[N&W] Re: What if?...

[nw-mailing-list at nwhs.org]

 >What if the J's and A's would have been fitted with poppit valves like
 >Pennsey's Duplex Drive  T-1s?  I have heard that a substantial increase in
 >horsepower is made available at high speeds...so long as the valves hold
 >up to the wear and tear of the railroad environment.  Does anyone care to
 >hazard any educated guesses as to how the speed and tonnage ratings of the
 >J and A on different districts might have been improved?

Nathan -

Poppet valves were, IMHO, developed too late in the day to benefit the steam
locomotive; the poppet's main feature was a reduction in exhaust back
pressure by separation of intake and exhaust valve events, unlike the piston
valve which reduced exhaust port openings while the reverse lever was being
hooked up, to the same extent that it was reducing intake port openings.
Poppet exhaust valves operated independently of the intake valves, and could
be open longer to accomplish the reduction in back pressure.  Franklin
equipped a Pennsy K4 Pacific with a set and the performance improvement was
amazing, but the K4 was a 'teens design with much room for amazing
improvement from a number of sources.  One of the K4's features was a factor
of adhesion of more than 4.0, meaning that its rated tractive effort was
less than 25% of its weight on drivers.  This was a great help, as it helped
keep the engine from being slippery due to the reduction in exhaust back
pressure.  Heartened by this, Pennsy equipped its T1 4-4-4-4 with poppet
valves, and wound up with a locomotive that was known to be extremely
slippery - it had a lower factor of adhesion than the K4.  The T1 had many
novel features, none of which had been tested in a fleet environment - the
duplex drive, the poppet valves, etc.  It is almost miraculous that the T1s
did as well as they did.

The J had a factor of adhesion of much less than 4.0, and relied on a number
of factors to make it successful - well designed and maintained running
gear, well designed and maintained valve gear, well designed and maintained
track structure (proper contact between wheel tire and rail is vitally
important), efficient sanding machinery, etc.  Even so, there were occasions
where Js had trouble holding the rail when the sand quit running for some
reason.  Again, IMHO, if the J had experienced the reduction in back
pressure afforded by the poppet valves, it might have been totally
unmanageable under bad rail conditions.  And, understand, the J was as fast
as it needed to be for the N&W.  The low drivers were there for a reason,
and poppet valves might have negated their benefit.  The Js horsepower curve
peaked just where it needed to, for the demands of N&W's service.  In normal
service, a J could take a heavy Pocahontas up Alleghany Mountain and
Bluefield Mountain at track speed under any rail conditions, and run the
same train fast enough west of Ironton to make up time into Portsmouth.  One
also has to consider the expense - would the cost of application of the
poppet valves (they'd have had to buy them from Franklin) have paid for
itself?

As far as the A is concerned - the same reasoning applies.  The A would run
as fast as the demands of N&W's service required.  A poppet-valve A might
have run a 16,000 ton train faster between Williamson and Portsmouth, but
the lack of back pressure might have resulted in the engine not being to
accelerate the train to that speed because of slipping.  As also had a
factor of adhesion of less than 4.0.

Again, the poppet valve probably didn't get a fair shake, because it came
along too late.  Apart from the T1, nobody made a fleet application of them.
But studies needed to be made of factors of adhesion and weight
distribution; if such studies were made on the two original T1s they weren't
extensive; the Pennsy was in a hurry for a locomotive to replace the aging
K4s and that was what they decided they wanted.

Pennsy sent a T1 down to the N&W, where it was tested between Roanoke and
Norfolk; it was also tested on Alleghany Mountain, where it slipped still
with tonnage routinely handled by a J.

Pennsy also had a Duplex-drive freight engine, the 4-4-6-4 Q2.  This
locomotive also suffered from adhesion problems, even though it was equipped
with piston valves actuated by Walschaerts valve gear.  Engine 6180 of this
class was actually sent to the N&W and tested on the Kenova District, where
it did not approach the performance of the 1210, which had been tested with
the dynamometer car some years before.  The Q2 was heavier than the A but
had less weight on drivers.  And there was a Pennsy Road Foreman with the
engine, who should have been able to show the N&W folks what tricks, if
there were any, to the 6180's operation.

 > I am not
 >including the Y6's because I don't believe they would have benefitted from
 >the poppits due to the fact that they were not high speed engines.
 >Could any increased performance and efficiency  have staved off the
 >advance of diesels?

Not on your life.

 >of diesels for a longer period?
 >
What killed the N&W steam engines was not their performance or lack
thereof - it was the performance per dollar.  When the diesels became
capable of supplying the performance N&W needed for less money, steam was
done.

EdKing