I've been turning over every rock I can get my hands on with respect to information with which to help reduce the trip data on the trailer.
I found what I believe to be an independent verification to the premise,that a trailer could actually reduce the drag of the tow vehicle combination.
The data is from Sighard Hoener's 1951 book,'Aerodynamic Drag,'Chapter 9 (B),pages 166-172,Fig.9.12,'Aerodynamic drag coefficients of a "standard" locomotive,a streamlined engine,and of a power car,measured (9.15) in combination with a tail car.
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Image (b) and (c) depict a streamlined NEW YORK CENTRAL R-R, steam locomotive with angled-roof tender,Cd 0.39,and a streamlined self-powered passenger railcar,Cd 0.42,both pulling a boat-tailed 'Tail Car' of Cd 0.10.
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While the Cd 0.10 'Tail Car' is certainly of interest,it was the streamlined coal tender which struck me.
The Tender is 37.6 feet in length,behind a 57.4-foot locomotive.The body of the tender begins,matching the aft-body of the locomotive,@ 137 sq ft projected frontal area,then at 50% length,begins a constant 9-degree roof slope,terminating at 89 sq ft cross-sectional area ( which matches passenger rail car dimensions).
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In the second paragraph of the chapter,Hoerner explains that the Cd of the locomotive/power-car can be derived,simply by subtracting the Cd of the 'Tail Car (0.10).
This gives Cd 0.29 for the Loco./Tender vs Cd o.32 for the power-car (both Cds are measured in front of a 'train').
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This suggests that the 9-degree 'fastback' Tender is actually streamlining the locomotive down to a lower drag than the constant-section power-car.From the numbers,a drag reduction of 9.3% is attributed to the effect of the Tender (trailer).
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With respect to the 'Tail Car,' it is 48.75 feet in length,with 11.75 feet of boat-tail.76% of the length is just skin friction,leaving 24% of the length as base drag.At Cd 0.10,it's pretty interesting when you consider the majority of constant section and length.
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I'll do the calcs some time to separate out the skin friction of the tail car,and try and get an image posted.Al's pretty busy today,no guarantees.
