john.r.davies Posted January 25, 2018 Report Share Posted January 25, 2018 I retired a while ago, and since then I've gone back to college, where I'm now studying for a degree in Motorsport Engineering. I need a research project and chose to investigate the crank damper pulleys that Triumph fitted to all the six-cylinder engines it made. The crank damper was needed to suppress 'torsional', twisting vibration in the long crankshafts, and has a rubber layer between the inner hub and outer ring. They were suspect even in the day, when they were new. Kas Kastner described in his Handbooks his technique to ensure that the outer hadn't shifted, which would make the timing marks on them completely false. Worse, a faulty damper could lead to crankshaft failure! Today, none of those dampers are less than forty years old, and many show the rubber to have deteriorated. How many still work as timing indicators, let alone to suppress crank vibration? My study has two parts: In the workshop, I'm building an engine rig with sensors on the pulley and flywheel to detect vibration, and I'm asking Triumpheroes about their experiences with the dampers. Please help me by completing the short survey questionanire I've put up on Survey Monkey? Go to https://www.surveymonkey.co.uk/r/GPTCDSG There are only five questions and it will take you less than two minutes! Thank you! John PS I'm posting this on several websites, to catch as many people as I can but no need to complete it more than once! Quote Link to post Share on other sites
Richard71 Posted January 25, 2018 Report Share Posted January 25, 2018 Survey complete! Not wishing to hi-jack your thread here John, but can anyone offer any info on the 6cyl damper pulleys supplied by the usual suspects, MOSS, Rimmer etc, are they NOS, repros, do they have timing marks, are they any good? Richard. Quote Link to post Share on other sites
Waldi Posted January 25, 2018 Report Share Posted January 25, 2018 Survey completed Quote Link to post Share on other sites
reginald Posted January 25, 2018 Report Share Posted January 25, 2018 Hi I brought a damper from moss last year it was well out of balance and did not run true,my brother has a specialist cylindrical grinding business he ground the out sides true to the bore, plus had to grind high spots from the vee which would have grabbed the belt.they appear to be very roughly machined tolerance wise,no trueing up when machining different parts of the damper eg. Turning around in lath chuck. After grinding it ran true allover within a thou, it was then balanced. It got rid of a vibration that ran through the car before and is know good. I was lucky to be able to sort it at no cost to me. A little bit more care in machining and it would be a good damper. Richard Quote Link to post Share on other sites
reginald Posted January 25, 2018 Report Share Posted January 25, 2018 Ps I do have the figures some where at home of how far it was running out, see if I can find them. Richard Quote Link to post Share on other sites
Tom Fremont Posted January 25, 2018 Report Share Posted January 25, 2018 I got a couple from MOSS here in the 'States years ago ( 10? ) and had them balanced as I saw no drillings in them, nor adequate timing marks. I subsequently got a NOS one on ebay ( showed the wrong p/n in the listing but I recognized it as correct ) and it's now in service on my concourse car. I since found another NOS one which is on the shelf. My driver uses a 50 year old one which seems to be fine. The front seal doesn't leak ( after 120K miles ) so it doesn't have to bear and endlessly refreshed oil bath. The MOSS ones, balanced and marked, are available if anyone wants one ( PM me ). Over here there are some specialists who refurbish these with new rubber and paint jobs. Damper Dudes is one such I've seen referenced. My concern, as I surmise John would share, is considerable doubt that proper diligence in the choice of rubber ( durometer, esp. ) has been done. After all, most of them wind up on show cars . Cheers, Tom Quote Link to post Share on other sites
Guest Posted January 26, 2018 Report Share Posted January 26, 2018 Survey completed. ... and PM on its way Menno Quote Link to post Share on other sites
ianc Posted January 26, 2018 Report Share Posted January 26, 2018 Richard (reginald) - did you notify Moss of the problem? I feel sure they would wish to know as there might be other dampers on the shelf with the same problem. Ian Cornish Quote Link to post Share on other sites
RogerH Posted January 26, 2018 Report Share Posted January 26, 2018 I retired a while ago, and since then I've gone back to college, where I'm now studying for a degree in Motorsport Engineering. I need a research project and chose to investigate the crank damper pulleys that Triumph fitted to all the six-cylinder engines it made. The crank damper was needed to suppress 'torsional', twisting vibration in the long crankshafts, and has a rubber layer between the inner hub and outer ring. They were suspect even in the day, when they were new. Kas Kastner described in his Handbooks his technique to ensure that the outer hadn't shifted, which would make the timing marks on them completely false. Worse, a faulty damper could lead to crankshaft failure! Today, none of those dampers are less than forty years old, and many show the rubber to have deteriorated. How many still work as timing indicators, let alone to suppress crank vibration? My study has two parts: In the workshop, I'm building an engine rig with sensors on the pulley and flywheel to detect vibration, and I'm asking Triumpheroes about their experiences with the dampers. Please help me by completing the short survey questionanire I've put up on Survey Monkey? Go to https://www.surveymonkey.co.uk/r/GPTCDSG There are only five questions and it will take you less than two minutes! Thank you! John PS I'm posting this on several websites, to catch as many people as I can but no need to complete it more than once! Hi John, are you looking at these dampers to see if they actually work? Have you got any samples of broken cranks to examine the fracture surface. The wet liner engine never had a damper fitted originally and had the mechanical fan. Many 'experts' state that if you remove the fan you must fit a damper (a harmonic damper). They use an MG damper as it fits. BUT where is the science. I have examined a number of broken cranks ( 10 or so) and none have shown torsional stressing. Failure has always been simple tensile failure - and normally around the #4 big end area. Good luck on a big subject. Roger Quote Link to post Share on other sites
john.r.davies Posted January 26, 2018 Author Report Share Posted January 26, 2018 Thank you, all! Anyone else, please add your contribution! I can't offer any opinion on the dampers available now, I haven't any experience of them, and I'm concentrating on the OE ones. But I'm shocked to read what Tom says! An out-of-balance damper pulley would seem as useful as a chocolate firewall. Roger, I have a collection of old dampers to test. So far I haven't measured any to see if their timing marks have moved, none are actually loose but several have manky-looking rubber in them. I'd love to have a 'known-faulty' damper to test, so if anyone has one they haven't thrown in the bin, please let me know! Glad to pay postage and make a contribution to a charity for it! And are you referring to 4-cylinder engines? In ignorance, I think that some TR3-4s had a form of damper, but that the design thinking then was that the shorter crank made it non-essential. Certainly Triumph never fitted them to any of the small chassis, 4-cylinder engines. And thanks for your observation of ten broken cranks(!) - to confirm, were these 6-cylinder cranks? Can you tell me anything more about them? I kept the questionnaire short and simple, and hope to follow up any reports where I can. Please PM me or email? Again thanks to all, for your interest and contributions - I report in due course. Bests, John Quote Link to post Share on other sites
RogerH Posted January 26, 2018 Report Share Posted January 26, 2018 Hi John, my broken cranks were all TR wet liner (four pot) cranks. Examination of the fracture face can tell the mode of cracking Roger Quote Link to post Share on other sites
roy53 Posted January 26, 2018 Report Share Posted January 26, 2018 Jon will you then be looking at the after market dampers ? Quote Link to post Share on other sites
RogerH Posted January 26, 2018 Report Share Posted January 26, 2018 John, this is no good. You will have to change the name. I keep calling them 'damp crankers' Is it me !! Roger Quote Link to post Share on other sites
john.r.davies Posted January 26, 2018 Author Report Share Posted January 26, 2018 Sounds like something that Joe Grundy suffers from! Alonng with his Farmer's Lung! Quote Link to post Share on other sites
Steves_TR6 Posted January 26, 2018 Report Share Posted January 26, 2018 Hi John As discussed i’ll hapilly donate my ‘seems to have slipped’ damper as soon as i get a replacement. Was awaiting the Moss sale, but with the above i’m not sure i want their product now! Steve Quote Link to post Share on other sites
john.r.davies Posted January 26, 2018 Author Report Share Posted January 26, 2018 Thanks, Steve! Just let me know! John Quote Link to post Share on other sites
Steves_TR6 Posted January 31, 2018 Report Share Posted January 31, 2018 I’m taking Tom up on his kind offer of a balanced and marked Moss damper, its somewhere en-route as i type. Once it arrives i’ll remove the old one and it’s yours John As ever with TR jobs i’m planning other stuff ‘while i am there’..... Possibly new timing chain seal/gasket Poly arb mounts if the rad has to come out....... Any other suggestions ?? Steve Quote Link to post Share on other sites
john.r.davies Posted January 31, 2018 Author Report Share Posted January 31, 2018 Most kind, Steve! You may be able to get the old one off without removing the radiator. An ordinary pulling spider has no room, but I postsd about a "limited access puller" here in my tools, Show & Tell thread: http://www.tr-register.co.uk/forums/index.php?/topic/62581-modified-and-fabricated-tools-show-tell/?hl=tools Good luck! John Quote Link to post Share on other sites
Tom Fremont Posted January 31, 2018 Report Share Posted January 31, 2018 Better grease the ARB bushings! They'll creak and groan like mad if you don't. I used Never Seize; spray lubes of Noah Veil. Of course the chain and sprockets should be renewed unless of recent fitment. Finally, if you are using rubber rack bushings I've got a lovely expander you can make yourself: Cheers, Tom Quote Link to post Share on other sites
PodOne Posted January 31, 2018 Report Share Posted January 31, 2018 Hi John Would be interesting to compare OEM, the unmodified Moss offering and a ATI damper to see if there is any worthwhile improvement in damping out vibration againist OEM and between the three given the cost esp of the ATI. One issue I foresee is that you would need a reference base line measurement taken from a new OEM damper on a fresh engine which will not be possibe as said the dampers are now all 40 years old a least even if it remained unused on a shelf the rubber will have deteriorated. Unless there are OEM specs available to describe exactly which resonances/vibrations that were to be addressed. Also would a solid damper suitably designed and balanced be jjust as effective or better? These would provide a much better cost alternative. Interesting project look forward to seeing some results. Andy Quote Link to post Share on other sites
john.r.davies Posted January 31, 2018 Author Report Share Posted January 31, 2018 It's all at an early stage, so please don't expect a report this year, although I will rpeort the survey in due course. My intention is to be able to compare different dampers on a test rig, but I don't know yet if my technology will be up to that. A solid damper? Please explain? The rubber damper uses the viscosity of the rubber ring. Others use an enclosed silicone liquidso, neither can be solid. There are "pendulum' dampers, and the "Rattler" style is a form of pendulum. Weights attached to the damper can move and absorb vibration energy as they do so - would you consider them, "solid"? I've heard that supercharger owners find that the viscous dampers can't cope with the torque that the pulley must transmit, and resort to solid pulleys. I wonder if suprcharged engines are not taken high enough for toriosn vibration to be a problem. JOhn Quote Link to post Share on other sites
Tom Fremont Posted February 4, 2018 Report Share Posted February 4, 2018 Richard Good offers a viscous damper at an eye popping price which is claimed to enable another 1000 rpm without other modifications ( from memory - do confirm if curious ). Cheers, Tom Quote Link to post Share on other sites
Steves_TR6 Posted February 6, 2018 Report Share Posted February 6, 2018 (edited) Nice surprise in the post today, delivery for Mr TR6 from Mr Fremont ! Looking forward to fitting, maybe at the weekend if it warms up a bit ! Steve Edited February 6, 2018 by SDerbyshire Quote Link to post Share on other sites
john.r.davies Posted February 6, 2018 Author Report Share Posted February 6, 2018 (edited) "another 1000 rpm" on what? Does that mean 7.5K or only 6? It mnakes a big difference, when a mean piston speed of more than 20m/sec is considered the most that can be tolwerated, unless special materials are used. For the 2.5L, 95mm stroke: An RPM of 6000 gives an MPS of 19m/s An RPM of 6500 gives an MPS of 21m/s An RPM of 7000 gives an MPS of 22m/s An RPM of 7500 gives an MPS of 24m/s Sorry, I had a nice table but they don't translate into posts! JOhn Edited February 6, 2018 by john.r.davies Quote Link to post Share on other sites
Tom Fremont Posted February 6, 2018 Report Share Posted February 6, 2018 (edited) "another 1000 rpm" on what? Does that mean 7.5K or only 6? It mnakes a big difference, when a mean piston speed of more than 20m/sec is considered the most that can be tolwerated, unless special materials are used. For the 2.5L, 95mm stroke: An RPM of 6000 gives an MPS of 19m/s An RPM of 6500 gives an MPS of 21m/s An RPM of 7000 gives an MPS of 22m/s An RPM of 7500 gives an MPS of 24m/s Sorry, I had a nice table but they don't translate into posts! JOhn For the TR250/6 engines of N. American specification that would be 6500 and 6750 rpm. A notorious specialist in the UK says factory pistons come unglued around 6500 rpm so to take advantage of the damper in question forged pistons ought to be fitted. " No other modifications " refers to the crankshaft and its bearing arrangement - stock setup sufficing there. Cheers, Tom Edited February 6, 2018 by Tom Fremont Quote Link to post Share on other sites
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