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Hub Design
welshy - 17/8/09 at 05:29 PM

hi,

I have made my rear swing arms which has involved turning down some mini hubs and then sleeving them in carbon steel tubing. Unfortunately the hubs are case iron so I can not weld the sleeve to the hub. I have decided to make some new hubs in carbon steel but wondered what tolerance is usually used on the bore of the hub? Any suggestions?

Cheers
Ben

nasty-bob - 17/8/09 at 06:18 PM

Hi Ben,

I'm not familiar with the mini hub assembly but I made my own version of the sierra hub so may be able to help.

Are bearings pressed into the bore? If so you will want a light interference fit between the bore and the bearing. Tolerance on the bore should be something like +0/ -0.05mm. Measure the bearing to get the nominal dimension.

If the arrangement is different post back and I'll have another go.

Cheers

Rob

mark chandler - 17/8/09 at 09:08 PM

I put my Sierra hubs in a lathe and turned them down, then just welded to them, Been okay up to now.

Regards Mark

welshy - 17/8/09 at 10:30 PM

Cheers for the replies. I believe the Sierra hubs are cast steel unlike the mini hubs so they should be fine to weld to.

The mini bearings are not a press fit as they can be removed by some labourious strategic tapping of the bearing with a drift. To fit them involve a large socket and some gentle tapping which suggests a very slight clearance fit.

I have been on the timken website who manufacture the bearings and they have a tool which shows the following tolerances,in inches (when there are two figures the first is the max and the second is the min).

Designation
Bearing Type -- TRB-TS
Part Number - Inner -- LM67049A
Part Number - Outer -- LM67014
Bearing Class 2
Unit Max Values Min Values
Nominal Bore Inches 1.2500
Nominal Outer Diameter Inches 2.4404

Nominal Bore Inches 1.2505 1.2500
Bore Tolerances Inches 0.0005 0.0000
Cone Stand Tolerances Inches 0.0040 0.0000

O.D. Tolerances Inches 0.0010 0.0000
Cup Stand Tolerances Inches 0.0040 0.0000
Overall Width Tolerances Inches 0.0080 0.0000
Overall Width Tolerances Inches 0.0010 0.0000
Maximum Radial Runout Inches 0.00150

Unfortunately i think the toleances refering to the bore are actually the bore of the bearing where the drive shaft locates.

nasty-bob - 18/8/09 at 05:07 AM

If you have to tap the bearings out, then it is slight interference, even if its a 0,0 interference. You wouldn't want to install the bearings with a clearance fit as everything would get a bit sloppy and it also gives the possibility of the outer race rotating in the bore which will cause wear.

Cheers

Rob

welshy - 19/8/09 at 10:19 AM

What do you guys think to shrink fitting the original machined down cast iron hub into the sleeve then locking it radially with a couple of set/grub screws?

My only concern is the interference fit may reduce the bore of the hub slightly although the bearings are taper bearings so in theory this will result in the cone part of the bearing being slightly out of position axially whilst still maintaining full contact with the cup.

andyps - 20/8/09 at 01:32 PM

quote:
Originally posted by welshy
Cheers for the replies. I believe the Sierra hubs are cast steel unlike the mini hubs so they should be fine to weld to.

The mini bearings are not a press fit as they can be removed by some labourious strategic tapping of the bearing with a drift. To fit them involve a large socket and some gentle tapping which suggests a very slight clearance fit.

I have been on the timken website who manufacture the bearings and they have a tool which shows the following tolerances,in inches (when there are two figures the first is the max and the second is the min).

Designation
Bearing Type -- TRB-TS
Part Number - Inner -- LM67049A
Part Number - Outer -- LM67014
Bearing Class 2
Unit Max Values Min Values
Nominal Bore Inches 1.2500
Nominal Outer Diameter Inches 2.4404

Nominal Bore Inches 1.2505 1.2500
Bore Tolerances Inches 0.0005 0.0000
Cone Stand Tolerances Inches 0.0040 0.0000

O.D. Tolerances Inches 0.0010 0.0000
Cup Stand Tolerances Inches 0.0040 0.0000
Overall Width Tolerances Inches 0.0080 0.0000
Overall Width Tolerances Inches 0.0010 0.0000
Maximum Radial Runout Inches 0.00150

Unfortunately i think the toleances refering to the bore are actually the bore of the bearing where the drive shaft locates.


Those are the bearing tolerances you have quoted there, rather than the fit for the bearing in the housing. From memory of my time at Timken I think the bearings should be a slight interference fit, and the fact that they have to be tapped into and out of place indicates this to be the case.