As part of the Flowering Elbow workshop we wanted a big entrance, the kind of size you get at garages, that you can drive vehicles through, throw open on sunny days to bring the outside in, and provide epic purge ventilation when you have blown up your experimental whatever. The problem was we also wanted it to be very well insulated so no one inside would freeze on winter days, and we would have very low energy requirements for heating. This ruled out the usual steel roll-up doors.
The Big Door-Wall
It is basically constructed of a big softwood frame (mortice 'n' tenon joinery), with a ply outer layer, sandwiching 100mm of celotex style PIR insulation (u-value of about 0.18). Above the 3 across ply sheets, is a large multi-wall polycarbonate window, to let in some light. Polycarb worked for this because it was lightweight and had an excellent u-value (a good insulator).
A few sets of rollerblade wheels rolling in a strip of old angle iron recessed into the concrete floor allow it to slide, while a few wheels on the top keep it vertical. To prevent the roller blade wheels developing flat spots, when the door is locked the whole thing is lifted a 1/2 a millimetre off the ground....
The lock is an RFID Arduino based system, that controls two motors at either end of the door (I have attached the Arduino sketch so you can download it if interested) . One Motor was a scrap treadmill incline control motor (it is geared to turn a ACME thread, slowly but with a great deal of torque). The other is made from an old skipped battery drill, an angle grinder gearbox, and the tread and nut from an old F-clamp. Safety micro-switches from scrapped microwaves provide the limit switches for both locking-lifting motors.
Small vid of us testing the drill/grinder lock/lift:
Flexible brush seals defend the bottom on both front and back, and the top of the door from draughts. The door jambs are sealed with old bike innertubes filled with foam and a bubble seal fabricated from old wetsuit material,
All in all quite a fun project.
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