POST 59 - JULY 2013 - WHEELS BALANCED - OR NOT ?

Back in January 2012 (Post 21) I moaned about the problems I've always encountered getting wire wheels balanced and on that occasion it was my Frogeye Sprite causing me the usual grief.  I have copied the relevant part of the post below:

Throughout my ownership it has always suffered to some extent from wheel balance problems and try as I may, I have never found a tyre depot that filled me with confidence; with endless attempts to get the wheels balance correctly.  I am pretty well barred from a couple of my local depots due to my insistence that they do a second check after achieving the usual 0-0 on the balancing machine first time round. Always, and I mean ALWAYS it no longer reads 0-0 when they very reluctantly put the wheel back on the machine. The reason, I'm sure, is that the cones are not designed specifically for wire wheels and the wheels fit on the machine slightly differently each time. That's why, when you take them back to the tyre depot you always hear the guy say "don't know who balanced these mate but they're a ******* mile out" Actually, it was you, last week, and you charged me twenty quid, is a not much appreciated response.

So here I am again with the problem of sorting the XK120’s brand new 16”x5” 60 spoke wires and Michelin Pilotes.  But this time things should be different – I saw a set of wheel balancing cones, made to precisely resolve the problem of fitting the wheels to the machines, advertised in JDC magazine.  The kit sold under the Cutteridge brand name comes with a 50 degree cone to fit both large and small spline wheels e.g.  Jag and Frogeye, plus outer 20 degree cones which effectively replicate the spinners for each of the two sizes.  Additionally there are 3 sets of inner spacers which will allow the kit to be fitted to most types of balancing machine.  Cost £180. With a total of 14 wire wheel, If it works it will be a worthwhile investment.  If it doesn't it'll still makes a great Chinese puzzle figuring out how to get all the bits back in the box.

 

Cutteridge cone kit for wires

First stop is a local depot with an excellent reputation, (and they don’t know me).  Problem is, its a brand spanking new machine and has some fancy pneumatic locking device so it’s one of the few machines the kit won’t fit.  Second stop is a garage that's had a fair bit of work from me so might be prepared to go the extra mile – Brand new machine with same Pneumatic gadget. 

Third stop is part of a National Chain doing mostly commercials but they have the right sort of machine.  Hoping to motivate the fitter I explain that if he can achieve a satisfactory outcome with my cone kit he’ll be inundated with wire wheel business. I could see by his expression that what I should have said of course was – If he can achieve a satisfactory outcome I promise not to tell anyone.

 The cone kit needed a spacer on the spindle to stop the wheel hitting the machines flange before it bedded onto the 50 degree cone. 

50 degree cone ready to accept wire wheel

The wheel and outer cone went on and it was all tightened up in the usual way.  It all looked good and away we went.  Alas, the by now familiar routine followed, once I had persuaded the guy to take the wheel off and put it on again.  A typical variation from the initial 0-0 would be say 15-30.  All four wheels produced similar results. Weights were moved around, different types tried, the machine switched off and on, re-calibrated and all manner of buttons pushed but to no avail. 

And outer 20 degree cone fitted which replicates the spinner

Eventually the gaffer appeared to see what was going on and proclaimed "it’s bound to be different if you put it on in a differently!” (experience will out!) After 2 hours of head scratching and a good deal of cussing we all agreed the exercise was a failure.  No charge, sorry about ******** up ye powder coating, now **** *** and don’t come back. Great thing about North East England – no ambiguity.

Discussing the problem with an acquaintance, he suggests I try a mate of his who owns a tyre fitting business and is possibly a little more analytical than the average employee.  He has a very new but non pneumatic locking type machine and I feel a little more confident that I might get to the bottom of this. 

I initially take in two wheels, first thing in the morning when hopefully the day’s pressures are minimal.  The cone kit requires a spacer as before and the previously semi balanced wheel now shows 45-60.  Very quickly this is adjusted with weights to 5-0, by now a more than acceptable result.  Then the acid test – off and back on - 30-20  I ask the operator to check the machine with a normal wheel and surprisingly he agrees.  Its a 14” alloy with brand new low profile tyre.  0-0 with around 70 grams added.  Then the acid test – off and back on – now 15-20.  The guy looked genuinely perturbed. 
  

So what’s actually going on here?  As far as I can ascertain the machines all work in a similar way.  I've come across all manner of complex explanations but in essence they all seem to boil down to this.  The spindle that the wheel is fixed to extends into the business part the machine.  The shaft is rotating in bearings set into ‘soft’ housings allowing some movement.  Transducers on the bearing housings measure shaft movement and another on the end of the shaft measures lateral movement.  I would guess that some form of rotating disc on the shaft, indexes / informs the programme where the movement caused by imbalance is occurring and the programme then calculates the most likely location of a given additional weight to correct the imbalance.  This is all purely conjecture as I've yet to find a satisfactory and simple explanation of the process.
 

I would guess that when a wheel is perfectly in balance all transducers register zero (0-0 on the machine) – Why wouldn’t they?  This is interesting (if correct) because it means that the wheel must be in balance at that point in time.  It can then only be down to the precise re-fitting of the wheel on the machine in order to re-create the same result.  Even with the special £180 mounting cones the consistency of attachment may not be sufficient to produce an absolutely consistent result, but I suspect it's a lot better than it might otherwise be.  The only other explanation is that all the machines I’ve tried over the years are randomly inaccurate.  Possible but unlikely.   
Another interesting thing is that all machines appear to have self calibration programmes, I suppose negating the requirement for an independent check.  Try googling 'wheel balance calibration services' – clearly not a popular business.  One of the depots even volunteered the information that their two machines always give different results!

The company that supplied and balanced my 140 tyres (also Michelin Pilotes) on a static balancer assured me they would be fine but they absolutely weren’t.  Again I tried two other companies with dynamic balancers, the second spending some time and getting them almost spot on but there was still some slight vibration around 75MPH.  I borrowed a static balancer which had been modified to specifically accept the larger hubs on 15 and 16” wire wheels.  It’s a very simple piece of kit and will certainly get you in the ball park but how good can it be when it relies on your perception of when the bubble is in the middle of the circle.  I put one of my newly balanced (dynamically)120 wheels on it and it did look spot on with the bubble almost dead central.   

 

Fresh from the Dynamic balancing machine - looks spot on

Then I added 3 nuts each weighing 17 grams – 51 grams in total to the rim – I barely saw it move and had a couple of mates verify the result just in case it was the previous night’s gin and tonic making me a bit cockeyed and upsetting the outcome. 

And with 50 grams added (3 x 7/16 nuts to the right)

 The single most frustrating thing in all of this is that I have never been able to establish how far out of balance a wheel needs to be in order to create some vibration.  Problem is, I would think there are a good number of other things involved that might exacerbate even very small vibrations caused by an out of balance wheel.  Worn suspension bushes, resonant frequency of suspension, wheel run out, tyre flat spots etc. etc., but I would have thought someone would have a rough idea.  My guess, is around 30 grams. (1 ounce).  Doesn't sound much but with a 30 gram weight whizzing around on a big XK wheel revolving at 750RPM (around 70MPH) I would guess that centrifugal force will multiply that many times.

The point is, the machines are designed to balance a wheel to within one gram.  Given that the most likely cause of vibration is wheel imbalance; naturally this should be the first thing to be ruled out for certain.  If you’re trying to locate a vibration but it persists even after you've seen 0-0 on the machine and been relieved of some hard earned, it seems you still can’t be absolutely certain that it’s not a wheel balance issue that’s causing the problem. 

So – next time you get your wheels ‘balanced’ stand well back then ask the operator to take the wheel off and put it back on to verify the 0-0 result – best of luck.  And I bet the parting words are “give it a run and see how it feels”.   

To be fair I haven't given my 120 a run since the wheel balancing saga so I might well be crying before I'm hit.  This weekend it's the big classic show at Newby Hall near Ripon which requires a drive up the A19.  A section of this road was re-surfaced a few years back and it must be one of the smoothest ten miles of dual carriageway in the country so ideal for a test run.  I'll let you know the outcome.

If anyone out there can throw any more light on this conundrum, add anything or just generally confirm my findings or otherwise perhaps you could email me at :
bob@sisnorthern.co.uk  

Next post beginning of August

POST 58 - JULY 2013 - A POST IN TWO PARTS

This post will be in two parts, this being the first. The second part will be completed on my return from Poole, Dorset to finally get to meet the cars first owner.  All being well this will happen on Thursday 4th July and I'll write up the visit over the coming weekend if not sooner.

My original plan was to make the 700 mile round trip the cars first major outing but a few well chosen comments from trusted associates made me think again.  The one that brought it home the most was to do with the point where bravery becomes foolishness.  I can't afford to miss this opportunity of meeting up with first owner Vernon Maitland OBE and with just 200 or so virtual miles on the clock (actually the speedo doesn't yet work because the cable end wont fit into its drive) the likelihood of having a trouble free drive down to Poole is probably less than 50%.  It still feels to me like a cop out but I must say that since taking the decision to trailer it most of the way my stress levels have reduced significantly.

As to the future of this blog now that the project is virtually complete, well, I still have a good deal of stuff to finish off, in particular the electric water pump project and some further work on the indicators and other electrical odds and ends.  The only difference is that the pace will be a little more relaxed but I still expect to be putting up a fortnightly post probably until autumn.

TRIP TO POOLE, DORSET
With an intended ETA in Poole of noon it meant an early 5.00am start for the 340 mile trip from North Yorkshire to the south coast.   I had driven the car over to friend Geoff's home the previous day, a distance of around 20 miles and even on this short trip a few gremlins appeared.  The drivers side rear corner seemed to have dropped an inch or so.  The gear lever had developed a sort of rubbery feel and in spite of great efforts to balance the wheels a distinct vibration could be felt at anything over 55MPH.  In some ways this was good as it validated the idea that driving around 700 miles without a few advanced shakedown trips would have been foolish.
Knowing that we could unload the car next to Vernon Maitlands home in Poole I was not too concerned about these minor problems so drove the car straight in to Geoff's very posh car transporter.  Worth mentioning that on the way over, my friend following in his BMW was showing 80MPH when I was showing 2500RPM  It will be interesting to see what the satnav says when I get around to checking.  My calculations indicated 71MPH at 2500 so either the Beemers speedo is wrong or my calcs are.  I'll let you know.  Also worth an article in its own right is the wheel balancing saga but as it is not yet fully played out, I'll save it for a future post.

By 11.00am we were about 18 miles from our destination with the Land Rover Discovery passing a string of HGV's on a fairly steep motorway gradient.  With cruise control engaged and the whole caboodle weighing I would guess around  four tons it proceeded to rapidly change down through the auto box in order to maintain its cruise controlled speed.  The rev counter whizzed round with each down change, then a warning light flashed and it went into limp mode.  We made a few attempts to un-crash whichever processor we had so badly upset but it would have none of it so we limped the final few miles to Vernons where the Land Rover Service man would meet us and hopefully sort it out.

Well met by Vernon's wife Monika and newly wed daughter Amber and Husband, Vernon quite a tall chap and very sprightly for I would guess 87 years had no problem climbing in and re-acquainting himself with his car (oddly I do still think of it as his car)

Vernon quickly at home

It was extraordinary to hear Vernon recall so many details about the car, how he came to buy it, with a good friend Alec Anderson buying one a little earlier, and registering it as KRU500, but it had to stay in Henley's showroom for quite some time because it was the very first one delivered to that branch.  Exactly what strings were pulled to extract a pair of early RHD 120's from Browns Lane I never did establish.  Vernon and friend Alec spent some fun time driving round Silverstone and from my initial searches on the cars history I just happen to have a fabulous photo of KRU500.  Its actually got a note on the back saying  'Happy Christmas - Silverstone 1950 - 100MPH - What Ho'  Does this car still exist - it's not on any XK data forum as far as I know. KRU600 was sold a year or so later generating a significant windfall profit, apparently due to a massive increase in vehicle purchase tax.

KRU500 - Alec Anderson - Silverstone 1950

KRU600 - Vernon Maitland - Exeter Trial New Years Day 1951

And zoom in - note hand position on steering wheel

4th July 2013  -  An amazing sixty plus years separate these two photos

Vernon with wife Monika

And finally a rare picture of a normally camera shy me with Vernon

Vernon and Monica live in Florida and only spend a few weeks each summer in the UK.  They will be leaving early next week and as Vernon says, as an octogenarian it becomes increasing difficult to look ahead, hence the need to ensure my commitment to meet up was discharged.

Fantastic view from Vernon,s balcony overlooking Poole harbour

Geoff signs off the warranty repair which mainly involved telling it that it only thought it was broken

The Jaguar / Land Rover service guy eventually arrives and plugs in his lap top.  Apparently the problem lay in some previous hiccough coupled with today's mishap.  He clears the fault, downloads a software upgrade and we're good to go.  I try to get him to pose with his laptop appearing to be plugged into the XK, it is after all a Jaguar, but he declines.   The irony of using a new Jaguar Land Rover product to get us there, as a pose to a rather older one, in order to mitigate the need to call for assistance is not lost on this very courteous and professional representative of the brand.

On the way back to my workshop, son Dan followed me in his Aston Martin Cygnet which he tells me he's pimped up and converted to a ''duckling' by fitting a Toyota iQ grill and binned the leather seats in favour of cooler cloth.  Trouble is, they won't let him join the AM owners club now.   In 5th gear I raise my hand at 2000 and 2500RPM and he tells me I was doing just short of 65 and then exactly 80 so I need to look again at my gearing calculations spreadsheet. This super high 5th gear felt perfect for dual carriageway cruising and had no problem whatsoever coping with any of the typical main road gradients encountered.

Next post mid July