[N&W] Re: Pennsy on the N&W

[nw-mailing-list at nwhs.org]

 >In the UK several classes of large express passenger loco's were
 >four cylinder, with two outside in the normal position and two parallel
 >inside, the valve gear often working through rocking links...
 >
 >This system was never tried in the US to my knowledge though a number of
 >three cylinder classes were tried including the UP 4-12-2 's.

  Alco built a pair of 4-cylinder 4-4-2s in 1909 for Rock Island. They
seem to have run well enough to avoid rebuilding, but not well enough to
warrant duplication.

David Thompson
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Regarding Gresely's conjugated valve gear, by which the combined motion of 
the two "outside" valve gear drove the valve motion of the single "inside" 
cylinder and piston:  bearings in the linkage wore quickly, which resulted 
in the center piston taking more than 1/3 of the total output, which 
resulted in excessive wear on the bearing on the cranked axle. The idea 
sounded good; maybe a case of not so good in the details.

In reading about the engineering history of British locos; Sir Nigel 
Gresley comes across as someone to be sent out of town when it came time 
for optimum design of valve gear.

Jerry Crosson