Saturday, November 21, 2009

Horn works

After many years in service the "Country" horns on 729 were found to require more than just a "tidy up". Having been hit by trees, birds and other objects the throats were extensively damaged and some parts missing all together.

These horns are a RVB 6320 -007 type and have been used on many NSW railcars for over 40 years. Amazingly they are still produced in Australia and are available from Sirens, Horns & hooters Pty Ltd in Queensland.
After removal from the car the modular assembly was dismantled and all parts examined.

The brass and copper "throats" or "trumpets" are held in with grub screws but having been exposed to the elements the screws resisted being undone and had to be drilled out and the holes retapped.

When correctly assembled these units have 3 trumpets of 3 different sizes. Each produce a different note and are listed by the manufacturer as being 420Hz, 520Hz & 600Hz.
The configuration used on the 620/720's has 2 throats facing the driving end of the car and one facing "backwards".

Fortunately some spare stock had previously been acquired so when our specialist "Horn fitter" arrived reassembly could commence immediately.
The pic below shows Jamie working with a big horn.

With the unit back together a final check of the diaphrams and air ways was conducted.

Several obstructions were cleared including a lot of grime and a hornets nest presumably established during the 629/729's period in storage.

The air line to the horns is piped up through roof above the drivers compartment and the horns are rivetted to the aluminium roof & frame.

Another job is completed ready for service and for the painters to apply their magic.