Prototypes and Testing

There are two prototypes:  Bamboo and PVC

*note:  Please see the "resources" page for much more detailed resources on how to do some of the steps described below.  They were incredibly helpful in our design process, so check them out!

Bamboo Prototypes

Heat treatment:

Overview:  
Step 1--use a propane blow torch on the surface of the bamboo.  This melts the wax on the surface, which can interfere with epoxy coatings.
Step 2--Place in an oven at about 390-400⁰F until the inside of the bamboo feels dry.  This will take practice, and we cooled the bamboo about every 20 minutes to monitor the drying process.  The purpose of this is to remove moisture, which can later influence splinting of the bamboo.  


Details:  
Great video:  http://www.youtube.com/watch?v=AT-UIWYepR4 (not ours, also in "resources" tab)
First, we just simply apply heat from propane blow torch until the bamboo “skin” turns brown.  The bamboo smells like popcorn during the process.  Remember to wipe down the bamboo after heat treating with damp towels.  
To treat the bamboo in the oven, we found that it is easiest to stick the culms directly on the oven racks (no need for cookie pans, etc.).  If you've never done this before, make sure to have some extra bamboo to experiment with.  Heat treat this in 20 minute segments.  Make sure you let it cool off after each 20 minute segment to access the dryness level.  You will notice a significant change in mass and sound produced (if you tap it on the counter) after significant moisture has been removed.  Bamboo will become burned/damaged if it is left in the oven too long.  Please note that heat treating bamboo often reveals existing flaws in the bamboo by making them more apparent.  When a small crack in the bamboo grows until the point that it deforms the bamboo (which it eventually will), this process is called "splinting."  Figure 1 shows the ideal results of bamboo heat treatment.  Figure 2 shows some extreme cases of "splinting," which we believe to have been caused by damage to the bamboo which occurred before heat treatment.  This damage included leaving the bamboo out too long in a very dry environment, which causes "popping"/splinting of the bamboo.  Since we ordered the bamboo from Oregon state (we wanted a species native to Kenya), which is very humid, this happens when you leave the bamboo sitting out in dry Arizona.  We should have started heat treating the bamboo ASAP after it arrived.  

Mitering

After heat treatment, we cut one of the edge of bamboo into 45⁰ angle by using a specific angle cutting saw as seen in Figure 3. We can also cut bamboo into specific lengths (5 inch) by using the “machine” cutting saw (a "band" saw), as seen in Figure 4. Then, we sanded the cutting surface so it had a smooth surface, as seen in Figure 5.  These tools were located in the machine shop of the second floor Design Studio in SCOB. 

Polyurethane Coating

When all the bamboo prototype pieces were cut and sanded, we applied polyurethane on the surface of the bamboo. We allowed the polyurethane to dry out overnight.  In Figure 6, Loc and Jenna were working on polyurethane treating in the fume hood. Figure 7 shows the set-up station when doing the coating process.

Joint Making

Covering the joint with hemp fiber and epoxy is considered as the most important step of the process. In Figure 8, Jenna and Loc were wrapping up the bamboo joint with hemp fiber (without epoxy, just for practice). We are supposed to apply hemp fiber after it is soaked in epoxy.  It should cover the joint, and there should be plenty of epoxy present.  This needs to be done in a fume hood or outdoors.  Make sure to read the MSDS first, and see our "project management" page for a list of exact materials we used.  After the joint is made, wrap electrical take (sticky side facing out) around the joint to compress it until it dries.  Let it dry overnight.  Figure 9 shows some bamboo wrapped with epoxy soaked hemp fibers under the fume hood.  Figure 10 shows the finished product of bamboo when the epoxies were dried out.

Testing

*at this juncture, this is not yet completed*
After finishing bamboo joint, we needed do to run tests on our prototypes to see if the bamboo prototypes (or more specifically, the joints) were structurally sound/strong enough for our device. The testing method idea was given to us by Dr. LaBelle. Basically, the different weights were hung from the joint until the joint broke or until we couldn't physically lift more weight only the joint.  (Shout-out to Clayton for helping life the 40 lb weights and to Micky for helping us learn to tie rope knots!).  One end of the string was attached to the bamboo joint, while the other side was attached to the weight. Idealy, the amount of the weight would be increased until the prototype reaches breaking/bending point. Measuring initial and final angles of the prototypes may also be useful.  We started from 23 pounds and ended with 40 pounds (we gave up on using heavier weights because of limited strength and experimental design). One 1 inch diameter prototype was broken at 23 pounds and one 1.5 inch diameter prototype was broken at 40 pounds. In Figure 12, Rachel was holding the bamboo piece at 35 pounds. In Figure 13, Clayton (a volunteer) was holding the bamboo piece at 40 pounds.

PVC Prototypes

PVC prototyping is used to calculate the dimensions and help to form a structure of the frame. Some 1’’ and 1 ½’’ diameter PVC pipes are used in this process. We also purchased some PVC corners and duct tape in order to connect the pipes together. Figure 11 displays some of the PVC pipes and corner we got from Home Depot and Lowe’s.  We are in the process of putting this together.  We plan on building the operation mechanism (gears, handle bar, etc.) concurrently so that we can combine the two.  This will further test whether the dimensions of our device are adequate before we build the final, bamboo frame.  

Figures 1—2:  Desirable and non-desirable effects of heat treating bamboo.

Figure 3—5:  Mitering and sanding bamboo for 90 degree angle joints.

Figure 6—7:  Polyurethane treating the bamboo.

Figure 8—10:  Process points of making joints from hemp fiber and epoxy.

Figure 11:  The unfinished PVC frame prototype.

Figure 12(left) and  Figure 13 (right) shows the process of doing the weight testing. In Figure 12, Rachel was challenged with 35 pounds. In Figure 13, Clayton was challenged with 40 pounds.