Timing Belt Pulleys Design and Installation Recommendations: General Guide Lines

General Guide Lines
There are several general guidelines which are applicable to all timing belts, including miniature and double-sided belts:

Drives should always be designed with ample reserve horsepower capacity. Use of overload service factors is essential. Belts should be rated of them costing only 1/15th of their particular 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 stress members should not be subjected to sharp bends or rough handling, since this may cause breakage of the fibers.

In order to deliver the rated horsepower, a belt will need to have six or more teeth in mesh with the grooves of the smaller pulley. The amount of teeth in mesh could be attained by formula given in SECTION 24 TIMING BELT DRIVE SELECTION PROCEDURE. The shear power of a single tooth is a fraction of the belt break strength.

Due to a slight side thrust of synchronous belts in motion, at least one pulley in the travel must be flanged. When the guts distance between the shafts is 8 or even more times the size of small pulley, or when the get is operating on vertical shafts, both pulleys should be flanged.

Belt surface swiftness shouldn’t exceed 5500 foot 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 ft each and every minute (33 m/s) is certainly permitted, whereas for GT2 belts, the utmost permitted swiftness is 7500 ft each and every minute (38 m/s). The utmost allowable operating acceleration for T series can be 4000 feet per minute (20 m/s).

Belts are, in general, rated to yield a minimum of 3000 hours of useful lifestyle 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 higher than 95%.

Belt drives are usually a way to obtain noise. The frequency of the noise level boosts proportionally with the belt rate. The higher the initial belt stress, the greater the sound level. The belt tooth entering the pulleys at high swiftness act as a compressor which creates noise. Some noise is the consequence of a belt rubbing against the flange, which may be the consequence of the shafts not really becoming parallel. As shown in Figure 9, the noise level is considerably reduced if the PowerGrip GT2 belt has been used.

If the drive is part of a sensitive acoustical or consumer electronics sensing or recording device, it is suggested that the trunk areas of the belt be ground to make sure absolutely uniform belt thickness.

For a few applications, no backlash between your driving and the driven shaft is permitted. For these cases, special profile pulleys can be produced with no clearance between your belt tooth and pulley. This might shorten the belt life, nonetheless it eliminates backlash. Number 10 displays the superiority of PowerGrip GT2 profile as far as reduced amount of backlash can be involved.

Synchronous belts are often driven by stepping motors. These drives are subjected to continuous and huge accelerations and decelerations. If the belt reinforcing dietary fiber, i.e., pressure member, along with the belt materials, possess high tensile power no elongation, the belt will never 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 components for the belt and pressure member are selected.

The choice of the pulley materials (metal vs. plastic material) is normally a matter of cost, desired accuracy, inertia, color, magnetic properties and, most importantly, personal preference based on experiences. Plastic material pulleys with steel inserts or metallic hubs represent a good compromise.

PRECAUTIONS
The next precautions should be taken when installing all timing belt drives:

Timing belt installation ought to be a snug fit, neither too restricted nor too loose. The positive hold of the belt eliminates the necessity for high preliminary tension. Therefore, a belt, when set up with a snug match (that’s, not as well taut) assures longer life, much less bearing wear and quieter operation. Preloading (often the cause of premature failure) isn’t required. When torque is usually unusually high, a loose belt may “jump teeth” on starting. When this happens, the tension should be increased gradually, until satisfactory operation is attained. An excellent rule of thumb for installation pressure is as demonstrated in Figure 20, and the corresponding tensioning push is shown in Table 9, both proven in SECTION 10 BELT TENSIONING. For widths apart from shown, increase drive proportionally to the belt width. Instrumentation for measuring belt stress is obtainable. Consult the merchandise section of this catalog.

Make sure that shafts are parallel and pulleys are in alignment. On an extended center get, it really is sometimes recommended to offset the powered pulley to compensate for the inclination of the belt to run against one flange.

On a long center drive, it really is imperative that the belt sag is not large enough to permit tooth on the slack side to engage the teeth on the tight side.

It is necessary that the body supporting the pulleys be rigid at all times. A nonrigid frame causes variation in center length and resulting belt slackness. This, subsequently, can result in jumping of tooth – specifically under beginning load with shaft misalignment.

Although belt tension requires little attention after initial installation, provision ought to be designed for some center distance adjustment for ease in installing and removing belts. Do not push belt over flange of pulley.

Idlers, either of the inside or outside type, aren’t recommended and really should not be utilized aside from power takeoff or functional use. When an idler is necessary, it must 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 should not be crowned (use edge flanges). Idler diameters must surpass the tiniest diameter get pulley. Idler arc of contact should be held to a minimum.

In addition to the general guidelines enumerated previously, specific operating characteristics of the get must be taken into account.

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