Lotus Elan

Final drive shaft dimensions

PostPost by: vincereynard » Thu Apr 15, 2021 11:47 am

I have to mic. up a pair of shafts.

Could anyone state the correct dia. for the bearing surfaces?

Thanks
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PostPost by: elated » Sat Apr 17, 2021 11:15 am

Wouldn't the inside diameter of the bearing race be an equally good starting point to determine serviceability?
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PostPost by: vincereynard » Sat Apr 17, 2021 11:44 am

A possibility but it introduces another variable. Having the definite figure would have been usefull but, apparently, it's a secret.
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PostPost by: Craven » Sat Apr 17, 2021 1:58 pm

Bearing ID is a notional 30mm, but if you are asking someone to give you the spread of interference tolerances which will probably be in micrometers you will be very lucky.
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PostPost by: gjz30075 » Sat Apr 17, 2021 7:04 pm

Vince, is there a difference in measurements between the two shafts?
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PostPost by: rgh0 » Sun Apr 18, 2021 12:49 am

Lots of detailed data on the various bearing manufacturers web sites on the required fits for specific bearings in specific circumstances and on their bearing tolerances

In general, Interference fit in a 30mm ID ball bearing normally has the shaft to be 0.002 mm larger for a light tapping push fit that is the minimum and may result in the shaft moving in the bearing in certain circumstance to the shaft being 0.010mm larger for a press fit. Anything larger than this interference may result in closing up the bearing clearances to much and accelerated bearing wear.

6206 bearings have a typical tolerance of the bore of 30.00 mm of 0.000 / -0.010 mm though typically they are very close to 30.000 mm. So you're shaft should be 30.002 mm to around 30.005 mm. The outer bearing seat on the Lotus wheel axle shafts is a light push fit and is typically around 30.001 to 30.002 mm. The inner bearing seat is typically around 30.002 to 30.005 mm for a tighter fit.

This is my best estimate of the fits, and from measurement of shafts I have but they are all worn originals or reproductions so I don't know how accurate they are versus the original Lotus tolerances

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