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Design of the Pyramid
Second Draft
(earlier draft available here)The pyramid will consist of a sturdy frame made out of scaffolding and heavy guy lines. We will attach 4 huge sheets of fabric to this to make the sides of the pyramid. We expect this to be a massive engineering effort. Here we will attempt to provide as much detail about our intended design as possible so that any interested or concerned parties may look over our plans. We welcome all comments! Please address them to pyramid-committee@egroups.com.
Here are top and side views of the frame. It will consist of a 56' tall tower built out of 8 sections system scaffolding with extensive internal bracing.
I'm sorry, but this diagram is a little incorrect. (It's getting worse too. A better diagram will go up sometime this week.) The biggest mistake is that the fabric will only be going up to the 4th level of scaffolding, rather than the 5th. Also, there is a 2' base below the first level of scaffolding which is not pictured. In this way, the fabric will rise 30' above the playa instead of the 35' shown. Also, the top will 58' high instead of 56'. I'm too busy with other things right now to update the diagrams. We refer to this as the tower. The tower is 10' by 10' made up of 4 towers each 5' across built together. System scaffolding is essentially adult tinker-toys -- it is highly versatile. This kind of construction is completely standard with system scaffolding. We're not relying (too much) on our own guesswork with the tinker toys to put together a solid structure. We might improvise a bit with decorations at the top however.
The main structural guy lines do not go all the way to the top of the tower since the fabric sides will only rise to the 30' level. The original idea was to have a sturdy frame built around the 30' level of the tower. This is what is pictured. The current design has the structural guy lines all attaching to a large metal ring floating in the middle of the tower. This ring will be about 5' across, and will be rigged to the tower independently of the guys. Structurally it will even out the load amongst all the guys and cause a minimal force to be transferred to the tower. Attaching the guy lines directly to the tower would probably result in the scaffolding being ripped apart.
The main guys will be anchored using large screw anchors. Such screw anchors are regularly used to hold up utility poles and radio towers. We were originally thinking of using 100 kip (100,000 pound) anchors, but realize that this kind of over-engineering would pose a buredon on us. Currently we are shooting for 30 kip anchors. Sinking them into the playa will be a pain in the ass, but I think we'll manage. Another question we're not sure of is whether the playa is strong enough to hold this kind of force in. We will have to balance estimates of the soil type of the playa against the size of anchor that we use.
Right now we are planning on using 7' long anchors with an 8" helical plate at the end. The anchors' rods are 1.5" square. We plan to drive them into the ground either with a large impact wrench or using a wheel of pain and lots of brute strength. (Slave volunteers will be richly rewarded.)
Another possibility which is gaining acceptance is the use of Manta Ray earth anchors. These anchors are much easier to sink than the Chance helical anchors. They do not have as much holding strength however, probably limited to about 14 kips in playa soil.
Steel cable and turnbuckles will be used for the guy lines.
In addition to these main guy lines there will be additional guys at several other levels for stability. These will not provide real strength against the heavy wind forces we anticipate, but are primarly there to keep the tower from shaking. They will also be used during the construction process to keep the tower in place. The lines will be trucker's straps, possibly lengthened with rope. We will anchor them with heavy steel stakes that closely resemble 3' long nails.
Once the frame is built, we will attach the fabric sides. There will be four huge pieces of fabric as such:
Each piece of fabric will be attached by lines running along the three long sides. These lines will probably be industrial webbing, although this is not certain yet. The line running along the ground will be anchored to the ground at regular intervals. The upright lines will parallel the four diagonal structual guys and will attach to the ground and tower at the same points. As such, each of the corner screw anchors (A1, A3, A5 and A7) will have three lines attached to it: The structural guy line and two lines for the fabric, one on either side of it.
We have not decided on a rigging plan for the fabric's lines, but we have several ideas. We must be able to hoist the fabric up using them. This will probably be done using strong pulleys and mechanical winches on the ground. It must also allow us to lower the fabric safely in the event of a storm.
The fabric sides will deliberately curve inwards towards the pyramid to reduce flapping in the wind. This will be done using equatorial lines running along the inside of the fabric.
The fabric will have loops sewn into through which a rope may be attached. These loops will run horizontally, paralleling the ground line but 10' - 20' above it. The ends of these lines will be anchored and tensioned to the ground. We call these the equatorial lines.
Because of this curve, the fabric will be completely underneath the four non-diagonal structural guys. (Those attached to A2, A4, A6 and A8.)
Decorations
There will be plank floors on many levels to mount sound and lighting equipment. The roof of the tower will have decorations mounted to it such as a large high-power Jacob's ladder and possible a large spotlight. We might also add smoke machines at the 30' level to have smoke billowing over the sides of the pyramid. The interior will be used as a dance space and as such will have a bunch of sound and lighting equipment. The sides will be internally lit by powerful blacklights, video projectors and colored lights. We hope the structure will be beautiful a beautiful landmark on Black Rock City's skyline.
A few notes on Safety
Except for emergency maintenance, NOBODY WILL BE ALLOWED TO CLIMB THE TOWER above the first level where the DJ will reside. In addition to signs, we will install countermeasures which will discourage climbing the tower by making it very difficult.Construction of the system scaffolding tower should be much easier than a traditional painter's scaffolding tower because each piece is much smaller and lighter. Even still, because of the great heights involved, all tower construction workers will be required to wear hard-hats and body harnesses roping them to the last stable level. We do not want anybody to fall off this tower while it is being built!
A document describing the wind loading of the pyramid is forthcoming. Feel free to bother us to get it online faster. The system is designed with to withstand a 60 mph gust with a factor of 2 engineering safety margin. We plan to take down the fabric sides in the event of a wind storm. An anemometer mounted to the top of the tower will give us an accurate measure of windspeeds.
We welcome comments! Please e-mail pyramid-committee@egroups.com