Against the motor's 2 Nm stall that allows an arm up to 588 mm, which is absurdly long. The real limit was not torque but cogging: a longer arm multiplies the motor's cogging torque through the whole system, so I chose the shortest practical arm, 50 mm. That choice is exactly what came back to bite me.

Then I measured the sag from the top of the travel versus the bottom and got a 1.5 to 2 mm band. That gap is friction, and it was large. Removing the actuator collapsed the band to about 5 mm of clean travel, which located the culprit: the motor's cogging torque, multiplied along that 50 mm arm, was fighting the suspension the whole way.

Body in orange, wheel in blue, road in grey. Passive on top, skyhook below, driving the same profile at the same speed.

Lowering RMS acceleration is easy if you ignore what it costs. The bench therefore logs the three quantities that size real hardware alongside comfort: peak suspension travel, peak tire deflection, and peak actuator force.

I started by researching the math behind inverse kinematics and robotic motion, then modeled the full arm in SolidWorks around accurate models of off-the-shelf components.

I started by researching the math behind inverse kinematics and robotic motion, then modeled the full arm in SolidWorks around accurate models of off-the-shelf components.

To put into perspective how small 1e-9 rad is, if you shined two lasers at the moon seperated by 1e-9 rad, the distance between them would be just over a foot.

• Derived the equations of motion with Lagrangian mechanics (full derivation typeset in LaTeX)
• Solved the coupled non-linear ODEs numerically in Python
• Swept initial conditions to map flip times and divergence behavior

The cannon is built from PVC piping, wood, duct tape, and epoxy, pressurized with a bicycle tire pump. Getting there meant pressure research to size the chamber, CAD models in Fusion 360 and Onshape, and a lot of hands-on work, such as hand sawing, PVC solvent welding, and epoxy joints.

The cannon is built from PVC piping, wood, duct tape, and epoxy, pressurized with a bicycle tire pump. Getting there meant pressure research to size the chamber, CAD models in Fusion 360 and Onshape, and a lot of hands-on work, such as hand sawing, PVC solvent welding, and epoxy joints.

Working from the component drawings, I modeled each part and built up the full assembly, then used Inventor Studio for rendering and animation of the moving engine.

A complete, animated V6 model, and a much deeper understanding of what every component in an engine actually does. The orbit render below was animated in Inventor Studio.

The arm was modeled in Onshape and printed on a Bambu Lab printer. An Arduino running C++ drives servo and stepper motors through motor drivers with joysticks and buttons for control.

The arm was modeled in Onshape and printed on a Bambu Lab printer. An Arduino running C++ drives servo and stepper motors through motor drivers with joysticks and buttons for control.

I modeled the bench in Onshape to work out geometry and loads, then built it with hand saws, wood joinery, and fasteners.

I modeled the bench in Onshape to work out geometry and loads, then built it with hand saws, wood joinery, and fasteners.