Montreal / Hexagram

You would think that after an epic marathon 2500 kilometer drive across the Canadian shield [in a Hyundai no less], a whirlwind tour of Ottawa, a new baby [and accompanying adventures... congrats to Darcy and Tanya and baby Petter] and exploring Montreal, that one could call it a successful trip and be done with it. This was only the adventure leading up to our hexagram adventures.

Our team: Kai Chang, Rachel Tennenhouse, Andrew Workman and myself, came to hexagram with a minimal understanding of what our collaborators from RPI had created in terms of a pneumatic structure in which we were supposed to embed / integrate our electronic devices. Up to that point, the only communication we had was a few teleconference calls fraught with technical difficulties and PDFs. Kai and I had worked late the nights before our driving to devise an environmental sensor that would work with inputs from human and pneumatic interaction. I'll import the posts from the pHnAeCuK blog for some illumination on these. Beyond that, we had only raw materials and some possible ideas with which to work with.

After much discussion and brainstorming, we decided to attempt to create a feedback loop that consisted of optical, acoustic, and physical triggers and responses. The loop / system was to be initiated by the environmental sensors that would respond to contact and changes in air pressure of the upright tubes. These would in turn send signals to the acoustic circuit - which would interpret / modify / emit the signal which would then in turn be sent to a acoustically triggered car. After being triggered by the sound, the car would move about on a tether attached to the structure. This movement of the structure would in turn cause the structure to deform and cause the tubes to jostle eachother, again triggering the environmental sensors and perpetuating the cycle.

Before we could set about any of these tasks, we first had to refine the pneumatic structure. Our major concern was air loss, as an array of leak points in the system meant we required a much greater air [ and louder - acoustic interference ] air supply. This also effected inflation times and structural rigidity. The main points of loss were the end seams of the tubes and where the tube attached to the PVC framework that served as its air supply. Each tube was constructed out of a solid cylinder / tube of 3mil polyethylene plastic bagging - sort of like the roll of bagging found for supermarket produce bags, but bigger and stronger. These were then welded with a single simple seam a la heat gun and pressure, and attached to the PVC frame /air supply with elastic bands.

My solution to these issues was twofold: For the welded seams at the top, there was a serious weakness in the actual sealing system. By folding the material over successive series of welds produced both a better seal, and meant that the force created by the air pressure was applied to the material itself, instead of applying tensional stress to the welded seam.


To solve the air leakage at the frame, Kai and I needed to make a trip to the local Canadian tire [about 10 blocks away, and POURING rain each time we had to go]. The seal was constructed out of automotive heater hose, ATV UltraBlack gasket maker / sealant, and some gear / screw clamps. The heater hose's purpose was to both increase the circumference [surface area] that the tube would contact with - meaning the tube could sit flatter with a minimal series of folds that air could escape through, and to provide a softer material for the clamp to sink into and improve the seal. The ATV went in between the heater hose and the PVC, sealing the connection and affixing the assembly to the frame. ATV should have been applied between the tubes and the heater hose, however we were constantly taking the tubes on and off, so this would have gotten rather messy.

I hope to get some drawings finished that will hopefully provide some clarity to all this. Ill put them up when I can. Anyways, the system was incredibly successful - the overall system still lost a little air through the vacuum and pinpoint holes, but our test bags held air at incredible pressures for sustained periods. In addition to max pressures from the compressors [about 100 psi], it even survived getting ridden rodeo style by Kai. I wish I had pictures of this, but honestly I was laughing too hard.

With the pneumatic system effectively functional, we shifted to electronics.
This is getting a little long here, so I'll continue this in the next entry.