As a Ringer of some 15 years experience on and off but no great expertise (Plain Hunt, Single Court and nearly Bob Doubles) I would agree with Yaldea in all he/she says about the ropes. We could probably debate at length about exactly how and why the clapper achieves its flight from one side of the bell to the other, but thats for another forum and there's probably more than several opinions to be aired (like at least as many as there are bellringers. No doubt some erudite fellow could blind us all with science in the end anyway).
Just to add that the wheel knot shown in the links above is pretty universal, and the main reason for having so much rope in the wrappings and frappings is to give you enough spare length to be able to cut out all the worn section that lives in or near the garter hole and work a long splice below the wheel.
As you can appreciate, the rope changes direction through 180 degrees or a little bit more at the garter hole every time the bell is turned over, often under some strain, especially when learners or rough handlers are on the bell. This happens every few seconds, sometimes for hours at a stretch, usually at least twice a week, over a period of some years. The rope is (should be!) adjusted up and down a little every couple of months to spread the wear, but eventually the fibres break down and having the extra for splicing virtually doubles the useful life of the rope. Terylene top ends are much less prone to wear in this way so are popular despite the extra expense. Nevertheless the extra rope is still there, cos it's traditional to have it, and what better reason would you need anyway?
The wheel knot used is described by Steve Coleman in his excellent series of books about ringing. In 'The Bellringer's Early Companion' he states "the wrappings and frappings... come from something called a shear leg lashing which is a knot that was once used to fasten two poles together in some kind of structure."
The beginning of the knot is a RT on the right hand post (nearest the garter hole) followed by the W&F, (similar to the first two moves in a monkeys fist) with the end passed down inside the wrappings and nipped on the inside of the first round turn. This is very secure but extremely easy to loose off and adjust.
To quote Coleman again- "A knot of some age, and apparently designed especially for bellringing by a person who really understood what he was about. Elegant, functional, and oh so beautiful to look at." What all the best knotting should be really!