Diff Oil Cooler FIA

[vstibbard]

I'll check paper work as it was shipped to Australia, the S2 26R was definitely in period with parts as specified in parts list, the all steel dry sump engine I know was homologated for Group IV, which I think was post 65 cut off.

I had arguments with eligibility officers in Australia over the alloy radiator, which I resolved when I provided the manual and parts list (which I must have found in the wiki) as they validated the spec. I had even shown them the original radiator!!!

[rgh0]

@Rohan:
What maximum temperatures would you want to have your gear oil?

In my experience the transmission/differential really really gets hot.
From my 10 years experience with tracking a Lotus Elise (gearbox and differential in one housing) I can tell that on track the gear oil rises up very very fast to 130 degrees Celsius after 15-20min driving and I always backed off to cool down again as I was told not to get it above 140 degrees Celsius because the gears and rings would become very weak and could break/loose their teeths. The Toyota gearbox is very fragile on 3./4. gear ... Shortly after the first experiences with measuring the oil temperatures I had an transmission oil cooler fitted with switch point on 95 degrees and never got above 120 degrees after. I think Graeme had the same transmission cooler like me on his Exige.
On road driving oil temperatures were only between 80-90 degrees so no cooler needed.

Of course I don´t know how it is/will be in the Elan but I would think it´s not much cooler?
And if the won´t get that hot the housing won´t too.


@Vaughan:
When did your car had been built and had the first race been pre ´66?
I will ask my assessor. He might say yes but I suspect the FIA would still reject the registration with diff cooler like with dry sumped engines.

From a lubrication perspective a Redline polyolester oil ( MTL or MT90 in your transmission?) should be good for many hours at 140C, maybe more. The casing may not like these temperatures with thermal expansion causing bearings to come loose in the case but that's a question of assembly tolerances in the original design. I don't believe you should have any problem with the steel gears or synchro rings ( brass?) themselves at these temperatures as no strength change occurs until much higher temperatures. At high temperatures some gear oils can become corrosive to brass but the Redline oils are good for higher temperatures. A cooler to keep the oil at 120C is not going to hurt if you can use one. If you cant on an FIA Elan then careful work on bearing fits should ensure you can run without a cooler with higher oil and casing temperatures. Generally a low viscosity high film strength oil like the Redline polyolester oils will also run at low temperature due to low friction compared to the original oils of the 60's.

cheers
Rohan

[vstibbard]

Rohan, does same hold for differential which is what this thread is related to, my elan came with diff cooler and pump fitted from factory,. the 26R has mag rear casing with additional boxes to help locate the rear casing to the aluminium nose casing.

It clearly worked, as my car used a 3.77 diff with ZF cam and pawl LSD did multiple 12 hour races in period without failure and the original diff, and gearbox are in fine condition.

[rgh0]

Rohan, does same hold for differential which is what this thread is related to, my elan came with diff cooler and pump fitted from factory,. the 26R has mar rear casing with additional boxes to help locate the rear casing to the aluminium nose casing.

It clearly worked, as my car hick in the long distance races used a 3.77 diff with ZF cam and pawl LSD did multiple 12 hour races in period without failure and the original diff, and gearbox are in fine condition.

Yes same comments apply to the Elan Diff. Back in the 60's with the state of lubrication technology then a diff cooler would have been required for reliability in long distance races. With the right assembly fits today and the best quality oils you could probably get away without it but it would not hurt to have one.

cheers
Rohan

[Vali]

I'll check paper work as it was shipped to Australia, the S2 26R was definitely in period with parts as specified in parts list, the all steel dry sump engine I know was homologated for Group IV, which I think was post 65 cut off.

Dear Vaughan,
did you got around to check your paper work regarding the diff cooler?

[vstibbard]

Apologies for the delay, my car, the third last S2 26R was built in late 65, shipped to Australia. It had an accident in its first practice, requiring a new shell that was shipped from UK and finally made its first race in Brisbane in June 66.

[Elan45]

My type 45/ 26R is fitted w/ the cross-roller halfshafts. I had long suspected these were required to be able to fit the S2 diff output shafts and the S2 outer hub shafts. The original owner, Dr Counts, was very friendly w/ the Lotus Components people. His widow told me stories about visiting the works while on a ski vacation to the alps.
Roger

PS: I've thought about using the ring gear inside the housing as a pump to move the fluid through the cooler. Looks like a free pump just sitting there.

[Frogelan]

The ring gear idea is very bright.

I'm no engineer but I wondered if the warmth of the oil combined with the general operational pressure spray might provide enough impetus to send the oil into a return circuit / breather bottle outside the diff.

If placed to the rear of the diff with a filling point in the boot, this could be quite a good way to do regular maintenance on a racer.

A simple trip to a breather bottle and back could possibly do no harm and Mr Appendix K has not outlawed filler arrangements so far.