Y4a to Y5 and subsequent retrofit for Y3's

[NW Mailing List]

Mike -
The first step was the improvement of the LP exhaust system.  The 2049
received a new pair of LP cylinders that took the exhaust o ur the top of
the assembly merging the two sides in a sort of bridge  pipe assembly that
conducted the exhaust through a pipe shaped like a shallow U that conducted
the exhaust to the exhaust stand in the smokebox.  The live steam from the
receiver no longer  had to share space with the exhaust .  The results were
impressive - the 2049 showed a marked increase in drawbar horsepower as
well as the speed at which that horsepower was produced.
This convinced the MP Dept that all future Y engines would have the
bridgepipe exhaust system.
When the 19 remaining Y5s were rebuilt in 1940-41 their bridgepipe front
engines were applied to random earlier 2000-series engines that happened to
need repairs.
Tom Dressler counted sightings of 2000s with bridgepipe front engines and
came up with 22 or 23 that were seen with them, meaning that their was some
front engine swapping that went on towoards the end.
- Ed King


On Wed, Feb 14, 2024 at 7:56 AM NW Mailing List <nw-mailing-list at nwhs.org>
wrote:

> Are there any articles in N&W magazines or annual reports about the
> retrofit of the first Y4a/Y5 batch from bolt-assembled frames to solid cast
> frames?
>
> What was the extent of this conversion; did the converted Y5's receive a
> whole new front engine with drivers/rods/valve gear/etc.., or did they only
> receive new frames with all the parts getting re-used?
>
> Finally, did the Y3's get immediately converted, as a Y5 was outshopped? I
> can't imagine leaving those big frames (or whole front engine) lying around
> the shop for very long.
>
> Mike Rector
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