Instructables - INVENTING SOMETHING TO DO WITH a OLD TRUNK IN THE BACKYARD

I have an old trunk in my backyard
The trunk is 18 ft height and the diameter at the top is 2.8 ft

I think I am obsessed with the geometry of truncated Icosahedron
(These and all others Platonics and Archimedians geometric solids)
but for this project, I will built a regular geodesic sphere

On the top  of a tree trunk in my backyard

before I do the real one, i decided it is better to make a prototype.  (I know all implications that occur when you scale a model or make with different materials :)

Dimensions for the real sphere:
To build a sphere with a radius of 4.25 feet requires:
70 Struts 2.63 feet each bend angle 18o
60 Struts 2.32 feet each bend angle 16o
52 Bolts, 52 Nuts, & 104 Washers


Originally I was at Safeway and bought 2 boxes of 100 straws for $3.99
Then I calculated the size of the straws based on the maximum possible length of the straw (5.5 inches)

Dimension for the model
The maximum possible size of the straw was 5.5 inches:
70 Struts 5.5 inches each
60 Struts 4.8 inches each
52 Bolts, 52 Nuts
model trunk diameter 5.99 inches
model trunk height 37 inches

The first step was to cut 70 straws (Struts) with 5.5 inches each and cut 60 straws (Struts) with 4.8 inches each. I made a small device to guarantee all cuts were the same without needing to measure one by one. I used a heavy trunk and a side of a table as a reference to cut.  I measured one time only, the heavy trunk did not move, so, all subsequent cuts are the same. (this technique guarantees the quality of the production process)

I bent and made holes in both sides of all 130 straws

I assembled the first pentagon with the short straws (4.8”) inside and the long straws (5.5”) outside.

I then assembled 11 other pentagons (total 12 pentagons) all the same.

The first assembly step was, in each vertices of the pentagon, I attached another vertices of another pentagon

I then attached the sides of the all pentagons

By repeating this operation again and you will have two half spheres ready to be connected.

Connect the 2 vertices of each pentagon with the 2 other vertices of  the other 2 pentagons 

I made it at Techshop

after that I got a piece of a tree trunk (diameter 5.99 inches and 37 inches in length)

I tied the geodesic sphere to the trunk

To mock the final product of this Intructable

Once the prototype showed satisfactory structure and stability, I decided to go for the real project

To make a quick test on the real size, I was at home depot and bought 5 pieces of 10 foot ¾ EMT Conduit 

After that I made 3 cuts in each. Two cuts with 2.63 feet (2” 7’ ½) and one with 2.32. (2” 3’ ¾) the result was 4 struts, 2 with 2.63 feet and 2 with 2.32 feet

Filed the ends

then bent all ends

then, I punctured to make a hole in each end

I made a 25/64 diameter hole in each end

After that I bent all ends with a angle of 18 degrees for the long ones and 16 degrees for the short ones

with all struts, bolts, washers and nuts ready, I started the assembly of one pentagon to check the overall process

Looks good

The next step was to buy 28 pieces of  10 foot ¾ EMT Conduit and make 11 more pentagons a total of 12 pentagons
About 320 feet of conduit ¾ 10’ (1408 Lbs ~ 700 kg)

As you can see, I made it at Techshop

The only step I feel deserves a comment in this part of the process was when I took all the remaining pieces,
with the support of the Dream Consultant of Techshop to help me find a better way  to quickly band the pieces to the correct angle 

Then I assembled the 2 half spheres

(see the video Instructable - Geodesic Sphere)

and put the two halves together to make my geodesic sphere

(see the video Instructable - Geodesic Sphere)

Then I drove home with my sphere safely tied to the bed of my truck

After 1 day I revised all plans including the detailed process to assemble the Geodesic Sphere in the top of the tree trunk, after all that, I discovered that the tree trunk did not reside on my property  :((

it was a bitter discovery,

well, anyway, never give up

any suggestions as to what I can do with my sphere?
be nice :)