Scale Weights


Paul Hillman
 

For what it's worth,(and to answer my own question about scale
weights versus NMRA weight recommendations), I did a couple of
calculations.

I calculated 2 HO cars, 1-38ft wood reefer & 1-50ft steel boxcar. I
took the reporting marks data off the car-sides and computed scale
weight, then computed the NMRA weights according to car length, as
follows:

38ft wood reefer, total prototype loaded weight=136,000lbs.
Scale weight=136,000lb./(87.1 cubed)x16 = 3.2930 oz.
NMRA weight=5.25"(length)x.5 oz./in. +1 = 3.6250 oz.

50ft steel boxcar, total prototype loaded weight=168,200lbs.
Scale weight=168,200lb./(87.1 cubed)x16 = 4.0728 oz.
NMRA weight=6.875"(length)x.5 oz./in.+1 = 4.4375 oz.

In both cases the NMRA weights exceed the scale loaded-weights by 9%
to 10%.

Referring to the NMRA car weights practices, it states the various
reasons for their recommended weights are, including, railhead
contour, wheel contour & proper truck-springing and equalization.
I'd wonder if Proto 87 standards would affect the NMRA results? (I
have used the NMRA weighing standards for many years.)

In referring to one of my perfectly-scaled freight-cars I could
say, "Everything is to perfect scale, including it's weight." You
think that might help it sell?

With all of the billions of scale details discussed on the STMFC, I
just thought that scale-weight might be a worthy tidbit. But at
least now I know that scale weight will equal, like, 4.0728 oz., and
not 628lbs.

Paul Hillman

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