[modeleng] Re: Conway

Hi Harry,

With a full sized loco, there is usually a copper inner firebox and a steel 
outer box, these two are held together by steel and copper stays. Also, the 
firebox tubeplate is usually copper and the tubes rolled into it are steel. 
Both metals have different rates of expansion as we all know but when an 
engine is running with the regulator open, a constant temperature is 
maintained. If the firehole door is opened with the regulator open, there is 
a great influx of cold air straight onto the tubeplate. This causes the 
steel to contract quicker than the copper and leads to leaking tubes and 
stays. If the door is opened when the engine is working, there is a flap on 
a hinge that should be lifted and this directs the cold air onto the 
firebed. If you remember that a loco working will generate up to 3000 deg f 
in the firebox so normal outside air will cool things drastically. I have 
seen one of our boilersmiths on the SVR, throwing a total paddy because the 
tubes that had been put in the loco only 2 weeks before were leaking and had 
been steam tight the day previous. Although it cannot be proven, the only 
sure cause was running with the firehole door open. Extra unnecessary 
expense and manpower to re-roll them again.

With boilers in 5" and 31/2" gauges, they are silver soldered copper 
tubeplates, barrels and tubes and whilst there is a slight difference in the 
expansion rates of silver solder, it is all "glued together" and doesn't 
suffer the stresses of a riveted steel/ copper boiler.
Hope this helps.

Dave.

----- Original Message ----- 
From: "Harry Wade" <hww@xxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Friday, June 16, 2006 1:09 PM
Subject: [modeleng] Re: Conway


At 01:03 PM 6/16/06 +0100, you wrote:
>is not good practice to run with the regulator open and the firehole doors
>open but does not have the serious results with a copper, silver-soldered
>boiler that it does with a steel one. - Dave

Dave,
   What are those results?  I've never heard mention of this.

Regards,
Harry

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