Reguarding 19th century locomotives, and their safty valves.

[Dusten Barefoot]

I've always wonderd what the extra two levers were, that connect to the safety valves of a 19th century steam locomotive. Are they emergency relief handles for manually opening up the safeties in case they don't pop, or do they serve a different purpose?

http://www.pacificng.com/ref/blw/style/stylediag/S51-QR-A12-HEAVY-1881.png

Rock On!
~Dusten Barefoot

[poliss]

Those are the steam whistles.  Drivers/engineers were not allowed access to the safety valves as they were often tempted to screw or weight them down to increase the steam pressure in the boiler when the loco was struggling. This often led to boiler explosions with fatal consequences.

[CNE Runner]

I agree with the reply from Poliss and would like to add something to his statement regarding the 'tying down' of safety valves by trainmen. In a 1907 address by John W. Thomas Jr. (the president of the NCSTL) he says; "An engine had stalled on the mountain; the engineer, whom you all know well, tied down the safety valves - there was no 'pops' in those days, put on the blower, sanded the rail, pulled the throttle wide open, perched himself on the side of the cut, and threw rocks at the old kettle, abusing her all the while, until presently the steam pressure went away beyond the limit, and the train moved off."

The amazing thing is that no trainman was in the cab when this 'maneuver' was carried out! This example illustrates the [sometimes] foolhardy manner in which early railroads carried out business.

Ray

[ebtnut]

My understanding (not having my John White book handy) is that those levers were indeed a part of the stafety valve assembly.  Much like a balance scale in your doctor's office, the shop mechanics hung weights from the ends of the levers that were calibrated to the safe steam pressure.  As with modern pop valves, one was set a bit lower than the other, essentially giving notice to the engineer that maximum pressure was being reached.  The other went off at the rated boiler pressure.  "Tieing them down" meant exactly that - the levers were tied down so they couldn't lift up at when there were supposed to. 

More modern pop valves had internal springs that were calibrated at the factory (or in the shops) and could not be "adjusted" by the crew on the road. 

[Johnson Bar Jeff]

I believe I remember reading somewhere a long time ago that one of the famous very early engines in American railroading, the "Best Friend of Charleston," blew up because the safety valve was tied down, but perhaps that story is apocryphal.

[richg]

I did a simple Google search for, early steam locomotive safety valves.
Below is one link.

http://www.locomotives-and-trains.com/steamlocomotive-5.html

I have read quite a lot of White's and Abdill's books where the author occasionally mentions the safety valves.
The early valves where adjustable as the safety valve was evolving.
The safety valve was being used on stationary power plants before the locomotive was developed. When applied to a locomotive, the track/road bed was rough and the valve would bounce around a lot. Things where quite crude back in the 1800's as locomotves where quite new.

Rich