7821 - Track & Lighting Maintenance Wagon
In 1983, LEGO introduced a second wave of sets for the train system, replacing some sets from the first wave. This second wave again came with several stand alone "extra" rolling stock sets, and this 7821 is one of them.
The model is a track & lighting maintenance wagon, although it looks like it's mainly designed for lightning maintenance. The wagon uses the same colour scheme as 7814, which makes them pair up pretty nicely as a maintenance train. The platform rotates, making the light post accessible to the worker minifigs. The platform must be locked in the central position when the train is running.
Interestingly, Ideas Book 7777 from 1981 contained a quite similar design.
In 1983, lots of new parts were released. This maintenance wagon uses the big new "space" stands (just like 7838 from the same year). There is also a light post, using the same design as set 7867, again from the same year. It looks as if Lego tried to use as much of the new parts in as many different sets as possible. Mission accomplished, this one works very well. The parts don't end in themselves, they all contribute to a harmonic design and nice working features.
The B-model wagon of 7821 contains everything needed for placing an altogether new light post.
Packaging (3D scan)
click to view the 3D scan