General Guide Lines
There are some general guidelines which are applicable to all timing belts, including miniature and double-sided belts:
Drives should always be made with ample reserve hp capacity. Use of overload program factors is important. Belts ought to be rated at 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 stress members shouldn’t be subjected to sharp bends or rough handling, since this could trigger breakage of the fibers.
To be able 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 teeth in mesh could be attained by formula given in SECTION 24 TIMING BELT DRIVE SELECTION PROCEDURE. The shear strength of a single tooth is a fraction of the belt break power.
Due to a slight aspect thrust of synchronous belts in movement, at least 1 pulley in the travel should be flanged. When the center distance between your shafts is 8 or more times the size of small pulley, or when the get is working on vertical shafts, both pulleys should be flanged.
Belt surface acceleration should not exceed 5500 foot each and every minute (28 m/s) for bigger pitch belts and 10000 feet per minute (50 m/s) for minipitch belts. For the HTD belts, a quickness of 6500 foot each and every minute (33 m/s) is permitted, whereas for GT2 belts, the utmost permitted swiftness is 7500 ft per minute (38 m/s). The utmost allowable operating velocity for T series is definitely 4000 feet each and every minute (20 m/s).
Belts are, in general, rated to yield at the least 3000 hours of useful existence if all guidelines are properly followed.
Belt drives are inherently efficient. It can be assumed that the performance of a synchronous belt drive is certainly higher than 95%.
Belt drives are usually a way to obtain noise. The rate of recurrence of the sound level increases proportionally with the belt rate. The higher the initial belt pressure, the higher 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 may be the consequence of the shafts not being parallel. As proven in Figure 9, the noise level is substantially reduced if the PowerGrip GT2 belt is being used.
If the drive is component of a sensitive acoustical or consumer electronics sensing or recording device, it is suggested that the back areas of the belt be ground to make sure absolutely uniform belt thickness.
For a few applications, no backlash between the driving and the driven shaft is permitted. For these cases, special profile pulleys could be produced without any clearance between your belt tooth and pulley. This might shorten the belt life, nonetheless it eliminates backlash. Amount 10 shows the superiority of PowerGrip GT2 profile so far as reduced amount of backlash is concerned.
Synchronous belts are often motivated by stepping motors. These drives are subjected to continuous and huge accelerations and decelerations. If the belt reinforcing dietary fiber, i.e., tension member, along with the belt materials, have high tensile power and no elongation, the belt will never be instrumental in absorbing the shock loads. This will lead to sheared belt teeth. Therefore, consider this into account when how big is the smallest pulley and the materials for the belt and stress member are selected.
The decision of the pulley material (metal vs. plastic) can be a matter of cost, desired precision, inertia, color, magnetic properties and, most importantly, personal preference based on experiences. Plastic material pulleys with metal inserts or steel hubs represent a good compromise.
The next precautions should be taken when installing all timing belt drives:
Timing belt set up ought to be a snug in shape, neither too limited nor too loose. The positive grip of the belt eliminates the need for high initial tension. As a result, a belt, when installed with a snug suit (that is, not too taut) assures much longer life, much less bearing use and quieter operation. Preloading (often the cause of premature failure) is not required. When torque is unusually high, a loose belt may “leap tooth” on starting. In such a case, the tension should be increased steadily, until satisfactory operation is attained. A good guideline for installation pressure is as shown in Figure 20, and the corresponding tensioning push is proven in Table 9, both proven in SECTION 10 BELT TENSIONING. For widths other than shown, increase power proportionally to the belt width. Instrumentation for calculating belt pressure is obtainable. Consult the product portion of this catalog.
Be sure that shafts are parallel and pulleys are in alignment. On an extended center drive, it is sometimes advisable to offset the powered pulley to compensate for the inclination of the belt to run against one flange.
On an extended center get, it really is imperative that the belt sag isn’t large enough to permit tooth on the slack aspect to engage one’s teeth on the tight aspect.
It is important that the frame supporting the pulleys be rigid all the time. A nonrigid body causes variation in center range and resulting belt slackness. This, subsequently, can lead to jumping of tooth – specifically under starting load with shaft misalignment.
Although belt tension requires little attention after initial installation, provision should be made for some center distance adjustment for ease in installing and removing belts. Do not power belt over flange of pulley.
Idlers, either of the inside or outside type, aren’t recommended and should not be used except for power takeoff or functional make use of. When an idler is necessary, it must be on the slack aspect of the belt. Inside idlers should be grooved, unless their diameters are greater than an comparative 40-groove pulley. Flat idlers should not be crowned (use edge flanges). Idler diameters must surpass the tiniest diameter travel pulley. Idler arc of contact should be held to a minimum.
As well as the general suggestions enumerated previously, specific operating features of the drive must be considered.