johny Posted August 21, 2022 Report Share Posted August 21, 2022 Ouch sorry to hear all that but all you can say is, could have been far worse! What engine is it running and in what state of tune? I can imagine manufacturing replacement drive shafts isnt so easy as the wheel end has to be surface hardened for the needle roller bearing to run on but without making the rest brittle and risking a failure.... Looks like the CDD uprated items should address the issues but at 1000+ pounds a pair😲 Link to comment Share on other sites More sharing options...
rogerguzzi Posted August 21, 2022 Report Share Posted August 21, 2022 29 minutes ago, johny said: Looks like the CDD uprated items should address the issues but at 1000+ pounds a pair😲 Hello All After having 2 were the yoke came loose on replacements! So I bought 2 from Fitchetts and they looked Very well made and the yokes looks as though they had been heat shrunk on and the splines were rolled not cut! They have done about 10 to 15k now with no problems Roger Link to comment Share on other sites More sharing options...
SimonS Posted August 22, 2022 Report Share Posted August 22, 2022 The car was sold as a 2.0, with a free flow manifold and running on twin SUs. The paperwork includes an article that is highlighted referencing a Cam with a higher lift on the inlet valve, but there is no evidence that it was fitted. Link to comment Share on other sites More sharing options...
Colin Lindsay Posted August 22, 2022 Report Share Posted August 22, 2022 Glad you’re ok in any case. I’ve had two halfshafts shear, one on acceleration in a Gt6 and one when moving off from traffic lights and both with little or no damage. The last was a refurbished shaft with about 200 miles done, max, so I went for new from Canleys. Link to comment Share on other sites More sharing options...
johny Posted August 22, 2022 Report Share Posted August 22, 2022 Looking at the photo it seems to be just the threaded end section that has broken off the shaft and it surprises me as I cant see there being much load on it other than the torque of doing up the nut. This should be 100 - 110 lb.ft and the machining in that area (keyway, turning of threaded part?) especially if combined with overtightening of the nut is likely to have allowed a crack to start and then it would only be a matter of time before disaster.... Link to comment Share on other sites More sharing options...
RogerH Posted August 22, 2022 Report Share Posted August 22, 2022 Hi Folks, A high torque MUST be placed on the nut in order to keep the shaft under a tensile load. If the torque is underdone it may allow flexing on the micro scale and cause failure. I would suggest the tensile strength of the thread run-our area is far in excess of the load required to strip the threads in the nut. I haven't a clue who manufactures your drive shafts but the 'repro' stub axles in a TR4A IRS as supplied by Moss are top quality. (I know yours are different). Your first port of call should be the garage as they will know what has been fitted. Roger Link to comment Share on other sites More sharing options...
NonMember Posted August 22, 2022 Report Share Posted August 22, 2022 44 minutes ago, RogerH said: A high torque MUST be placed on the nut in order to keep the shaft under a tensile load. I really can't see how you figure it achieves that! The only thing that nut acts on is the hub, and there is NOTHING else holding the hub against anything other than the taper on the shaft. So the only "tensile load" provided by that nut is at the root of the threaded bit. The reason you need high torque on that nut is to force the hub onto the taper with enough clamping force to provide the friction needed to stop it spinning. Link to comment Share on other sites More sharing options...
Steve P Posted August 22, 2022 Report Share Posted August 22, 2022 Is it that photo or does it look like the nut has come off and the wheel/hub etc has followed it?. Mine broke at the keyway so hardly any left sticking out like that. Steve Link to comment Share on other sites More sharing options...
johny Posted August 22, 2022 Report Share Posted August 22, 2022 Open the photo in a separate tab and zoom in, its only the complete threaded end portion thats gone which as I say seems unusual. As NonMember says the nut is torqued up to get the hub to sit firmly on the taper although the key is also there to transmit drive. This arrangement works very well as many have found when trying to pull the hub off! Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 22, 2022 Report Share Posted August 22, 2022 have a close look at the fracture point its an old problem but hydrogen enbrittlement on threads is well known they must copper plate the threads when the case hardening is done to the shaft or the threads become very brittle and snap off like as shown all very suspect Pete Link to comment Share on other sites More sharing options...
RogerH Posted August 22, 2022 Report Share Posted August 22, 2022 Hi Non-Member if the nut is simply holding the tapers together then why is the torque recommended to be so high. A mere 10lbft will do that - BUT the hub will soon fall off. According to other posts there is also a key in place. I shall take my many years of engineering experience and go read a comic Roger Link to comment Share on other sites More sharing options...
NonMember Posted August 22, 2022 Report Share Posted August 22, 2022 Hi Roger, Read my earlier reply. I explained it in terms any half-decent engineer would understand. Do you really think that tiny woodruff key will suffice for the torque of a standing start? Is that what your "many years of engineering experience" tells you? Enjoy your comic Link to comment Share on other sites More sharing options...
johny Posted August 22, 2022 Report Share Posted August 22, 2022 I think the confusion lies in where you Roger said: 'A high torque MUST be placed on the nut in order to keep the shaft under a tensile load.' It sounds as if you think that doing up the nut is putting the whole drive shaft under tension which of course it doesnt as its merely clamping the hub onto the taper. The only axial force this type of drive shaft is subject to is from the side load on the wheel when cornering. The recommended torque for tightening the nut is about the same as used on a few other fixings like the diff and gearbox couplings etc. Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 22, 2022 Report Share Posted August 22, 2022 many early jap cars had plating brittlement nice shiny bolts and pins till you tried to remove them and click two peices if the thread has sheared of pretty flush with the shoulder of the shaft its a heat treatment cock up not over torqued as the nut would likely give in first and if done up correctly the taper as we know takes a lot to shift it out of the hub flange if the keyway was ommitted or sheared then unwanted rotation would possibly break the taper , but for the threaded end to drop off is not a torque problem pete Link to comment Share on other sites More sharing options...
Roger Posted August 22, 2022 Author Report Share Posted August 22, 2022 18 hours ago, rogerguzzi said: the yoke came loose on replacements Sorry, daft question again RG: Can you please explain the quote above a bit more in detail? The CDD kit comes with shafts & yokes if I understand their website correct. Did the yokes & shaft supplied from CDD fail when you assembled things (never driven) or did you drive the car and they came loose after X miles? I have never taken these things apart on neither my Herald nor my Vitesse, I have no idea how they fit together or should be assembled. So far only two CDD shaft customers have replied. One happy and one dissapointed customer! Thanks for your feedback everyone. Roger Link to comment Share on other sites More sharing options...
rogerguzzi Posted August 22, 2022 Report Share Posted August 22, 2022 1 hour ago, Roger said: Sorry, daft question again RG: Can you please explain the quote above a bit more in detail? The CDD kit comes with shafts & yokes if I understand their website correct. Did the yokes & shaft supplied from CDD fail when you assembled things (never driven) or did you drive the car and they came loose after X miles? I have never taken these things apart on neither my Herald nor my Vitesse, I have no idea how they fit together or should be assembled. Hello Roger The shafts I am talking about are the standard type. Have a read of this thread. Spitfire Drive Shafts - Drivetrain - Sideways Technologies (sideways-technologies.co.uk) 1 Link to comment Share on other sites More sharing options...
johny Posted August 22, 2022 Report Share Posted August 22, 2022 1 hour ago, Roger said: Sorry, daft question again RG: Can you please explain the quote above a bit more in detail? The CDD kit comes with shafts & yokes if I understand their website correct. Did the yokes & shaft supplied from CDD fail when you assembled things (never driven) or did you drive the car and they came loose after X miles? I have never taken these things apart on neither my Herald nor my Vitesse, I have no idea how they fit together or should be assembled. So far only two CDD shaft customers have replied. One happy and one dissapointed customer! Thanks for your feedback everyone. Roger Looking at the CDD kit its hard to see how anyone could be disappointed (except with the price!) as they seem to have covered every possible weakness of the original design: wider needle roller with inner race so no surface hardening needed, bigger ball race bearing, stronger shaft, keyway machining, bigger trunnion etc. Link to comment Share on other sites More sharing options...
rogerguzzi Posted August 22, 2022 Report Share Posted August 22, 2022 1 hour ago, johny said: Looking at the CDD kit its hard to see how anyone could be disappointed (except with the price!) as they seem to have covered every possible weakness of the original design: wider needle roller with inner race so no surface hardening needed, bigger ball race bearing, stronger shaft, keyway machining, bigger trunnion etc. Hello All I think a bit OTT unless you are racing or have a very powerful engine but then the diff would break! Roger Link to comment Share on other sites More sharing options...
Colin Lindsay Posted August 22, 2022 Report Share Posted August 22, 2022 8 minutes ago, rogerguzzi said: Hello All I think a bit OTT unless you are racing or have a very powerful engine but then the diff would break! Roger 1 Link to comment Share on other sites More sharing options...
johny Posted August 22, 2022 Report Share Posted August 22, 2022 12 minutes ago, rogerguzzi said: Hello All I think a bit OTT unless you are racing or have a very powerful engine but then the diff would break! Roger yes although a couple of the mods like the needle roller running on its own inner race rather than directly on the shaft and better machining of the keyway would be nice to have regardless of the engine power output... Link to comment Share on other sites More sharing options...
iani Posted August 22, 2022 Report Share Posted August 22, 2022 28 minutes ago, rogerguzzi said: Hello All I think a bit OTT unless you are racing or have a very powerful engine but then the diff would break! Roger I bought them as I'm a fan of Alasdair Southall's work, I have his uprated sliding spline shafts on my TR6, I also have his hubs & drop links fitted. When I decided to update my GT6 I wanted to remove weak points, the CDD shafts seemed a sensible choice, mated to my blackline LSD 3.63 diff & Sprint OD Gearbox. They are expensive but so was replacing all standard parts with new, I am confident in the quality of CDD components, I haven't always felt the same about standard stuff. Link to comment Share on other sites More sharing options...
RogerH Posted August 22, 2022 Report Share Posted August 22, 2022 6 hours ago, NonMember said: Hi Roger, Read my earlier reply. I explained it in terms any half-decent engineer would understand. Do you really think that tiny woodruff key will suffice for the torque of a standing start? Is that what your "many years of engineering experience" tells you? Enjoy your comic A small woodruff key will assist a well torqued taper to stay in place. A decent tensile load will support the thread run out by removing other unwanted loads. Good bye. Roger Link to comment Share on other sites More sharing options...
Pete Lewis Posted August 23, 2022 Report Share Posted August 23, 2022 time to smile pete 1 Link to comment Share on other sites More sharing options...
Badwolf Posted August 23, 2022 Report Share Posted August 23, 2022 (edited) Gentlemen, this is not what we expect on this forum Edit - This comment was posted in respect to other posts which have subsequently been deleted. Edited August 23, 2022 by Badwolf Explantion 4 Link to comment Share on other sites More sharing options...
NonMember Posted August 23, 2022 Report Share Posted August 23, 2022 2 hours ago, Badwolf said: this is not what we expect on this forum My apologies. I was trying to correct factual errors in Roger's posts but allowed myself to get riled by his attitude. I shouldn't have. There is no "tension" on the shaft from the nut. The woodruff key does next to nothing in use. The nut is torqued up to COMPRESS the taper so that the hub doesn't spin. Those are the facts. 1 Link to comment Share on other sites More sharing options...
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