Description of new Mermaid wagon June 2009

After visiting a model railway exhibition, and buying some books, I was inspired to build
some new wagons in 8mm scale.

Having made a 12ft wheelbase wagon for the Grampus drop-side wagon, the Mermaid
was an interesting wagon to build with a similar wheelbase.  I kept the same brake gear
tubes as the Grampus but the real Mermaid does not have braces between the wheels,
so there are no tubes representing them.  This leaves room for another method to be used
to attach parts to represent the wheel hubs.

I had to alter the wheelbase to fit the curved slopes, along which the rollers roll to give
the Mermaid its characteristic side tip action.

There are three sets of rollers, as on the real wagon.  When in a tipped position, the
set of rollers furthest from the tipping side is raised off the roller track.  I used red belts
to keep the other rollers on the tracks.  As the hopper moves to one side, the small slot,
through which the belts are fed, resists the sideward movement because the slot is narrower
than the distance between the two outer roller sets, around which the belts are secured.
This means the belt on the side to which the hopper is tipped is in tension.  The other belt
is moving towards the centre of the slot, so it becomes slack.  This allows the other side of
the hopper to lift off the track until its belt is taut again.

I used some tiles with a lip to keep the hopper from moving along the wagon.  Some part of
the lip is always in contact with the hopper parts, at every position.  The corners of the lips
make contact with the underside of the hopper base, allowing the hopper base to be posed
in a tipped position, as shown in the photos.

Each door is pivoted at each end of the hopper.  The string with studs is a substitute for the
chains on the real wagon, whose tension in the tipped position raises the door on the tipping
side.  I might use a chain with stud ends instead, depending on the length and tension required.
The doors stick a bit because some of the brick connections are by only 1 stud.

Robert Hendry's book "British Railway Goods Wagons in Colour" (ISBN 978-1-85780-094-4)
Pages 72 (picture) and 94 (4mm scale diagram) were useful.

It is tempting to modify some parts, especially the axle pins on the ends, but I'll keep mods
to a minimum as the wagon progresses.

Mark Bellis
June 2009