[modeleng] Re: Tall Tales?
- From: "Andy A" <AndyA@xxxxxxxx>
- To: <modeleng@xxxxxxxxxxxxx>
- Date: Sat, 5 Mar 2005 02:17:15 -0000
Hi Barrie
Not all piston heads are hollow, the LNER preferred a one piece forged head
and rod. Priming is the carry over of water into the cylinders. It is caused
when there is a high water level in the boiler. Water is drawn over into the
regulator, making it hard to shut, along the main steam pipe and
superheaters into the cylinders. The symptoms can be detected by a muffled
exhaust sound, or signs of water at the chimney top. It is dangerous because
it can cause the cylinder covers to blow out due to the hydraulic pressure
and the possibility of connecting rods getting bent, hence the existence of
pressure relief valves on the front and rear cylinder covers, not to be
confused with the cylinder drain cocks. The effect of the hot water in the
cylinders and steam chest will also act like a steam cleaner and remove all
lubrication from the surface of the bore. The effects and symptoms are the
same in both full size and model size! If you have a boiler that primes
badly it may be time for a descale.
Andy
----- Original Message -----
From: "BarriePurslow" <Barrie@xxxxxxxxxxxxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Friday, March 04, 2005 7:21 PM
Subject: [modeleng] Re: Tall Tales?
Roger,
These tales have been distorted somewhere along the line!
The first one refers to "Princess Elizabeth" which had a core plug come
unscrewed in one of its pistons in an inside cylinder. (The pistons are
hollow). This took up the clearance between the piston and cylinder end
cover causing very serious damage to the piston, cylinder, slidebars and
motion work. The loco was retreived by Ian Riley's men, one of whom is a
mate of mine and gave me this info.
The second one refers to "Blue Peter" which was departing Durham with a very
high water level in the boiler. The driver was rather over enthuiastic, the
loco primed very badly, lost its feet and slipped so much that it destroyed
many pieces of motion work. This is from my mate referred to above who has
seen a video of the incident in which pieces of motion work can be seen
being thrown in the air! It is now part of a training video for aspiring
mainline steam crew. Apparently when a large locomotive primes badly the
solid water passing through the regulator valve makes it impossible to close
the regulator, the water then flashes into steam in the superheaters which
were very hot as the loco had been standing in Durham station for a while.
The vast volumes of steam produced then do the damage referred to.
Barrie Purslow
Warrington UK
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