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Ashley James
Unregistered guest
Posted From: 195.149.1.6
| | Posted on Friday, 23 January, 2004 - 06:39: |    |
The thread concerning crankshaft dampers was discussed some time ago on this site. In the last few days some discussion has taken place on some aspects of the dampers on the RREC site, which is only accessible to members. I thought that the following edited extract might be of interest. As a matter of courtesy I contacted Norman Geeson who wrote the reply for permission to quote this section.
"In the case of the damper. I think that possibly the term "metalastik" has been used in a genral way to describe the commercial damper as a desired fitting on the car version of the six cylinder. I am not sure whether you are all referring to a true "Metalastik" damper on R-R's own version consisting of a rubber mounted dry friction damper. As this damper was fitted to all commercial engines mentioned, up to at least 1960, and to all Phantom IV car engines.
Rolls-Royce only fitted their own rubber mounted friction damper on commercial engines during the life of the six cylinder car engine. This standard damper was emobodied in the crankshaft belt driving pulley, which formed the intertia mass. In the later versions, the pulley was carried on eight circular rubber studs mounted on the central boss, which was rigidly attached to the crankshaft nose. The rubber studs only provided resilience, clamping the belt pulley by means of springs, betwen two Ferodo discs, produced the damping. This arrangement acted rather like a lanchester damper. On B81 engines, of circa 1960, the assembly was either RE24128 or UE6269 depending on the belt grooving. This R-R damper gave quite VARIABLE results, but was acceptable on the commercial engines, which were generally limited to 3750 rpm.
"Metalastik" dampers were tested between February 1958 and April 1960 as a cheaper COST option only to the R-R commercial damper. At the time they gave equal, but no better results than the R-R rubber mounted damper, which itself gave scattered results.
This goes some way to answering the question as to why they may not have been fitted on six cylinder car engines. In any case the car engine was out of production before the tests on Metalastik units were complete.
The Metalastik damper as you may know, is a completely different animal to the R-R rubber type, in the way that it consists of a tuned rubber bonded between the inner and outer pulley mass. Without doubt they have been improved over the years. At the time of the 1958-1960 tests a non-bonded Holset damper was also tested with equally good results to the Metalastik.
In connection with viscous dampers, Alan is probably right that a modern unit would do the job. I cannot however visualise such an arrangement preventing unwanted vibrations being transmitted to the gear train. Incidentally R-R did in fact try out a 10" Girling viscous damper on the early 3.75" bore, although only briefly and with no thoroughness, but it was found to make the situation worse. had they pursued the visocus coupling, longer term, things may have been very different.
In recent years I have spent a considerable amount of time, some weeks in fact, researching seemingly untold facts and dates on the car's dampers and spring drives. Including the full history, part numbers and drawings of the slotted type dampers and Ferodo washers. This was in preparation for writing an article on the most recent history, an article that is now nearing completion. What surprised me, even astounded me was not the saga of the cotton duck washer, we all know the problem in that quarter, but the following;
Probably more words have been written about R-R crankshaft dampers and spring drives than any other R-R subject. Yet nearly half a century after the demise of the six cylinder damper, the operational problems, and there are many more than friction washers troubles, have never been mentioned.
Wo now have a situation where various substitutes are suggested, rather like sizing a brake lining and not knowing whether it is to be fitted on a car or a jet aircraft! If the damper does not operate dynamically as everyone believes, and it does not, then how do alternative materials or for that matter poundages fit into the picture. The design, static testing of slipping poundage's suggested new friction materials and calculations are one thing, what happens actually in operation is quite another.
The spring drive for instance is interdependant upon the friction of the damper. A seized damper soon finishes off radial springs. An offset spring drive does not exactly assist damper operation, nor timing for that matter, a situation that exists when radial springs are incorrect. A recent survey of the radial springs shows that most of them that have been fitted recently do not even conform to the drawings. Let alone the spring loads, they are not even wound the correct way!!
No friction material on this earth will operate, including Tufnol, unless certain conditions are met, and none appears in the manuals. For instance the pressure plate assembly moves axially and lifts off the friction washers during certain engine conditions. This made worse by axial movement of the outer damper rim assembly as a whole. We even read of discussion on the make up of the fibre directions on cotton duck or its alternatives, and thread rolling. Rather irrelevant when the presser plate pressure is lifting off the friction medium.
Different materials and setting poundage's abound and everyone sets slipping loads with clean opil. Who ever heard of one of these engines feeding absolutely clean oil, after the first few thousand miles, to the friction washers? Who has ever used sludged oil to set damper slip loads?
Mention is often made in articles of the slotted damper and Ferodo washers, fitted to the last 4.5L engines. Very few if these dampers will now exist as originally they were only fitted to 94 engines, investigation does however indicate that in spite of R-R's thoughts that they could give trouble, most seem to have performed quite well.
Where are the printed details or research on the background, parts and drawings? This was also the only time a Ferodo friction material was used in the car engine damper.
A few questions; most answerable with some research, and I hope a few answers, but it might promote some thought.
Regards Norman Geeson. |
Bill Coburn
Prolific User
Username: bill_coburn
Post Number: 100
Registered: 4-2003
| | Posted on Friday, 23 January, 2004 - 09:11: | |
Ashley/
I want to thank you for your thoughtfulness in putting the article on dampers from Norman Geeson on the Australian web site. Can I ask who Norman Geeson is? That question is not meant to be impertinent but impressionable or not I find knowing the credentials of the writer a help in absorbing the article. It is so refreshing to read about the cars without the spin merchants around. I am in Canberra and have an ’84 Spur and an S2 Bentley and ‘look after’ a variety of other post-war cars. I am 66 and retired and it gives me a strong interest and denies me the tyranny of bowls and golf! I have been producing a monthly newsheet titled ‘Tee One Topics’ for nearly three years. The thing was put together originally to prove to the tea and bikkies members of our local Club that owners were interested in how their car ticked. It deals almost solely with day to day problems and solutions and so far is very well accepted. I avoid the detail that Norman Geeson has addressed since there would be very few of my hundred odd readers who would be interested. There is also the fact that few readers have immediate post-war cars. I can empathise since I restored a ‘B’ series Silver Dawn from the chassis frame up but in this country I am an exception. With due credits I will reproduce your edited contribution to the web and try to throw in some general guff about crankshaft oscillations. I do this in the hope that such writings are not lost in the sea of documentation that appears to abound in the repositories.
Sincerely
Bill Coburn
|
Ashley James
Unregistered guest
Posted From: 195.149.1.9
| | Posted on Friday, 23 January, 2004 - 21:55: | |
Bill, Norman is so well known over here in the UK that I had not considered an explanation was necessary. Norman is an R Type owner who has worked on these cars since the early sixties. His experiences with the cars have put him in close contact with R-R over the years and more recently he has been trawling the company records at the Hunt house in order to document the history of the development and maintenance of the early Post war sixes.
Norman probably knows more about the cars than anyone.
R-R were not as meticulous as they might have been with workshop manuals, some have errors in them and workshop practices that evolved over the years and that overcame various problems, were not always documented outside the company. Norman has written much of this up and it appears on the RROC site, some on the BDC site and in the RREC club bulletin.
As the damper is a major talking point but not one where solutions are forthcoming, it seemed a good idea to highlight Norman's work as he may be close to offering a more satisfactory long term fix. Ashley
|
Alexander R Lynch (139.134.58.153)
| | Posted on Wednesday, 27 November, 2002 - 17:40: | |
From Alex Lynch & B111 JN 1950 MK V1 - I am about to dismantle and inspect the vibration damper as I have a suspicion that all is not well within. I believe that the RROC of America published an artice on the procedure but have not been able to locate a copy - can any one help. I have the workshop manual which is clear enough but I suspect that ther are some procedures not fully explained. Access to parts is no problem and I would appreciate any experience that members have had - regards Alex |
Bill Coburn (203.51.30.134)
| | Posted on Wednesday, 27 November, 2002 - 21:31: | |
Lex, No doubt you have perused the index in the Mk VI Registrars site which covers all the Flying lady writings on the damper. Frankly there is nothing other than boring hardwork to setting the things up. Do be prepared however to machine the relevant faces before starting. Co-incidentally I wrote a tongue-in-cheek article in the Tee One Notes which follows and might be of interest.
For those who have spent countless hours ‘ironing’ the duck washers in the slipper flywheel fitted to pre-vee eight engines the harmonic balancer to the left fitted to the vee eight must be a gross anti-climax. The aura around the original balancer almost approached that of witchcraft. Originally developed very early last century by another manufacturer the Factory decided that this was the answer to a very early problem they had with the nose of their 6 cylinder cars’ crankshafts snapping off! All car engines have to contend with crankshaft oscillation. Imagine the inertia of a torque converter full of oil at one end of the shaft and a cylinder firing at the other end. The shaft obviously has to flex radially. But then having wound itself up, the torque converter catches up and
keeps going, twisting the poor beastie the other way. And that is only for one firing. If you start loading up the front end with pulleys etc to drive all manner of gadgets it becomes a mathematical
nightmare. The answer is to put yet another wheel/disc/pulley on the front end of the shaft with another bit attached to it that can flap around and confuse the whole setup. By now, my son, an automotive engineer will be crying in the wings and searching for the geriatric services in the Yellow Pages. But the original Rolls-Royce contrivance used a slipper flywheel that could oscillate through a small arc around a disc keyed to the front end of the crankshaft. Springs were interposed between the two bits to cushion the movement and the whole lot sandwiched between cotton duck washers internally to provide a friction. The amount of friction was seen as the clue to the perfect functioning of the gadget and involved assembling it with no springs and ‘ironing’ the duck washers until the right amount of friction remained. Frightfully complicated, laborious to set up and as far as I can gather of little effect. The outer casing of the slipper drive initially was bolted together and fed with oil from the crankshaft. The oil inevitably carried muck from the engine which lodged in the slipper drive as it acted as a centrifuge and eventually the whole assembly was so full of sludge nothing could move. Later in the early post war cars they did provide slots for the oil to escape but one wonders whether that did much to help. A clue to whether all this was manna for the spin doctors and little else, is that the commercial version of the Mk VI/Dawn engines which dimensionally and functionally were identical had no slipper flywheel, but used the simple harmonic balancer fitted to your common old Fords and Holdens which ran perfectly smoothly and didn’t break crankshafts.
And so the Vee Eight came along and having a much shorter crankshaft the damping problem was much simpler. And above is a picture of the damper dowelled onto the front end of the crankshaft. It is as usual in two pieces, inner and outer connected by nothing else but some very stoutly bonded rubber. This balancer has done an estimated 750,000 miles and looks little the worse for wear so I suspect it will not be a high usage item for our cars in the future.
I suspect you will find that the more likely problem is very worn timing gears. Perhaps when you find out we can hope for an article. |
Alex Lynch (139.134.58.153)
| | Posted on Thursday, 28 November, 2002 - 11:18: | |
Thanks for the humour Bill - it looks as though I will need one to accomplish this job! - Lex |
Jim Bettison (203.166.57.11)
| | Posted on Friday, 29 November, 2002 - 11:19: | |
Alex: B20JO at this end.
Been down the track you're starting, and I'll take no issue with what Bill says. If you didn't laugh, you'd have to cry ...
I think the essential points concerning the renovation of the Spring Drive (so called in the Parts Book) are:
1: Ensure that the various plates, etc, that compress the duck washers are refaced - at least to 50% of their area.
2: Preferably use new duck washers as specified. I don't know if this is vital; I know that some cars in my area (Adelaide) used a material known in the electrical insulation trade as SRBF (Synthetic Resin Bonded Fibre) of about 0.0625" (1-16") thickness in rebuilds. Before assembly, the SRBF plates (the material is quite rigid) had the glaze broken with a medium abrasive cloth. This material was used in the spares "drought" of a few years back, with apparently no bad outcomes (and this includes my own car). However, it may be that duck is now available from suppliers; certainly it can be got in UK, and I can give you some contacts for supply if you need them. When I was in UK last month I visited some of the specialists in repair and renovation, all of whom worked on the principle that duck was available, the outcomes were good - so why change? (Sorry for this little diversion.)
3: Set up the unit as in the workshop manual. There are no tricks. You may need to reset or replace some springs to get the slipping poundage.
4: As Bill has poined out, the assembly is a pretty good centrifugal filter. A modification is to drill 3 holes radially at 120 degree intervals from the collection dam in the rear wheel to allow oil, etc, to escape. (This may have been done previously.)
5: When all finished, run the engine every couple of weeks - at least. The duck material tends to accumulate moisture, the steel rusts, and - bingo - everything bound together.
The story of the development of this device is something else again - look at it in some of the R-R/B histories. Sufficient to say that there's no magic in the torque poundage specified for set-up: it was derived quite empirically from a series of tests as the set-up that worked best ... and there was I thinking that most of this stuff was divulged by Moses, when it was Henry all the time ...
Good luck - Jim. |
Richard Treacy (62.202.243.55)
| | Posted on Friday, 29 November, 2002 - 18:15: | |
The SRBF plates in my opinion are far superior to the cotton duck originals. I have a bunch of new cotton washers, but run the fibre washers instead. The cotton washers can easily stick to the plates (mine were years ago when they were only 12 months old), whereas the fibre ones have never stuck. If the car is not run every few weeks at least, expect trouble with cotton washers as the plates rust and the cotton soaks up sludge. You can feel if they are stuck when using the crank handle. |
Bill Vatter (66.20.179.38)
| | Posted on Saturday, 30 November, 2002 - 00:13: | |
Richard's and Jim's recommendations have been endorsed by RR as well. (Or is it the other way around? depends on how old Jim and Richard are.) The cotton duck washers were replaced about the time the Clouds arrived, B212ZY to be exact, and "drain slots" accompanied this change to allow for some circulation of oil. These washers were referred to as "Ferodo" which I understand to be a brand name that also shows up in clutch facings and brake shoe linings. Currently the name is "Tufnol," which I suppose also to be a brand name, and they are available in the UK for about £10 each. This compares with about £45 each for the cotton duck. In my opinion, for £10 each it is worth going for material known from experience to be effective, rather than using some other material that may or may not work as well.
I hope you have found the FL article you are looking for. It appeared Nov./Dec. 2000 and was written by James Pate. It is very good, especially for its directions for disassembling the center hub that is held together with springs. If I had a scanner, I would help you with this article myself, but I am sure there is someone else who has probably already got to you with it.
When you read this article, I have additional comments regarding removing the starter dog nut and pulling the damper from the nose of the crankshaft:
1. An air operated impact wrench will take the nut off. This is a tool I generally do not like to use because it destroys parts. However, the air impact wrench is doing the same thing as the slogger bar.
2. The special tool James made to remove the nut holding the damper is certainly the sophisticated way to remove the nut. Good for James to have taken the time and effort to do it right. For those who are impatient, a steel drift against the notches of the nut will also work, possibly to the disadvantage of the cosmetic appearance of the nut. If you make or find the special tool, the warning James offered for the starter dog nut regarding long breaker bars also applies here. Long breaker bars can tweak your crankshaft, an expensive mistake for sure.
3. After removing the nut holding the damper on, pull the damper by placing a suitable distance piece under the starter dog nut so that it will press against the end of the crankshaft when tightened. be careful to place it so that the pressure will be squarely aligned with the center of the crankshaft, but resting against the edges which is the crankshaft proper. The center that you are looking at is actually a plug closing the center oilway in the crankshaft. Then get your air impact wrench again and tighten it down, which will pull the damper off. Some very stiff grease will hold your distance piece centered while you put the starter dog nut back on. Whenever using an air impact wrench to remove parts or in this case to pull the damper, adjust the wrench to the lowest torque that will do the job. Too much torque can easily cause damage.
Good luck with your project. |
Bill vatter (66.20.179.38)
| | Posted on Saturday, 30 November, 2002 - 00:19: | |
Further comment with regards to #3 of previous post. The part to which the starter dog nut attaches must be refitted with its 4 nuts in order to pull the damper after removing the damper nut. Sorry this was not clear. |
Bill Vatter (66.20.179.38)
| | Posted on Saturday, 30 November, 2002 - 01:41: | |
Question for Jim Bettison:
You state:
"1: Ensure that the various plates, etc, that compress the duck washers are refaced - at least to 50% of their area."
Do you mean to imply that 50% of the area might be imperfect with corrosion pits? I would be interested to know if a damper is effective with imperfect surfaces as you seem to imply. As we both know the surfaces will have corrosion pits if the cotton duck washers have stuck to the surfaces, and this is the situation with almost every car that has not run for an extended period, which is about all cars. The thickness limits of the metal pieces restrict grinding to renew the surfaces, particularly with regard to the central disc because it has two surfaces ot consider, and not grinding would be preferred if the damper will still meet the torque specification for slippage, and be uniform is response to torque, i.e., break-away torque not much more than running torque. |
Alex Lynch (139.134.58.153)
| | Posted on Tuesday, 03 December, 2002 - 18:32: | |
Dear Jim, Richard & Bill - thankyou all for taking the time to offer your help and suggestions. I have sourced the article in FL and it makes for a great read if not a little daunting in its detail. I have reached the stage of removing the starter dog and I can see its going to be a bitch. Looking at it did nothing to release its grasp on the crank. I placed the car in gear etc and can see why you suggest the use of an impact wrench. I am in Melbourne so tomorrow will visit my friendly mechanic who has offered to help and see if I can borrow a slogger bar??? I have no idea where you all hail from so let me know in your next communication. With sincere thanks - Lex Lynch |
Jim Bettison (203.166.57.11)
| | Posted on Tuesday, 03 December, 2002 - 20:50: | |
Ladies and Gentlemen (correct way to address a large assembly, I think ...)
To pick up on some points. As to the material of the washers; a check around here (we're in Adelaide, Lex), finds a lot of support for Richard's endorsement of SRBF (I got the name partially wrong in my previous posting: in full, generically, it's Synthetic Resin Bonded Fabric. "Tufnol" is one of the brand or trade names by which it's known here. Further advantages can be added to Richard's list of SRBF attributes; particularly, you can select a thickness of SRBF which facilitates setting-up the damper springs. In my case, the springs were packed out by about 3/16" in order to get the sought poundage on the torque lever - see a later comment. Also, SRBF doesn't accumulate moisture, as Richard points out, and seize up the plates with consequent rusting.
"Ferodo" is a brand name for a line of friction materials used for brake linings and clutch friction plates, as Bill points out. To my knowledge, the manufacturers of Ferodo and Tufnol are quite different companies.
As to resurfacing: some of the plates in the spring drive will almost certainly be pitted. We have also seen plates that have also been worn with grooves circumferentially, so that they look rather like metal clutch plates and flywheels that have been in extended service in the transmission chain. Like them, the spring drive should be restored by regrinding the surfaces. In the case of the spring drive, metal which is taken from the drive plates will need to be made good by packing the springs, as spoken of above, or by selecting the washer thickness - which is only practicable with SRBF.
As a judgement, people here would remove by machining (grinding) only as much metal from the drive plates as is necessary to have 50% of the area machined - and let the duck or SRBF washers bed themselves for the rest.
Hope this helps. Do let us know how you get on - Jim. |
Bill Vatter (67.35.51.7)
| | Posted on Tuesday, 03 December, 2002 - 21:31: | |
Lex,
I am in the south-east US, Atlanta.
You wrote "I placed the car in gear etc." and "slogger bar ???"
These lines suggest to me you do not yet have the concept of how to get the nut off. Sorry to be picking at you, but YOU MUST NOT TWIST THE NUT OFF BY HOLDING THE CRANKSHAFT STILL FROM THE REAR. If you do this you stand a very real chance of putting a twist in the crankshaft and causing you a very expensive repair. What's more, your car will be out of service for a long time while you take it apart to replace the crankshaft.
This would be the very worst kind of mistake and damage you can experience: that which you caused yourself. It could ruin the hobby for you, by making you dislike the car.
Th proper way to remove the nut is with IMPACT. The slogger bar is just a special-made long hex ring spanner that you bang on the end with a sledge hammer. While you may be rightly reserved on using the impact wrench, this is what a slogger bar does also, except with the impact wrench you have more control. Raise the torque setting on the impact wrench gradually until you get enough zowie to take off the nut. It could take as much as 300 ft.-lb. to do the job, or as little as 100 ft.-lb.
If you are set on a slogger bar, look at Flying Lady page 5744 (May/June 1999) for pictures and words on what it is and how to make and use one.
Regarding your comment: "Looking at it did nothing to release its grasp on the crank." I respectfully disagree with you on this point. Sometimes taking a break, talking with friends, reading the books, and just generally contemplating the problem will in fact work miracles. If nothing else, it will keep you from screwing up by doing something foolish, like using a 4 ft. breaker bar with the car in gear and the hand brake set. Sometimes I am very sure that when the parts get the message you are really serious about facing the challenge they present, while you are mustering the proper forces to engage the parts in proper combat, they will yield without much struggle, knowing beforehand they cannot prevail. |
Bill Vatter (67.35.51.7)
| | Posted on Wednesday, 04 December, 2002 - 01:57: | |
Gentlemen:
I wish to correct myself regarding the Company's use of cotton duck and Ferodo washers. A friend shared with me a small piece of amusing trivia:
RR was supplied with cotton duck washers by a single manufacturer. Eventually their machine which made the washers broke down, and it was not repairable. This supplier asked RR if the Company would like to participate in the cost of a new machine, which the Company declined. Enter in Ferodo washers. However, the cotton duck supply must have been straightened out and thought superior to Ferodo because during Cloud production, the Company returned to using cotton duck washers in the dampers.
Currently another friend is having some difficulty getting consistent friction resistance in his damper which he rebuilt with Tufnol washers. Apparently there is inconsistent oil distribution between the washers and steel discs, drums, etc. when using Tufnol. Some modifications of the washers have been proposed to aid the flow of oil, but I am not personally familiar with this. In summary, I think there are reasons for using cotton duck as well as Tufnol, and the best material is not universally agreed upon by experts. |
Bill Coburn (203.51.30.134)
| | Posted on Wednesday, 04 December, 2002 - 11:09: | |
Hello again Lex from Canberra
Your observations on the starting dog brought back memories. With the Dawn I had the advantage of the engine on the bench and for some reason held the crankshaft at the opposite end of the dog (sump off piece of wood jammed in crankcase) and just using my very large break bar was horrified at how much the shaft twisted. The solution ( I was not very quick even then you know) was to move the block of wood to the front throw and with considerably more leverage (the handle of my floor jack)the dirty dog came free. How time dims the worst memories!!! Anyway my money is on your hiring a rattle gun and the appropriate socket and you will be home and hosed. |
Richard Treacy (217.162.170.219)
| | Posted on Wednesday, 04 December, 2002 - 18:55: | |
Yeah. I used several blocks on several crank throws because I thought the crankcase would split apart. That is the tightest nut in the business. |
Alex Lynch (139.134.58.153)
| | Posted on Wednesday, 04 December, 2002 - 19:04: | |
Dear Jim, Richard and Bill - I have now placed the vehicle out of gear but left the hand brake on - borrowed a compressor and rattle gun - some time later- well yes it did come off and not as difficult as I thought mind you taking all day to remove one nut nobody would want to employ me as a paid mechanic! So next, remove the timing cover and see whats there. Just a query- with regard to the timeing, the manual says to set it up on no1 at inlet open and note flywheel markings then prior to removal of the damper to do the same again but on no six so that the meshed pinion and timing wheel can be marked for reassembly - correct? I am not really dim, but why do it twice unless to check. I will deceide about the ducks V tuffs later on but I am glad to have created a discussion on the subject and for all your input I truely thankyou. Better wipe the grease off the keyboard and return to the adventure. Regards Lex |
Bill Vatter (67.35.51.7)
| | Posted on Wednesday, 04 December, 2002 - 23:47: | |
Tp preserve the camshaft timing you need to mark three things:
1. THE GEAR MESH BETWEEN THE CAMSHAFT AND PINION GEARS. Do this by wiping clean a couple of teeth and put a drop of paint between two teeth on the pinion gear and then rotate the engine so that the paint picks up on a camshaft gear tooth. Later after everything is reassembled, you clean up the paint so that it will not enter the engine. After removing the damper you may wish to make a more permanent mark on the pinion gear if your cleaning up everything is going to remove the paint. The camshaft gear should not be disturbed so the paint should remain.
2. THE PINION GEAR ORIENTATION TO THE CRANKSHAFT. The four studs sticking out on the front of the damper from which you remove the 1/4 bsf nuts to get at the damper nut are attached directly to the pinion gear and will not be removed during your overhaul. Mark one stud end. (I suggest a cross mark on the end with a hacksaw that will not come off during cleaning.) After removing the nose piece of the damper, but before removing the damper, mark the end of the crankshaft in a similar manner to match the location of the marked stud. The end of the crankshaft will be sitting out there all bare and beautiful, and it will be quite easy to put your hacksaw mark on THE END of the crankshaft. DO NOT MAR THE JOURNAL SURFACE that the damper nose runs against. With these two marks, you can be sure the camshaft is properly timed when you reassemble everything. However, a third set of marks is needed to make sure you have the damper reassembled correctly. Without the third set of marks you can reassemble the damper such that there is no possible way for your pinion-cranckshaft orientation to be aligned. This is because there are four ways to put the damper hub together but three ways to put the damper on the crankshaft. Therefore you could be off by 30 or 60 degrees if you assemble the damper in a different orientation from the as-found orientation.
3. THE ORIENTATION OF THE DAMPER CENTRAL HUB ASSEMBLY. After opening the damper but before disassembling the central hub mark the orientation of the two solid pieces. (Again I suggest a permanent mark, a hacksaw scribe or a center punch at the center of the central disc adjacent to the stud you marked earlier with a hacksaw. Do not mark the friction surface of the disc or disturb the tapered surface that is keyed against the crankshaft, but anywhere else should be fine.) These pieces are the central disc and the pinion gear. (This is the disassembly of the radial springs part where you will learn some colorful new phrases to describe how much fun you are having. You will certainly know for sure when you are about to disassemble these pieces because you will precede the disassembly with considerable scratching of your head.)
Be patient and ask questions as you proceed. On removing the many-dogged nut that holds the damper on, you will note it is secured by tabs of a washer that is itself dogged to the crankshaft. The nut is right-hand thread. Make a socket like James described in the FL article or you can tap it off with a steel drift. (Pull the damper as described in my earlier post.)
Personal opinion, the crankshaft damper is Rolls-Royce engineering at its highest level of elegance. An engineer cannot help but marvel at the design. If you understand how friction and springs work together to dampen shaocks it will become beautiful before your eyes. |
Richard Treacy (217.162.170.219)
| | Posted on Thursday, 05 December, 2002 - 06:38: | |
Sure, mark everything, but how can you be sure that the last guy (overhauler or even factory assempler) got it right ? The marked positions are only the starting point. Remember, turn the crank fro the flywheel, do it a few times to be sure, and observe the 30 thou rule when setting the mesh each time. Every postwar 6 cylinder I have driven feels quite different, and U put this down to valve timing.
The Grey Book is a little vague on timing of Silver Dawns, but tells curiously that the Dawns are to be set with the valve timing 10 degrees late and the Bentley on TDC. This partially explains why the Dawn and Bentley drive so differently. The rest is explained by the twin SUs on the Bentley. |
Bill Vatter (67.35.51.7)
| | Posted on Thursday, 05 December, 2002 - 16:20: | |
Richard is right, does not hurt to check to make sure camshaft is timed right after putting it back together. However, if it turns out to be off time, it isn't very easy to set it, a trial and error procedure, and the original camshaft has studs in the end which need to be romoved or pull the damper back off to change the camshaft gear mesh with the flywheel. Best to not loose what you start with. Chances are the camshaft is correct before you start. |
Jim Bettison (203.166.57.12)
| | Posted on Thursday, 05 December, 2002 - 17:23: | |
I have known of a couple of engines that were incorrectly timed in consequence of the timing gear having apparently been set up to the incorrect flywheel marks. And you need to know the part number of the camshaft fitted to know which are the correct markings. If it's wrong, it's mostly not so wrong as to cause big troubles, but to take the zip out of performance.
We had a thread running on this subject in this site, back about 15 or 16 July of this year, I think, under the head "Camshaft - what's in a number?" or some such similar. Lex, you might find it useful, or interesting (or both!!!) to have a look.
Good luck, Jim. |
Alex Lynch (139.134.58.153)
| | Posted on Thursday, 05 December, 2002 - 18:32: | |
Well the beast is finally out, thanks to you all for the imput, just before I left I was unable to resist taking the cover off for a look. This engine was restored only ten years ago yet the damper has set solid. There are no broken springs and the plate is intact to the point that it is stuck to the friction drum on both sides. Internally even with what I regard as overservicing the interior along with liquid oil had semi dried sludge around the perimiter. Not a good look and the reason for this whole exercise. From what I have read the answer is to provide a series of exit holes from three to six according to those who have followed this procedure. I favour three holes on the circumference only because the lack of lubrication would cause to Cotton Duckwashers to stick whick was I believe a Factory consideration in maintaining the damper full of oil. Bill thankyou for your remarks and dutifull attention has been paid to them. More to follow - Lex |
Richard Treacy (217.162.170.219)
| | Posted on Thursday, 05 December, 2002 - 19:38: | |
Congratulations. Getting that damper off without damage was the only heart wrenching moment in overhauling my motor.
Which washers will you use ? Although some purists insist on cotton duck, I recommend the SRBF fibre ones, but this is only my opinion based on my experiences: yes, the Ferodo brand was marked on mine. All that tuning to a specific poundage is a bit superfluous to me when every cotton-washered damper I have seen has been stuck solid after a year or so. Even if not siezed, after how long will the poundage change ? About ten minutes I expect afer a bit of heat and sludge. Rather an approximate reading with fibre. It will work properly anyhow and never stick solid.
My R-Type is in Canberra, but I live in Switzerland. Maybe I'll bring it here soon. I can only run the car every 3-6 months unfortunately, but the damper is still not stuck (I check it with the crank handle) with its fibre washers. With cotton I am sure it would have stuck years ago.
I overhauled the damper in 1981, 150,000 miles ago, so I think this speaks for itself. Since then I have opened it twice, but have not replaced the washers as they were nicely clean, free and like new (I have an unused set on standby, but not required). Between 1969 and 1981 and over 100,000 miles, the damper was overhauled three times using cotton duck, and each time it stuck after a year or so, and was solid when removed for overhaul. |
Bill Vatter (67.35.51.7)
| | Posted on Thursday, 05 December, 2002 - 23:49: | |
Gentlemen:
Here is an interesting document which contains experimental data on different damper materials.
http://www.rrocncr.org/technical/Damper1.doc |
Bill Vatter (66.20.176.252)
| | Posted on Sunday, 15 December, 2002 - 03:03: | |
Gentlemen, and in particular, Alex:
In the US RROC there has much discussion over the years concerning crankshaft damper friction disc materials. This is not a new topic of debate, but a renewed interest and effort in this subject currently exists.
There is evidence that Tufnol, which is a particular brand or type of synthetic resin bonded fabric (SRBF), is NOT a very effective material for the crankshaft damper because when it is used, the acceleration forces on the camshaft gears will be high, resulting in noisy gear train or excessive wear to the aluminum camshaft gear. This results from a relatively large difference in the static and dynamic coeficients of friction inherent with SRBF.
Advocates of cotton duck should be aware the original material, which was radially woven on a special machine, is unavailable anywhere, except perhaps in some unidentified stash of NOS parts, and the machine originally used for this manufacture no longer exists. Cotton duck you may see offered today at retail is not the same as the original, and some have suggested the weave of the currently available material is inherently weaker than the original.
Much research has been done in this area, and an effort is underway within the RROC (US) to identify the best material for this application considering both performance and availability, and to obtain a sufficient amount for persons who want to use this to rebuild their dampers. The materials that function best based upon scientific tests are unfortunately very specialized, with attendant availability problems (can't get it from retail sources, and material manufacturers sell only to sub-component manufacturers in large volume).
These materials are designed with controlled friction characteristics for use is a hot oily environment as a friction surface, such as in automatic transmissions. As you may be aware, much progress has been achieved in the past 30 years in developing smoothly-operating, high-reliability automatic transmissions, attesting to progress in developing high performance friction materials for this application.
Those of you who may wish to participate in a subscribed purchase of material in bulk (cut your own discs from flat sheet stock) are invited to email me at vatterb@bellsouth.net for additional information. |
Alex Lynch
| | Posted on Saturday, 15 February, 2003 - 19:50: | |
Just in case you all thought that the task in hand had defeated me I would like to point out that Xmas and January are particularly busy for me and as I opted to reinstate to the original specs by installing Cotton Duck Washers the delivery from England was conducted at a very gentlemanly pace - needless to say I have finally rebuilt and installed the damper along with addressing a few other repairs but have yet to test the unit. Thankyou all for your help,opinions and suggestions. As it turns out the whole proces was not as daunting as I had at first imagined there being no damage to the spring plate with just minimal build up of sludge after ten years and 30,000 Miles of motoring. You may be wondering what persuaded me to opt for the C.D.W. I found that the Ferodo discs that had been installed in 1990 had adhered to the backing plates due to lack of oil finding its way between the surfaces. There were two addional washers placed behind the backing springs and as this was repaired during the original engine restoration I have no idea of what poundage was applied. As the radiator was removed this is now away for a top tank off clean and should be back by next week. I shall let you know of the results of my endevours then - Regards Lex Lynch |
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