Like a cross between traditional belting and chain, timing belts include a main body and engaging surfaces — a.k.a. teeth. They’re used to synchronize motion on everything from copiers to conveyors. They’re also useful (because of their flexibility) in tight places that don’t necessarily need timing and (because of their power density) in portable designs that must be kept light.

The shape, material, and design of synchronous belt teeth greatly affect output motion and performance. Upper limits are determined in part by tooth shear strength, in turn defined by tooth cross-section, pulley engagement dynamics, and material. Cost-effective rubber often carries the highest load, so many industrial belts are made of neoprene. On the other hand, newer polyurethane often works where rubber fails. It is more resistant to harsh chemical environments, allows more specialized profiles and machining, and perhaps most importantly, can boost tooth shear strength.