When searching for a possible explanation for our screaming bevel boxes I wanted to see how BMW makes their bevel boxes on their motorbikes (which don’t scream) In a German motorcycle magazine I found a picture of a rear wheel drive of the BMW 1200 GS. And as you can see on the pictures they looks similar except the support of the pinion wheel !!
The picture on the BMW unit shows that the pinion shaft is supported on both sides. But ………. (so far as I can see) in the Qauife bevel box there is NO support on the end of the pinion shaft !! For the pinion shaft it has only one bearing in the main housing and probably one more bearing in the screwed on removable bearing housing which get attached to main housing. (so far as I can see on the picture) So both bearings of the incoming shaft are on the same side.
When driving, the pinion wheel is trying all the time to push itself out of the crown wheel due to the force on it. Because there is only support on one side of the incoming shaft, it will create (depending on the load) a huge force on this bearings. The bearing near the crown wheel will get a force away from the crown wheel. The force on the bearing in the removable housing will be to the opposite direction ! Due to this force, the shaft try to move the removable bearing housing (which is bolted on the main housing) to one side. And because it’s just bolted on there will be always some movement possible.
When shimming the whole unit for optimum play between the teeth there is no force on this removable bearing housing. When driving and applying force on this removable bearing housing it will be forced in one direction. But that direction will create more play between the teeth of the pinion and the crown wheel Which also results in the fact that optimum shimming will be impossible, because when shimming this force on this removable housing is not there. So far as I know the amount of noise is very critical to the amount of play between the teeth. So everyone can understand that if we get more play we’re getting noise. Explains also why the noise is gone when taking your feet of the throttle because the force is gone which pushed the pinion wheel out of the crown wheel so don’t create the biggest play possible anymore.
This also could explain the leaking which some boxes have on the incoming seal because the shaft will be pushed all the time to one direction/side in the seal (also because of the length leverage bearing and seal) The difference in noise level when hot can also be created by more play between the wheels due to the expansion of the housing.
Is my simple view correct ? I don’t know but it looks to me a explanation for the noise. What can we do about it ? The best way would be a better layout (like BMW) but that means there need to be complete new bevelbox developed. Perhaps a better fixation for the removable bearing housing to the main housing will also do the job so the two housings will more act as one piece.
Who can we blame for this ? Quiafe ? They say: We made it how MMC told us to make it. Can we blame MMC ? They say: It’s constructed by Quiafe and they are the specialist in this field. We only can hope that a company ( Garage 56 ? ) develops a better constructed piece of machinery (like the upgrade of the compensator to the Centa unit)
