Scottish Carties

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Scottish Cartie Association Forum Topics
Updated: 19 min 4 sec ago

humberbridge soap box

June 10, 2017 - 22:05
humberbridge 1 st july been missed again off the calender 

Wheel Drag

May 16, 2017 - 09:27

When you are sitting on the start line of a race, you have a fixed amout of potential energy. The secret to winning is to convert as much of that energy as possible into speed, and to do that you need to minimise the energy you lose to moving air out of the way and rotating your wheels.

A rotating wheel has 5 sources of drag/energy loss;

  • Rolling resistance - the drag caused by your tyre's contact with the road surface
  • Bearing resistance - the drag caused by your wheel's bearings
  • Rotational inertia - the energy needed to spin your wheel up to speed (a.k.a the flywheel effect)
  • "Displacement" drag - the aerodynamic drag caused by moving the wheel through the air
  • Rotational drag - the aerodynamic drag caused by spinning the wheel (a.k.a the windmill effect)
Drag source
Behaviour
Rolling resistance
Increases with total weight. Decreases with tyre pressure. Tends to decrease with wheel diameter 
Bearing resistance
Decreases with wheel diameter
Rotational inertia
Increases with wheel diameter
Displacement drag
Increases with speed and wheel frontal area
Rotational drag
Increases with speed and wheel diameter