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Every driver should be some kind of engineer, and every engineer who works on a race kart should have some idea what the driver is feeling. This is the engineering half of that trade: short lessons in the physics of a race kart, written by the analytics side of Mankin Racing for the driver, and published here for anyone else who wants them.

Each lesson is one page. The numbers come off a real kart - a Birel RY30 running Briggs LO206 in CCKRA - and its actual session records: real lap times, real tire pressures, real gearing. The data lessons use traces from a lap model of that kart until its data logger arrives; every one of those pages says so at the top. Where a number is uncertain, the lesson says so. Where a claim can be checked at the track, the lesson tells you how.

There are no answer keys on this site. That's deliberate.

1. 01Units, and the check that catches wrong reasoningGoing deeper: the contact patch when the tire isn't a balloon
2. 02Gearing, the only engine lever the rules leave you
3. 03Weight transfer, or why the inside rear has to lift
4. 04Tires, the only four things touching the trackGoing deeper: why grip is not proportional to load
5. 05Braking and corner entry, where the rear goesGoing deeper: why a kart brakes with the rear wheels only
6. 06Energy, and where a lap is actually won
7. 07The friction circle, one grip budget for everythingGoing deeper: the circle is an ellipse, and it moves
8. 08Front geometry, the four knobs that decide how the kart turns in
9. 09Reading a trace, the lap as a graphGoing deeper: the calculus he already did
10. 10Comparing two laps, where the time actually goes
11. 11Heat and the engine, or why a night race is a different motor
12. 12Statistics for the stopwatch, or how many laps a claim needs
13. 13The chassis as a spring, or the half of the lift lesson 3 left out
14. 14Aerodynamics at 55 mph, and the draft in numbers
15. 15A lap-time model, the physics of lessons 2-7 in one loop

The full fifteen-lesson plan →

Mechanisms

The lessons above are the physics of the lap. These are the physics of the parts: each machine on the kart that turns a small effort into a large one, or a flow into a force, or a material into a structure. Shorter pages, one principle, one equation, a worked number from our kart, three problems, and something to go find in the garage.

Whenever a page uses a piece of math beyond arithmetic - a ratio, a square, a fourth power, a square root - there is a boxed note that says what it is and how to use it. Nobody needs to have taken a physics course to read these. The math is explained where it appears.

1. M01Leverage, the oldest force multiplier on the kart
2. M02Hydraulics, the lever made of fluid
3. M03Friction, the machine that turns squeeze into stop
4. M04The centrifugal clutch, the part nobody explains
5. M05Springs, everything on the kart that pushes back
6. M06The carburetor, a fuel pump with no moving parts
7. M07The four-stroke cycle, and why the engine is sealed
8. M08Air cooling, how 51 fires a second stay at 400 degrees
9. M09Why magnesium is lighter than aluminum, and why the frame is steel anyway
10. M10Why a tube is stiff, and why axles come in soft, medium and hard
11. M11Fasteners, or why a torque number is really a stretch number
12. M12Bearings, or why rolling beats sliding by a hundred to one
13. M13The instruments, or what's inside the three tools you trust