 mph gearing and a more aerodynamic nose for 120mph gearing. Automobiles at 50 mph spend almost 1/2 required horsepower to overcome drag.

What possible advantage would a blunt nose provide on a train geared for 100 mph when a more aerodynamic nose was deemed appropriate for 120 mph gearing?

In this case, the blunt nose allows for cars to be coupled together.

Going back to the rear of the train, I suspect that parasitic losses from the open tail aren't all that great. Amtrak could experiment with retractable fairings to create a chopped-off teardrop shape and see if that affects efficiency appreciably, but I suspect that the fuel savings would be balanced by the possibility of breaking the thing. Likewise, it could be a good idea to have a retractable deflector attached to P42s for Superliner consists, but I suspect that most would get damaged or stuck in the most inconvenient places.

While it probably posed more complex switching issues to get the cars in the right places, the Santa Fe had the right idea with the baggage dorm from the El Capitan which had a transition roof up to the Hi-Level cars which Amtrak later acquired and used for a while... as without it there is probably some level of drag the blunt face of the superliners create without transition from the baggage cars behind the P42s.

The problem with brinigng something like this back into service is baggage cars are used on all routes. They would have to make sure these cars stayed on routes with Superliners.

I suspect the AAR & the Test Center may already be working on this. You may get one result with the Superliners. You may get another result with the freight doublestacks, excess height cars, etc. Adding to the difficulty would be any wind working for or against the train. I suspect the worst offenders may be the empty flat car that have a container or two on the tail end.

While on the subject, I wonder how many open hoppers should have tarp covers similar to those used on dump trucks. Anyone unlucky enough to follow one knows what I'm talking about.

David Benton wrote:Whats at the back of a vehicle is just as important as whats in the front

Good point: One of the earliest examples of developing an aerodynamic rail vehicle was the McKeen Car.

The problem was that the engineers at the time thought that the "wind-splitter" front was more aerodynamic...when the train would have been more aerodynamic with the "wind-splitter" at the rear.