Day 71.5 – 3D Printers are Ready

Engineering – I came in over the holidays to finish fixing and setting up my room’s 2 Printrbot Simple 3D printers.

They say it’s important to step away from teaching while on holidays in order to not burn out. I’ve been looking forward to this though, I’m interested in the technology and wanted the time to focus on getting them going.

I haven’t printed much yet. I had to swap out a z-axis, replace and cooling fan and then calibrate the z-axis sensor. I then printed a spacer part that the spools of PLA will sit on. So far things are going ok. Perhaps I will come in again to test print a model of a Greenland paddle, as part of a project I’m designing for Math 8.

Day 71 – Last Day Before Break

Hockey – Not a lot happened today. I had to say goodbye to a couple of students that were returning to their home countries of Brazil and Italy.  Most of my math 8 students wrote a quiz on rates.  And most importantly, the teachers once again beat the students in hockey. I played center and generally kind of sucked, but it was a lot of fun. I had problems with shooting and passing with my right elbow. This is left over from my bike accident years ago and the titanium plate in my forearm. I can’t put too much stress on this arm or the bones/plate/tissue/stuff really begins to hurt. I’ve been strengthening the arm but it’s still a weak point for me.

Day 70 – Onshape

Engineering Physics – I had students sign up for as this is the program that I would prefer that they use this year. Today is our last class for the year but once kids got started on onshape, they were very engaged.

Why choose onshape?

A little bit of history on me… I was a mechanical engineer for 15 years and did a lot of 3D modeling. I was first introduced to Pro Engineer in 1994. Pro/E ran on $15,000 unix stations and the software was $11,000. We also used AutoCAD on our desktop PC. A few years later I was using Solidworks on the PC. Solidworks had a typical windows UI and a $4000 license, and was a huge improvement for users imo.

Years later I wanted to do some 3D modeling at home. Solidworks was selling a $100 educator license but the license expires after 1 year, so that was too expensive. Pro/E had its educator software for $100 with no expiry date, so I purchased. It worked ok, but I was shocked at how “unix like” it still was. I think this was around 2010.

In 2014 I took another look at 3D modeling software and found out that Autodesk was giving free licenses to educators for its Inventor Pro software. I installed it and was blown away. It seemed like it was pretty much a copy of Solidworks and it was free. Fantastique! The only downside was its huge hard drive space needed – something like 30 GB. I guess I could get it down by uninstalling certain features. But HD space is a bit of an issue these days now that my notebooks have smaller SSD drives.

This past year I started reading about AutoDesk Fusion 360, which is a cloud based solid modeling package. It is based off of Inventor, it’s free, and it has pretty much all of the features I need without taking up HD space. Doing some searches then led me to Onshape. Onshape is similar to Fusion 360, and it was created by the folks who made Solidworks. I checked it out and liked it even more. So Onshape it is!

There a many other 3D modeling programs out there, some are surface modelers (Sketch Up) and some are solid modelers. I would stay away from surface modelers especially if you are going to do 3D printing. Some of these packages are a lot simpler than Onshape but I’m not sure they are any easier to use. At the end of the day, you have to: sketch on a plane, extrude your sketch, do more sketches and do more extrusions and cuts. So I’m only going to explicitly teach Onshape but of course I will help students if they want to try some other software (at their own peril).

Day 69 – Shortened Math Class

Math 8 – Today was a shortened day. The fun part was going over rate questions and some students being unsure of heart rate before and after exercise. That led to us all taking our heart rate and then I got the students to run on the spot, do jumping jacks and then do burpees. We went around the room saying what our heart rate. Some students would say they lost count, at which point I would tell them that there isn’t a law against starting over.

It was all kind of fun, but the lesson did reveal that undercurrent of helplessness. I didn’t count right the first time, therefore I can’t do it.

Day 68 – Phrustrating Physics

Physics 11 – Today we had two main tasks. First, the students wrote a quiz with 4 different learning objectives: drawing force diagrams, determining if forces are balanced or unbalanced, knowing what vectors are, and Hooke’s Law. In general the quiz wasn’t done very well and since there were four learning objectives, class overall averages dropped by almost 5%. I think many students simply did not study.

We also finished the Fnet lab and analysis. I’m very fuzzy on whether it was worth it.  These videos are best used as secondary teaching tools, but I used it as the initial tool since we don’t have good (ie any) lab equipment for Fnet experiments. I really hope to get some probeware next spring so we can do labs like this hands-on. Doing this exact lab with probeware means that:

  • lab software shows the x-t and v-t graphs instead of abstract numbers and calculations
  • each group can ran multiply experiments with relatively quick data collection
    time can be spent on analyzing and thinking, instead of calculations

Day 67 – Ratio Quiz

Math 8 – Students had a quiz on ratios today and they did pretty good. By far the biggest problem students have is determining what is being compared in a question. In the above question, students that struggled had a hard time figuring out what the ratio 2:3 referred to. Once this is figured out, the rest seems to go ok.  I think we ended summarizing that ratio problems involve three things: determining what is being compared, working out equivalent ratios, and then determining which is bigger.

Day 66 – Fnet Direct Measurement Video

Physics 11 – Students analyzed a video which shows a fan cart accelerating on a low friction track. Through some data recording and calculations students were able to find the force of the fan and the acceleration of the cart.
I’m very unsure of the usefulness of this lab activity. The real goal of seeing and thinking about force and acceleration is likely being lost in calculations and figuring out what is going on with the video.  Stay tuned for next class…

Day 65 – Bathtub Problem

Math 8 – Today students worked on the bathtub problem. It was totally solvable and as a result we saw a lot of success. The problem was difficult enough to stimulate discussion and reveal initial misconceptions though. Most groups first thought the solution would be 45 minutes. I think the logic was that if you add an hour and 30 minutes and then average/split it between two, you get 45 minutes. Listening to student conversations, there would inevitably be someone who would speak up and say something like, “That doesn’t make sense! If you use just hot water it only takes 30 minutes, it can’t take longer by adding even more water!”

Day 64 – Arduino Sketches

Engineering Physics – While some students finished their timer sketches last week, many are still working on theirs. However, most students are very close to finishing. I’m asking that students put comments in their code. There are two schools of thought on commenting code: comments should explain what you’re doing; comments should explain why you are doing what you’re doing.

For this project I’m asking students to comment using the latter scheme. I don’t need to know what the if statement is doing, I want the student to clearly explain why they are using it. I’ll go through the programs and give feedback on this.

Day 63 – Least Common Multiple

Math 8 – Today was a pretty quiet day. The kids did some practice questions, and we spent some time going through what is a Least Common Multiple. First I had to find out if the students actually knew what an LCM is, which was a harder job than what you’d imagine.


We finished with voting on finding which ratio is bigger. This led to a good discussion on comparing ratios, equivalent ratios, and problem solving. Which is bigger, 17/32 or 17/33? This can be confusing, but students know that 17/2 is bigger than 17/33. Therefore 17/32 has to be bigger than 17/33.