This is the roof coated with fiberglass.

Only the white had the UV protectant. We will paint it to match the siding and so it absorbs some heat from the sun and melts off any ice or snow accumulation which could be more of a problem than summertime solar heating. Solar heating in the observatory can be dealt with by a dedicated a/c unit which will be installed. Weight of the finished roof is 380 lbs sans the insulating foam on its interior surfaces, maybe another 10-30 lbs. We added the lift hooks for the crane so we don't bend the drip flange around the bottom with lifting straps. The hooks have an extension on the underside for hold down attachments, either temporarily during construction or permanently for when the roof is “homed".

The roof will move up, over and down with 2 cantilever arms which are outside the observatory and are attached to the front and back corners of the roof. The powered arms go through the middle of the observatory wall on both sides and connect to the lower rear (southern) edges of the roof. The motor drives these arms in an arc via large sprockets and two chains in the interior of the observatory. The chains run to smaller sprockets on a shaft spanning the inside rear of the observatory. This shaft is driven by a variable speed reversible D/C motor. Another pair of cantilever arms attach to the lower front (northern) edges of the roof and are anchored to the northern roof of the house. This arm is an unpowered passive follower and will also travel in an arc.

The observatory roof will set down on the northern downward slope of the house roof. Speed control is achieved by a combination of gear ratios and varying the motor speed. All of the hardware is stainless steel as much of it is outside the structure itself. The design calls for 15 rotary bearings which are food grade units. The grease in the bearings is supposed to be edible but I thought I’d save that for cracker spread at the grand opening gala.

The design is being tweaked as it is built, but it works with a model and just has to be strong enough to avoid excessive torque forces on the roof with no flexure of the structure due to differential motion of the powered arms. This is primarily achieved by use of keys and keyways, rather than welds or set screws, and by over-engineering the mechanism to tolerate much larger forces than anticipated the structure will ever be subject to. In other words, its really industrial strength. I have no doubt that an adult could ride the roof while under operation and not cause a failure. Safety interlocks, multiple limit switches, time-out switches, moving-part guards and emergency shutdown capabilities are all part of the design as well.

One concern is the average wind velocity in the vicinity is one of the highest in the nation (with frequent strong gusts), even greater than it is for the large wind farm sites in California and much greater than the so-called Windy City. In fact, the only wind farm in the state is 5 miles away and it’s placement there was no accident. With our design, I believe anything short of 60 mph winds should be of no concern other than to perhaps cause the moving roof to vibrate or shudder a bit. In the “home” closed position, the shingles on the roof would no doubt blow off before the observatory roof was in danger of failing. The strength of the mechanism itself is probably great enough to obviate the need for additional hold-down locks, though they will nevertheless be installed so as to not have to test the theory.

It is difficult to explain in words how this will all work, but it will become apparent as the web site evolves and new images are posted as the mechanism is assembled on site. As far as I know no one has done anything like this. It's main advantage is allowing low observatory walls with a view of the horizon with no chance of the roof striking the scopes even when they are at their highest point.