Synchronous Belts & Sheaves are used in applications where you want the Driver and Driven shafts to remain perfectly "Synchronized". We'd like to make a comment here concerning "terminology". While we refer to the metal driving and driven devices as "Sheaves" (as we do for other belt drive systems), manufacturers, may and will, refer to these devices as "Sprockets" based on the "toothed" profile of the device. In this discussion, we will refer to them as "sheaves" and this presentation of information will concentrate on Synchronous, Timing and Double Sided Timing belt equipment.

Synchronous Belts & Sheaves - These belts and sheaves have different "tooth" profiles to maintain synchronism based on manufacturer, horsepower carrying capability and application.

While manufacturer specific drive designs exist, there are standards for synchronous and timing belt drive dimensions and profiles. Synchronous belts are made in 8MM and 14MM sizes. This dimension is the distance from the centerline of "tooth" to the centerline of an adjacent tooth, measured in millimeters. In addition, this dimension is the "depth" of the tooth profile from the bottom of the belt to the outer extremity of the tooth profile. Belt width is another industry standard and most major manufacturers have designs for widths of 20MM, 42MM, 65MM, 90MM, and 120MM. Some of the smaller manufacturers may limit their line by not supplying all widths but for the most part, all will have these widths and any limiting might very well be on the total belt length, which would limit the maximum distance between the driver and driven equipment.

Timing Belts & Sheaves - Timing belts are similar to the synchronous belt in that they have "teeth" that keeps the driving and driven devices "in time", much like we talk about a car engine being "in time".

One of the things you will notice about a timing belt is the tooth profile. Most manufacturers use a "square" tooth profile. One of today's uses for the timing belt is the print carriage on a typewriter or computer printer. This carriage must remain accurately positioned for the print characters to be aligned properly. A timing belt is perfect for this application. Light weight, low cost, precision and repeatable positioning, and quiet operation.

Industry standard sizes exist for these belts and sheaves just like the synchronous devices.

Double Sided Timing Belt - The final type is a "Double Sided" or twin power belt. This is a timing belt with teeth on both sides compared to teeth on one side and a smooth belt on the outer circumference. These are specialty belts that are used when you have an application which you wish to drive shafts from both the bottom and top or maybe an easy way to drive multiple shafts in a serpentine type of configuration. These are certainly rather rare and, as such, are very limited in pitch, width and pitch length.

With all of these possibilities you can see why you need the expertise available at A.R.& E., the next time you need to size and purchase a Synchronous Drive System.

Sheaves for these drive systems come in "Bore to fit" types as well as those that use a "Tapered Bore Bushing". Most users will prefer for the "Tapered Bore" design for convenience sake but sometimes the sheave is so small you'll find it necessary to have it "bored to size". In this case, it can either be ordered from the factory with the proper bore (which may take some time) or you can have the A.R.& E. machine shop do the modifying for you. It'll probably be a lot quicker!