Just so you are clear. I am working on a 5/8 3v "hub and strut" dome. I am using the directions colin provided to make this into a flat base dome (with 5 stut types) on the thread "issues with 3v". The dome radius is as stated 3535mm.
The question I need answering is:
Are the spaces between the drill holes worked out relative to the number of holes?

[ Comments 8 ]

posted by
David

12/04/2007 12:30:57

Forgot this part
So for hub with a circumference of = 228.8mm; would this make 6 spaces of = 38.1mm (228.8 divided by 6) ; 5 hub spacing = 45.8mm; 4 hub = 57.7mm.

posted by
Colin

12/04/2007 15:37:27

Hi David
Use angles (in degrees) rather than spacing (in mm)
If you use the 57.7mm spacing method for the 4 way base hubs you`ll end up with 90 degrees between the struts(+).You need 60 degrees between the struts and therefore use only half the tube circumference on the base hubs.

posted by
David

12/04/2007 22:18:10

I assume that it is 60 degrees for all hubs (6/5/4). Drill one hole and measure degrees out from that.

posted by
colin

13/04/2007 02:12:23

The angle will be from the center point of the hub. Pentagons use 72 degrees (360/5) and hexagons use 60 degrees (360/6). The base hubs are half hexagons so they also need 60 degree angles.

posted by
ryan

20/01/2008 19:37:59

for colin: here you state that the six-way connectors and base connectors have equal angles of 60 degrees. Yet, under you 3v hub and struct construction method.... it looks like certain 6-way connectors have angles from 62 to 56 degrees.... which is the corrects spacing angle...or does it depend on the method?

posted by
Colin

22/01/2008 04:39:26

Hi Ryan
The latter angles (62-56 deg) are the technically correct ones. The 60 deg angles were provided to simplify things for building a first time basic dome frame. With hub and strut domes, you`ll find the small clearance of the hole drilled in the hub will allow a fair degree of movement, well beyond 4 degrees :)
Another variable is that timber is seldom straight or square :)
Having said that,it`s always better wherever possible to work to a tolerance of 1mm and 1 degree. Domes are quite forgiving though especially larger domes. In comparison, very small panel types domes will need the accuracy and craftmanship of a swiss watchmaker if its going to fit together perfectly :)

posted by
Colin

22/01/2008 15:00:35

Just to clarify the angles illustrated on the "Make your own 3v geodesic dome hubs" page.
Some (5 in total) of the base (4 way) hubs are all 60 degrees and some are not. You will need both types, the plain green 60 degree ones (5) fit in the middle of the half hexagon and the multi-coloured ones (10 in total) with various angles fit to the bottom corners of the base pentagons. Five of the ten multi-coloured hubs are reversed as the pentagons have a left and a right side resting on the ground.