lightweight freight cars (was Re: roofs)


Patrick Wider <pwider@...>
 

--- In STMFC@..., timboconnor@c... wrote:

Pat, although the physics of moving freight cars is real and had real
operational consequences (e.g. more fuel, more power) I don't think
the Return On Investment for lighter cars was ever as compelling as
say, increased car capacity, or roller bearings, or cushion underframes,
and so on. So while railroads dabbled in lighter car designs I think the
primary focus was on overall operating cost reduction. Nowadays (if I
may be permitted) considerable sums have been spent on lighter coal
cars, but it has to be pointed out that due to wind resistance, empty
coal cars going back to Wyoming require almost as much power & fuel
as the loaded coal cars! Railroads once again have discovered that
greater capacity (to 286,000 lbs) has a faster payoff than worrying
about fine-tuning the tare-to-weight ratio.

Tim O'Connor
Uncle!!! Darn it. I've let myself get trapped into a discussion that most subscibers to this
list couldn't care less about (am I right guys?) even though it is about freight cars (well sort
of). When I originally listed the desireable characteristics of a freight car roof, one that I
listed was lightness. That's all I said. I still stand by that simple concept. SRE also thought
it was a selling point (I'll now leave Wonder Bras and advertising out of my discussion -
they're not in my area of expertise nor do they concern freight cars and Mike is watching).
Heavy roofs, all else being equal, don't make sense. Lightness is desireable, especially
where it may lower the vertical cg of a car and improve its rolling dynamics. Of course,
additional friction snubbers in the spring groups may help here. When taken to extremes,
such as the experimental lightweight box cars, it had adverse repercussions. Absolument!

I do agree that weight has little impact on the rolling friction of a freight car. I was more
concerned with the component of the gravity vector (weight) aligned with the pulling faces
of the couplers when the car is being pulled upgrade {it's just the sine of the (grade) angle
times the weight of the car}.

Pat, signing off on this one before the thread is 20, 30, or 40 e-mails long and when I
finally agree that heavy freight car roofs are good. All in all, I think Mr Spock would agree
with me that that statement would be "most illogical."

Pat Wider

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