Hi Tony P

The friction rule taught from the sixth form is an empirical law, not absolute. There are many seeming anomalies ie slick tyres, lapped tapers... etc. Clutches often grip better with material removed. The exact response in any application is often not certain. Soft linings were considered very sensitive to temp; may degrade during a single stop, so the practical effect of width is indeed debatable.

Hi Alan

I have only documented four errors in Williams, none clearly on the recent long list, and one which you agreed with (vehemently).

My main concern is that despite other appropriate books now available, Williams is regularly recommended as the introductory text for Seven newcomers whatever their car. It tends to set them on the hot up trail which is not now so appropriate for many standard cars or their original cranks.


Re the Tahiti, the photo I particularly remember (from over 60 years ago!) was looking down on the crew in the hold filling the bucket. Our local inter island ferry recently lost its prop....

Newcomers looking for general info may find the post Books and Manuals useful.

Bob Culver

Location: Auckland, NZ

Mr Culver,

"The friction rule taught from the sixth form is an empirical law, not absolute. There are many seeming anomalies ie slick tyres, lapped tapers... etc. Clutches often grip better with material removed. The exact response in any application is often not certain."

Not sure about your memory and the sixth form but -

When you increase the surface area, pressure between the two contact surfaces decreases because
Pressure = Force/Area
Now, this decrease in pressure due to the force cancels out the increase in the frictional force thus developed on increasing the area.
Hence the frictional force becomes independent of area of contact surface.

Slick tyres and the coefficient of friction? Not sure about your reference to lapped tapers?

Tony.

Although not approved by some, thank goodness for asides on this Forum. Led, amongst other things, to the intriguing mention of Ruairidh’s class following the Mongolia chummy. It would be difficult to devise anything more likely to capture the imagination and interest of youngsters. (Some aspects, like the loss of the second tent, would even interest teenagers). Certainly beat following the fizzled Air Race, or vague travels of Marco Polo in my day.
If I thought I could have taught that sort of thing instead of maori hocus pocus I might have pursued teaching.

Bob Culver

Location: Auckland, NZ