General Guide Lines
There are several general guidelines which are applicable to all or any timing belts, including miniature and double-sided belts:
Drives should always be made with ample reserve horsepower capacity. Usage of overload program factors is essential. Belts should be rated of them costing only 1/15th of their respective ultimate strength.
For MXL pitch belts, the tiniest recommended pulley will have 10 teeth. For other pitches, Table 8, should be used.
The pulley diameter shouldn’t be smaller compared to the width of the belt.
Belts with Fibrex-glass fiber tension members should not be subjected to sharp bends or tough handling, since this may cause breakage of the fibers.
In order to deliver the rated hp, a belt must have six or more tooth in mesh with the grooves of the smaller pulley. The amount of tooth in mesh could be attained by formula provided in SECTION 24 TIMING BELT DRIVE SELECTION PROCEDURE. The shear power 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 a single pulley in the get should be flanged. When the center distance between your shafts is 8 or more times the diameter of small pulley, or when the get is operating on vertical shafts, both pulleys ought to be flanged.
Belt surface swiftness should not exceed 5500 feet each and every minute (28 m/s) for bigger pitch belts and 10000 feet each and every minute (50 m/s) for minipitch belts. For the HTD belts, a swiftness of 6500 feet per minute (33 m/s) can be permitted, whereas for GT2 belts, the maximum permitted acceleration is 7500 feet each and every minute (38 m/s). The utmost allowable operating speed for T series is normally 4000 feet each and every minute (20 m/s).
Belts are, generally, rated to yield a minimum of 3000 hours of useful life if all instructions are properly followed.
Belt drives are inherently efficient. It can be assumed that the effectiveness of a synchronous belt drive can be greater than 95%.
Belt drives are often a way to obtain noise. The regularity of the noise level raises proportionally with the belt acceleration. The higher the initial belt stress, the greater the sound level. The belt teeth entering the pulleys at high velocity become a compressor which creates sound. Some noise is the result of a belt rubbing against the flange, which in turn may be the result of the shafts not really getting parallel. As proven 
in Figure 9, the sound level is substantially decreased if the PowerGrip GT2 belt is being used.
If the drive is part of a sensitive acoustical or electronics sensing or recording device, it is recommended that the trunk surfaces of the belt be ground to make sure absolutely uniform belt thickness.
For some applications, no backlash between the driving and the driven shaft is permitted. For these cases, special profile pulleys can be produced without any clearance between the belt tooth and pulley. This may shorten the belt existence, but it eliminates backlash. Physique 10 displays the superiority of PowerGrip GT2 profile so far as reduction of backlash can be involved.
Synchronous belts tend to be driven by stepping motors. These drives are put through continuous and large accelerations and decelerations. If the belt reinforcing fibers, i.e., stress member, along with the belt material, have high tensile strength and no elongation, the belt will not be instrumental in absorbing the shock loads. This will lead to sheared belt teeth. Therefore, consider this into consideration when how big is the tiniest pulley and the materials for the belt and tension member are chosen.
The decision of the pulley materials (metal vs. plastic) is a matter of cost, desired accuracy, inertia, color, magnetic properties and, above all, personal preference predicated on experiences. Plastic pulleys with steel inserts or steel hubs represent a good compromise.
PRECAUTIONS
The following precautions should be taken when installing all timing belt drives:
Timing belt installation ought to be a snug fit, neither too tight nor too loose. The positive grip of the belt eliminates the necessity for high initial tension. Consequently, a belt, when installed with a snug match (that’s, not too taut) assures much longer life, less bearing use and quieter procedure. Preloading (often the cause of premature failure) isn’t necessary. When torque is definitely unusually high, a loose belt may “leap tooth” on starting. In such a case, the tension ought to be increased gradually, until satisfactory operation is attained. An excellent guideline for installation stress is as demonstrated in Figure 20, and the corresponding tensioning force is demonstrated in Table 9, both shown in SECTION 10 BELT TENSIONING. For widths other than shown, increase power proportionally to the belt width. Instrumentation for measuring belt pressure is available. Consult the merchandise portion of this catalog.
Be sure that shafts are parallel and pulleys are in alignment. On an extended center drive, it really is sometimes recommended to offset the driven pulley to compensate for the inclination of the belt to run against one flange.
On an extended center get, it is imperative that the belt sag is not large enough allowing tooth on the slack part to engage one’s teeth on the tight side.
It is important that the frame supporting the pulleys be rigid all the time. A nonrigid body causes variation in middle length and resulting belt slackness. This, subsequently, can lead to jumping of teeth – specifically under starting load with shaft misalignment.
Although belt tension requires little attention after initial installation, provision ought to be designed for some middle distance adjustment for ease in installing and removing belts. Usually do not force belt over flange of pulley.
Idlers, either of the inside or outside type, are not recommended and really should not be utilized except for power takeoff or functional make use of. When an idler is essential, it should be on the slack aspect of the belt. Inside idlers should be grooved, unless their diameters are higher than an equivalent 40-groove pulley. Flat idlers must not be crowned (use advantage flanges). Idler diameters must exceed the sm
allest diameter get pulley. Idler arc of contact should be kept to a minimum.
As well as the general guidelines enumerated previously, particular operating features of the get must be taken into account.