doubt third conical couple bearing

[meek851]

Good evening to all,

I came across this image (taken from the schaffler site).
I noticed that the shaft is supported by 3 bearings (two conical rollers and one roller). They always told me that 3 or more bearings should never be mounted on a tree (because it is difficult if not impossible to align them). the system would be hyperstatic and difficult to calculate, force could arise. However there are those who argue that putting another bearing as in image increases system life (absorbing a radial load) and would like to improve our machines so. What do you think?

Do you ever use more than two bearings?
What are the shortcomings to take? What are the advantages/disadvantages?

Thank you.

 

[TETRASTORE]

rightly as you have pointed out we are in the presence of a hyperstatic system with the risks arising from possible, even minimal, disalignments that could determine avaries especially to the conical bearings. if the support with the two conical bearings is pre-worked, assembled and plugged to the body then together finished on the working center, you get a high precision so you can dare with this solution, if instead it is finished separately, personally I would not feel to recommend it to everyone.
However, we are talking about a leading company that has tested and introduced processing methods that can surely guarantee a certain duration due to the increased load capacity offered by three bearings.
Moreover, companies that have a solid background as well as economic and technological resources can afford to raise the asticella by breaking those that have always been considered limits.

is a bit like the solution of only one bearing to support the screw on some series of gearboxes, delegating part of this function to the two bearings of the coupled motor; Also in this case we have a hyperstatic system, extra with an alignment that is not very precise, but the data say that this solution works and has been accepted by the market.

 

[meccanicamg]

hyperstatic systems are on the agenda, but you need to know how to mount these gearboxes.
the two x-paired bearings make the radio/axial but being very close they are not able to support the arrow at the end of the shaft. in fact create a kind of small zipper with small swings. in tip is mounted a radial roller bearing to hold the bending. can dilate in one way. Therefore the tolerances of the shoulders must be made adequately less/less.
Think about when you make the spindles that there are maybe a dozen bearings... .

 

[Calender]

It is not a dogma that the support on 3 bearings, resulting in hyperstaticity, involves a worsening of the operating conditions. if the presence of another point of support (under external load), seeks a benefit or not, taking into account the induced force in the worst case, it should be analyzed case by case. Most technicians today are convinced that the behaviour of the system is not foreseeable in these conditions, but with today's calculation tools and the possibility of validating the field with experimentation, I do not see the problem sincerely. Of course we must carefully choose how to work the components and do an analysis of tolerances as the god commands (as the other users have already suggested)