LA28 Speed Trainer — Crafting a High‑Performance Wooden Dart Launcher

Ever since I was a kid, I liked building things that move. There is something satisfying about taking a simple material like wood and turning it into a working mechanism that actually shows speed. Motion is one of the easiest ways to understand engineering because you can see the results instantly. When something accelerates, glides, or shoots forward, you get immediate feedback about whether your design was successful or whether it needs improvement. That feeling of watching something you built come to life is what inspired this project.

For this build, I wanted to challenge myself to create something fast, clean, and precise. I wanted a mechanism that feels engineered instead of something that is simply put together. The result is the LA28 Speed Trainer, a wooden rail launcher designed to explore motion, speed, and consistency. It is a fully wooden system with a smooth sliding carriage and a hand shaped dart. There are no electronics and no special parts. The entire build depends on accurate cuts, clean alignment, and tight tolerances so the mechanism behaves the way it was designed to.

This project focuses on craftsmanship and motion. It explores how wood can glide when the rails are aligned correctly. It shows how a shape can travel in a straight line when the carriage is balanced. It demonstrates how a simple idea can become a functional mechanical system when the design is intentional. Every part of this build can be made with basic tools and a bit of patience, which makes it accessible while still feeling like a real engineering challenge.

The LA28 Games celebrate performance, precision, and improvement. Athletes train by measuring speed, refining technique, and repeating the cycle until every movement becomes intentional. Engineers follow the same process. You design something, build it, test it, and refine it until it performs the way you want. The Speed Trainer became my way of exploring that mindset in a physical form.

By modeling the launcher in Fusion 360, building it from wood, and testing different dart designs and rubber band tensions, I followed the same design, build, test cycle that drives Olympic innovation. The LA28 Speed Trainer is not just a wooden launcher. It is a hands on demonstration of how performance improves when design and iteration come together.

If you want a project that combines clean design, hands on building, and a clear look at how motion works, this is a great place to start. Let us get into it!

Wood Materials

1. Balsa wood sheets (for the rails and the carriage's top)
2. 75 pcs 1/4 x 1/4 x 12 inch balsa wood sticks (square dowels for the carriage's legs)
3. Unfinished wooden strips (general support pieces and alignment guides)

Dart Materials

1. Cereal box cardboard (for shaping the dart's body)
2. Aluminum foil (for forming the curved nose of the dart)

Tools

1. Craft knife or X-Acto Knife
2. Cutting mat
3. Ruler or straightedge
4. Sandpaper (optional, fine grit for smoothing rails)
5. Wood glue or tacky glue
6. Pencil for marking cuts
7. Clamps or tape (optional but helpful for holding pieces while drying)

3D Modeling Software

1. Fusion 360 (used for modeling the rails, carriage, and dart before building the physical version)

Before you begin cutting any wood, start your project inside Fusion 360. Digital modeling is one of the most important parts of the engineering process because it lets you understand how a mechanism will behave long before you build it. For the LA28 Speed Trainer, the rails are the foundation of the entire system. They control how the carriage moves, how stable the motion is, and how efficiently the dart receives energy.

Create a new component for the rails and sketch two long rectangular beams. Use construction geometry to define the exact spacing between them. This spacing is extremely important because it determines how the carriage legs will sit on the rails. If the spacing is too narrow, the carriage will bind. If it is too wide, the carriage will wobble. Adjust the spacing until the movement feels smooth and predictable.

Once the rails are sketched, extrude them and add the support blocks underneath. These supports keep the rails level and parallel. Misalignment is one of the most common causes of friction in physical builds, so designing these supports digitally helps prevent problems later. The Fusion 360 video for this step shows the full workflow, including sketching, extruding, and checking clearances.

The carriage is the moving part of the system, so it needs to be modeled with care. Begin by creating a new component in Fusion 360 specifically for the carriage. Instead of starting with the top plate, start with the legs. The legs determine how the carriage sits on the rails, so they must be modeled first to establish the correct geometry.

Sketch a single leg and dimension it to match the spacing of the rails from Step 1. Use the gridlines to position the leg accurately relative to the rails. Once the first leg is complete, create three more and place them in a rectangular layout. These four legs form the support structure for the carriage. The spacing between the legs must match the spacing of the rails so the carriage can glide smoothly without tilting. Even a small tilt can increase friction and reduce launch speed, so take your time to get these measurements right.

After the legs are positioned correctly, create the top plate. Sketch a simple rectangle that sits on top of all four legs. This plate distributes the pulling force from the rubber band and provides a stable platform for the dart. Use parametric dimensions so you can adjust the size of the plate later without rebuilding the model. Once the sketch is complete, extrude the plate and join it to the legs.

Insert the rail component into the assembly and use the Inspect tool to check clearances. Make sure the carriage sits level and does not collide with the rails. You can also check the center of mass to confirm that the carriage will stay balanced during motion. If needed, adjust the thickness of the top plate or reposition the legs until the carriage feels stable and centered.

The Fusion 360 video for this step shows how to assemble the carriage digitally. It demonstrates how to align the legs, test the movement, and verify the fit before building the physical version. This digital simulation gives you confidence that the carriage will move smoothly once it is built from wood.

The dart is the part of the system that actually shows speed, so it needs to be modeled with care. In Fusion 360, you can create a clean, aerodynamic dart shape using a combination of offset planes, circles, and a loft. This method gives you a smooth, curved nose that looks intentional and performs well.

Begin by creating a new component for the dart. Start on the main origin plane and sketch a 5 millimeter circle. This circle forms the base of the dart and sets the overall diameter. Keep the sketch fully constrained so the shape stays consistent if you adjust dimensions later.

Next, create an offset plane above the first sketch. Offset it by 9 millimeters. This plane will hold the second sketch that defines the tip of the dart. On this new plane, sketch a 0.1 millimeter circle. This tiny circle represents the point of the dart and helps create a smooth transition from the base to the tip.

With both circles sketched, use the Loft tool to connect them. Select the 5 millimeter circle as the first profile and the 0.1 millimeter circle as the second profile. In the loft settings, change the end condition to Point Tangent. This creates a smooth, curved nose instead of a sharp or flat transition. The tangent condition yields a clean, aerodynamic shape that looks professional and performs better during launch.

Once the loft is complete, you will have a simple but effective dart body. You can adjust the length, diameter, or taper by modifying the sketch dimensions or the offset distance. This flexibility is one of Fusion 360's strengths, as it allows you to refine the shape without rebuilding the model.

The Fusion 360 video for this step shows the entire process, including creating the offset plane, sketching both circles, lofting the profiles, and setting the tangent condition. When this step is finished, you will have a clean digital dart model that guides the physical build.

I’ve also attached the full Fusion 360 (.f3d) file for the dart below so you can explore the complete model yourself.

To begin the physical build, use the cutting template shown in the image above. All of the dimensions you need for the rails are already included in that image, so you can follow it directly without needing to measure anything manually. This ensures that the physical pieces match the digital Fusion 360 model as closely as possible.

Place your balsa wood sheet on a flat surface and lightly trace the outlines from the template using a pencil. Keep your lines clean and consistent so the cuts follow the intended geometry. Once the shapes are traced, move the wood onto a cutting mat and begin cutting with a craft knife or X‑Acto knife. Make several light passes instead of trying to cut through the wood in one stroke. This technique keeps the edges sharp and prevents the wood from tearing.

After cutting out the rail pieces, compare them to the cut‑out reference images above. These images help you confirm that the shapes and proportions match the intended design. If any edges look rough or uneven, use fine grit sandpaper to smooth them. Clean edges reduce friction and help the carriage glide more consistently.

Before moving on, place the two rails side by side and check that they are identical in length and height. Even a small difference can cause misalignment later. This step sets the foundation for the entire build, so take your time and make sure the pieces match the template exactly.

The dimensions for the legs and the top plate are shown in the image above, so you can follow them directly without measuring anything extra. These pieces must be cut accurately because they control how smoothly the carriage will glide.

Start with the legs. Use your 1/4 x 1/4 inch balsa wood stick and measure out 4 centimeters. Mark the line with a pencil and cut it cleanly using a craft knife on a cutting mat. Make several light passes so the wood does not split. Repeat this until you have four identical 4-centimeter legs.

Glue these four legs together in the arrangement shown in the image above. They should form a tight, square block. Hold them with clamps or tape while the glue dries. Make four of these leg blocks in total. These blocks will support the carriage top and keep the movement stable.

Next, cut the top plate. Place your balsa wood sheet on the work surface and trace the outline from the image above. This plate sits on top of the leg blocks and forms the platform that holds the dart. Cut it using the same light‑pass technique. If any edges feel rough, smooth them with fine grit sandpaper.

Before gluing anything, place the leg blocks under the top plate to check the fit. The plate should rest evenly on all four blocks. Once everything lines up, you are ready to assemble the carriage.

To build the dart, start by creating a simple cardboard core. Roll a strip of cereal box cardboard into a tight tube and secure it with glue or tape. This core gives the dart its shape and keeps it lightweight.

Next, make the aluminum foil top. Shape a small piece of foil into a smooth, rounded nose. Press and form it until it fits cleanly over the cardboard core.

Once both pieces are ready, attach the foil top to the cardboard core. Press the foil firmly so it wraps around the front of the tube and holds its shape. The final result should look like the completed dart shown in the image above.

With all the pieces cut, you can now put the full launcher structure together. This step is very simple. Just glue all the cut pieces together exactly as shown in the image above.

Start by attaching the rail supports to the underside of each rail. Make sure the rails stay straight and parallel. Once the rails are stable, place the carriage on top to check the fit.

If everything slides smoothly, glue the remaining alignment pieces and support strips in place. Keep the rails level while the glue dries so the carriage can glide without friction.

Once the glue sets, the full rail assembly and carriage are complete.

To begin evaluating the LA28 Speed Trainer, we started with the original cardboard‑and‑foil dart. This was the first version we built, and it looked clean and aerodynamic, but we needed to see how it actually performed on the rails. We tested it using two different rubber bands: a loose band with low tension and a tight band with high tension. Each launch was recorded in both normal speed and slow‑motion so we could analyze acceleration, stability, and overall speed.

These first tests helped us understand how the launcher behaved under different tension levels and whether the dart design was efficient enough to show clear differences between the two rubber bands.

Initial Test Results (Cardboard Dart)

Test 1: Cardboard dart, loose band, normal video — Speed Score: 6/10

Test 2: Cardboard dart, loose band, slow‑mo — Speed Score: 6/10

Test 3: Cardboard dart, tight band, normal video — Speed Score: 10/10

Test 4: Cardboard dart, tight band, slow‑mo — Speed Score: 10/10

From these early tests, we saw that the tight band produced much faster launches, but the cardboard dart’s weight made the results inconsistent. Sometimes it launched smoothly, and other times it dipped or slowed too quickly.

After reviewing the slow‑motion footage, we realized the cardboard dart was too heavy for consistent testing. The extra mass made it harder to compare the rubber band tension because the dart absorbed too much energy. To improve accuracy, we iterated the dart design and created a new paper dart specifically for testing.

The paper dart was lighter, easier to accelerate, and more sensitive to changes in rubber band tension. This made it ideal for collecting clean, repeatable data.

This step reflects the engineering mindset: when the data is unclear, you adjust the design and test again.

With the new paper dart ready, we repeated the exact same tests:

1. Loose rubber band (normal + slow‑mo)
2. Tight rubber band (normal + slow‑mo)

This gave us a complete second round of data, allowing us to compare the performance of both dart designs under identical conditions.

Second Test Results (Paper Dart – Iterated Design)

Test 5: Paper dart, loose band, normal video — Speed Score: 1/10

Test 6: Paper dart, loose band, slow‑mo — Speed Score: 1/10

Test 7: Paper dart, tight band, normal video — Speed Score: 5/10

Test 8: Paper dart, tight band, slow‑mo — Speed Score: 5/10

The lighter dart made the differences between the loose and tight bands much clearer. The loose band barely moved the paper dart, while the tight band produced a noticeable improvement.

Through this project, I learned how important it is to treat engineering as a cycle instead of a straight line. Modeling the launcher in Fusion 360 helped me predict problems before they happened, but the real understanding came from building and testing the physical version. I learned how small changes in weight, tension, and alignment can completely change the performance of a moving system. Switching from the cardboard dart to the lighter paper dart showed me how much mass affects acceleration, and the slow-motion footage helped me see details that are impossible to catch at full speed. I also learned that testing is not just about collecting results. It is about noticing patterns, finding weaknesses, and deciding what to improve next. Most of all, I learned that iteration is not a setback. It is the part of the process that makes a design stronger, faster, and more reliable.

Completing the full testing cycle brought the entire LA28 Speed Trainer project together in a way that shows the complete engineering process from start to finish. After building the rails, shaping the carriage, and crafting the dart, the real learning happened when we began launching, recording, and analyzing the results. That inconsistency became the turning point of the project and pushed us into the most important phase: iteration.

By redesigning the dart and switching to a lighter paper version, the system became far more responsive to changes in rubber band tension. This allowed us to see clear differences between the loose and tight bands, and the slow‑motion footage made it easy to score each launch with confidence. The lighter dart revealed exactly how much energy each band delivered, and it helped us understand how mass, tension, and alignment all work together to affect speed.

What makes this project meaningful is not just the final launcher but the entire journey behind it. Modeling the system in Fusion 360, cutting each piece by hand, assembling the structure, testing it, realizing what needed improvement, and then testing again — that is the full engineering loop in action. Every launch, whether fast or slow, added to the understanding of how the design behaves in the real world. Every adjustment made the system more refined and more predictable.

By the end of testing, the LA28 Speed Trainer wasn’t just a wooden launcher. It became a complete demonstration of how performance improves through design, iteration, and analysis. The data showed which combinations were fastest, the slow‑motion footage revealed how the carriage and dart behaved, and the entire build proved how much precision matters when working with wood. From all eight tests, the cardboard dart with the tight rubber band was clearly the best performer, while the paper dart with the loose band was the slowest and least effective.

Thanks for following along with this project. I hope you had fun building it, testing it, iterating it, and bringing the entire LA28 Speed Trainer to life! :)