Thursday, January 07, 2010


I'm now in Melbourne, jobless and enjoying every moment of the housewife lifestyle. Laundry, dishes, cooking, surfing, reading and studying. The missing element from my daily routine is tidying up after toddlers, which I actually do occasionally when we visit Jean’s cousin and his kids.

Tomorrow, I start work at a marketing company selling credit cards and financial products. I do not expect to do very well, but the sales training will be a good eye opener to a different world.

The internet connection is strangely slow. After being used to the blazing connection speeds in china (its so bloody fast because just about anything interesting is blocked by the government), this is quite agonising. 480 kb/s is simply unacceptable.

I've had a slow epiphany over the duration of the past week:
In motor sports and the auto industry, wheel slip is an important term in determining how much friction the tyres and road are generating.

A commonly accepted approach is that the tyre produces maximum friction when it is slipping a little (usually to the order of 5%). Roughly speaking, a car travelling at 100 km/h and accelerating heavily will have its driving wheels spinning at 105 km/h.

However, it is not necessary that the tyre surface actually slips against the road surface. This is because the measured speed of the tyre is actually measured at the wheel’s shaft. The tyre’s surface will move at 105km/h (as in example above), but the portion of tyre contacting the road will be moving at 100 km/h.

This can be understood by considering the tyre surface alone. The tyre surface spins around the shaft at 105 km/h, but at the area where the surface touches the ground, the surface speed slows down to 100 km/h. This is possible because the tyre surface is elastic, and can compress a little. The rubber at the surface will be moving at 105 km/h, then when it nears the contact area it sort of bunches up a bit and slows down to 100 km/h. Once past the contact area, the rubber loosens up again and speeds up to 105 km/h.

This action of bunching up is reasonable, when you consider the elasticity of the material. The bunched up material is under compression, and will help transfer force from the hub to the contact patch.

Sleep now, work starts tomorrow.