|Grubby looking thing!|
|With mounting flange and whistle-mounting elbow|
|Whistle valve roof-mounted in Isebrook|
|Whistle valve roof-mounted in William|
|Front-mounted whistle (the valve is inside)|
|Conical valve (not to scale!)|
|Valve seat inside end of valve body|
|Spring and retainer which screws into the end of the valve body|
|Rod (not much more to say on this!)|
The steam pressure holds the conical valve in place until the lever is used to push it open. This is a sudden action which is also terminated abruptly by the steam forcing the conical valve shut again. Hence the whistle valve enables a quick 'pop' to be achieved as well as the long 'poop'!
There is one more aperture in the valve body shown with a copper tube attached in the Isebrook valve picture (but, oddly, not on William).
When it's all assembled, it looks like this.
|Note the elegant MDF cab front substitute and supporting clothes' peg!|