You will find a series of seven Bertie videos under the Beginners' Guides section. I have included one here
Here Peter Clarke treats us to a "Railway Channel" type intro before we see his Roundhouse Bertie fitted with the standard Chuffer. We have Peter to thank for spotting that it needed to be mounted lower than standard.
Here is another video from Phil Sixsmith demonstrating the Chuffer on a much modified, radio controlled Roundhouse Bertie. The R/C gear is in the tender. Here the Chuffer is a "special" fitted to one exhaust only. The other exhaust has a simple chuff pipe which vents below - hence the odd beat.
Here is my modified Roundhouse Bertie hauling Swift Sixteen and scratch built stock at the Summerlands Light Railway.
There are more Bertie videos in the Beginners' Guide section