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 designed with ample reserve horsepower capacity. Use of overload provider factors is essential. Belts ought to be rated at 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 size should never be smaller compared to the width of the belt.
Belts with Fibrex-glass fiber pressure members should not be put through sharp bends or rough handling, since this could trigger breakage of the fibers.
In order to deliver the rated horsepower, a belt will need to have six or even more teeth in mesh with the grooves of small pulley. The amount of teeth in mesh could be acquired 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 power.
Because of a slight aspect 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 the smaller pulley, or when the travel is working on vertical shafts, both pulleys should be flanged.
Belt surface swiftness should not exceed 5500 ft per 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 acceleration of 6500 feet each and every minute (33 m/s) is certainly permitted, whereas for GT2 belts, the utmost permitted acceleration is 7500 feet per minute (38 m/s). The maximum allowable operating rate for T series can be 4000 feet each and every 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 is definitely greater than 95%.
Belt drives are usually a way to obtain noise. The frequency of the sound level raises proportionally with the belt velocity. The higher the initial belt stress, the greater the noise level. The belt tooth entering the pulleys at high acceleration act as a compressor and this creates sound. Some noise may be the consequence of a belt rubbing against the flange, which could be the result of the shafts not really becoming 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 recommended that the trunk surfaces 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 situations, special profile pulleys can be produced with no clearance between your belt tooth and pulley. This might shorten the belt lifestyle, but it eliminates backlash. Physique 10 displays the superiority of PowerGrip GT2 profile so far as reduced amount of backlash can be involved.
Synchronous belts are often driven by stepping motors. These drives are put through continuous and huge accelerations and decelerations. If the belt reinforcing dietary fiber, i.e., pressure member, along with the belt materials, have high tensile strength no elongation, the belt will never be instrumental in absorbing the shock loads. This will result in sheared belt teeth. Therefore, consider this into account when how big is the smallest pulley and the components for the belt and pressure member are chosen.
The decision of the pulley materials (metal vs. plastic) is certainly a matter of cost, desired precision, inertia, color, magnetic properties and, most importantly, personal preference predicated on experiences. Plastic material pulleys with metallic inserts or metal hubs represent a good compromise.
The next precautions ought to 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 grip of the belt eliminates the necessity for high preliminary tension. As a result, 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 unusually high, a loose belt may “jump teeth” on starting. When this happens, the tension should be increased steadily, until satisfactory operation is attained. An excellent guideline for installation tension is as demonstrated in Figure 20, and the corresponding tensioning pressure is proven in Table 9, both proven in SECTION 10 BELT TENSIONING. For widths apart from shown, increase power proportionally to the belt width. Instrumentation for calculating belt pressure is available. Consult the merchandise section of this catalog.
Make sure that shafts are parallel and pulleys are in alignment. On a long 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 get, it really is imperative that the belt sag is not large enough allowing tooth on the slack side to engage the teeth on the tight aspect.
It is necessary that the framework supporting the pulleys be rigid at all times. A nonrigid body causes variation in center range and resulting belt slackness. This, subsequently, can lead to jumping of tooth – specifically under beginning load with shaft misalignment.
Although belt tension requires little attention after preliminary 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 within or outside type, are not recommended and should not be utilized aside from power takeoff or functional make use of. When an idler is necessary, it should be on the slack part 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 advantage flanges). Idler diameters must exceed the tiniest diameter travel pulley. Idler arc of contact should be kept to a minimum.
In addition to the general guidelines enumerated previously, specific operating features of the get must be considered.