General Guide Lines
There are some general guidelines which are applicable to all or any timing belts, including miniature and double-sided belts:
Drives should be designed with ample reserve horsepower capacity. Usage of overload services factors is important. Belts should be rated of them costing only 1/15th of their respective ultimate strength.
For MXL pitch belts, the tiniest recommended pulley could have 10 teeth. For additional pitches, Table 8, should be used.
The pulley size shouldn’t be smaller than the width of the belt.
Belts with Fibrex-glass fiber pressure members shouldn’t be put through sharp bends or tough handling, since this could cause breakage of the fibers.
To be able to deliver the rated hp, a belt must have six or even more teeth in mesh with the grooves of small pulley. The number of tooth in mesh could be acquired by formula given in SECTION 24 TIMING BELT DRIVE SELECTION PROCEDURE. The shear strength of an individual tooth is a fraction of the belt break strength.
Due to a slight aspect thrust of synchronous belts in motion, at least one pulley in the drive should be flanged. When the guts distance between the shafts is 8 or more times the diameter of small pulley, or when the drive is working on vertical shafts, both pulleys should be flanged.
Belt surface swiftness shouldn’t exceed 5500 feet per minute (28 m/s) for larger pitch belts and 10000 feet each and every minute (50 m/s) for minipitch belts. For the HTD belts, a swiftness of 6500 foot each and every minute (33 m/s) is normally permitted, whereas for GT2 belts, the utmost permitted rate is 7500 ft per minute (38 m/s). The utmost allowable operating rate for T series is certainly 4000 feet each and every minute (20 m/s).
Belts are, generally, rated to yield at the least 3000 hours of useful life if all guidelines are properly followed.
Belt drives are inherently efficient. It can be assumed that the performance of a synchronous belt drive is normally higher than 95%.
Belt drives are usually a way to obtain noise. The regularity of the sound level increases proportionally with the belt quickness. The higher the original belt pressure, the greater the sound level. The belt teeth entering the pulleys at high acceleration become a compressor and this creates sound. Some noise is the consequence of a belt rubbing against the flange, which in turn could be the consequence of the shafts not really being parallel. As proven in Figure 9, the noise level is considerably reduced if the PowerGrip GT2 belt is being used.
If the drive is part of a sensitive acoustical or consumer electronics sensing or recording device, it is suggested that the trunk surfaces of the belt be ground to assure absolutely uniform belt thickness.
For a few applications, no backlash between your driving and the driven shaft is permitted. For these instances, special profile pulleys can be produced without any clearance between your belt tooth and pulley. This may shorten the belt existence, nonetheless it eliminates backlash. Physique 10 displays the superiority of PowerGrip GT2 profile as far as reduction of backlash is concerned.
Synchronous belts are often motivated by stepping motors. These drives are put through continuous and huge accelerations and decelerations. If the belt reinforcing dietary fiber, i.e., stress member, and also the belt material, have high tensile strength no elongation, the belt will not be instrumental in absorbing the shock loads. This will lead to sheared belt tooth. Therefore, take this into consideration when how big is the smallest pulley and the components for the belt and tension member are selected.
The choice of the pulley materials (metal vs. plastic) is normally a matter of cost, desired precision, inertia, color, magnetic properties and, most importantly, personal preference predicated on experiences. Plastic pulleys with steel inserts or metal hubs represent an excellent compromise.
PRECAUTIONS
The next precautions should be taken when installing all timing belt drives:
Timing belt set up should be a snug in shape, neither too limited nor too loose. The positive grip of the belt eliminates the necessity for high initial tension. As a result, a belt, when installed with a snug match (that’s, not as well taut) assures longer life, much less bearing put on and quieter procedure. Preloading (often the reason behind premature failure) isn’t required. When torque is usually unusually high, a loose belt may “leap tooth” on starting. When this happens, the tension ought to be increased gradually, until satisfactory operation is attained. A good rule of thumb for installation pressure is as proven in Figure 20, and the corresponding tensioning force is shown in Table 9, both proven in SECTION 10 BELT TENSIONING. For widths other than shown, increase force proportionally to the belt width. Instrumentation for measuring belt pressure is available. Consult the product portion of this catalog.
Be sure that shafts are parallel and pulleys are in alignment. On an extended center travel, it is sometimes advisable to offset the powered pulley to compensate for the tendency of the belt to perform against one flange.
On an extended center drive, 
it is imperative that the belt sag isn’t large enough allowing teeth on the slack part to engage one’s teeth on the tight part.
It is necessary that the framework supporting the pulleys be rigid all the time. A nonrigid frame causes variation in middle distance and resulting belt s
lackness. This, in turn, can lead to jumping of tooth – especially under beginning load with shaft misalignment.
Although belt tension requires little attention after preliminary installation, provision ought to be designed for some middle distance adjustment for ease in installing and removing belts. Do not push belt over flange of pulley.
Idlers, either of the within or outdoors type, aren’t recommended and should not be used aside from power takeoff or functional make use of. When an idler is necessary, it must be on the slack aspect of the belt. Inside idlers must be grooved, unless their diameters are higher than an comparative 40-groove pulley. Flat idlers must not be crowned (use edge flanges). Idler diameters must surpass the tiniest diameter drive pulley. Idler arc of contact should be kept to the very least.
In addition to the general guidelines enumerated previously, particular operating characteristics of the travel must be taken into account.