Thursday, March 30, 2006
Molds, molds, molds... molds
The piece came out very nice. The color is great. We do have to refine our fabrication technique a bit because there are still a lot of little (and less little) flaws here and there.
It takes much longer to do all the molds than we were afraid of... even Peter joined the fabrication line to finish all the pieces. aaaaarggggghh.....
New fabrication procedure (yet another test!)
To have more control over the consistency of the wall thickness of our pieces, we decided to make two seperate parts that have to be connected afterwards. This guarantees that the layers are layed properly, because they can be reached at any point, and that the integrated aluminum joint sits in the right position.
We added some blue pigment. We -on purpose- didn't put enough color in the resin, resluting in this nice transparency that you can see on the image.
We drove all the way to Springfield, MA, to buy fiberglass and resin. After talking to Joe, the fiber-man, we decided to go for polyester resin instead of epoxy. It is much cheaper, cures much faster, and is much stiffer than epoxy. Sounds exactly what we want/need. We also bought more expensive fiberglass cloth: a bi-directional weave with fiberglass mat stitched to the back that allows us to build up thickness much faster and to absorb the resin better.
We started what seemed (and later prooved to be true) a crazy task: assembling the six molds that would allow us to work in parallel.
Since polyester smells extremely bad, we decided -in order not to loose our paint shop privileges- to do our tests with the new material outside. The quick tests done yesterday came out very well and look really promising!
Thursday, March 23, 2006
Crushing the boomerang
Our five foot long piece didn't fit in any of the load testing machines and therefore we had to build a frame to test it. Stephen Rudolph and Dr. John Germain from the Civil Engineering testing lab set up the frame and ran the test with us. They helped us out even though we asked them on very short notice. Thanks!
The piece failed due to plate buckling caused by the bending moment induced because of the boomerang geometry. This loading case was chosen because we wanted to proove that the piece would still hold loads in an extreme state when anything else would have failed. Well... it didn't! It only held 500 lbs... but we learned some valuable lessons. With a small -and hopefully last- design iteration we can prevent this.
Let's conclude that luckily we did do a load test?!
Tuesday, March 21, 2006
Opening the sarcophagus
And there it is: our first structural element!! We succesfully took the it out of the mold, only damaging the mold slightly. The ceran wrap that had to prevent the piece to stick to the mold did an excellent job. It needs to cure a bit longer, but it feels already extremely strong and stiff. The real test will be Thursday when we load test it in the Civil Engineering Lab.
The model for the mold, with cutting files integrated, is made enitrely parametrically using Catia; the pieces cut with the lasercutter and assembled using puzzle pieces. Exciting to see that this extremely lightweight mold seems to perform pretty well! We included all the hardware (axles, cable/muscle connections, pulley system...) so that this prototype resembles the actual piece as close as possible.
Hopefully the "boomerang" comes out of the mold as we "expect"?! After approximately 48 hours of curing we will know.
Wednesday, March 15, 2006
Tuesday, March 14, 2006
3 seconds of eternal fame and glory?
Today we were invited by the BBC to talk about our mini-skyscraper. After a lot of waiting, we finally got our chance for 5 (?) minutes of fame. We were interviewed by the very tall Dan Cruickshank. So... if everything goes well, we'll appear in Dan Cruickshank’s Marvels Of The Modern Age, a documetary on the future of architecture on May 30th on BBC2!!
Good news from Festo, fabricator of pneumatic muscles. They are very excited about our project and offered to sponsor us! Not official yet, so, let's wait and see....
Sunday, March 12, 2006
Mold for fiber glass pieces
We will use a negative mold with a inflated blatter on the inside to form the fiber glass boomerang elements. The mold can be cut on the lasercutter out of 1/8" plywood and plastic. This allows us to "outsource" this process to friendly helpers.
Making a parametric model of the cutting pattern for the model wasn't as obvious...
Tuesday, March 07, 2006
A paper mockup (half size) of the negative mold for the boomerang pieces. It is made out of developable surfaces. The actual mold could be made in the same manner using very little and cheap materials (wood and thick plastic), using the lasercutter since every piece fits in the bed of the machine and the process is fast and reliable.
We started ordering materials today. The budget is rapidly disappearing!
It is getting there...
The new scheme is based on our calculations. The shape is responding to the forces in the system creating a more elegant structure. It is interesting to see how the structure -all of a sudden- starts to make sense when it is no longer 'random' but following the flow of forces.