Virginian Coal Cars
NW Mailing List
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Wed Aug 12 16:03:31 EDT 2020
I have a few comments on the H-9 hopper car derailment tendency based on
my quite fallible memory of things some half century ago and my lack of
any available documentation. I hope others can provide additional comments.
The 50-ton H-9 hopper cars had non-snubbed trucks, which means their
ride qualities were comparable to the uncontrolled bounce of an
automobile without shock absorbers. I remember N&W Test Engineer Bob
Pilcher telling some of us that he had been called out to investigate a
major derailment and determined that the cause was a soft spot in the
track followed immediately by firm track in a highway grade crossing.
This transaction from a depression of the track under load in the soft
spot to the firm track caused an non-snubbed H-9 car in the train to
bounce off the track at the crossing, causing the general derailment.
I recall that the rock and roll problem was coincident with the
introduction of N&W H-ll hopper cars, which had 36' 2" truck centers
(H-9 truck centers were 21' 4") closely matching the 39' between most
rail joints. These rail joints become displaced downward under traffic,
and this displacement of the rail begins some distance on either side of
the joint, meaning that it is possible for two wheels on each side of
the car to be in a rail depression at about the same time. Because rail
joints are generally staggered on one rail relative to the other, the
car would rock to one side and then half a rail length farther would
rock to the other side. It was found that this harmonic rocking was
sever enough to cause an H-ll car to rock off the track when moving in a
narrow range of train speeds. I think this led to an operating rule
that stated if a train with these cars could not gain speed to get above
the critical rocking range, then the speed had to be reduced below the
critical rocking range.
On 8/10/2020 8:40 AM, NW Mailing List via NW-Mailing-List wrote:
> Okay, I'll admit to wondering why the specific limit for NKP coal
> cars, and not Wabash, VGN, P&WV, or .??
> Circa 1960, N&W accident investigators concluded that a derailment had
> been caused by an
> N&W H-9 hopper. The H-9s had a 50-ton capacity, friction-bearing
> trucks, and peak ends. Between
> 18 and 22 MPH, the H-9s had a tendency to rock and roll. N&W then
> issued special instructions
> that loaded 50-ton hoppers (inc. VGN, N&W, NKP, and others) were not
> to be placed in through
> freight trains unless approved by the Superintendent. Trains handling
> the loaded 50-tonners were
> to avoid speeds 18-22 MPH and the maximum speed for the train was 25 MPH.
> When coal loadings decreased, the 50-tonners were stored so that coal
> drags didn't have to
> contend with them. One place they were stored was Island Yard in
> Lynchburg. Then one night,
> some pirates floated down the James, docked at Island Yard, jacked the
> hoppers up and took the
> brass out.
> In the 1970s, the computer geeks concocted a program that simulated
> train movement. What they
> needed was actual information to compare a computer-generated trip
> with an actual run. The System
> Operations Center (SOC) drafted number dummies to record speed, meter
> readings at ever mile post,
> and delays. One item - power had to be a single class of diesel units
> -- no mixing EMD with Alco,
> etc. No GP-9s mixed with GP-35s. When I reported to South Yard for a
> trip to Norfolk, the train I
> was to ride had three SD-45s, 180 loaded hoppers, including 3
> H-9s. Harry
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