I've had one of these for years!

From memory - there is a plastic 'sound box' inside the tender and an arm which hangs down to the rear axle. The end of this arm is coated with a 'sandpaper' like substance. Around the rear axle is a metal (copper?) clip, part of which extends slightly and scrapes against the 'sandpaper' arm causing the 'chuff chuff' sound to be made.

I don't remember the 'arm' being copper coloured (thought it was black) but I may be wrong.

Have found a copy of the original loco service sheet online but the tender is not included.

Will have another look when I get home later!

 

Hi try this link - most of the Hornby Service Sheets are there. You might just find what you're looking for.
It's an interesting site, too.
NERBob

http://www.modeltrains.net.au/hornby/service_sheet_menu.asp

 

Hi NERBob,

That's the site I found too - really useful source - but I could only find service sheet details for the loco itself not the tender. Did Hornby ever include the tender on one of these sheets?

Geoff

 

Don't know if you sussed it out, but here's some pics that may help.

http://www.flickr.com/photos/ennbee09/