simple vs. compound

[NW Mailing List]

I will add that the Y class ran out of power quickly at A class speeds due
to restricted steam flow in to and out of the low pressure engine.  If
designed to do it a 58" drivered compound could handle any train an A could
at the same speed.

If the N&W had desired that the Y class low pressure front engine would
have needed to be 3 cylinder not 2.  Also each of the 3 LP cylinders would
have needed 2 piston valves per cylinder not 1 along with other design
changes.

Would N&W have been wanted to trade increased complexity for having a
single locomotive to do what an A and Y did with the higher efficiency of
compound? Hard to say but the simple Y7 concept that would also allow for a
single road locomotive was never built.

John Rhodes

On Wed, Sep 27, 2023, 7:23 PM NW Mailing List <nw-mailing-list at nwhs.org>
wrote:

> 1. Class A front cylinders steam pipe question (NW Mailing List)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 27 Sep 2023 14:48:20 -0400
> From: NW Mailing List <nw-mailing-list at nwhs.org>
> To: NW Mailing List <nw-mailing-list at nwhs.org>
> Subject: Class A front cylinders steam pipe question
> Message-ID: <mailman.4044.1695841027.3083874.nw-mailing-list at nwhs.org>
> Content-Type: text/plain; charset="utf-8"
>
>
> Mike and others:
>
> I am far from the most knowledgeable person on this query of yours but the
> first difference is the A's were 4-cylinder simple engines whereas the Y's
> used the steam twice; first to rear cylinder under high pressure which was
> then directed to those big bulging front cylinders that reused that exhaust
> steam before blowing out the stack.
> That's the Cliff notes version. If you want to know more there are books
> that describe the methodology of what and why things were when it came to
> simple vs. compound. And then there were those real dandies, the 3-cylinder
> compounds that have never read the N&W ever tried. Some American RR's did
> but most didn't like them because they were apparently maintenance
> headaches. That said European RR companies loved them and they were quite
> prevalent over there.
>
> In the few videos that actually have genuine original sound for a
> 3-cylinder, it sounds mighty strange for that 3rd sounds like it's out of
> synchronization. Fascinating.
>
> By the 1930s or so, the compounds were getting out of favor for most RR's
> except the N&W and that's due in large part because they designed theirs
> for the job they were to do, something other RR's did not, hence the
> failures. Also, those big front cylinders were heavy and those babies
> tended to beat the rails and joints to death, literally.
>
> Big Boy was simple 4-cylinder as was the N&W A that first came around a
> few years before Big Boy. So were SP Cab Forwards, another designed
> innovation JUST for the job required. There others as well, B&O EM-1's and
> perhaps the greatest of them all, the C&O H-8, the Allegheny. I wish I had
> seen one of them in service but alas poor yorick, did not.
>
> Bob Cohen
>
>
> ________________________________________
> NW-Mailing-List at nwhs.org
> To change your subscription go to
> http://list.nwhs.org/mailman/options/nw-mailing-list
> Browse the NW-Mailing-List archives at
> http://list.nwhs.org/pipermail/nw-mailing-list/
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://pairlist6.pair.net/pipermail/nw-mailing-list/attachments/20230929/f68c26ad/attachment.htm>