Sunday, 31 May 2015

Motorcycle Handling & Chassis Design

Tony Foale's brilliant engineering manual, Motorcycle Handling & Chassis Design, gives you an inside, technical look at how motorbikes operate.  It also gives you some idea of just how precarious the act of piloting a motorcycle is.  Much is said about how free people feel when riding and the physics behind flying on two wheels makes it that much more magical.

That first time you roll on the throttle and your feet leave the ground not to come back down again for miles, you get that sensation of flight.  Your senses are alive on a motorbike as the world makes itself felt in many different ways.

The naked exposure you feel when riding is obvious.  What is less obvious are the hidden forces at work that allow you to do crazy things like hang sideways while cornering.
Anyone who has seen a racing motorcycle suddenly hit the ground can speak to how suddenly these balancing forces can fall out of sync.  Foale's book is full of helpful diagrams that clarify some pretty arcane physics.

Cornering on a bike is one of the most complex and misunderstood aspects of riding.  Keith Code does a good job of explaining this in Twist of the Wrist.  Foale's approach is more interested in the mechanics of the machine and how it handles the forces working on it.

From a rider's perspective, corning is a balancing act, but from the suspension's perspective things get a lot heavier when you're bending into a corner.

Compared to a car, motorcycles have very different dynamics that often surprise riders when they are testing the extremes of two wheeled dynamics.  Reading Foale's book (though he pitches pretty hard) is worth it even if you're only getting a sense of just how differently the 'integrated system' that is a motorcycle works.

Foale also gets into the geometry of the motorcycle.  From wheelbase and centre of gravity to more complex issues like how suspension height changes those fundamental forces.  Of course, in a corner a the suspension is severely compressed, changing the bike's responses in dramatic ways.  You get a real sense of how connected and complicated the physics of riding is after reading this book.

The copy I read was the 2002 version, but he still managed to work some of the newer computer based analysis of motorcycle physics.  Static pressure and its role on aerodynamics is a relatively new aspect of motorcycle theory, but Foale covers it.
You can find the latest version of this technical manual online from Foale's website, but you can get a good idea of what it's all about from Google Books.  I'm curious enough about changes and updates that I think I'm going to spring for the new PDF ebook.