General Guide Lines
There are some general guidelines which can be applied to all timing belts, including miniature and double-sided belts:
Drives should always be designed with ample reserve hp capacity. Usage of overload provider factors is essential. Belts ought to be rated of them costing only 1/15th of their particular ultimate strength.
For MXL pitch belts, the smallest recommended pulley will have 10 teeth. For additional pitches, Table 8, ought to be used.
The pulley size should never be smaller compared to the width of the belt.
Belts with Fibrex-glass fiber tension members shouldn’t be subjected to sharp bends or tough handling, since this may cause breakage of the fibers.
In order to deliver the rated horsepower, a belt will need to have six or even more tooth 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.
Due to a slight part thrust of synchronous belts in motion, at least 1 pulley in the drive should be flanged. When the guts distance between your shafts is 8 or even more times the size 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 larger pitch belts and 10000 feet per minute (50 m/s) for minipitch belts. For the HTD belts, a swiftness of 6500 feet each and every minute (33 m/s) is definitely permitted, whereas for GT2 belts, the maximum permitted quickness is 7500 foot each and every minute (38 m/s). The utmost allowable operating quickness for T series is normally 4000 feet per 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 is certainly greater than 95%.
Belt drives are usually a source of noise. The rate of recurrence of the sound level increases proportionally with the belt rate. The higher the original belt tension, the higher the noise level. The belt teeth entering the pulleys at high swiftness become a compressor which creates sound. Some noise is 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 sound level is substantially decreased if the PowerGrip GT2 belt is being used.
If the drive is component of a sensitive acoustical or electronics sensing or recording device, it is recommended that the trunk areas of the belt be ground to assure 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 the belt tooth and pulley. This might shorten the belt existence, but it eliminates backlash. Number 10 shows the superiority of PowerGrip GT2 profile so far as reduced amount of backlash can be involved.
Synchronous belts tend to be motivated by stepping motors. These drives are subjected to continuous and huge accelerations and decelerations. If the belt reinforcing fiber, i.e., stress member, as well as the belt material, possess high tensile strength no elongation, the belt will not be instrumental in absorbing the shock loads. This will result in sheared belt tooth. Therefore, consider this into account when how big is the smallest pulley and the materials for the belt and stress member are chosen.
The choice of the pulley material (metal vs. plastic) is definitely a matter of cost, desired accuracy, inertia, color, magnetic properties and, most importantly, personal preference based on experiences. Plastic pulleys with metal 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 in shape, neither too restricted nor too loose. The positive grip of the belt eliminates the need for high initial tension. Consequently, a belt, when set up with a snug suit (that’s, not too taut) assures longer life, less bearing put on and quieter operation. Preloading (often the cause of premature failure) is not 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 steadily, until satisfactory operation is attained. An excellent rule of thumb for installation stress is as shown in Figure 20, and the corresponding tensioning push is shown in Table 9, both shown in SECTION 10 BELT TENSIONING. For widths other than shown, increase push proportionally to the belt width. Instrumentation for measuring belt stress is available. Consult the merchandise portion of this catalog.
Make sure that shafts are parallel and pulleys are in alignment. On an extended center drive, it is sometimes recommended to offset the powered pulley to pay for the tendency 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 teeth on the slack aspect to engage the teeth on the tight part.
It is important that the frame supporting the pulleys be rigid at all times. A nonrigid frame causes variation in center range 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 made for some middle distance adjustment for ease in installing and removing belts. Usually do not push belt over flange of pulley.
Idlers, either of the inside or outdoors type, are not recommended and should not be utilized aside from power takeoff or functional use. When an idler is necessary, it should be on the slack side 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 smallest diameter travel pulley. Idler arc of contact ought to be held to a minimum.
In addition to the general recommendations enumerated previously, particular operating features of the get must be considered.