Thursday, January 21, 2016

This week on big fred's cosplay and engineering shop! Death by FEA! Quadcopter Design! Oh my!

This post is...3 months late. I've been lazy. But things are changing. so here it is now, with more stuff than planned!

Dark Repulsor

As per my usual forgetfulness, I didn't take pictures of the beginning of the build. So here is where I started actually taking some.

So I ran into some issues. I tried using the router to get he blade part down to thickness, but being the careless person I am, I mixed conventional cuts with climb cuts. Now, normally climb cuts on a router table are dangerous, but I was cutting through at most 1/8th inch at most, with a tiny half inch bit, so I wasn't too worried. The problem is that, on a climb cut, wood acts a bit like brass, and the bit tends to bite. It bite so much, that the bit can actually get pulled out of the router! This happened a bit here. Since I will have to cast pieces for this sword, I decided to take the repair as a practice in casting. I taped the side and cast resin into the depression. It worked surprisingly well! I did screw up though since I didn't have much 5 minute epoxy left, I mixed it right IN the hole, so I ended up with some uncured resin inside the patch.

So much filler resin!

Then I started scribbling directly on the base of the blade to do the...dragon...decoration...THING.

Which I then imported into Inventor and traced in order to print.

Death by FEA and quadcopter design

GMC-4351, Conception Assisté par Ordinateur; Computer assisted design, my nemesis. Sincerely, this class has been the worst one in my whole program so far. It had promise, and then failed them. It's a 3 credits class, but takes the time investment of at least 6 credits. Not only that, but it is overly theoretical. The teacher really doesn't help; his classes are a mess, his notes are...well, he doesn't get through his notes, but they're more math-heavy than the Kreyzig (A math reference book that pretty much has all the math ever used in engineering). We spent half the semester studying curves (Hemite's splines, Cubic Splines, Bézier curves, B-Splines), and we're barely starting to see the theorethical background of FEA.

There is one good thing coming out of that class though; We have to do a project. Since my partner didn't have an idea, and because we have so many people from GAUL doing analysis on the rocket, I convinced him that we should design my quadcopter's frame. So instead of just rule-of-thumb designing it, we'll be doing proper FEA on it, so that's cool. It'll also force me to actually work on it...which...erm, I was about to do! I swear! I wasn't looking at batteries for the Mango Scooter! Nope! Not at all

To simplify the design, because at first the teacher hinted that we'd have to do some FEA by hand...or at least build the general rigidity matrices by hand, we went with everything being straight;

Von Mises equivalent stresses on the MK1 structure
MK1 was way too flexible for my taste. Everything was 3mm thick carbon-fiber-isotropic-equivalent, in order to simplify stress calculation and then do a layup based on the "flow" of those stresses. So we added a stringer on each side of each arm. Here's the displacement on the final MK3:

Mango Scooter

Or maybe I was looking at batteries...$300USD of batteries...and that would only give a...humm...let's see, 37 Volts motors = 10 S, 70 Amps/ 10*2.2Ah = 1/3.18 hours...or about 18 minutes...for 400 moose dollars(more like 500 as of the posting of this) of cells. That would be at full power though, so...realistically...maybe 30 minutes? Maybe I should just buy a hoverboard

2016 goals so far

After 3 weeks, those started badly. So far it's easy to do the time on rocksmith and my Ocarina practice. The 10 exercises are a bit harder. I should've decided on a time of study per week instead, which could have included reading books, doing exercises, studying with flash cards, and so on. So far, I've skipped every calculus exercises, concentrating instead on Linear Algebra. I've been reading Gilbert Strang's book on Linear algebra, along with watching his lecture on computational science and engineering (18.06 and 18.085 on MIT's OCW). For programming practive, i've been using CodeWars. So far i've been doing problems in Python...but I can't wait for C and C++ to be added to that website!

I also started slowly translating SPARC's rules in french in order to maybe try starting something in the area...maybe.