Draft / Smokebox vacuum J, A, Y6

[nw-mailing-list at nwhs.org]

Which is really not a lot of vacuum.  15" H2O = 1.1" Hg = .0368 atm = (-.54 lb/sq.in.), or about 1/2 psi negative pressure.  But you wouldn't really need a lot, I guess.

John Simmons

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Sent: Monday, May 15, 2006 8:39 AM
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Subject: Re: Draft / Smokebox vacuum J, A, Y6


There are detailed test data for the J and Y6 prior to
final modification, but nothing so far for the A  or
Y6b and modified Y6's re: smokebox vacuum. 

For those who are curious, smokebox vacuum is not the
same as back pressure (measured in lbs/sq.in.), but
rather the result of the entire front end design -
exhaust nozzle, stack configuration, steam volume and
exhaust pressure.  The higher the vacuum, the more air
that can be drawn through the firebox.  It is measured
in inches of water.

For the J, based on the 1945 tests on C-burg Mtn and
the 1948 tests from Poe to Suffolk:

Roanoke-Elliston - 7.2 in. water, 44.65 mph, 1065 tons
Elliston-C-burg - 15.2 in. water, 24.58 mph, 1758 tons
Elliston-C-burg - 15.7 in. water, 36.78 mph, 1065 tons
Poe-Suffolk - 7.5 in. water, 60.99 mph, 1506 tons
Poe-Suffolk - 10.5 in. water, 67.34 mph, 1506 tons
Poe-Suffolk - 16.0 in. water, 70.61 mph, 1506 tons

Summary

Crusing at moderate track speeds, smokebox vac would
be about 7.5 in. water.  Working flat out on grades
and with heavy loads at high speed - 16.0 in. water

The following Y6 information is based on 1947 tests
between Roanoke and Bluefield.

Roanoke-Bluefield - 9.5 in. water, 22 mph, 2800 tons
(empties)

Bluefield-Roanoke - 11 in. water, 20 mph, 9300 tons
Glen Lyn-Dry Branch - 13 in. water, 21 mph, 9300 tons
Glen Lyn-Walton - 12 in. water, 21 mph, 9300 tons

Hope this helps,
Dave Stephenson



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