There is an old thread on this from about 10yrs ago, so I'm looking for updated information specifically on a top down build for a large dome. Our camp has a 6v / 50 ft geodesic dome which I believe is 1" EMT struts (direct connection at verticies, no hubs). Online calculators tell me this should weigh in around 750 kgs or so. We want to do a top down build for the key advantage that many people can work simultaneously at ground level. I've built a dome before and I know about all the general tips such as having the struts organized etc etc. I'm specifically interested in how to LIFT the dome in a cost effective manner without resorting to having lots of people act as manual lifting jacks. The load needs to be supported by a machine for safety and so we can make best use of manpower.
My questions are as follows:
1. Scissor lift option: has anyone done this and if so, what mechanism/strategy did you use to spread the load across multiple vertices? I am considering to attach 11 straps at each vertex/hub on the 2nd layer down (ie: next layer down from center top pentagon) directly to the metal railing of the lift platform. Does this sound like a good idea or do I need something higher up (eg: some sort of post on top of the lift platform) to attach the straps at a higher central point? Any other tips? I already know that we need to rope it up from outside and keep tension to prevent it folding inwards as it grows larger downwards. Do we really need a lift capacity rated above approx dome weight or are the specs quoted generally less than true lift capacity? What is rough cost of renting one for 8-9 days out of Reno these days? Can these be rented without a special licence? Does anyone want to share the cost of renting one of these??
2. Floor crane option: this would use 2-4 floor cranes (aka 2 ton engine hoist). I would probably add a spreader bar to each crane and attached 2-3 straps (to load at 2-3 hubs) and then only lift one side of the dome at a time while the other rests on the ground. This option is certainly cheaper because those hoists are only about $250 each. Problem: max boom height is not high enough to lift from 2nd layer up and attach a new layer underneath. So is there likely to be an issue lifting from ground level layer, since the bottom layer bolts are yet to be fully tightened, and they need to be loosened anyway to attach the new layer?
Any other options that are tried and tested for top down builds? We hopefully will have enough manpower on standby to even lift manually if we have to.
Thanks
