Category: Projects

Design Challenge: The Foam Wood Derby

I’ve always wanted to run a super face paced pinewood derby style race. As I designed some simple, messy projects for the 8th grade as sort of fun one off projects, I decided to make the idea a reality.

The design is simple. Each group (or individual if your group is small enough) has two deliverables. A car carved out of foam, and a top and side drawing of the car. They get a basic set of materials. A block of floral ‘wet’ foam, 2 axles and 4 wheels. And they get a simple set of tools. Basic measurement tools, speed squares and surform carving tools.

I introduced the challenge quickly, then let the students loose. To avoid having students completely destroy their blocks instantly, I made the drawings a prerequisite to getting the carving tools. The drawings could be simple, but I required a detailed full scale engineering style drawing.

Once the drawings were approved, they were off to the races. However, floral foam is mess. Super messy. I had complaints of allergy like irritation, the foam staining white shirts, dust in their eyes. All sorts of things. However, after stressing caution, using aprons and generally being more mindful, those complaints dropped off. Perhaps this would be a good project to do in a larger space or even outside.

With the designs carved, students were free to attach their axles and wheels. I could have stopped the groups and stressed the importance of being patient with this step, being precise and ensuring straight and square axles. However, I let them at it, though I did stress that our speed squares would be a great benefit to this step.

The axles and wheels came from Pitsco. Sure, you could 3D print wheels if you have the time, but laser cutting in wood was too soft and acrylic was too brittle. A soft thermoplastic is what these wheels need to be made of, and at $0.15 a piece, it was worth avoiding the headache.

Finally, we race. I used a scrap board at first…but we really needed lanes as cars continued to collide with one another. I used some foam board to make short walls hot glued to the edge of the board. Problem solved.

A simple single round elimination was enough to have a good final race, while minimizing the winners vs losers. You can even enforce a ‘When you lose, you become a cheering squad member of the team that beat you’, ensuring an exciting final race while making all of the students feel a part of the races through the end.

Finally, have students reflect on the process. I had a short discussion, then had students go and post to Seesaw. I got lots of really awesome reflections, lots of great critical thoughts, some great doodles and awesome photos.

Looking back, this little design challenge went pretty well. The kids loved it, it was inexpensive (~$1.50 per group), and was quick to run. In the future I think it could be slowed down to highlight the engineering drawings in more detail, perhaps print wheels, and focus on nice and straight axle holes.

Part Cost Cost / Kit Source
Floral Foam (72 when halved) 35.50 (price fluctuates on amazon) 0.50 Amazon
Pitsco Axles (100) 6.50 0.13 Pitsco
Pitsco Wheels (100) 15.50 0.62 Amazon
TOTALS 57.50 1.25

Surform Tools – $2.99

Speed Squares – $2.99


3D Printers as Construction Toy Factories

The 3D printer is the hottest tool to bring into classrooms these days. They are the talk of the town. In lots of ways, they are amazing machines. It possibly more ways, they are tricky classroom tools. Most of them take plenty of tinkering and tuning, print times are long (a 1 hour print for all 50 students in a grade can be a week or more in the making), upkeep is time consuming. Lots of little quarks.

However, where they have excelled in my classroom is in printing construction brackets. If we aim to print small parts to be used to let students build bigger structures you can kill a few birds with one stone. Print times are reduced, and you have a build to pull students away from the computer screen.


I wanted to share a few examples, and how I use them in my classroom. First up, the simplest. Brackets to join straws at different angles. I took inspiration from Makerbot’s Speedy Architect project for this one. These pieces are tiny, taking less than 10 minutes on our Printrbot Simple Metals using my super-duper fast printing profile. Currently, the 6th grade is designing architectural models using these brackets. They will be adhering to uniform proportional scale for the structure (about 1″ to 10′), and will be closely monitoring a the cost of production. Straws cost $100 per inch, and 3D prints cost their real life cost, times a thousand, or about $20 per basic bracket.


I’m super excited to see how this project turns out. There are lots of great math connections to the 6th grade curriculum using the scaling and the economy system. The structures are bit innocuous from the structural engineering perspective, but the amount of iterative design & 3D printing we can pull off while printing such small parts will make this project worth while. We are lucky enough that each of our groups of 4 will have their own 3D printer to operate during class time, keeping the project rolling at a fast pace.

Up next, there are the balsa wood brackets, that came from the Zazouck project on Thingiverse. These parts are a bit different than the straws in that I use them exclusively as construction tool. The parts are all printed ahead of time, sorted into different types and they are used to do rapid fire construction challenges. Most recently students were tasked with building a 12″ bridge, while controlling for the cost of parts and materials used to build the bridges.


These pieces are great for rapid construction. They lack in the structural consistency that using glued joints might give you, but they let students build quickly. Often, balsa breaks in the brackets, but a drill bit reams them out pretty easily. These are great bits, and took about 30 mins to print a set of each piece. To get a classroom set of about 20 of each part, I had the machines running constantly for a few days. But now they are done and we have our own custom construction set…in colors that match the labs floors!

Last up, we’ve got the most complicated component yet. The craft stick brackets. These pose the most difficult design process of the three, but I think it gives the most rewarding final product. Requiring constantly being aware of stick orientation in regards to slot location on the brackets. I think the challenge of the design makes these an awesome candidate for creating a lesson on using Fusion 360 assemblies to virtual design structures before printing them. This is something I’ve got in the pipe for the 7th grade next semester.
1025160920All of these follow a basic principle. Find a material that is cheap and plentiful in you lab, and design brackets to join them at different angles. Have students design the parts, even model the whole structure in CAD before printing. Cut down print times, end up with bigger and cooler parts…its a win win all around. Have you done any construction projects like this? Let me know!

Simple, inexpensive classroom woodworking projects.


I’ve really taken to woodworking this year. I think the ability to transition from high-tech to low-tech in the same space is a powerful experience for my students. Using the lovely mini-week program, I had 7 students for 3 full days of nothing but woodworking. We had a blast, and made lots of amazing things. Today, I want to take the time to show off some of these simple woodworking projects that were big hits, were cheap to do, and reasonably safe to pull off in the classroom.

The Pencil Holder – Introduction to Drill Press

The pencil holder is simple. Start with a 4″x4″ fence post, chop into square 4″x4″x4″ chunks, and let students drive holes to fit pencils. I used an 8′ piece of douglas fir from the big box shop that cost me around 10 bucks. That’ll make 24 pencil holders at a cost of about 40 cents a piece.  I let the students mark out the center points for their holes, and let them at it.

The Tea Candle Holder – Introduction to the Miter / Hand Saw


The tea candle holder was a simple project. Start with a 2×4, cut it down to about a 12″ section, and drive 3 holes for tea candles using a spade bit. We rounded our corners using the belt/disc sander, and one student split the 12″ section into 3 separate pieces. She even finished with contrasting dark danish oil and boiled linseed oil. It turned out amazing!

Simple Cutting Board – Introduction to the Bandsaw


The last simple project was a cutting board. I picked up a 6′ length of 7″x3/4″ poplar board from the big box store, and split them into cutting board blanks that were around 10″ long. The challenge was to sketch out a simple design to give the board some character, cut it on the bandsaw, and put down a coat of mineral oil. This was super simple, and super rewarding.

The Finishes


I wanted the students to experience the challenge and joy of finishing their projects. That meant lots of hand sanding (foam sanding blocks are worth the investment!), and hand rubbed oil finishes. I had a small selection to choose from, a danish oil, boiled linseed oil, tung oil finish and a wipe on poly. This final step in each of the projects too the experience above and beyond and the students had a blast.


Woodworking doesn’t need to start off with complex joinery, or fancy hardwoods. Some of the best projects take just a few cuts, a few holes and a coat of finish. The students had a blast learning about the tools, and were all extremely proud to walk out with all of their projects.

Experiments with the ESP8266


I’ve been meaning to jump on the Internet of Things bandwagon, but I’ve just been a bit turned off by the price point. I built a simple temperature logger for my fermentation fridge using a Spark Core, but the experience was not that straightforward…or as straightforward as I wanted it to be for using in the classroom.

Then the ESP8266 came around, and then it got Arduino support and then I couldn’t keep away. I’ve been tinkering with the idea of creating a super easy to use Wifi connected device that would allow my students to more or less flip a switch and start collecting sensor data wirelessly. The lesson would result in creating active data visualizations, not the details of creating this wireless data streaming device. The ESP8266 looked like it could provide a cost effective solution to this little challenge.

So I snagged a few ESP8266s from eBay and got them out of the bag yesterday. I tried to use the little ‘carrier board’ that came in the $7 eBay kit, but couldn’t get code over. Tracing the board back, I found I wasn’t able to manipulate a few pins I’d need to ground for programming then disconnect…so I soldered up a pretty shoddy little protoboard and connected it to a breadboard. A big thanks to Alasdair Allan on the Make Magazine blog for an article that got me through building this board and programming the board.

I got the data pushing out to easily enough using some example code by Liam Marshall on The code went over in no time, and connected directly to the network instantly. I was super surprised…I expected a bigger struggle. I actually has less trouble with the ESP8266 then the Spark Core. (Which I still have configured to pump data directly in to Google Sheets instead of a service like Phant.)

Now that the data is streaming, it is time to start creating the ease of use component…which is the hard part for sure. I’m going to aim to create a simple Python front end that will pipe the SSID and password into the code and reprogram the board. Alternatively, I might simple try to pump the data over serial into precompiled code to avoid running into programmer issues. Once I can get it to a ‘plug it in and tell it the SSID and password’ point, I’ll start thinking about where to collect the data. Likely I’ll set up a install and collect the data that way.

Check out the data stream here.

See the code below.

Home brewing on the small scale

This year I’ve decided to dive head first into home brewing. To get back on the horse, I’ve built a new small scale 1 gallon all grain system. This has a ton of pros; its small enough for my tiny kitchen, it is quicker and cleaner, cheaper per batch and makes it easier to brew lots of batches. That being said, I’m still working out the system, but it is coming along pretty well.

3 Vessels

The system isn’t a brew in a bag setup, but sort of a miniature all grain set up. I built the mash tun out of a 2 gallon beverage cooler with a stainless mesh bottom made from a hose. Nothing crazy, but I haven’t had any stuck mashes, and I can hold temp pretty well (+/-2 degrees) during an hour mash (as long as I preheat the tun). I’ve got two 30 qt kettles, one liquor tank and one for the boil. I want to add valves to these kettles at some point in the future, but for the time being, this works perfectly. The mash comes out looking great, and hitting preboil volumes and gravity no problem thanks to Beer Smith.

1 gallon brew
The 3 vessels.


The mini mash tun, fitted with a ball valve holding steady at 154F.


Recirculating Chiller

My sink is hopelessly small. I couldn’t fit a bucket, let alone a kettle. I decided to build a wort chiller nice and simple. Some 3/8″ copper hose very loosely wrapped and connected into a small Harbor Freight submersible pump. I load up a bucket with about 2 gallon of the coldest tap I can get, and I’m usually around 75F in 15 minutes. I’m really happy with how this came out, it was a fun little thing to build.

The chiller set up, sitting in the boil and sanitizing.



1 Gallon Jug Fermenters

I’ve been fermenting each batch in 1 gallon jugs, and have had no issues getting into a strong ferment. Everything after that has been the struggle. At first, I built a little temp controlled water bath with an aquarium heater and left that to keep the temps around what I thought was 68F, but turns out was way too warm, more like 75. The first two batches came out wonderfully vegetal. The next two batches were pulled mid ferment from this hot bath, but I think the damage was done. Now, the temps are rising and it is easy to maintain 64F ambient in the house. I’m likely going to move into 2 gallon buckets shortly. I worry that the 1 gallon jugs don’t supply enough head room, both for krausen and for aeration. I’m still experimenting with the fermentation, but hopefully I’ll have that locked down soon.

The product, just after pitching. Lots of cold break still settling.

Moving Forward

Getting this new system up and running has been a blast. I’m still getting the hang of it, but it has been easy and not heartbreaking to ruin a few batches as I figure out what the hell I am doing. I love the approach of brewing often, and brewing experimentally. I’ve been trying anything and everything, meticulously controlling variables, digesting as much reading material as possible and getting absorbed into the hobby like never before.

Keeping track of all the numbers.


new hops
Experimenting with these new southern hemisphere hops. The galaxy’s look and smell wonderful.


Brew buddy Poppy, ensuring no squirrels mess with the brew day.



Getting artsy with gift giving & laser cutting.

Over the last few months, I’ve been making lots of gifts between birthdays and the holidays. For these gifts, I turned the the laser cutter to make some unique and goofy gifts.


The jewelry I’ve made has become more an experiment in post processing then in design or fabrication. I’ve been using very basic shapes (mostly from the KG Flavor and Frames font series), or the traditional monogram style to create basic shapes in wood and acrylic. Then it was off to spray painting, washing, laquring, masking, etc. I’m still no where near finished with this. I’ve really enjoyed the experimental design with attention to detail nature of making jewelry.

Layering wood and acrylic.
Layering wood and acrylic.
Experiments with masking.
Experiments with masking. I liked the result of leaving clear acrylic masked to make ‘windows’.
Showcasing some of the finish products
Showcasing some of the finish products

Making Maps:

This project is certainly the most challenging I embarked on. I attempted to extract map data from OpenStreetMap to use as vector lines to create a thin street mesh that can be layered onto a contrasting based board. In the end, I feel defeated to the monster pile of vector data that my computer was not quiet able to handle. I simply raster engraved it. Hopefully I will lock this process down later and will have some details to share.

Detail of the engraving.
Detail of the engraving.
The mess of vector data
The mess of vector data
Laser engraving in action
Laser engraving in action
The engraved result on baltic birch.
The engraved result on baltic birch.

The final map framed and ready to be hung.
The final map framed and ready to be hung.

Medal Rack

My father spends more time running races then not, and he has amassed quite the collection of medals that ends up hanging off of post next to a vanity mirror in his bed room. Under the wise suggestion of my mother, I made him a rack for the medals to live on. The box is simple dovetail joint in 1/4″ red oak boards. 3 dowels are off set from one another on the top to create a cascade of medals on display. This project was a ton of fun, but I ended up completing it quite close to the buzzer and the rush left plenty to be desired. I would love to try to remake this again, but the joinery was so simple that I think I would use hand tools to do it in the future. (Feel free to download the Sketchup model. The joints are not designed with any kerf in mind, so it isn’t perfect.)

The model designed in Sketchup.
The model designed in Sketchup.
Red oak medal rack with laser cut dove tail joinery.
Red oak medal rack with laser cut dove tail joinery.
The completed rack, hung and displaying medals.
The completed rack, hung and displaying medals.

Various Boxes

I’ve learned recently that it is all about presentation. So I made some ornate little dove tail boxes on the laser cutter. These are generally generated with Makercase, and some edits are made to fit the various gifts. I’ve found these are no nearly as useful in the grand scheme of things. Some funk foam would go a long way to keep things from bouncing around in the box.

A mini pétanque set needed a better home then a tin tube. This box looks pretty, but the balls move a bit too much...not to mention the pea sized cochonnet.
A mini pétanque set needed a better home then a tin tube. This box looks pretty, but the balls move a bit too much…not to mention the pea sized cochonnet.
Jewelery box works great, but could use something to keep the piece in place.
Jewelery box works great, but could use something to keep the piece in place.

In Summary:

The laser cutter is such an amazing tool. With a bit of goofy design, and lots of experimentation, you can make some really inexpensive & unique gifts. I’d love to hear any feedback! I’ll be rolling out details on some of these projects in the future, so check back!

Reading Milliohm Resistances With The Arduino

I’ve recently been attempting to read milliohm resistance with the Arduino, and I’ve found out it isn’t terribly easy. The main cause is that the Atmega chips 10bit ADC doesn’t provide the resolution needed. As a result, I’ve been hunting for a different method, and I have come up with what I think is the best solution.

Using four-terminal sensing, or kelvin resistance measurements, we will use a constant current supply and some Ohm’s Law-Fu to read a voltage that is proportional to the resistance.

Lets start with some theory, and Ohm’s Law. First off, we are going to be looking for resistance, so lets put Ohm’s Law in terms or resistance:

[latex]r= frac{v}{i} [/latex]

Now we know that we need voltage and current to determine the resistance. So, we’ll need to build a current supply, with a constant output. For example, if we generate a constant 1 amp current, than we will have a handy relationship:

[latex]r= frac{v}{1} = v[/latex]

Given a 1 amp source, we are given that resistance is 1:1 proportional to the voltage.

Lets take a look at a circuit.


This circuit is our constant current supply. Using the LM-317, and a resistor between the adjust pin, and the voltage out pin, we create a basic constant current supply. Using a 120 ohm resistor, we will be generating a 1amp current. However, when we use Arduino, we have the power to do some calculations, we we are going to scale the current down by a factor of 10, and replace the 120 ohm resistor with 12 ohm resistor, resulting in a current of 100mA, or 0.1amps.

With our constant current supply, the next step is to measure the voltage across the resistor we want to measure.



Now we have our constant current supply powered by the Arduino, supplying 100mA across our resistor. We are going to run from the resistor, to the A0 pin on the Arduino, and the other side to ground. Any low ohm resistor can be put in place of the 12ohm resistor, just keep in mind that you’ll have the read the resulting current with a multimeter, than enter that value into the code. In my example, I built with a 10ohm resistor, that resulted in ~125mA, so my code uses 0.125 as my current.

Lets go ahead and throw some code onto the Arduino, and try to read the voltage, do some math to generate the resistance, and read it out!

const float currentSupply = 0.125; // The current generated by the LM317 and 10ohm Resistor
const float referenceVolts = 5;        // the default reference on a 5-volt board
const float resistorFactor = 1023; //Full scale this time.
const int resistancePin = 0;         //Resistor / output from 317 circuit connected to analog pin 0
void setup()

void loop()
int val = analogRead(resistancePin); // read the value from the sensor
float volts = (val / resistorFactor) * referenceVolts ; // calculate the voltage
float resistance = volts / currentSupply; //Use voltage to calculate the resistance

Now that we’ve got some code, lets test it out. I tested this with a few low resistance coils and inductors, each reading within a few hundreths of my multimeter measurement. I’d consider this a success!