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What I learn from Hadi
I just had a long meeting with Hadi Sajadi and I need to jot down some notes.
The 3/4″ pipes will not stand up under 90 mile per hour winds at 16′ lengths. So we have several ways to deal with this:
- We can use large diameter pipes. but this will ruin the aesthetics of the sculpture.
- We can lower the height of the piece altogether, but this may not work in such a large space.
- We could build into the plan a way to repair the sculpture if it breaks in high winds.
- Or use a combination of all three methods.
From the pods down to the rods we are structurally sound if we increase the wall size of the branch assembly by about 50%.
The rods could be 1/4, 5/16 and 3/8″ diameter. (1st compromise).
The overall height could be 24′ (2nd compromise).
The center stalk could be 1 1/4″ diameter SCH80 pipe (3rd compromise).
The tall outer stalks could be 1″ SCH80 pipe (4th compromise),.
The short outer stalks could be 1″ SCH40 pipe (5th compromise).
At a lower size this might not add too much to the budget…must calculate.
I must start writing a good paragraph explaining why we need to build in a maintenance clause in case of catastrophic storms.
What Hadi did agree with is the base design.
New thought…
What if the rise from the top of the vase base to the top of the shortest stalk was reinforce with guy wires. This could get that extra 6′ back. We might be able to run the guy wires further up if we can make them an attractive element of the sculpture. I must build it in fusion to see what it looks like.
Intro
The budget is $25,000, which is low for this kind of sculpture. So we’ll need to be careful not to promise more than we can deliver.
Much of the engineering issues have been worked out via trial and error. The prototype is still standing through this difficult winter so we know we are close in terms of structural integrity.
Overall Dimensions
The sculpture we are proposing is called Prairie Grass. It is 32 feet tall.
The base is in the shape of a slender vase and is made of core-ten steel, measuring 10′ tall and 28″ at it’s widest diameter.
There are nine stalks of grass. Eight stalks create a 1-foot diameter circle with the ninth at its’ center. The stalks are 3/4″ SCH40 stainless steel pipes at various lengths. The tallest (center) stalk is 16′ and the shortest is 4′.
We will need 5, 20′ by 3/4″ stainless steel pipes for the 9 stalks. At $170 per that is $850.
The branches are made of stainless steel rods ranging from 5/16″ down to 3/16″ in diameter. The seedpods are 3d printed in ASA filament.
Issues of Concern
The sculpture will be in the center of an apartment complex that wraps around it on 2.5 sides. See site render at top of page.
The site circle is quite large and will also accommodate visitor parking. The sculpture will need to be large enough not to be dwarfed by such a large site.
“Prairie Grass” is a kinetic sculpture. Even a gentle wind will keep it in constant motion. Movement will greatly enhance the artwork’s physical presence. And the fact that it is 32 feet tall will help it fully occupy the space.
And after dark it will command a much stronger presence as it will be lit from below with a programmable LED flood light system that changes color in response to weather forecasts.
Hadi, our engineering concerns revolve around how to build a structure that can remain flexible and still stand up to 90 mile an hour winds.
Seedpods
The seedpods are 7″ by 1/2″ in diameter. For this project they will be all white.
The seedpods shown here are made from PLA filament, which is made from plants. However, PLA is not recommended for outdoor use because it is susceptible to UV light. So we will be using ASA filament for this commission.
An advantage to using ASA is it is much stronger. The disadvantage is that ASA is more difficult to 3d print because it requires an enclosure with temperature control and venting.
Cluster Creation
We explored a variety of ways to create clusters of seedpods at the head of a branch. This method works best.
The stainless steel wire between the seedpod and the branching structure is 1/16″ diameter stainless steel. It’s actually sourced as stainless steel welding rod (Blue Demon ER308/308L).
Cluster Branch Housing
The cluster branch housing is 3d printed in PLA but will be printed in the stronger ASA filament. The housing loosely slides down over the stainless steel rod.
We have designed STL files for 1/4″, 3/16″, 5/32″ and 1/8″ rods. However, the increased height of this project requires that we increase the rod sizes to 5/16″, 1/4″ and 3/16″. The two lower sized rods could kink in high winds. They haven’t so far but I’d rather sacrifice a little movement than take the chance.
The 1/16″ stainless steel wire is dipped in glue then inserted into one seedpod all the way up to about an inch from the top. Then the other end of the wire is glued into the branch hole, which goes all the way down to the stainless wire.
Hadi, we used clear Gorilla glue for the prototypes, but I’ll be looking to you to specify the best glue to use for longevity. Note, this is a time-consuming process so a two-part glue may not be practical.
These need to be redesigned with 50% thicker walls and 3d printed with ASA instead of PLA. -Hadi
Primary Branch Attachment
Currently we are using 3d printed plugs between the primary branches and the stainless steel tubes.
These plugs will need to be redesigned for the 3/4″ stainless steel tubes, because the prototype was made from 1/2 inch electrical conduit. We used this method for the prototype because we do not have welding capability in house.
Note, we are trying to make it possible to install this sculpture without using heavy equipment. However, depending on how heavy the vase base is, this may not be possible.
This should work fine and it allows for easy removal if damaged. -Hadi
Also, these will be printed in ASA with 100% infill, which means solid. -Remo
The Vase
The prototype did not have a vase. We added this to try to get more height and make the sculpture feel more substantial and less susceptible to vandalism.
The vase is formed of 8, 28″ x 10′ 1/8″ core-ten steel blades welded together to form the vase shape.
This should be able to be made out of 2 sheets of 10′ by 4′ 1/8″ core-ten steel. Each sheet cost $460. We estimate this can be fabricated for $2500 including the cost of materials, but we could be off on this.
It would weigh about 400 lbs. I wish there was a lighter less expensive way to create this vase base.
If base is submerged in concrete, coat with black tar before poring. -Hadi
Hadi, the holder for the nine stalks is 3″ deep. Do we need more depth?
Yes, must be 6″ deep. -Hadi
The steel is only 1/8″ (11 gauge). Is this enough? Well we need any cross bracing?
This might need to be 3/16″ -Hadi
Is there a better way to do this?
Yes, spot weld it during installation so it can be easily removed if damaged. -Hadi
The Branch Structure
Each stalk pipe can fit up to 7 rods depending on the diameter of the rod used. We plan to use 6 rods per stalk. The first and tallest is the only 5/16″ rod used and it goes in the approximate center. Then one 1/4″ rods and four more 3/16″ rods will fill in the gaps. There might be room for two more it we found it necessary.
All these sizes and need to be redesign for large diameters once we decide what changes need to be made to ensure structural integrity. -Remo
Number of SS Rods
The rods come in 12-foot lengths.
5/16″ costs $28 each. We will need 5 lengths = $140.
1/4″ costs $18 each. We will need 5 lengths = $90
3/16″ costs $12 each. We will need 14 lengths = $168.
Total cost for rods = $398.
More Facts & Figures
Here are a few for stats that should help with stress testing.
- 9 stalks hold 6 rods in each
- Each rod holds 10 wires/pods
Soo the total number of pods is 540.
- 3 bunches of wire/pod assemblies weigh 1 pound.
- 10 pods/wires make a bunch.
So all 540 of the pod/wires and holders weigh about 18 pound.
The 9 stalks (3/4″ SCH40 SS Pipe) are the following feet in length. 18, 16, 14, 12, 11, 9, 8, 6 & 4…totaling 98 feet.
The rod lengths are as follows.
9 – 5/16″ diameter SS (5 – 6′ long)
9 – 1/4″ diameter SS (4 – 5′ long)
36 – 3/16″ diameter SS (2 – 4′ long)
Total length 108′