Taper Roller Bearing Preloading

[aagoyle1]

Hi

I am a student undergoing a training program. And I have an assignment on taper roller bearings. Now since these bearings have to be preloaded, I have issues with that concept.

Taper roller bearings are usually preloaded with shims etc. this process seems really time consuming! Is there a way to load them with the help of coil springs? how is it done?

Thanks in advance!

[wildwestpat]

Pre load on the bearing can be arranged in a number of ways. The problem with spring loading arises when the supported thrust is acting against the spring. Thus the spring loading has to be greater than the thrust load peaks. Peak thrust loads are often difficult to define.

Other factors to consider are temperature expansion increasing or reducing the pre load. For example vehicle wheel bearings are often taper roller bearings and the garage mechanic will slaken off the pre load so that the bearings are not over loaded when the hub heats up due to the heat generated on braking due to the disc or drum being mounted on the axle supported by the tapper roller bearings.

Suggest you consult the SKF bearing selection pages on the web if you get the chance. From my perspective know the actual working thrust to be accomodated - add a margin for safety - decide on the best way of providing adequate preloading. Then and only then decide if spring loading is OK - shaft stiffness could be compromised if the peak thrust load approaches the spring force exerted (this implies that a much bigger spring is needed). The mechanical methods of providing the pre load would include shims and methods involving a threaded shaft with a lock nut and collar to bear on the inner of the race way. BUT thermal expansion must be taken into account or you might exceed the bearings capabilities. Look at the bearing manufacturer's data sheets as well as their recomended mounting methods.

Belleville washers would provide the high compressive force and would only require a retainer that was in the form of a plate containing the oil seal screwed to the bearing housing. However the spring will wear on the crest of the washer and will weaken the spring this may give a high maintenance liability at the expense of easy assembly. Angular ball bearings (including magneto types) are used in electric motors with spring washers but the motor drive shaft is not designed to take any of the load from the machine in which the motor is used. The tapper roller bearings are normally used for low speed high thrust loads where good shaft stiffness is required You might make special belleville washers to act between the non rotating parts of the bearing support but these will be expensive even in large quantities. Again look at the manufacturers data as high compressive force springs are a specialist item.

Hope this helps. Regards Pat