REPORT - New splined stub axle's from Winchester

[Aceca289]

I apologize if I hijacked this thread with the photos of my axle failures. I thought that providing photos of the stock arrangement might help people visualize the inherent problems that have led to the need for a new solution and prompt some thoughts to help solve Rob's concerns. Nigel Winchester's axle design looks like a good way to resolve this situation and I hope the solution is as simple as adding a castellated nut and split pin as can be seen in the photo of the stock axle and mentioned in one of the earlier posts.
   
   In my case, Robin suggested that the hub might have been loose on the shaft. Does anyone know if there's a need to re-torque the axle nuts after some particular mileage interval (with the stock set-up)? I certainly want to maintain good axle health on my Aceca going forward.[:)]
   
   Thanks,
   
   John

[AcecaRacer]

All -
   
   Thank you for your spirited responses to my post.  I know we all share in the Achilles heal that is the keyed axle.
   
   Firstly, let me say that the various posts on the keyed axles served a very helpful purpose in showing everyone what can happen.  This is extremely helpful as we can then better understand what we are dealing with.  I suspect, like me, we are mostly visual learners, so many thanks for the postings, pictures and insight.
   
   Now, I would be happy to post the pictures of the new axles so you could see their design...if I knew how.  At first glance, they are beautiful in their construction.  Robust in every way.  However, unlike the stock axles that have a threaded end with a castellated nut, they have a threaded core that then is held in the hub by a simple bolt and washer.
   
   So, picture the male splined stub axle being inserted into the female hub and held in place by a bolt and washer.  No cotter pin or safety wire to hold it in place...just torqueing and Loctite. Not good.
   
   What we have now done, is to create a thick washer that has "legs" that extend down into the splined end of the shaft thus preventing the washer from being able to rotate.  We have then created another fitted washer (with a hexagonal center milled out of it) that slips over the torqued bolt head and slides flush to the lower washer.  Both washers have also been pre-drilled and threaded to hold a 3/16 screw which when inserted now holds the the two washers tightly in place and thus prevents the bolt from rotating - that's the theory anyway.
   
   So, now we have a mechanism that should hold the bolt on either side in place.  We will see as I am racing this weekend at Sears Point in Sonoma.
   
   Again, I have pictures of the new axles to share and will also take pictures of the "fix" for you all to see and comment on.
   
   If someone can help me figure out how to post those pictures, I would really appreciate it!
   
   More to come!
   
   Rob

[AC Ace Bristol]

Rob.
   
   Lock tabs. Locktight and Grub Screws are all methods of location and securing, However  should the threads be handed as per our Spinners thereby as the assembly rotates it is continually tighteneng [?].[?].
   
   Just a observation,  We all know this is the Achilles Heal of the Ace / Aceca and your thread has drawn our attention to the problem and well on the way to Solving the Problem .[:)]
   
   Good Luck this weekend at "Sears Point", May it all hold together... Keep it on the black stuff, Enjoy  and Finish.
   
   A great informative thread, appreciated by many......[;)]
   
   Keith ..[:)]

[nikbj68]

quote:Originally posted by AC Ace Bristol: Rob... should the threads be handed as per our Spinners thereby as the assembly rotates it is continually tightening [?].

quote:Originally posted by AcecaRacer:After removing the knock-off of the left rear...The bolt had broken the Loctite seal and had spun 6 FULL REVOLUTIONS!...I also decided to check the right axle. It had rotated 4 revolutions!

Although a left-hand thread might help, it wouldn`t be the solution. Best of luck with your locking tab arrangement.
   Posting photos info here, 5th post down, or you can email them to me & I`ll 'host 'n' post' them. [:)]

[AcecaRacer]

All -
   
   I have just spoken to Nigel to bring him up to speed on this thread and also what I have been working on here.  He is VERY keen to understand the specific issues and has become aware of the main issue of our discussion.
   
   He is in the process of designing a MKII version which would mirror the original design in providing a male threaded end instead of a a female threaded core.
   
   In the mean time, he has also been using a tabbed washer to hold the bolt in place.
   
   Like the good chap he is, he has offered to send me his MKII version when completed FOC and swap out my MKI version.
   
   In the mean time, I am also sending him some additional design input to deal with a few other issues that we have found...including chamfering etc.
   
   I just wish he used email and the internet!
   
   I will be sending the pictures I have of the shafts as they are and also the fix we have created to Nick who has graciously offered to help.
   
   More to come...Rob

[Robin A Woolmer]

That looks interesting, however following discussuions with Gerry Hawkridge he has decided to make a new upright to use a similar bearing & drive arrangement to the FIA Cobra using double Timken taper bearing system which is a well proven design approach, this will ensure full support of the hub which will have the splined drive. hopefully this will be available in a few months.
   Robin

[nikbj68]

quote:Originally posted by AcecaRacer: I will be sending the pictures I have of the shafts as they are and also the fix we have created to Nick

And here they are:(Click any photo to link to a larger version)The Stub axle/ hub units:
   
   
   
   And from a different angle.
   
   
   
   Rob`s description: A thick washer that has "legs" that extend down into the splined end of the shaft thus preventing the washer from being able to rotate. Another fitted washer (with a hexagonal center milled out of it) that slips over the torqued bolt head and slides flush to the lower washer. Both washers have also been pre-drilled and threaded to hold a 3/16 screw which when inserted now holds the two washers tightly in place and thus prevents the bolt from rotating.
   
   
   
   And finally, how it looks in place. As Rob says, an elegant solution!
   
   
   
   The result is this, Rob chasing down a P3 Alfa Romeo [8D]:
   
   

[AcecaRacer]

Well done Nik!  Many thanks.

[dkp_cobra]

A picture says more than 1000 words. Really nice. The setup looks quite similar to the solution used at the MK IV rear hubs. Well, there you have the bolt on the inner side not the outer side. To prevent the bolt from loosening after mounting a small hole was drilled into the head of the bolt into the axle and a splint was pushed into this hole. Works perfectly but if you disassemble it you will never fit this hole again.
   
   Maybe another solution without the small screws whould be that the "legged" washer has one flattened side. Between the washer and the bolt a looking plate can be used.
   
   

[3.8Jaguar]

Nigel's set up certainly looks beefy enough and the last post obviously answers the concern  on the securing of the retaining nut, this is one solution to the problems in hand.
   
   The assembly of the original AC rear stub axle assembly is critical in its original form. The pre load and positioning of the bearings is critical and can only be achieved in conjunction with full contact of the taper on the stub axle, The key way only represents a percentage of the drive load required, the majority of torsional drive should come from the correct linear load and full seating of the stub axle taper to drive hub.
   Any damage, corrosion pitting, grinding marks or disparity between tapers on the hubs and stub axles will reduce the coefficient of friction between the two components also the incorrect linear prelaod on the tapers due to incorrect assembly to achieve the correct pre load on the bearings will result in the reliance of the 'Key' having to transmit more torque than its design limits.
   
   There are stress risers associated with the key way and is more likely to be a point of failure coupled with incorrect material specification or heat treatment if all is assembled correctly.
   
   We have found that if the assembly of these items is carried out correctly to the correct specification the original design is capable, with good reliability, of transmitting 150 FT/LB of torque for a 900KG car on 550x16 Dunlop Racing and 200 Ft/Lb for a 750Kg car on 550x16 Blockley 5 std tyres. On these two examples we have 'Never' had a stub axle breakage or significant key way enlargement in 7 years.
   
   
   www.bristolengineering.co.uk

[B.P.Bird]

James has gone to the heart of the matter. It is the taper which has to transmit the torque not the key. Interesting that when Alan Turner designed the Greyhound rear hub he used LH and RH threads, side to side, on the inner locking ring and the bearing stack pinnacle nut. Completely different design of course, but the self tightening principles are the same.