Dome building: One big lift or little lifts?

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A year on and quite unbelievably, I am now suddenly closer to placing a dome "upstairs" on the prepared and now weathered observatory building.  I had planned to hire a Manitou MT1135 which has massive overcapacity in reach, height and load. The next smaller hire MT625 can't lift the dome high enough nor reach out far enough to clear the building, mounting and veranda.

The dome has considerable self-height which would dangle below the lifting "hook." Plus any rope extension or strop stretch. I'm still juggling with ideas for safely supporting the dome for the lift. Ropes or lifting strops would need serious overcapacity and careful arrangement.

I need to avoid imploding the dome with inward forces and there really isn't much to tie onto. I would imagine the need for a trestle arrangement under the base ring to avoid stressing the dome itself. That raises the problem of clearing the support wheels and its removal after the lift. Lifting by a sturdy crossbar lodged under the open slit framework would be very risky to the integrity of my dome construction. A dome is strong in compression but can fly apart with unusual lifting forces.

Now I'm talking myself out of using a telescopic loader and re-considering carrying the gores upstairs myself. I could easily build a temporary 2x4 jib "upstairs" and use my boat winch to effortlessly lift the gores one at a time. That would put me, and them, in a far better place for rapidly adding them to the prepared base ring & slit framework upstairs. I only need to be inside the dome to assemble the gores together. So my usual stepladders are fine. No external, aerial acrobatics on tall ladders or tightropes required. Guinness will be so disappointed but I didn't have odd coloured socks to wear anyway.

I have already lifted the base ring onto the support wheels twice and brought it back down again. So I know that's doable. The gores are numbered and should drop straight into place on a level base ring. With the prepared and safely supported slit framework already fixed in place. I've had loads of rehearsals putting the dome together on the ground stands. I even removed a complete gore yesterday just for weighing. Say about a quarter of an hour total for removal and refitting. The stainless steel bolts went through the ribs effortlessly thanks to drilling 1/2mm larger clearance holes. I've spent a lifetime trying to force bolts though the same size holes as themselves!

I'm assuming the gores will be completed and sealed as separate units before lifting individually. That would just leave sealing between them before bolting the gores together upstairs. Painting could be done on the ground or later with a roller on a stick. I'm rambling a bit here but wanted to point out the potential difficulties and advantages of each lifting approach. Even if it is only another script reading rehearsal for myself as the solo act.

The wind and weather are important factors. The weeks of fine and sunny weather could easily change. High winds need serious consideration. The dome must be rotatable to avoid spinnaker effects when only half assembled. So I should seriously consider having the shutters ready to go on before raising the dome by either method. I'd better get cracking or ice and snow could intervene.[again]

Thursday update: I finished the last two rib extensions nearest the slit. I'd been putting it off for ages because of the very acute angles. So I dug out the cheapo 12" disk sander and took mere seconds to match the angles and lengths perfectly.

I really need to make my lesser-used power tools much more accessible. Their sheer weight means they don't get lifted off the floor from under loaded shelves and junk. If I don't use them, often enough, I can't practice to become highly skilled at using them. I sanded the ends of the ribs while crouching on the shed floor. It doesn't have to be like this. Too much junk!

Another Thursday update: Somebody of the CN forum suggested I use eye-bolts through the base ring for the lift. That's actually a great idea! Because projection into the wheel space will be minimized on the final lower. I can reinforce the base ring & dome for the big lift with a simple, crossed timber bracing pattern. These will safely avoid the central telescope mounting if I remove the 30" long saddle first. I really don't want to take the heavy mounting down again!

Being relatively short sections of timber the cross-braces will be quite light and easily removed from the observatory once the dome is safely in place. They need only be bolted together for easy dismantling.

I have hardly been doing anything to the dome in the present hot weather as it hovers around 80F. I set up a blue awning but it doesn't reduce the temperature. It is claimed to have a 50 SPF [sun protection factor] but the heat of the sun can still be clearly felt in its shade. It does have the advantage that I am not blinded while looking upwards while fitting components.

Click on any image for an enlargement.

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