Tonnage Ratings and Weather Reductions for Locomotives
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Mon Dec 17 10:48:42 EST 2018
Definitely not TMI. Leakage in cold gaskets in “glad hands” would explain the reduction in train length (as clearly shown in the 1973 time-table instructions that Jimmy showed). Less cars equals less glad hands equals less leakage. Got that.
But prescribed tonnage reductions for locomotives in the steam era would not necessarily equate to less “glad hands”. Seems like there are possibly two different issues going on here (and therefore two different solutions). Was locomotive thermal efficiency greatly affected by falling temperatures? Obviously journal-box oil viscosity would be. Other factors?
John Garner, Newport VA
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Sent: Sunday, December 16, 2018 9:19 AM
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Subject: Re: Tonnage Ratings and Weather Reductions for Locomotives
Probably another reason was the difficulty of getting air through a longer train. As temperature dropped, air connections tended to be less secure, as in the gaskets between air hoses in the “glad hand’' between the cars – that old bugaboo called “leakage” reared its ugly head. The power brake law required the air pressure on the caboose to be within fifteen pounds of the feed valve setting on the locomotive, and on really long trains it might take an hour or so of pumping up to get the pressure on the caboose; this was necessary before the brake test could be made and leakage had to be within prescribed limits. Several yards had “yard air” which could be coupled up to an outbound track of cars to charge up the brakes; there was even a device called a “time o test” (if I recall) which could make the brake test and check leakage on a track of cars.
Hope this is not TMI . . .
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Sent: Saturday, December 15, 2018 8:36 PM
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Subject: Tonnage Ratings and Weather Reductions for Locomotives
By time-table instructions train tonnage in the steam era was reduced as ambient temperatures fell. Reductions were as much as 25% at temperatures below 0 degrees F (Rating G).
Were there multiple reasons for this reduction? Was the primary reason the increased rolling resistance of cars with friction bearings? Were other factors involved?
Thanks, John Garner, Newport VA
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