Rob Roy

[Tony Bray 1Participant @tonybray1]

As a newcomer to locos can some one tell me what pupose does the dome serve on the boiler please and of course the fitting below it

[Tony Bray 1Participant @tonybray1]

[Russell EberhardtParticipant @russelleberhardt48058]

It’s to allow the collection of steam well above the water level in the boiler. A pipe sticks up into the dome to collect (reasonably) dry steam for the cykinders.

 

Russell.

[Richard ParsonsParticipant @richardparsons61721]

Can anyone help me? I am designing a machine (if I can get the metal). It is a sort of shaper. My problem is that the machine I want is quite small, but if I am making it and writing it up for others I may as well make it a bit larger so that others will also find it useful.
What I want to know is how large would the casting be for the inside cylinders of a 5” gauge loco?
Rgds
Dick Parsons

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Richard ,

 

Typical British inside cylinder locomotives would be 16 to 18 inches bore by 20 to 26 inches stroke .

 

Maxmum casting size for most published designs is 4 1/2″ by 4 1/2″ by 2 3/4″ to 3 1/2″ high depending on arrangement of valve chest . Many are smaller .

 

It never pays to cramp the specification of a machine tool – room for vices , clamps and jigs often take up as much room as the job itself and in your case for a shaper the tool would need to completely clear the work at both ends and by a good margin if you want to avoid setting up problems for the workpiece and tooling .

 

I understand from your previous postings that your shaper has some novel features and I would be interested to see what these are .

 

Whatever the detail design of you machine remember that a shaper needs massive rigidity .

 

Regards ,

 

MW

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Tony ,

 

Russel has already told you the primary purpose of the dome on a steam locomotive .

 

The mechanism inside most domes is the regulator . This controls the amount of steam flowing from boiler to cylinders . It is usually worked by a rod which goes to the back of the boiler and out through a gland to an operating handle in the cab .

 

There are numerous designs of regulator . The most common are variations of a disc with a hole uncovering a steam port by varying amounts and ones based on a slide valve like the one at the cylinders . Less common types have screw down valves and poppet valves . Regulators need not always be in the dome – some, especially more modern engines , have the regulator in the smokebox .

 

A secondary but quite important purpose for the dome is to give access to the internals of the boiler during major repairs – some of the domes on early engines where so big that with the cover and regulator removed an apprentice could clamber in .

 

MW

[Tony Bray 1Participant @tonybray1]

From Tony Bray Thank you for the info on the Dome quite simple really but as a newcomer i needed help it make sense of the drawings now. Best wishes this is a really helpful site.

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