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 program factors is essential. Belts ought to 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 could cause breakage of the fibers.
In order to deliver the rated horsepower, a belt must have six or even more teeth in mesh with the grooves of small pulley. The amount of teeth in mesh may 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 more times the size of the smaller pulley, or when the get is operating on vertical shafts, both pulleys should be flanged.
Belt surface rate 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 acceleration of 6500 feet per minute (33 m/s) is certainly permitted, whereas for GT2 belts, the utmost permitted swiftness is 7500 feet per minute (38 m/s). The maximum allowable operating velocity for T series is usually 4000 feet per minute (20 m/s).
Belts are, in general, rated to yield a minimum of 3000 hours of useful existence if all instructions are properly followed.
Belt drives are inherently efficient. It can be assumed that the effectiveness of a synchronous belt drive is usually greater than 95%.
Belt drives are usually a way to obtain noise. The frequency of the sound level boosts proportionally with the belt rate. The higher the initial belt pressure, the greater the noise level. The belt teeth entering the pulleys at high acceleration act as a compressor and this creates noise. Some noise is the consequence of a belt rubbing against the flange, which could be the consequence 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 electronics sensing or recording device, it is recommended 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 without any clearance between your belt tooth and pulley. This might shorten the belt lifestyle, but it eliminates backlash. Figure 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 subjected to 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 and no elongation, the belt will never be instrumental in absorbing the shock loads. This will result in sheared belt teeth. Therefore, take this into consideration when how big is the smallest pulley and the components for the belt and pressure member are selected.
The decision 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 material pulleys with metallic inserts or metallic hubs represent a good compromise.
The next precautions should be taken when installing all timing belt drives:
Timing belt installation ought to be a snug fit, neither too limited nor too loose. The positive grip of the belt eliminates the need 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) is not 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 rule of thumb for installation pressure is as shown in Figure 20, and the corresponding tensioning force is proven in Table 9, both proven in SECTION 10 BELT TENSIONING. For widths apart from shown, increase drive proportionally to the belt width. Instrumentation for calculating belt pressure is obtainable. Consult the merchandise section of this catalog.
Be 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 part.
It is necessary that the body supporting the pulleys be rigid at all times. A nonrigid body causes variation in center range 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 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 used aside from power takeoff or functional use. 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 must not be crowned (use advantage flanges). Idler diameters must surpass the smallest diameter travel pulley. Idler arc of contact should be held to a minimum.
In addition to the general guidelines enumerated previously, specific operating features of the get must be considered.