Historical Article - Nov 1992 - Good Vibrations

This year saw the re-introduction of the damper ring originally fitted to the Cooper ‘S’ engines and used extensively by a multitude of racers – until its demise instigated by the cessation of production by BL some 10 or so years ago.  Very unfortunate as this was broadly recognised as being THE crank damper to use on any performance of rally/race engine to deal with odd-ball harmonics produced by the 3 main bearing ‘A’ series engine.  Midget and Sprite racers mourned the loss more than Mini owners, as the current “thick” damper causes clearance problems – the damper hits the cross member under hard braking/severe engine braking.

Other problems caused by using the only available damper (as used on all 1300cc non ’S’ production A series engines) were really only restricted to its high speed performance.  It was not really developed to cope with engine speeds over 7000 rpm, its high rpm damping not being particularly adequate and a tendency to fall apart after relatively short periods of use.  The continual high speed acceleration/deceleration of a race engine – and the severity of each – twists the outer section on the rubber sandwich.  This causes the rubber section to break up, and in some cases causes the outer to come adrift from the inner section.  Undesirable is an understatement!  The break up also causes the pulley to become out of balance – worse than running without a damper at all.  This is a common cause of the flywheel “picking up” on the crankshaft nose – the out of balance pulley causing the flywheel to “fret” on the crank.

When used in race conditions it is highly recommended to carefully inspect the one piece damper after 3 or 4 events.  If the rubber sandwich has any cracks in it at all (usually visible from the back, or engine side) then it should be replaced.  This applies to the longer stroke cranks more so.  It is therefore not unreasonable to have to fit a new crank damper 3 or 4 times a year.  Not the best of situations, but cheaper than destroying an engine.

Being a keen racer, with more than a passing interest in developing the horse power potential of the venerable A series engine with reliability, I embarked on the “damper ring crusade”.  The obvious place to start is at the beginning.  I know Metalastik had originally produced the damper (easily deduced – it is stampedinto one of the pressings!) so I contacted them.  Due to the saleof their automative harmonics damping departing to Freudenberg lock, stock and barrel) I would have to try them.  They had all drawings, patterns, etc. so they should be able to help.  Now, I wouldn’t say that Freudenberg are deliberately, erm, “cagey” with their replies to technical enquiries, but they certainly play it close to their chests.  After a number of telephone calls to various different people there it was clear that unless I wanted a couple of thousand producing they weren’t interested, except of course at enormously uneconomic prices.  They had absolutely no plans to remanufacture themselves, but didn’t want to sell the drawings either.  Apparently the tooling was destroyed ages ago.

As this had proved fruitless, I then contacted a company called Holset.  I was put in touch with an extremely helpful chap who gave me a brief but useful crash course in damper use and design.  At the end of the day they could produce a damper to required design, but once again were not economically viable – despite being vastly cheaper than Freudenberg.

A period of investigation into the application of a commercially available item was indulged.  Richard Longman had already successfully done this for the Metro racers, but was still somewhat out of the ball park price-wise, as a fair amount of  adaption was needed and would not really fit a Mini due to its enormous diameter.  All kinds of units were considered, but most did not have the correct damping, and nearly all would be a major task of adaption.  Hmm.  Time was trotting along and, despite learning a fair amount about Torsion Vibration dampers, I was not much nearer to production.  The next step was to talk to a few of my learned colleagues in the A series business – Glyn Swift, Phil Hepworth, Mike Parry, Steve Whitton and all – to try and establish if the A series really did need a proper damper, even if it needed one at all.  Opinions and experience were discussed – which led to further investigations into currently produced items.

 
Fluid filled dampers have become the “in thing”, so a foray into that field seemed appropriate – although nothing was expected to come from it.  I wasn’t far wrong.  I did learn a little about what they constituted and how they worked – but it would seem they were really developed for larger engines, and once more were prohibitively expensive.  Some of the more, erm, “elitist” A series tuners seemed to consider the expense justifiable – but to the many impoverished Mini racers I really couldn’t see it.  If we could afford to spend Ferrari type money, we’d be running them wouldn’t we?  All this was becoming somewhat trying – but if there’s one quality I possess, its perseverance.

Enter my cousin, Peter.  Whilst discussing my labours with him, he suggested a chat to a friend of his maybe worthwhile – a man employed as a “rubber technician”.  After further discussion, a little more in-depth instruction in the whys and wherefores some progress was made.  As far as reconstituting an old unit for testing even.  This was marvellous stuff!  Light at the end of the tunnel?  Well, nearly.  Despite being 50% cheaper than the cheapest quote so far, careful consideration determined that the market place would not really stand the sale price required to make production worthwhile. 

Whilst investigating all these different possibilities, production of the original “S” item was never out of my sight.  After all, this was specifically designed for the job – and therefore ideal.  Thinking back to discussions with the man from Holset, it was obvious that the only one that would REALLY o was as per original.  I had already established a ball park price for the metal bits whilst pursuing production with my cousin.  The technology involved in the rubber and the pressurised , thermo-bonding process seemed to be the expensive bit.  So this became the major point of investigation.  Fortunately, at one of the shows Mini Spares exhibited at, a company dealing in such processes emerged.  Not only did they specialise in the technology we required, but they were also a limited production company, i.e. we did not need to have thousands made.  Small batches at sensible prices.

A visit to their premises revealed exactly what we were after.  Their technical expertise was apparent from the start – production components for a wide variety of highly technical applications from World War Two Memorial Trust (doing stuff for spitfires, Lancasters, Shackleton’s etc.) to Formula 1 (not allowed to disclosed any secrets!).  Their quality was of the highest standard, production schedules more than sensible, quantities just right, AND at the right price.  Almost stuff that dreams are made of!

To-wit, the original type of split damper will be once more available.  This will fit those toothed belt crank pulleys purchased from us.  Those that wanted to use tooth belt drive systems, but didn’t because of the lack of a damper need worry no ore.  For those that still wish to run the standard “V” belt system, Mini Spars have reproduced the original “S” crank pulley too. 

AEG454        Standard “V” crank pulley         £30.55
12A67        Damper ring                £49.35
C-AHT146    Locking plate                  £2.88

All prices are historical

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