Chris59 Posted August 20, 2009 Report Share Posted August 20, 2009 Hello, I have removed 2 days ago a broken crankshaft from a TR3A engine. As you may guess, nobody will accept a broken crank for reconditionning So, where should I look first to find a good one, regrind if necessary (not more than - 0.10) and hardened, with shells ? Thanks in advance for your help, Cheers, Chris. Quote Link to post Share on other sites
AMD333 Posted August 20, 2009 Report Share Posted August 20, 2009 Dear Chris, I have had mine made in steel which I think is the best. I can give you the adres of the man who did it : http://www.crankshaft.be. I am very pleased with it and can have 5500 revs continously. If you prefer the one which came out of my engine I have to look as I must still have it somewere stored. Do you need it urgently? I live in Belgium but are coming to the UK at the end of october. Let me know. Kind regards Pascal Quote Link to post Share on other sites
Chris59 Posted August 20, 2009 Author Report Share Posted August 20, 2009 (edited) Hello Pascal, I would like to find a good one for late September, so it's not really urgent. A steel one will certainly be very expensive ? I live in France, near the Belgium Border (Valenciennes), so may not be to far from you ? Cheers, Chris. Edit : interesting website, but I don't speak Flemish, unfortunatly. Edited August 20, 2009 by Chris59 Quote Link to post Share on other sites
RogerH Posted August 20, 2009 Report Share Posted August 20, 2009 Hi Chris, out of curiosity - 1 Did the crank drive the original mechanical fan or had it been removed and electric fitted. 2. How many miles had it done before breaking 3. Where on the crank did it break - usually on the rear web at the 4th big-end bearing. 4. Can you supply a pic of the fracture faces. Roger Quote Link to post Share on other sites
Chris59 Posted August 20, 2009 Author Report Share Posted August 20, 2009 Hello Roger, 1 Did the crank drive the original mechanical fan or had it been removed and electric fitted : original fan on this car (a friend's TR4 crankshaft broke at the front main journal because of the lack of fan....) 2. How many miles had it done before breaking : no idea, sorry, but it is all original, never regrind. 3. Where on the crank did it break - usually on the rear web at the 4th big-end bearing : just between the 4th conrods journal and the rear main crank journal (what is the "web" ?) 4. Can you supply a pic of the fracture faces : argh, I am not at all good at this kind of modern technology. Will try my best ! Cheers, Chris. Quote Link to post Share on other sites
RogerH Posted August 21, 2009 Report Share Posted August 21, 2009 Hi Chris, your answers were as I hoped in the light of your disaster. Many people attribute broken cranks with the removal of the original mechanical fan. Yours broke with it fitted. The area where your crank broke is very typical of the great majority - 4th big-end bearing to rear main web. The web is the flat section of metal joining the big-ends to the mains and gives the piston the desired travel. Your friends crank breaking at the 1st bearing is unusual but not caused by fan being absent in my opinion. I hope you get a replacement soon and get you on your way again. Roger Quote Link to post Share on other sites
vivdownunder Posted August 23, 2009 Report Share Posted August 23, 2009 It's a fact of life that four pot TR's break crankshafts, with or without the fan or the fan extension. Cars with thin belt conversions and a damped pulley have been known to break them. Built up fatigue over the years is a suspect, and some experts say it's running for long periods on the critical rev band for harmonic vibration. More so the half band of about 3100prm, which is roughly open road speed, as the more dangerous circa 6200rpm is less used. The early TR's severe overdrives are speculated as a contributing factor, due to the shock load through the motor as it instantly changes revs up or down. As a precaution I only drop out of overdrive after slowing right down for a roundabout or the like, and give the clutch a quick jab when engaging the O/D. It would be interesting to know if crank breakages lessened after the softer engagement TR4A O/D was introduced, but obviously there's no data base. And cars without overdive break cranks too. !!. Obviously there's a weakness, and it's really just a lottery as to when your number comes up. Strangely, the last car I saw with a broken crank could be started up, and the engine ran, with noise something like a failed piston where the top had come off. Regards, Viv. Quote Link to post Share on other sites
Mychael Posted August 23, 2009 Report Share Posted August 23, 2009 It's a fact of life that four pot TR's break crankshafts, with or without the fan or the fan extension. Cars with thin belt conversions and a damped pulley have been known to break them. Built up fatigue over the years is a suspect, and some experts say it's running for long periods on the critical rev band for harmonic vibration. More so the half band of about 3100prm, which is roughly open road speed, as the more dangerous circa 6200rpm is less used. The early TR's severe overdrives are speculated as a contributing factor, due to the shock load through the motor as it instantly changes revs up or down. As a precaution I only drop out of overdrive after slowing right down for a roundabout or the like, and give the clutch a quick jab when engaging the O/D. It would be interesting to know if crank breakages lessened after the softer engagement TR4A O/D was introduced, but obviously there's no data base. And cars without overdive break cranks too. !!. Obviously there's a weakness, and it's really just a lottery as to when your number comes up. Strangely, the last car I saw with a broken crank could be started up, and the engine ran, with noise something like a failed piston where the top had come off. Regards, Viv. I tend to agree with Viv, your numbers up or it's not. My first TR ( a private import, 1961 model) had spent the greater part of it's life as a completely stock non-overdrive car. It had about four yrs driving with an overdrive here in Australia and of those four yrs perhaps 18 months with no stock fan.. Then one day the crank just broke. If the overdrive and/or the lack of fan was the cause then I think it would have appeared much sooner. My current TR a 1958 model has had overdrive all it's life and no fan (but with a harmonic damper) for about 4 yrs and so far no failure of the crank. Mychael Quote Link to post Share on other sites
BrianC Posted August 23, 2009 Report Share Posted August 23, 2009 (edited) My current TR a 1958 model has had overdrive all it's life and no fan (but with a harmonic damper) for about 4 yrs and so far no failure of the crank. Nothing like tempting fate Mychael - hope you stay lucky. Strangely, the last car I saw with a broken crank could be started up, and the engine ran, with noise something like a failed piston where the top had come off. True - mine went a very long time ago - see Lightened flywheel - how light for fast road use? 6000 miles on rebuilt engine, and so far, so good (hope I'm not tempting fate too ) Edited August 23, 2009 by BrianC Quote Link to post Share on other sites
RogerH Posted August 23, 2009 Report Share Posted August 23, 2009 (edited) Hi Viv, your concern about the shock of the O/D would impart a shearing effect on any part of the crank and produce a fracture face at the crack site to confirm this. All the failures at the 4th big-end journal web (most typical failure site by a long way) are tensile failures due to some form of flexing not shear. So keeping banging your O/D in and out (if you dare ) Whenever you have the crank out of the engine have a look at the 'big-end journal to web' radius. It should be clean and smooth. However many have machine (lathe tool) marks which are stress risers. On the 4th big-end these marks are a serious concern. Carefully Rub them down and if posible do an MPI crack check. It may be possible to remove very small cracks by having the journal reground (not too sure about that one). Roger Edited August 23, 2009 by RogerH Quote Link to post Share on other sites
vivdownunder Posted August 23, 2009 Report Share Posted August 23, 2009 Thanks Roger - great information about a possible cause and solution. It's been a subject plagued by guesswork for decades. A nearby TR engine rebuilder always has a few crankshafts in his workshop, so I'll see if he can find one with these lathe marks, so we'll know exactly what to look for and eliminate. Regards, Viv. Quote Link to post Share on other sites
Chris59 Posted August 23, 2009 Author Report Share Posted August 23, 2009 "Strangely, the last car I saw with a broken crank could be started up, and the engine ran" : Both engines (TR3 & 4) I have found with broken cranks, at the front or rear web, were running with the crank broken. In fact, I was sure on the second one (rear broken crank) that it was broken before the thrust washers, because the noise nearly disappeared when the clutch was pressed ... Chris. Quote Link to post Share on other sites
Mychael Posted August 24, 2009 Report Share Posted August 24, 2009 "Strangely, the last car I saw with a broken crank could be started up, and the engine ran" : Both engines (TR3 & 4) I have found with broken cranks, at the front or rear web, were running with the crank broken. In fact, I was sure on the second one (rear broken crank) that it was broken before the thrust washers, because the noise nearly disappeared when the clutch was pressed ... Chris. When the crank broke on my first car it was when pulling up a hill, horrible vibration and noises but still running and drive able (albeit only as far as needed to get safely off the road). Mychael Quote Link to post Share on other sites
Chris59 Posted August 26, 2009 Author Report Share Posted August 26, 2009 Thanks to the help of TonyTR4, I may have found a replacement crankshaft. I will be in England tomorrow to see a TR2 and another 6, and hope to collect the crank on the same day . Chris. Quote Link to post Share on other sites
TR4AIRS Posted August 26, 2009 Report Share Posted August 26, 2009 Last year we had a crankshaft failure in our TR4A. We rebuilt the engine with an original crankshaft. I've been afraid ever since to drive it the way I'd like. Next time I won't hesitate to buy a forged steel crankshaft from Nuyts, having been to his workshop and having seen his skills and equipment. Kind regards, Kristof. Quote Link to post Share on other sites
Chris59 Posted August 28, 2009 Author Report Share Posted August 28, 2009 Kristof, I understand your point of view, but the owner of the broken crank' TR3 will not pay for a steel one. I have collected the crank yesterday, with an engine bloc. Will now take any measurements to check the condition of the crank itself. And I have bought the TR2, so my fleet keep "growing" with TR2, 3A, 4IRS, 6, 7 and several others toys ! Chris. Quote Link to post Share on other sites
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