Week 11- Super glue and baking soda

During my time in secondary school I had many of opportunities to build circuits for different projects I was undertaking. For the most part though it was a case of finding a suitable circuit to make for the project with small changes rather than designing myself. Even for my final project, the skeleton of the circuit was predetermined and there wasn’t much room for changing it other than programming the chip to carryout outputs depending on the inputs. For one of my group projects here, I am designing and building a breathalyser. This time round though I designed the whole circuit and then the printed circuit board (PCB) layout. We sent off the design to be made and I’m looking forward to getting back my very own PCB that I can then solder the components into.

I had a small respite from project work to head to kayaking on Tuesday evening before we were due to laser cut the airfoils (blade cross sections) for our wind turbine on Wednesday. As part of a different module, I had spent most of the previous weekend running code and all of Monday figuring out the optimum blade cross section for our solution. One of the other team members took on the role of turning the design into a CAD model and a set of drawings to be cut. Unfortunately, he made the CAD on the 2017 version of Solidworks. This meant when we came to cut the foils, the files wouldn’t open on the university computer system. Thankfully we were told we could come back on Thursday to cut if we sorted out the drawings. The same guy ended up redoing the entire thing on the 2015 version, ready to cut on Thursday.

Thursday came and we cut out the foils successfully on the laser cutter. Each foil has two holes in it for struts which connect it to the neighbouring foils. The idea behind this was to add stability and to make setting the angle between each foil easier (the foils are supposed to taper from nose more into the wind to nose more perpendicular to the wind). I had checked that the first CAD model was correct but I had assumed that it would be redone exactly the same. As you might have guessed, it was not. The tapering of the angles was in the wrong direction which would make the blade highly ineffective. We spotted the mistake when we tried to put it together without glue just to get a feel for it. I went back to the lab technician to see if it would be possible to cut again but was told the cutter was fully booked for the next week. I asked for her to let me know if it comes available and that I’d come running so hopefully it all works out!

Now that we essentially had an entire spare set of foils we had a bit of room to play around with gluing methods. We did some experimentation with hot glue, super glue and other impact adhesives before discovering that super glue reacts with baking soda to harden almost instantly and forms a very strong bond. Doing more research, this method can be used to fix car radiators so would definitely be suitable for our needs. Although, spooning out white powder with a little metal spatula in the corner of the lab is perhaps a little suspicious looking. I just didn’t want someone using the idea!

Considering how the week went in terms of that project I thought a lesson of the week regarding failure would be appropriate. I was learning about testing materials and products before they can be brought to market and how testing, particularly in the aerospace industry, can be very rigorous. There was a new plane design being proposed and it went through the various tests, starting with strength and stress testing and then moving onto fatigue testing where they set up a giant rig and recreate all flight conditions many times to see how the plane would cope. Once the limit was reached they divided this by four as a safety factor meaning that it would need repairs 25% of the way through its projected lifetime. Yet, somehow, the planes were crashing after about 20% of their projected lifetime. Three or four planes crashed or failed before they realised that by testing the plane’s strength and stress capabilities, they were work hardening the metals (metals can be made harder by changing their crystal structure through force such as a swordsmith beating a blade with a hammer just after casting). This meant that the tested planes were stronger than the ones just being manufactured for flight!

At the end of the week I met up with some of the hikers from the Abel Tasman and enjoyed some music in one of their apartments. There was quite a lot of Frank Sinatra played. On Saturday, I had frisbee training before I watched one of my teammates play for the NZ u20 team against the Australian u20 team in Australia via live stream. On Sunday, there was supposed to be a frisbee social event during the day but due to thunderous downpours it was cancelled. I ended up filling the day with cooking, cleaning and doing more project work before I borrowed Harry’s car to go do a shop for the rest of the semester as I had finished off my supplies. The shop included 10kg of potatoes, 5kg of rice, 5kg of pasta, about 30 tins of beans, sweat corn, chick peas, lentils and chopped tomatoes, 5kg of oats and plenty of sultanas among other things! The freezer is looking well stocked and I’m ready for the weeks ahead.