911R Nadella Driveshafts

[fetuhoe]

We just had the opportunity to rebuild a pair of the 'Competition' style Nadella Driveshafts which I believe were fitted to the 906 and the 911R.

Re-building these shafts is quite challenging as several of the required parts are difficult to source.

The Universal Joint isn't too bad to find but the shafts which provide the articulation at the other end are unavailable and we had to manufacture a small batch of suitable parts.

We made them from an A2 Air-hardening tool steel, heat treated them to around 62HRC and then ground them to size.

The Rubber V Seals that are needed when the joints are staked were also unavailable and we had a batch made from a suitable Viton Rubber.

We were lucky to find a reasonable quantity of the correct 'staking' washers a few years ago so re-assembly was fairly straightforward.

We honed the bores to the correct fit for the bearings, check balanced the main drive shaft and very accurately centred the shafts used for the half joints.

We have successfully rebuilt a number of Nadella Shafts in the past but this is the first set of 'competition' shafts we have seen and I believe they are quite hard to find.

We have also re-manufactured the Castle Nuts used to retain these shafts in the Trailing Arm Hub from a Grade 5 6AL4V Titanium along with a Thrust Washer manufactured from 17-4PH Stainless Steel hardened to an H900 Temper to prevent galling.

[210bhp]

Nice looking work.
What's the difference between these and standard Nadella shafts? Beefier?

Regards
Mike

[fetuhoe]

They are Tubular rather than solid which means they are much stiffer for a given weight and will also have a much better 'critical' speed.

[911hillclimber]

Complex design when simpler solutions were available.
Why was this design used? I don't know, but did anyone else use them?

[fetuhoe]

I am not sure that there were 'simple' solutions available at the time.

These shafts were initially used on the 906 but I am nor sure if they were used on any earlier cars.

At the time the Rzeppa - now more commonly known as a Lobro - CV joint was extremely rare and not in common use.

Minis for example used Hardy Spicer Joints and suffered problems despite limited wheel movement.

The Imp used a UJ on one end of the drive shaft and a Rotoflex on the other end. Reanult R8 Gordinis used Swing Axles similar to the Beetle.

The main problem is that the relatively long suspension travel needs an arrangement that allows quite a significant amount of 'plunge' and a sliging spline would generate too much axial force for the transmission.

Before a spline can slide it must overcome the friction generated by the locked in torque and this can result in quite high loads.

These joints allow a decent amount of plunge with very low axial force although their configuration does create a torque due to the veelocity change with angle and this does lead to their failure and the need for regular maintenance.

They were used on the majority of 1965 cars but were being replaced by 1966 by Lobro Joints unless a ZF LSD was specified in which case they were supplied up to 1968. This was to do with the configuration of the 904 Style LSD.

I would agree that a Lobro is a much better choice but t'Nadellas' are now becoming pooular to re-fit on restorations of 1965 and early Race/Rally Cars where they would have been an OE part.

[911hillclimber]

Interesting, thank you.
I was thinking of the Elan system or the common rubber joint used in Motorsport a lot around that time.
Icahn see suspension travel was the issue with many a design.
The normal Uj on the back has to deal with a lot in the rear.
Always thought the early Jaguare rear drive shaft used on the E type, S type etc was neat and simple though hardly light.

[fetuhoe]

I think the trailing arm arrangement on the 911 doesn't help either.

[PhilipB]

The hollow Nadellas were used on 904s. They were also an option in the 911 Sports Purpose catalogue as late as 68.


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[LGK6D]

The Nadella's were necessary (at that period) on anything fitted with a factory LSD as the output flanges were Nadella only. I have a German friend with a 68S ordered new fitted with the SportKit 2, LSD and Nadella drive shafts. I'm not sure if his are hollow though. I'll ask him.