4-8-0 M-2 class

[nw-mailing-list at nwhs.org]

A number of RRs used that type of relief valve ­ ATSF¹s newer power comes to
mind.

I believe that relief valves relieved pressure buildup in the cylinders when
the loco was coasting and the valve gear was ³hooked up² so that steam
couldn¹t move from one end of the cylinder to the other.  (They may also
have helped to keep cinders, etc., from being sucked into the cylinders
while coasting.)  Without them, I believe that engineers had to keep the
throttle cracked a little so that the loco was working very lightly, even
though the train may have been braking.

I chimed in because no one else had; I¹m sure that others have more
definitive comments.

Pete Groom

On 7/11/04 7:33 PM, "nw-mailing-list at nwhs.org" <nw-mailing-list at nwhs.org>
wrote:

>> Hi,
>>  I have a question about the cylinders on some 4-8-0 M-2 class locos, the
>> 1150-1160 numbers. On the cylinders of some, there is a protrusion off the
>> side of the middle of the cylinder, with square ends.
>>  . . .
> Sorry Tony, 
> They are pressure relief valves.
> . . . 
> 
> Mark Lindsey
> 
> ________________________________________
> NW-Mailing-List at nwhs.org
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> 


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