Who could have imagined that one day we would be flocked to us with a complaint of torn belts. “But let me,” the reader will say, “how can a belt designed for an effort of one ton break - the motor is not capable of such a thing!” Indeed, the new one will not break. However, while sliding, he rubs the edge against the flange of the roller, wears out more and more, and a collapse is inevitable. The desire of the belt to slide off the roller can be explained by various reasons. In recent years, we increasingly see defective belts - of variable stiffness in width. They crawl right after the first start of the motor. We turn over such a belt. Crawled in the other direction - it remains to remove and throw it away. This disease is not treated.
In any store you can see videos from different suppliers. What is common? Firstly, in the design of the bearing (usually cheap, single-row) and the clown. When adjusting, the latter is held with a miniature key with two pins, and not with a bulky “30” key, as it was before. What guided the developer - a mystery. An additional key in the master’s arsenal is where is the cost savings! But the most unexpected consequence of "technological progress" is that cars with a bent M10 pin, on which the roller is fixed, fell to us soon. The belt slides off the roller, the edge rubs against the flange - and the end is natural.
How do woe-masters bend a hairpin? The eccentric is fixed in position with the weak key, and the nut is tightened with a serious “17” wrench. And they drag it “from the heart” - who would ever think of controlling the tightening torque, as it should, with a torque wrench! Instead of the intended one - a maximum of 4.2 kgf.m, it turns out so much that it is not possible to keep the eccentric from turning, especially if the master on the physics of this matter has a vague idea. He pressed harder - the hairpin bent. It is imperceptible to the eye, but, in our experience, a shift of its end by at least 0.1 mm is already capable of causing a skew of the roller, “driving” the belt.
But the biggest nuisance that awaits the unfortunate master or car owner is the tearing of the aforementioned studs out of the hole in the aluminum block head. Repair outside the factory floor is not easy. Attempts to quickly drill a hole with a drill and then “cut” the thread usually end with an axis skew …
In this case, we manufacture a conductor (Fig. 1). First, with a hole with a diameter of 10.3 mm - for reaming holes for the stud. (The master drills, the assistant holds the conductor tightly.) Then we drill the conductor up to 12 mm - under the tap M12x 1.25. Having cut the thread in the head, we grind the repair stud.
See how many problems. But tightening the nut with crazy effort is completely unnecessary. But pulling …
Another minus of the roller is its single-row (as a rule!) Ball bearing. There are clearly “conflicting” requirements: if there are no gaps, the bearing will not be able to work, but the greater the gaps, the more likely the assembly will skew under the load from the tensioned belt, if it is even slightly offset from the plane of symmetry. Why not put a double row bearing? Both on the VAZ 2105 engine and in the rollers of the first front-wheel drive cars. But now they’ve saved it. What do car owners do? When buying videos, we carefully select only those in which the play (at least in the hands) is not felt. And before installation we add grease to the bearing - very often it is practically absent there.
The running part of the video is a special song! Some people have not forgotten how great the tension roller of the VAZ 2105 engine worked. The running part is a high-precision steel part. Measuring a plastic roller with a micrometer, it is easy to find such “miracles” of geometry, which is a shame for the manufacturer. The working surface may be oval, stepped, conical, etc. At high speeds here “in miniature” is the same as with wheels when driving fast on a broken road - vibrating, the belt slides even with a little effort.
The next frequent culprit of the vagaries of the belt is the pump. Skewing its axis is unacceptable. A common reason is bearing wear, which we have talked about more than once. The most unpleasant impressions are left by an increased production defect - this is when the pump casing itself is skewed relative to the unit. Such defects must be eliminated in the factory.