The technical and aesthetic challenges that have to be surmounted in crafting a fine tourbillon are reasons why they are especially prized. One very basic problem, is power. Mainsprings should be kept as weak as possible in order to reduce wear, but they need to be powerful enough to deliver sufficient energy to keep the balance of a watch oscillating at optimum amplitude. A tourbillon or other mobile escapement design comes at a cost: the more gears you put between the mainspring and the escapement, the more power you lose due to mechanical disadvantage and friction. Putting the escapement on a moving platform, or putting a tourbillon in motion by making the whole movement rotate, means that extremely high precision has to be maintained if the watchmaker is to avoid using a mainspring so unrealistically powerful as to put undesirable wear and tear on the watch (and produce undesirable power fluctuations as well).

[Excerpt from an article first published in September 2011]