Splicing and Clamping Synchronous Belts

The question is often raised if it's possible to cut a synchronous (timing) belt into a custom length and splice the belt back together when a standard length does not fit the application. To answer this question: yes it can be done, but not very easily. Splicing two ends of a synchronous belt can be done when the belt is made with a particular type of polyurethane construction and additional polyurethane is used as "glue" to attach the ends of the belt. After this splicing process you can expect about 40% of the initial strength of the belt. This is because once you cut the tensile cord you've eliminated the strongest part of the belt. The spliced section is now the weak link of the belt, and like your co-ed softball team, you're only as strong as the weakest link. There are currently no processes to splice together a rubber synchronous belt.

Clamps are often used to attach two ends of a synchronous belt together. If this is done, the clamp must be contained on the belt span between the two pulleys. If a clamp ever attempts to ride over a pulley, catastrophic results will surely follow. If a clamp is used to attach two ends of a synchronous belt, a minimum of 6 teeth in mesh on each side of the belt is recommended. Anything below 6 teeth will lower the belts available working strength (6 teeth = tensile strength of belt), and premature belt failure from tooth shear is more likely to occur.

Synchronous Belt Storage

Did you know that something as simple as storing your belts properly can make a huge difference in your belts life and performance? Here are a few storage recommendations that will keep your belts out of trouble, and performing the way they were designed to.

Whenever possible, store your belts in the original packaging until the moment it is ready for installation. This is the best way to keep from damaging the tensile cords of the belt.

Keep the belts away from direct sunlight and moisture. One way to avoid this is by keeping your belts away from windows.

Keep the belts out of the heat. Do not store your belts near heaters or radiators. Make sure that they are not in the airflow of a heating device.

Don’t store belts on the floor. This may seem a little over the top, but floors are high traffic areas, and a belt could easily be stepped on or rolled over, causing tensile cord damage.

Keep the belts away from chemical exposure. Any place that has solvents in the air could damage your belts. This includes chemicals such as ozone, which could be present near transformers or electric motors.

Belts should ideally be stored in a cool dry environment at a temperature of 85 degrees F or less with lower than 70% relative humidity. If done properly, a belt can be stored for up to 6 years.

Synchronous Drives Operating in Environments with Dust and Debris

Dusty environments do not generally present serious problems to synchronous drives as long as the particulates are fine and dry. Note, though, that particulate matter can act as an abrasive resulting in more rapid belt and sprocket wear. Damp or sticky particulate matter deposited and packed into sprocket grooves can cause belt tension to increase significantly. This increased tension can impact shafting, bearings and framework and can even result in belt tensile failure. Static electrical charges within drive systems can sometimes attract particulate matter, so may need to be dissipated to ground.

Debris should be prevented from falling into any synchronous belt drives by using screens or guards. Debris caught in belt drives is generally either forced through the belt or may result in a stalling of the system. In either case, serious damage will occur to the belt and related drive hardware.

Gates Flat Idler Pulleys

Idlers are included in belt drives for a variety of reasons (e.g. to apply the proper pre-tension or increase the belt wrap angle on a pulley). In the past, the Gates idler product line consisted of idler sprockets, brackets, and idler bushings. However, Gates recently introduced flat idler pulleys to give designers additional flexibility.

The flat idler pulleys can be used with the existing idler brackets and they are available in a range of sizes for use on both synchronous and V-belt drives. Available sizes and technical details regarding Gates idler product line are available at www.gates.com/idlers/.

Custom Synchronous Belt Sizes

There are two types of custom synchronous sizes, a different width and a different length.

Making stock belts in custom widths is usually easy to do. Synchronous belts are made on a mold that makes a single wide belt which is then cut down into the individual belt widths. If you need something other than a standard width, we require that you purchase the slabs worth of the custom width because we must set the tooling up to cut the whole slab. The number of belts will depend on the mold size and the width you are requesting.

Making custom lengths is much more difficult. Each size length is made on its own individual mold. In order to do a custom length not listed in our catalog, we have to machine a new mold for that size. This means that you will be charged for tooling fees and minimum order quantities, which is usually not feasible except for equipment manufacturers that will be placing large orders.