Right ISO fit for a bearing in a aluminium housing

[ddillen]

Good day everybody,
My name is Dillen and I am a member of a formula student team in The Netherlands. Currently we are designing our first own produced planetary reduction gearbox for our electric AMK motors. The gearbox will be a stepped/compound configuration. Due to data of other formula student teams we know that these types of gearboxes can heat up to 90 degree celsius (194 F) during hard use. The housing of this gearbox will be made out of 7075-T6 aluminium. A 2 row angular contact ball bearing needs to be interferenced fitted with the outer ring into the housing. The bearing has an inner (bore) diameter of 50mm and a outer diamter of 90mm. The problem I face is how do I determine the right iso fit for the bearing seat in the housing? The aluminium housing expands alot more than the steel outer ring of the bearing. At all times i need to make sure it stays in an interference fit.


I came a cross AN tolerance rings. Does somebody have experience with these rings. And are these rings suitable for a bearing that connects the wheelhub to the gearbox housing.


Thank you in advance for your time and effort.

 

[TugboatEng]

This is a thrust bearing. It needs to be retained by more than OD interference. A clearance fit like H7 or H6 simplifies assembly and disassembly but will require a retainer plate. The amount of interference required to positively locate a thrust bearing will cause internal clearance issues within the bearing.

 

[MintJulep]

All of the major bearing manufacturers have design engineering guides, calculation tools and real application engineers to help the designer use their products correctly.

For example, Timken: https://engineering.timken.com/engineering-tool/bearing-fitting-practice/

 

[pmbrunelle]

I have used tolerance rings a few times; the waves are not necessarily equal all around, and there is a necessarily a gap between both ends of the metal strip, so these factors will result in some eccentricity, which may affect your shaft centre distance.

Also, the tolerance ring is springy, so gear-separating forces will cause the bearing to shift; you should study whether this compliance matters to you.

The tolerance ring manufacturers have some information about their products, but in all likelihood, some prototype rings would need to be manufactured so the relevant data can be measured.

I haven't taken apart too many automotive gearboxes, but I don't think that tolerance rings are commonly required to hold outer bearing races in aluminium cases.

 

[ghostdigital]

Tolerance rings are not generally used in high loading applications, wheel hub and gearbox bearings. These components are most likely utilized in friction or alignment applications.

For actual bearings to seat or race application I would use ABEC or ISO industry standards. If you select an industry (manufacturer) bearing they often provide recommend fits and form tolerances which you should consider.

These guys provide some overview of tolerances for ABEC and ISO:

Ball Bearings ABEC Standard Tolerances Data

Ball Bearings ABEC Standard Tolerances Data. The following are Annular Bearing Engineers Committee (ABEC) for ball bearings quality classes.

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