Written by Serena & Lauren, with support from Yoel, Jack, and Zach.

It's Monday morning, and that can only mean one thing - it's time for the project reveal. The anticipation rises, and a spontaneous drumroll begins. Serena announces the theme: "Thrills, Spills, and High-Speed Action," which Gever claims originates from the beginning of NASCAR. The tinkerers gasp and grin.

And then she explains - this week, we'll be building high-speed, human-powered, rail carts, which we'll race on Friday in a series of time trials. Each team must make two runs from Terminus to Tinker City, and for each run, each cart must contain two tinkerers.

This group is stacked with a lot of Tinkering School alumni, many in their third, fourth, or even fifth summers at Tinkering School. We deliberately chose an incredible technically complicated project from the group to tackle.

To add to the challenge, teams must work within a set of materials constraints. Each team will receive one sheet of plywood, 40 linear feet of 2x3, 20 linear feet of 2x4', 6 skateboard wheels, 2 train wheels, and $40 to spend on at the hardware store when we go tomorrow morning.

We divide into teams - for the first time in Tinkering School history, we'll have six teams this week.

On Piki: Sol, Megan, Austin and Katelin

On Nooi: Jo, Ana, and Michael

On Sqiki: Liora, Stephanie, and Zach

On Kablooi: Lauren, Mar, and Pascal

On Panda: Charlotte, Audrey and Sage

And then they're already off and planning, meeting with their teams, and sketching initial designs.

Nooi plans their approach.

Each team receives a box with a spreadsheet and a bundle of bolts. Each team is responsible for logging their own wood usage, and staying within their materials limits.

The conference center starts to get stuffy, and teams head out side to investigate the remnants of previous cart design attempts from the past five weeks.

They measure them, paying attention to wheel-spacing and width. A large part of Tinkering School is about learning through iteration and failure - these past carts have each failed, at some point, in some respect, and the tinkerers seek to extract those lessons before they delve into their own designs.

In addition to their carts, each team is responsible for repairing and maintaining a significant section in our 300+ feet of track. The first 150 feet have been up for five weeks now, the rest has been standing for three weeks. Use has worked loose many of the connections, other segments have gaps or significant spacing variations between the rails. Gever explains the importance of track repair and improvement to the group.

And introduces them to our standard unit of width - 20" across, from inside edge to inside edge. The piece he's holding - our "Track Caliper" will socket over track of the right width, so we can use it a a guide and as the official means of testing and track calibration.

We take a stroll down the track, and Collaborator Serena points out other flaws that need to be addressed, as well as shows each team which segments they have been assigned.

It's hard to resist playing with past week's projects, especially when they happen to be so conveniently present in your workspace. Pascal tries the train turntable.

And Audrey gives Stephanie a ride on one of the cart bases from two weeks ago (Session D).

Then it's time for Gever's special "Structural Engineering 101" series. He gathers the group at Terminus, and talks about weight distribution through a structure - how does weight get from the top of this board to the ground? In a cart, how does weight get into the wheels?

Then he stands on it, and challenges the tinkerers to think about how much of his weight is going into each end when he stands four-fifths of the way down the board.

Then for the real test of strength - how many tinkerers can we get on the board before it breaks?

Four people bouncing up and down seems to do the trick.

Forensic analysis reveals that the wood rotated, and a crack ran all the way down until it found weakness at a knot in the wood and split through.

Then Gever explains the power of triangles - adding just one diagonal across this parallelogram dramatically increases the strength. Instead of just the force of the screws keeping the parallelogram from twisting, the wood in diagonal has to be compressed or stretched. Because wood resists compression and stretching, the resulting quadrilateral is an order of magnitude stronger.

After lunch, groups focus their efforts on track repair. One of the most common methods for fixing a chunk of track is cutting out the old piece and splicing in a new one. Jake and Emma work together to remove an old, warped segment.

We've purchased a new chop saw for out at midway station. Collaborators Jay and Lyman have spent the morning building a level table for it.

Another issue with the track is that it isn't a uniform width. Charlotte uses the "track caliper" to check whether the rails are correctly spaced.

Gever shows Rory how to use the circular saw, then offers to help by making or starting the cut for her.

Rory responds in true Tinkering School style: "I'm gonna do it!" And do it she does.

Austin drill-presses through a 2x3's - he's making wheel boxes for his team.

Sol's trying to build a jig with which to bend conduit.

Miles and Sage are working together to realign the track.

We're starting to see a semblance of cart skeletons. Austin clamps together the Piki cart.

Michael pauses on his way to measuring and cutting a piece of wood.

Lauren writes out a cut list for the Kablooi cart base.

The circular saw is in heavy use today. Ana makes a cut.

Portrait of a Tinkerer: Emma's skeptical of the camera.

Elijah's hat has somehow made its way onto the tip of a windmill blade.

Some of the track wood has screws that are just permanently embedded. They've acquired the nickname "devil screws," and are labeled here accordingly.

Portrait of a Bucket of Screws.

Teamwork can make anything happen. Together, Team Panda carries a slab of plywood.

Portrait of a Tinkerer: Jo

Portrait of a Portrait Taker: this is the wide-angle lens we broke last week, now dissasembled.

Liora works on removing the guide-wheels from one of the Session D carts. Each team gets 6 skateboard wheels, but they have to retrieve them themselves.

Collaborator Jay helps Lauren and Pascal investigate a joint.

Sometimes, the camera captures the most beautiful moments. Nik blows sawdust to clear the drill press bed.

After dinner, it's up the playground to romp. Elijah tries acrobatics over the stack of hay bales.

And then we visit with the animals, and pet the barn kitties. A good end to a hard day.

Today, tinkerers thought. They're stepping up to the technical nature of the challenge, figuring out their group dynamics, finding a rhythm, and working hard to make plans. We're looking forward to seeing how this all comes together.

Session F: Day 2 - "Thrills, Spills, and High Speed Action!"