3v - 5/8 domes, useful information
Some example domes built with hubs
4m diameter we think.
Yellow: Short, Blue: Medium, Green: Long.
Thanks to Yanney.
With some metal band-strapping braces to further secure the hubs.
Thanks to Timo in Germany.
Metal band-strapping braces to further secure the hubs.
How many hubs?
61 in total.
6 x 5-way hubs
55 x 6-way hubs
When you build the dome, the bottom ring of 6-ways will only have four populated sockets. We use 6-ways here so that people can add another layer to their dome if they want to. You can also use two ball connectors in the spare sockets to connect your dome to your base.
How many sticks?
165 in total.
30 x Short sticks
55 x Medium sticks
80 x Long sticks
Our calculator tells you the lengths of stick you need for a given diameter.
Using another calculator
If you're using a regular dome calculator you need to take off 87mm from each length it gives you to account for the space that the hubs and ball connectors take up at the points. (Most calculators give you the point-to-point distances.)
Use millimetres as your unit for accuracy.
Using inches? – work to 1/16 of an inch.
Measured from the lowest points in the base.
A = 0.594 x diameter.
B = 0.563 x diameter.
C = 0.491 x diameter.
D = 0.457 x diameter.
E = 0.351 x diameter.
F = 0.317 x diameter.
G = 0.188 x diameter.
The base ring is made up of 5 x Mediums and 10 x Longs, and 15 x 6-way hubs.
10 of the base hubs will sit on a slightly higher plane, it isn't a big difference so you can chock or shim once in position, which is what most people do.
Note that the base ring is 0.9837 x the master diameter of the dome as the 5/8s base section is slightly smaller than the diameter at the halfway point. In practice that doesn't equate to much, but if dimensions are critical it's worth knowing that this difference exists.
You can investigate the Kruschke method which introduces an additional length to create a flat base, there is a calculator here. Choosing 'Kruschke' in the 'Subdivison method' drop-down within the acidome calculator also shows how to do this.
The principles of the build are the same as in the 2v; start in the middle and work your way out connecting as you go. If you can't connect then you need to lift the hub above to enable the connection to be made. Our core guides explain more.
The dome will be self-supporting up till 3/8s. The last layer can fold under as it's past the half way point and starts to come back in towards the centre of the dome.
For this step it's good to have a few extra people to help support the dome as you add in the last layer. In some cases we've built the 3/8s section to the side and laid out the base section in position.
You can then lift the 3/8s section up and move it over the base. Then one person can connect in the base layer. This works quite well. This film of the Pollution Pods art installation gives a sense of this process.
How many people?
For smaller domes 2 people can manage the build. 3 or more people is helpful for larger domes. And if you're going to lift the 3/8s section or move the whole dome into position then at least 5 people is advisable.