New AC Ace/Aceca Rear Hub Tapered Spline Conversion Kit

[dkp_cobra]

Hi,
does anybody know the AC Ace/Aceca rear hub tapered spline conversion kit made by TripleM: https://www.triplembyjswl.com/stock-parts/ac-ace-aceca-rear-hub-tapered-spline-conversion-kit-new-product-_15.shtml

[Robin A Woolmer]

I understand a number of these kits have been fitted to several cars in UK & USA, the only issue which may be a problem is the type of nut used which works by deforming the axle thread so potentially causing some thread damage, it might be better to use the traditional castle nuts with a split ping to retain it!
I am not aware of any failures!

Robin

[B.P.Bird]

The whole question of rear hub drive failures on Ace and Aceca is quite interesting and I wonder if the continued effort to beef up the actual component is, possibly, missing the point ?
I remember, as an enthusiastic schoolboy, being disappointed when a Vanwall suffered yet another throttle linkage failure and could not finish a Grand Prix. How difficult can it be to strengthen the component which is failing I asked? Not so simple it seems as the problem persisted until it was discovered that the linkage was resonating in tune with one of the engine's harmonics.
So there have been hub failures even with the rather beautifully engineered modern substitute. Indeed A.C. experienced the problem very early in Ace production and increased the size of the rear hub pinnacle nut as well as including the maintenance instruction to check tighten the pinnacle nut after the first 500 miles, again at 1000 miles and thereafter at every service: Therefore I wonder if one should look a bit deeper at what is really going on ?
It seems to me that there is every possibility that the hub failures (early size, later size and modern substitute) might all be caused by something less obvious than insufficient hub strength. My bet would be on the exceedance of the maximum angularity limits of the Hardy Spicer universal joints. Most of us are aware that, annoyingly, one cannot rotate a rear wheel through 360° when your Ace or Aceca is jacked up i.e. all weight taken off of the wheel and the suspension allowed to droop. If you apply sufficient force the wheel will turn over with a nasty 'over centre' action. At the same time the suspension will compress, lifting the spring and then dropping it again as the universal joints bind and unbind. Imagine this happening with the car in motion - the whole corner will experience large repetitive loads. You might as well take a sledge hammer to the hub. Can this occur with the car driving on road or track ? Well yes it can and does: Any manoeuvre which unloads the suspension can exceed the angular limit of the universal joints. Obviously we don't make a deliberate habit of launching in to the air from a humpbacked bridge, but these cars were designed for brisk cornering and leaving the inside wheels unloaded is not difficult on dry roads, add in the odd unfavourable bump or hollow and the drive shaft may give a hammer blow to the hub.
I am completely unqualified to prove any cause and effect, but it does seem to me that the suspension should not be allowed to droop to the extent that the universal joints bind. Excessive droop on the front suspension should not be allowed either because of the contact between chassis and steering track rod, but that's another story. In both cases the solution is to use the Spax reduced travel dampers. Of course only time will tell if preventing excessive droop will improve hub outer driveshaft life.

[Robin A Woolmer]

Barrie
You have made some interesting observations, I know JSW who make the axle conversion have some CAD capability, it might be nice if they have the capability to do some simulations & stress analysis on the axle, however the loads you indicate are quite complex!
An interesting observation on Fundamental part resonance, when CEO of a HT Switch-gear Company one of the 12KV units had failures of the Copper electrodes, following some analysis it was found that the electrode had a sympathetic resonance to the line frequency,  the electrode was redesigned to change the fundamental part resonance!
This is often overlooked by Engineers, the Weller engine crankshaft has similar issues!     

[Klassik Metall]

I fitted this setup to a customers car a couple of years ago & so far it has been trouble free.
There were no issues regarding fitting & everything was a straight swap for the original components.
My only slight complaint was that the hubs & shafts weren't zinc plated, which considering the price was a little disappointing.
In this particular case the customer had the parts zinc plated before fitting.
I didn't have any issues regarding fitting the lock nuts & didn't feel that they would cause any thread damage when removed.
However, I would personally have preferred a castellated nut & spit pin arrangement.
Overall, I think that this kit is a good solution to a not uncommon problem.

I'd also like to point out that all the failed original style shafts that I've seen, have failed due to the sharp corners on the locking key &
the less than perfect seating of the tapered components.
When I fit the standard setup I lap the taper on the shaft into the hub with very fine grinding paste & then check the fit by blueing.
I also replace the standard keys with ones with rounded ends that completely fill the recess in the drive shaft & remove the major stress raiser.
I've yet to experience a failure when the parts are assembled in this way & when I've taken them apart they need considerable pressure
to separate the parts, I normally have to use a hydraulic press as I cant separate them with the usual hub puller.

I also agree with Barrie about the standard rear dampers allowing the drive shaft UJs to lock up on full droop.
I fit custom made Koni classic dampers that are around 30mm shorter than the standard set & allow more "spirited" cornering.

Regards, Luke.

[dkp_cobra]

The kit from Triple M neither zinc plated not painted due to their tolerances. They do not recommend to zinc plate these parts.
Beside Triple M also INracing has a set of driveshaft and hub in the original style with key. There parts are a around 10% more expensive than the kit from Triple M. I think if you have to replace one side and want to keep it original the INracing is a good option. If you have to replace both sides and originality is not the most important thing the Triple M kit is a good choice.
Unfortunalety, both sides of my Aceca have to be replaced  :(

[dkp_cobra]

I understand a number of these kits have been fitted to several cars in UK & USA, the only issue which may be a problem is the type of nut used which works by deforming the axle thread so potentially causing some thread damage, it might be better to use the traditional castle nuts with a split ping to retain it!
I am not aware of any failures!

Robin

The kit arrived today. The nut has been changed. It is a normal nut now and it should be secured with blue Loctite. So, no deforming of the axle thread anymore.

[Aceca289]

Indeed A.C. experienced the problem very early in Ace production and increased the size of the rear hub pinnacle nut as well as including the maintenance instruction to check tighten the pinnacle nut after the first 500 miles, again at 1000 miles and thereafter at every service

This is good information...I understand that the proper "set-up" of the rear hub with the standard keyed axel is important so the load is carried by the taper and not the key...so maintaining the tightness of the pinnacle nut sounds appropriate for good axel health. My axels were replaced fairly recently (mileage wise), so I'd like to follow these guidelines to possibly avoid future axel failures.  Can someone explain the proper "set-up" when installing the hub? Is there a specified torque to apply to the pinnacle nut? If so, I'd imagine it might be a minimum torque that one might have to exceed to advance the nut to the next castellation, in order to insert the cotter pin (split pin)??

Thanks in advance for any assistance regarding checking the pinnacle nut for tightness.

John

[Robin A Woolmer]

JSW Have a CAD capability which was used to design the parts, why not contact them for the recommended torque for the nut torque?
They might also have  recommended fitting instructions, the design still relies on the taper to so they may suggest a hub fitting load/Force before the nut is fitted & torqued up!
Robin 

[dkp_cobra]

JSW recommends a torque of maximal 120ft/lbs for the main nut.

[Aceca289]

Is the same torque required for the original AC axel setup? I'm not replacing my axels with the new splined ones. I was looking for the typical specs for reinstalling an original AC hub and axel...and maintaining the tightness of the Pinnacle nut.

Thx

John

[B.P.Bird]

Pinnacle Nut Torque:

"7) No torque figures are given in the General Instructions and on the early 5/8" BSF Pinnacle Nut I have used 150 lbs/ft – something of a shot in the dark as, even if the shaft, B60074, was made from EN12 steel we have no idea of its heat treatment. In any event, so far, that figure has not produced any damage. For the later 3/4" BSF pinnacle nut, using the same logic, one might go to 260 lbs/ft, however I have not tried that so you're on your own. It is important to re-torque these Pinnacle Nuts frequently. A.C. obviously identified the taper hub/shaft joint as a vulnerable part of the design early on, not only increasing the size of the Pinnacle Nut, but also revising the re-torqueing advice in the later General Instructions to 'first 500 miles, again at 1,000 miles and thereafter at each service.' This would be every 500 miles if you read the service list under the Lubrication Chart - page 46, Ace and page 56, Ace Bristol. As you torque up on the bench some helpful blows with a heavy copper mallet, using a suitable pad, on the centre of the outer drive shaft flange against a padded immovable object for the Hub to sit on, will help to get the taper as tight as possible."

This was a paragraph from some Hub Notes I wrote a while ago for Ace and Cobra and which are available to A.C.O.C. Members, as noted in ACtion
Barrie

[Robin A Woolmer]

Barrie
The 3/4" BSF Thread was changed October 1958.
Robin 

[brucerudin]

I fitted this set when building my Ace Bristol. The car gets hard rally use and the engine STRONG.  Absolutely no issues fitting or using it.  Why replace an original part like this with an acknowledged weak link?  More than happy to use my Rack and pinion steering, full synchro close ratio gearbox and overdrive.  Great car.

[TTM]

Good evening,

Has anyone ever looked into having a clamping nut made to fit our Aces' hubs rather than the original layout using a nut with securing pin?
I believe this would be a worthwhile upgrade as it would allow disposing of possible shims used so that the nut aligns with the hole in the hubs for the securing pins, and may also not loosen over time, or perhaps not quite as easily as the original "pinnacle" nut. As much as I enjoy servicing my Ace I must concede that the need to retighten the rear nuts every couple of hundred miles is getting a little long in the tooth.