Cam Gears, Belt Pulleys and Sprockets, what makes them different?

SPROCKETS

PULLEYS

GEARS

I am taking this moment today to reflect on a common misconception. To begin with it may be hard to describe as the terms are engraved into our young vocabulary over the past decade or so. First of all , cam gears as we have grown to call them are really Sprockets or more specifically Cogs. A Gear is always meshed against another gear or on a shaft like in a transmission. We do call those gears, and that's correct. I am unsure of how cam cogs became gears. Now Motorcycle guys you notice are more in tune ( no pun intended) with what the bike parts are called. You notice that the Rear device that the chain loops over is called the rear sprocket. Sprockets have teeth that penetrate a chain for grip, Cogs are like sprockets in a way that they have teeth on them but there is NO METAL TO METAL CONTACT. Cogs have teeth on them with a belt that wraps around that also has teeth. Gears have metal to metal contact all the time. Now the last power transferring item I will cover is the Pulley. In a car we have a pulley on the crankshaft ( part of the motor that turns) this is nicknamed the " Crank Pulley" All the other pulleys are on your Alternator, Water Pump, Oil pump, power steering and Air conditioning. All of these other pulleys are nick named " accessory pulleys" . Pulleys have belts that go across them WITHOUT teeth. Pulleys can be made with a lip on each edge of the pulley to keep belts from falling off. The worse symptom that usually occurs with belt systems is premature wear and squeaking from the belts being " a little off" rubbing on the inside lip of the pulleys.

So Lets Recap!

Gears- Gears transfer power by meshing directly against another gear, this is direct metal to metal contact ( unless gear is made of plastic) this is NOT involving any belts.

Sprockets- Normally found on motorcycles these have teeth to grip a chain. The chain has hole the sprocket teeth actually penetrate and is all metal to metal contact ( unless the chain is plastic)

Cogs- Cogs have teeth to grip and mesh perfectly with teeth on a matching belt. The belt can be driven by one cog and passed across other cogs making them turn together in UNISON making them ideal for timing as everything must turn together. There is no metal to metal contact only the Cog with a rubber belt passing over it and stretching to another identical cog. ( like with cam gears)

Pulleys- Pulleys are the most common belt type. Pulleys have grooves and a lip on each edge of the surface that the belts cross. If two pulleys are out of alignment the belts will rub the lip and squeak. There are no teeth for belts and they often slip when loose or become stretched. Pulley systems have one main pulley that drives all the accessory pulleys by a belt without teeth connecting them.