Chuff pipe making

[Big Jim]

I know that Summerland Chuffed are the bees knees, but now being a skint student again I would like to have a go at making my own.
I have seen a description of how to make and exhaust enhancer in an old magazine, but I can't find the damn thing now.
Anyone got any plans or descriptions. If I remember it was just a question of crimping the end of the pipe and filing a slot in it. However I can't remember if there was anything more technical to it.

[tuppenced]

This is an accidental chuff pipe, Jim.

The essence of the Summerland is that the exhaust is squirted across a sharp edge inside the chimbley (not the smokebox), while the smokebox provides a Helmholtz Resonator to deepen the tone (like the drum of a referee's whistle).
(There, I've told you the technical bit now.)

The text is pixellated to fit it into the forum's file-size limit, and may be easier to read if downloaded and enlarged.

[Big Jim]

Thanks for that.
I shall have a play around