Crown Wheel

PostPost by: TWebb » Mon Oct 31, 2022 3:53 pm

It is not unusual to lighten crown wheels in racing applications.

Any experience with doing so in an Elan gearbox?
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PostPost by: bitsobrits » Tue Nov 01, 2022 12:29 pm

There are no crown wheels in an Elan gearbox....the crown wheel is found in the diff.

And of all the things you could do to improve performance in an Elan, I would think lightning the crown wheel would be about number 1346 on the list.
Steve

Elan S1 1963-Bourne bodied
Elan S3 1967 FHC pre airflow

Formerly:
Elan S1 1964
Elan S3 1966 FHC pre airflow
Elan S3 1967 FHC airflow
Elan S4 1969 FHC
Europa S2 1970
Esprit S2 1979
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PostPost by: Ianashdown » Tue Nov 01, 2022 2:23 pm

Not impossible, but tough to do in a hardened Crown Wheel.

Ian
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PostPost by: TWebb » Tue Nov 01, 2022 3:02 pm

Yes. The diff.

Thanks Ian
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PostPost by: Andy8421 » Tue Nov 01, 2022 5:22 pm

Ian, Its a strange thing to want to lighten.

I could sort of understand it if the Elan had a live axle, but with IRS, the diff is sprung weight. In terms of rotational inertia, it has a small diameter, and even in 4th gear, is still geared down by the diff ratio. If improving acceleration is the aim, far better to lighten the flywheel or crank.

What was your thinking behind this?

Andy.
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PostPost by: Ianashdown » Tue Nov 01, 2022 5:28 pm

I am not the O

Ian
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PostPost by: TBG » Tue Nov 01, 2022 10:16 pm

Oh! D
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PostPost by: Ianashdown » Tue Nov 01, 2022 10:32 pm

That was supposed to be OP!
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PostPost by: Andy8421 » Wed Nov 02, 2022 7:20 am

Andy8421 wrote:Ian, Its a strange thing to want to lighten.

I could sort of understand it if the Elan had a live axle, but with IRS, the diff is sprung weight. In terms of rotational inertia, it has a small diameter, and even in 4th gear, is still geared down by the diff ratio. If improving acceleration is the aim, far better to lighten the flywheel or crank.

What was your thinking behind this?

Andy.

Apologies Ian & the OP, I wasn't paying attention.

Question still stands though, I did a bit of googling and all I could find was reducing overall diff weight to reduce unsprung weight, so I am still in the dark about why this would be done on an Elan.
68 Elan S3 HSCC Roadsports spec
71 Elan Sprint (being restored)
32 Standard 12
Various modern stuff
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PostPost by: Ianashdown » Wed Nov 02, 2022 2:08 pm

Having worked in the design office of a racing gearbox manufacturer I can give some input. We lightened the Crown Wheel on high end racing ‘boxes, F1 but not FF, because we lightened everything we could. But doing it while it was still soft, before heat treatment, is a very different proposition than after it is hard.

The amount that can be removed is quite small, and the effort very high. I think there are other places I’d look to save vehicle weight. The affect on rotating mass will also be small as a percentage of the rotating mass.

My advice, look elsewhere, there are easier places to lighten, even on an Elan!

Ian
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PostPost by: TWebb » Wed Nov 02, 2022 4:05 pm

Ian,

Thanks for the reply. That is the reasoned reply I was hoping to get from this group.

It was a question. Nothing more.

Thanks
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