I haven’t written an accident analysis for a long time. I recently got a group of photos, which are very strange. I took them up and shared them with you. A friend was doing after-sales work. As a result, the service station gave him a problem. Because it involved the problem of making claims after their products were maliciously damaged, he sent them to discuss with me. The result was not seen or known. He was shocked at first sight of flange nuts.
As an old saying goes, cars are fun. Things can’t cheat, but people can cheat. Let’s take a look at the accident photos first:
A 6×4 dangerous goods tractor makes abnormal noise during driving, and finally the transmission shaft falls to the ground; After making a rescue call, he tried to get out of the toll station. After meeting with the rescue vehicle at the service station, the maintenance personnel found that the rear section of the transmission shaft fell together with the input flange of the middle axle. At the same time, he found that the rear output end of the aluminum alloy gearbox housing had been partially cracked.
Cracks at the root of the input flange bearing seat of the transmission rear cover have been clearly seen at the place where the circle is drawn in the above figure. After the vehicle was towed back to the service station, the maintenance personnel found that the whole rear auxiliary box shell had been broken into several pieces, and the rear auxiliary box lacked support after the bolts were loosened.
According to the analysis of simple accidents, normally, the locking of the input flange of the medium bridge is usually a composite type, which is either self-locking at the same time of pre tightening or pre tightening and fixed with a positioning cotter pin, because the medium bridge has a transition box after all, There are uncertain factors in the overall clearance between the driving and driven gear set of the transition box and the middle axle (for example, the increase of chassis clearance caused by gear wear leads to the increase of impact load at the input end of the medium axle). Because the rear auxiliary box of the transmission is broken and completely disassembled, the user and the service station communicate that there are some problems with the transmission, so the upward feedback is that the transmission shaft and the input end of the medium axle are damaged due to the problem of the transmission. However, from the current site, we can take a look at the medium axle input Status of end (inter axle differential input shaft):
Question 1 (yellow circle in the figure above) the spline groove at the input end of the interaxle differential is gnawed, and the head pre tightening thread is also momentarily pulled by the input flange The width (with spline groove) is the same as that of the rear input spline. This situation may occur only when the input flange nut is loose and the transmission shaft expansion joint has a certain expansion amount. When the positioning is lost and the slight conical rotation will be shortened by a radial force, and then the input flange of the middle axle is ready to disengage.
Question 2. The position of (red circle in the figure above) is the glue coated. According to the truth, it is impossible for the new car that has not been disassembled to carry out the overall painting operation after assembly. This state of not cleaning the glue leakage and not painting.
While waiting for the accident photos, we collected a picture of the correct shape of the flange nut of the medium bridge input from the relevant card friends of the Forum:
The status of relevant parts of the vehicle in this fault is:
The yellow arrow in the figure above shows the scratches caused by dragging the transmission shaft after it fell to the ground. The red arrow clearly shows some traces of oil stains. At the same time, this unparalleled lock nut can be clearly seen in the middle seam between the input flange and the transmission shaft flange fork.
According to the photos taken by the service station, it is obvious that the self-locking nut of the output flange of the gearbox has not fallen off, and the residue of the output part of the auxiliary gearbox has fallen off from the rear auxiliary gearbox of the gearbox as a whole.
In fact, all previous macro performance can relatively reflect the general cause of the accident, but it will change when it is reported by the service station! In the process of communication with the user and the service station, between the service station and the service section of the headquarters, and between the manufacturer and the manufacturer, I think there may be more than n questions:
For the transmission shaft, only the main body is seen, but the middle axle input flange and the nut are not reflected. The cold residue of the gearbox will make many people look like the gearbox is broken. In this case, the service section of the headquarters intuitively judged that the joint and several liability was caused by the damage of the gearbox, but the damage of the input end of the intermediate axle inter axle differential was not reflected. If the gearbox manufacturer was asked to compensate for the overall loss, wouldn’t it be like there is no silver here?
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