Crown Wheel

[TWebb]

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

Any experience with doing so in an Elan gearbox?

[bitsobrits]

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.

[Ianashdown]

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

Ian

[TWebb]

Yes. The diff.

Thanks Ian

[Andy8421]

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.

[Ianashdown]

I am not the O

Ian

[TBG]

Oh! D

[Ianashdown]

That was supposed to be OP!

[Andy8421]

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.

[Ianashdown]

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

[TWebb]

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