PowerPoint Presentation

Rock-it Science: The Physics of Roller DerbyMegan K. Pickett(Deviled Meg, #1701)Lawrence UniversityUniversity of WashingtonJet City Roller GirlsWomens Flat Track Derby Association

The Basics of Roller DerbyRule 1.3.2: The team with the most points at the end of the game wins.

Watch your Rose City Rollers Defend their Championship here in Portland Nov 4-6!

The Basics of Roller DerbyTends to be a bit physical.

The Basics of Roller DerbyTends to be a bit physical.

Two Jammers:

Jammers score a point for every opposing players hip they pass (legally) once they get out of the pack for the first time. Oh, yeah

Each team has 4 blockers that make your life miserable

Unless you make it miserable for them

Evil JammerNice JammerNice BlockersNice BlockerEvil Blocker(Loredai KillMore)(Lotta Issues)(Banana Ramya)(LuLu Palooza)

WTF?

Huzzah!Lead Jammer

My Work Here is Done

Basic Motion

Derby Stance

Basic Motion: The Cross Over

Basic Motion: The Cross Over

Power and speedby pushing to the side.

Friction from the wheel edges = power. Non-pushing wheels provide roll.

Turns body toward center trackfalling around the circle

Navigating the Track148.5 feet on the inside236.5 feet on the outside.

Every skater must be able to complete 27 laps/5 minutes = 12 mph

Jammers ~ 33+ = 15 mph(Fc~400 N ~ 2/3 W)

Speaking of Friction: Best Friend and Worst EnemyWheels, Cushions, Toe Stops are given durometer ratings

20A = rubber band40A = pencil eraser70A = Running shoe sole

78A = Outdoor wheels88A95A = lighter skaters*95101A = heavier skaters*

(100ish = shopping cart wheel)

Speaking of Friction: Best Friend and Worst EnemyBut surface conditions means different wheels (potentially) for every venue...

Wooden FloorgrippySport Courtranges from grippy to slick with bumpsPainted Cementgrippy to slipperyHockey floorslipperyMasoniteI hate you

Why? Friction is a contact force. Does it matter? Sorta.

Slippery floorExcellent for most stops: snow plows, hockey stops, power slides, T-stops

Grippy floorExcellent for turnaround toe-stops

and general Jammer fun

Static, Kinetic, and Rolling Friction

Static, Kinetic, and Rolling Friction

Rolling Friction = Drag Force

Additional Dissipation due to wheel deformation, bearings, flex in trucks/plates/kingpins

F = CrrN.

=> Torque. Hence the different wheels. Best estimates are around Crr ~ 0.01

Static, Kinetic, and Rolling FrictionWheels! Big Wheels, Little Wheels, Wide, narrow, cores, urethane pours.

I = MR2 for each wheel.

Momentum Transfer: The Whip

Arm Whips, Hip Whips, Shirt Whips, Legging Whips, Leg Whips. All Newton, All the Time

Momentum Transfer: The WhipArm Whips, Hip Whips, Shirt Whips, Legging Whips, Leg Whips. All Newton, All the Time

Overtime400,000 N/m2 to break a human femur (not difficult at 15 mph with a 100 kg blocker falling on you.

Concussion rate: 10% players 3+ concussions (average playing time before a concussion is 3.5 years

League Bacterial Flora

Overtime