(Note: I wrote this for the Tasmin, last century sometime...!)
The doors on the Tasmin fixed-head coupe are constructed as follows (the drop-head being similar and differing mainly in the construction of the door glass frame).A substantial framework of steel box section is welded to the vertical hinge tube at the leading edge of the door. The frame pivots around a 1/2" steel rod, using plastic bushes pressed into the top and bottom of the hinge tube. The steel rod is supported at each end by an angled steel bracket, bolted through the GRP bodywork to a reinforcing tube inside the car. The lower end of this tube is bolted to the chassis.The door shell itself (made from two GRP sections joined together) is simply slid over the steel framework and secured at leading edge by two bolts, and trailing edge by two screws. The door catch mechanism is held by screws through the trailing edge of the door and the framework inside it. A guide/ support frame for the door glass, fabricated from lengths of channel (which on the early cars is actually a length of steel sheet formed into the 'H'-section) is lowered into the door and held in place by two bolts through the door bottom, and three self-tapping screws through the triangular plate at the front of the frame. A length of angle connects the front and rear upright sections of the frame, and a simple felt-covered draught-excluder strip is clipped to the lower edge of the angle, inside the door. The door glass channel is fitted with a velvet-covered rubber liner to allow the glass to slide smoothly and quietly. (On the DHC the frame is essentially two separate runners, at front and rear of glass. The front one is fabricated with the triangular fillet plate at top front of door.)
The window-lift motor assembly is bolted to the inside of the square recess in the door (4 bolts), and rearward of this is another recess to which another pivot for the window-lift is secured (2 nuts). Note that the drop-head has an adjustable travel limit for the glass: this is a simple Bowden cable affair (suspiciously similar to the brake cables on a bicycle!) that is anchored to the rear glass channel lower mounting by a steel bracket.The internal and external door catch releases (and the lock button) are connected to the catch with simple steel rod linkages; the internal release being located in the recess just above the window-lift motor mountings. Various access holes in the inner face of the door shell are closed off with sheets of polythene, glued around their perimeters. The armrest/ doorpull is held in place in the sloping rectangular recess by six countersunk self-tappers (the doorpull being retained to the armrest by Nyloc nuts which are accessible once the armrest assembly is off the door).
If the car has the 'aerodynamic' mirror pods fitted, the mounting screws for the pod are hidden by the triangular section at top front of the door trim panel.
Interior trimming of the door is performed on the early cars by two panels, the upper in vinyl-clad GRP and the lower made from hardboard covered in velour material. Both panels are secured by plastic clips at various points around their perimeters, which fit into holes in the door shell. Later cars had a one-piece GRP panel with a ‘bulging’ armrest. Initially the door release on this was in a similar position to the early cars (although a Metro release was used to drag the aesthetics into the '80s!) but for all late production the door release moved to a tidier location behind the door pull. The panel may be just a tight push-fit on the door, or may have some fixing screws at its lower edge. Finally, the door-release trim plate and the ashtray are screwed into place and the door lock button pressed onto the end of its control rod. Later cars had the ashtray in the centre console, of course.
POINTS TO NOTE
3. The early upper (GRP) trim panel for the door can suffer from cracking if care is not taken when fitting. Lower the door glass and locate the front end of the trim panel over the door top edge, then swing the trim down at the rear, feeding the lock control rod through it's hole before thumping the plastic clips into place
4. Avoid using excess force on the screw which secures the internal release trim, as the plastic is brittle and will crack around the mounting hole, causing the trim to fall off. Difficult to repair and hard to find in breakers' yards now. It probably goes without saying, but the hardwood lower trim panel on the early cars is not the best mounting point for loudspeakers, even if you are completely undemanding of audio quality. Apart from the lack of rigidity which high-output speakers need, the amount of water that enters the door will soon destroy the speaker cones. Later cars incorporated a GRP drip guide that direct the water away from the speakers, and the later GRP door panel is also more rigid, but it’s as well to be aware of the pitfalls before spending your money on Pioneer’s finest.
5. The steel reinforcing posts fitted inside the ‘A’ and ‘B’pillars are bolted through the GRP shell to the sill plates. A length of plate is welded to the bottom of the tube and bent to conform to the sill angle. This plate is the first bit to corrode, usually along with the outer sill plates and the chassis tubes! Once it rusts through, the door pillars have less strength, as they are basically relying on the GRP to hold everything together. If you find that the sill tubes and/or plates need repair, it’s as well to check these reinforcements as well.
The window-lift mechanism (taken from the Rover SD1!) looks like this once removed from the door:
One point to watch out for is the pinion pivot; if you notice a lot if juddering when the window is being lowered, but lifting is OK, check the condition of the pivot. It's a simple arrangement of a shaft turning in a pressed metal 'bush', but once it wears as in the picture below, repair is probably impractical:
New replacement window lift mechanisms are still available from Rimmer Bros. as of march 2013; they can also be found via online auctions.