REPORT - New splined stub axle's from Winchester

[AcecaRacer]

Fellow AC'ers
   
   I thought for the benefit of all, that I would write a brief (not really) report on my recent acquisition of a set of newly manufactured stub axle's purchased from Winchester Motorsport.  I know that several of you have recently bough them as well.
   
   A bit of background - BE603 is a race car, so all bets are off in terms of normal usage. After having sheared two sets of key's on my original channel and key configured axles, I was desperate to find a more reliable solution.  This known "Achilles heel" has vexed AC owners for decades and Nigel's offering looked to be a Godsend.
   
   Found on the inside back cover of each ACtion Magazine for the last few months, the Winchester Motorsport advert boasted "No more taper drive shaft failures! 1" 10-Spline conversion for Ace/Acea (sic). Call for details"
   
   Firstly, let me say that dealing with Nigel as a vendor was a pleasure.  Although he is quite the dinosaur in terms of technology - no email, no voice mail, when I did connect with him, he was a great chap to speak to.
   
   After discussing my current dilemma, Nigel assured me that he had what I needed to make my problem disappear.  So, betting on his British honor, I wired the better part of $2,000 to him for the privilege of having his cure to what ailed me.
   
   After about a week of shipping, they finally arrived and were eagerly unpacked.  At first glance, they looked fantastic.  All shiny and robust looking, along with those 10...no wait...8 splines(?) to drive the mighty 140 BHP Bristol power to the rear end.  All was right in the world.
   
   After a thorough inspection, these new axle's looked like they were just the thing to bring my Aceca back to life.  However, there were a few design flaws that were worth noting in terms of potential areas for failure as well as one area in particular that should definitely be redesigned.
   
   Fast forward to the installation.  Anyone who has worked on the rear end of an ACECA/Ace know it is not for the faint of heart. Clearances designed for elves and specialty tools for sure. I was assured that the new axle's would be a "direct replacement" for the original...How many times have we heard THAT?
   
   Well, damned if it wasn't true!  Although the swap out took the better part of a full day, it was indeed a straight swap out with minimal headache. True, getting the hub to fit right did take some heating etc., but the key thing is that I did not have to do any reshaping or modifications to get the parts to eventually fit.
   
   Now here is where it gets interesting.  Both axle's were put in and the bolts were assembled with Loctite and set at 80ft/lbs of torque for safe measure and off we went to the races.  The Rolex Monterey Motorsports Pre-Reunion.
   
   With her newly installed power transformers, the ACECA performed as expected and we completed 10 laps of practice at Laguna Seca with no incident. The rear end seemed to be firm and true and there were no noises or extraneous issues to deal with. Delight!
   
   The same results were delivered throughout the weekend with another practice session, a qualifying session and the the final race.  Well done!
   
   The following weekend came and I took BE603 out on the track for another practice session at Laguna Seca for the much anticipated Rolex Monterey Motorsports Reunion.  All went well and my times were looking better than the previous tune up sessions.
   
   My next practice session came the following day and out we went.  2 and a half laps in, after coming out of turn 4 and heading down the straight for turn 5 I shifted into 4th gear and the tach hit the rev limiter almost immediately!  I clutched in again and put the gearshift perfectly into place and ZOOM the revs spiked again.
   
   Was this deja vu?  Was it happening again?  How is it possible?  Those axles looked blood bullet proof!  I was furious.
   
   So, I limped off the track and was eventually towed back to the paddock.  My weekend was now shot to hell.  I put the car on jacks and while in gear was able to spin the left rear tire...busted stub axle - AGAIN!?[:(!]  Really unhappy.
   
   So, I decided to have a look.  After removing the knock-off of the left rear, I was shocked to find the bolt lying unattached inside.  Upon removal, I was able to look into the hub and see light on the other side. WTF?  The bolt had backed out and the shaft had pulled itself out!
   
   Now, at least I had something to work with.  The shaft had indeed not sheared, but just fallen out.  Unfortunately, due to the mechanical dynamic of a half shaft spinning freely inside the edges of a hug, the splines were now pranged up a bit and so was the inside of the hub.  Due to the tight tolerances, they would not go together for love nor money.
   
   After spending 90 minutes getting the shaft off, I hand filed the spline ends flat again and also did so with the hub.  Bingo...they went together.  Weekend saved!  Or was it?
   
   I reassembled the axle/stub combo this time with super duper Loctite (supposed to require a torch to release the glue)and I torqued to 100lbs. to be safe.  She sat overnight while I headed to the bar for an overdue bottle of tequila with my name on it.
   
   The next morning, the practice session was completed without incident and all was well.  I decided to pull the spinner to see if everything was tidy.  Unfortunately, it was far from it.  The bolt had broken the Loctite seal and had spun 6 FULL REVOLUTIONS!  Incredible!  We were well on our way to repeating what happened the prior weekend.  Not good.
   
   So, I re-glued and re-torqued the bolt AGAIN so that I could finish out the weekend.  After the morning qualifying session, I repeated the process yet again so that I could make sure that my axle was not going to drop again...or worse.  I also decided to check the right axle.  It had rotated 4 revolutions!  This was nuts...literally
   
   So, what does this ALL mean?  Due to a couple of design flaws, I feel that these axle's really must not be used for racing without some form of modification...which I am working on as we speak.  It is simply not tenable to re-torque your stub axle's after every 30 miles of hard driving.  It is insanity.
   
   The left axle should have had a reverse thread bolt to offset the natural loosening effects of the left hand rear wheel.  I am currently fabricating a fix that will hopefully stop this nonsense and make my investment worth while.
   
   Don't get me wrong, I do believe that these are indeed nice replacements for a standard road going car...maybe.  However, I still believe the mechanical forces are far too strong even in a mild driving condition to not naturally unscrew the left hand bolt.  I will defer to others who may have bought them for that purpose.
   
   In the end, the actual design is far superior to stock and will no doubt be 100% more reliable, but unless you want to re-tighten them after every short drive, you may want to be wary.
   
   Once I have completed the design of the bolt "keepers" I will try to post the pictures in hopes they may provide help to others.
   
   Sorry for the lonnnnnnggggg post. But I felt the background and true experience might be helpful.
   
   Cheers,
   Rob

[lew]

Hi Rob,
   I read with great interest your epistle on the stub axles,both informative and amusing.
   I was intrigued to read that your car has 140 BHP. My B2 modified to D2 specs is supposed to have about 125 but it feels like only 100. It is as I bought it.
   Consequently it is my intention to rebuild the engine to search for the missing horses.However it would make sense to me to try and add a few more ponies at the same time.
   Perhaps you, or anyone else could tell me what mods are done to try and liberate said ponies so I could incorporate in the build.
   
   Cheers
   Lew

[Robin A Woolmer]

Has anybody tried using the standard tapered axle shaft & fitting a second drive key on the opposite side of the shaft & slotting the hub to suit?
   This would double the engagement & maintain the integrety of the assembly ensuring that the bearings are both fully supporting the hub!
   
   Robin

[shep]

I have had 2 stub axle failures on my Ace, and another whilst racing David Emmans' Ace at Silverstone earlier this year. Each time a crack which starts where the keyway is machined into the stub axle, has been the cause of the failure. David ordered a pair of Nigel's stub axles, but was concerned that the design ha been modified, and the hub was now retained by a bolt with no locking device. He was concerned that with the heat and stress of racing the bolt would work loose and the stub axle fall out. As Rob said, the parts look superb, but we believe a locking device is necessary. I am not sure whether Robin's idea of a double keyways would work, as the axle would have an even smaller cross section than with one. The torque and stress on the shaft would be the same so I would prefer no keyways rather than increasing one to two. Some destruction testing is required. Andy.

[Robin A Woolmer]

Shep
    If there is a stress riser due to the sharp corners then maybe one could consider a radiused slot in the shaft & fit the keys with rounded tops to engage into the shaft slots? it needs a little imagination.
   The Nigel Winchester design clearly will transmit the torque but i do not understand how it couples the hub/stub axle intimately to the pair of bearings?
   The alternative is to adopt say the tried & prooven Cobra design & have special uprights made, that should solve it once & for all! but at a cost.
   
   Robin

[nikbj68]

Isn`t the shaft drilled to accept a castellated nut & split pin? That should sort it.
   
   I recall 20+ years ago an acquaintance with a Lister XJS had a similar 'undoing', but his released the wheel bearing and chewed the brake, wheel & tyre to bits. Not funny.

[Aceca289]

quote:Originally posted by Robin A Woolmer
   

    If there is a stress riser due to the sharp corners then maybe one could consider a radiused slot in the shaft & fit the keys with rounded tops to engage into the shaft slots? it needs a little imagination.
   

   
   Robin
   
   My father broke at least two axles over the over the many years he drove my Aceca as a daily driver. Each time they broke in the way Shep describes..."a crack which starts where the keyway is machined". No racing involved...just the torque of the hipo 289 taking its toll at intervals over 120,000 miles. When the axles were removed for a recent rebuild one keyway was observed to have enlarged to nearly twice its normal width. I noted that the keys were cut square (causing a "sharp corner"), so I had new ones shaped to fit the radius slot as you have suggested. I believe this not only potentially reduces the stress point as you describe, but also distributes the load over a slightly longer length of the keyway. Time will tell how well this works over the next 120K miles.[;)] At least I have two more spare axles to use up.
   
   The following pictures should help everyone see what I have explained. A second Keyway may be a viable option although I don't know how hard it would be to pull an axle with a second Key.
   
   John
   
   
   
   New Axle - From early 80's AC Works stock
   
   
   Worn Axel - Note larger elongation near bottom of keyway slot indicating increased stress at this point
   
   
   Broken Axle – note break occurred at bottom end of slot where the increased elongation of the slot was noted above.
   
   
   Wow, my first time at posting photos and it worked. This is fun! [:D]

[Robin A Woolmer]

These are clearly very dramatic failures & it does point toward the stress risers in the keyway slot, it also indicates that the hub is fretting & likely loose on the shaft, so it could be a combination of the two but does also indicate a marginal design for the loads now being applied!
   To ensure the intergrety of the bearing design/assembly, the hub must be very tightly held on the shaft to act as one part for the bearing system to be fully effective, a loose hub will impose a turning load on the outer bearing, this may also be the case with the Nigel Winchester Splined Shaft design, this, may result in what is being found where the assembly becomes loose!However i have no detailed knowledge of Nigel's design.
   More work is needed to resolve the issue?
   
   Robin

[Bill P]

quote:Originally posted by AcecaRacer
   
Fellow AC'ers
   
   I thought for the benefit of all, that I would write a brief (not really) report on my recent acquisition of a set of newly manufactured stub axle's purchased from Winchester Motorsport.  I know that several of you have recently bought them as well...........................
   
   
   Cheers,
   Rob
   
   

   
   Rob
   
   Have you spoken to Nigel Winchester?
   
   Bill P

[Robin A Woolmer]

No, would be happy to do so though!
   
   Robin

[Bill P]

quote:Originally posted by Robin A Woolmer
   
No, would be happy to do so though!
   
   Robin
   

   
   Sorry Robin, I meant Rob Fisher!
   
   Bill P

[Robin A Woolmer]

Bill
   No but he can see the forum activity, i have written to Andy Shepherd following discussions with Gerry Hawkridge on the basis that this is a safety critical issue & must be resolved particularly as the cars have considerably more torque now, AC clearly was aware of the design weakness in this area in the late 50's when designing the Greyhound & Cobra axle assemblies.
   
   Robin

[nikbj68]

It doesn`t look like the stock shafts are case hardened, could this be a factor in the dragging of the keyway, rather than shearing at the corner of the slot?

[Bill P]

It seems that this topic has strayed away from the original post by Rob Fisher.
   
   Rob's concern on the new type shaft was that the bolt which he had Loctited and torqued to 80ft/lbs and later 100ft/lbs had loosened - no mention of shafts shearing at the keyway after replacing the original system.
   
   The topic has now diverged to discuss shearing at keyways with no comment on Rob's "locking arrangement" and/or the usefulness of a right-handed and left-handed/reverse threading for the bolts.

[Robin A Woolmer]

Bill
   To make effective comment one needs to know how the parts fit together, so if that could be explained then it may be possible to make an effective comment as i suspect that the hub is loose fit on the shaft rather than being in intimate contact, if that is the case then the hub can possibly move & not be fully supported by both bearings in the upright!
   What is required is a cross sectional drawing showing how the hub is located in the assembly. How many of these conversions are being used?
   Robin