The Mystery of the Rim Maxarets

The Axle Maxaret problem was one occasion where a swift answer was found to a hitherto unrecognised problem. On the other hand, there were repetitive problems that just never seemed to go away. One such was the constant stream of Rim Maxarets that landed on my desk from the RAF.  This bit of kit had been around for a long time, bolted onto the legs of RAF aircraft almost since time immemorial. Rather than being hidden neatly inside the axle the rotating lump of lead was driven by a small rubber-tyred wheel running on the aircraft wheel itself, opening and closing a hydraulic valve to control the deceleration.  These would arrive on my desk with a label from the RAF maintenance depot "Brakes failed. Pilot called for nets" or something on those lines. I would send these 'defective' items to the test house, and they invariably came back with a clean bill of health. After a few months of this, I discussed the recurring nature of the issue with one of the ex-Navy matelots in the office, learning that the Navy had never liked the idea of the indicator pin that protruded from the casing on the RAF versions, and the naval version was always supplied without it.
PING!
A light lit up in my head. The pin was OUT when the brakes were OFF. If it froze OUT, might the brakes stay OFF? Even in summer, a Lightning patrolling for an hour at forty or fifty thousand feet would arrive back at the airfield cold-soaked, freezing and possibly wet from cloud or rain. I picked up the Maxaret sitting on my desk and set off for the laboratory - where the cold-test kit lived - and which, in the months I had been at Dunlop, I had yet to visit. Down Swallow Lane and through the small door in that vast featureless wall - and found I had entered a different world: a world of a distant past.

Stunned, I stopped and stood taking in an astonishing sight (and feel).  The vast earth-floored space was filled with BIG machines driven by belts - BIG belts - from shafts high above, turning machines spinning wheel-rims of all sizes. The whole place was shaking with a low-frequency vibration, and had the feel of a previous century. This was one of the earliest surviving parts of the Dunlop empire, and, as far as I know, is still there, having had several new owners and a management buy-out. Surely it doesn't still have that archaic works?

The Laboratory was on the far side of that building, and after a good deal of discussion involving sighing on their part ("but we did this years ago") and insistence on mine, my 'failed' Rim Maxaret was set up in the test rig with an agreed program of wetting and freezing.  On my return the following day a small group of us gathered to see the result, and Bingo! The indicator pin froze OUT and the brakes failed. Whoops! Talk about egg on faces. The Assistant Chief Designer was summoned and shown the result. Unlike that earlier experience where I had been silently accused of showing everyone up, I was thanked for spotting the problem and we established a warm working relationship that was to produce more useful results later on. Another case of fresh eyes seeing things in a new light.

 This wasn’t the end of the Rim Maxaret story. There was another twist still to come.

 

The case of the Axle Maxarets

 

In those days (I can't imagine it's like that now) all seventeen of us in Quality Control wore suits and occupied a personal desk in a large first-floor office, using our own private tools to dismantle and inspect the items placed in front of us.  One day I received a package containing two Axle Maxarets from a small German airline. The attached label was quite clear and simple: "Rough & grinding":  And so it proved, setting my teeth on edge as I turned the shaft, so out came the tool-kit to dismantle the first one.  The Axle Maxaret was a very simple device - about the length of a Christmas cracker, but twice the diameter, fitting neatly inside the axle of the aircraft undercarriage. Not much more than a cylindrical lump of lead driven by a sun and planet gear chain, it opened and closed a hydraulic valve controlling the brakes as the rotating weight either overtook the wheel, or got left behind.

 

Opened up, the cause of the "graunching and grinding" was immediately obvious. All three of the planet gears had their teeth milled off-centre, over-cut on one side, gradually disappearing to nothing diametrically opposite.  Out came the drawing to show a requirement for a VERY tight tolerance, requiring EVERY single gearwheel to be checked on a fixture on which was mounted a clock micrometer.  Clearly, none of the gears in these two units had been checked as required, so the next step was to visit the vast machine shop and find the appropriate inspection bench. Sure enough, there was a substantial mound of these small gears piled up in front of a cow-gowned inspector laboriously checking each gear over three pins using a micrometer in time-honoured fashion. When I commiserated with him over his labour of love and asked where the specified inspection fixture was, he told me that he had never seen it in the three years he'd been doing the job. The next step was to see the Machine Shop Superintendent - a very proper, large, and somewhat formidable character who always called me Mr Nurcombe on the basis that he might have to give me a proper rousting one day - in his glass office at the centre of the vast machine shop.  After revealing the samples grasped in my palm I trotted behind him across the machine-shop as he strode briskly between the machines. From now on I was merely a spectator. After a quick glance at the table with the pile of gears, he called out to the machinist who had been lurking unseen behind his machine, and who clearly knew what was coming. "John, bring me your mandrel." and, very sheepishly, a worn home-made mild-steel tool was handed over.

Now all was clear. The two operatives had done the best they could - by their own lights - to keep production going, and in that respect could only be commended. What they SHOULD have done, of course, was to stop the job until the correct equipment was supplied.

And where was that precision hardened steel mandrel and the inspection equipment?  It took me less than three hours to find them on a shelf in the wrong Tool Store where they had languished for some three years.

 

Office Politics 2

I have had the great privilege of working for two great British industrial companies when they were both at their peak: BSA (at Group Research in Mackadown Lane) in the early 1960s and Dunlop In the late 1960s. Within a decade of my leaving them,  both had collapsed completely. (Not that I'm suggesting it was anything to do with me, Guv'.)

BSA Motorcycles had been facing fierce competition from abroad, and put all its capital into developing a new three-cylinder series, but got the launch wrong in the early 1970s. I was working for Atlas  Aircraft in South Africa at the time, and I recall the shock of reading of their collapse.
Dunlop also got it wrong, having for decades made a set range of tyres from which vehicle manufacturers could choose. It found itself wrong-footed by more nimble competition stealing their business by giving their clients more choice.  Having left it too late to change, the bulk of the business was bought by the Japanese company Sumitomo while the Coventry aviation engineering gem was snatched by another UK engineering business whose name escapes me.

Now that all of the items on which I worked as a Defect Investigator in the then-new Quality Control Department are on display as ancient artefacts at the Baginton Aviation Museum in Coventry, I think I can tell the stories of my time there.

My understanding is that the Quality Department was established in 1966 after my boss Humphrey Squire had attended a meeting in the USA held to discuss the difficulties being experienced by the Moon-Lander Space program. The result was a new thrust to get a proper grip on manufacturing. It's not easy to understand just how much has changed, but it's clear now that it's nothing short of miraculous that wartime equipment worked as well as it did.

When I was first ushered into the vast Dunlop machine-shop in Swallow Lane, it was surprisingly quiet. At least a third of the machines were silent, with their operators sitting reading newspapers alongside enormous piles of components - all on "stop".
I was told that the scrap-rate  - a key measure of a manufacturer's success (or failure) - was in excess of 25%.
Three years later, thanks to Humphrey Squire's new Quality Department, that figure was reduced to less than 2.5%. Machine Capability measurement had been a key factor, tho' my part was played in identifying design and manufacturing faults and tracking down the causes.  A sort of fascinating Accident Investigation bureau but thankfully without the accidents.

More soon on anti-skid Maxarets, both Rim and Axle, and the shocking variation in test-rigs that revealed even more nasty but educational surprises.

Attention to detail...

There are lessons in life which are more than just a good story.  Sometimes the difference between life and death is purely fortuitous.  The lesson here, in this story of foolish youth, is that one careless error could have killed someone.  Attention to tiny detail is IMPORTANT....

Very early on as a motorcyclist - in my first year at work at West Midlands Gas Board - I had a narrow escape from injury or even death on a friend’s bike, and I nearly died of laughter afterwards.

One of my young colleagues had turned up for work on a rather clapped-out BSA Winged Wheel power-assisted bicycle. With nothing better to do at lunchtime, we decided to "hot" it up, as young men do. Off came the silencer, followed by a few more tweaks before I mounted the saddle to test the 'improvements'. The yard was "L" shaped, ending at a brick single-story office wall, so from the farthest corner I engaged full throttle and pedalled like mad round the bend until, with around 25mph on the clock, and at the very last moment, I slammed on the brakes. I recall being more than a little dismayed to see both bicycle-type brake-blocks shoot straight out of their holders and a few seconds later hit the wall at full speed. Fortunately, my horizontal motion was converted into a vertical climb, and I recall seeing the rainwater gutter pass me as I went up, then pass me again when I went back down, landing in a heap on the wreckage. My colleague was much more concerned about the interesting shape of the forks and front wheel than about my health, although my hysterical laughter at my lucky escape might have influenced him. As I pointed out later, I might have saved his life. The brake-block holders were fitted back-to-front, and he could have been killed out on the road. As he was more concerned about getting the wreckage home and how to explain the mishap to his Dad than about the detail, I don't think the logic was fully appreciated.

Office Politics 1

In the mid 1960s I was the youngest new arrival in the Defect Investigation Department of a large aircraft component manufacturer in the English Midlands, and was placed in the care of Brian, a pleasant quietly-spoken man, to be shown the ropes. "This'll keep you quiet for a while." he chortled, picking up a device about the size of a large pineapple made of aluminium. It was a Follow-Up Control Valve controlling the nose-wheel steering of the Fokker F27 Friendship whilst on the ground, via a wall-mounted steering wheel.  The controls of the F27 are, somewhat unusually, entirely pneumatic rather than hydraulic, and Brian explained that the type was plagued with steering problems while taxying, the pilots unable to steer a straight path, wandering down the taxiways as if they had been on a drunken binge. The problem was causing everyone a lot of grief, and it had been in the department for months. The device had been repeatedly taken apart and every item inspected under a microscope, but it was still a complete mystery causing the company considerable embarrassment.

While he was telling me this, clutching the item in his hands, I could see a roughly figure-of-eight-shaped spring spanning two stout pins on the side of the casing, one of them clutched tightly by the spring, and the other floating around between its two not-quite-parallel legs.  As a cyclist and motorcyclist well used to tinkering I took the description to be a classic case of back-lash somewhere in the steering, and immediately suspected this as a likely cause, but it was so obvious I thought I'd better say nothing until I'd had a closer look. If it WAS the problem, surely others must have seen it earlier.

As instructed I took the device down to my gliding friend Jim MacDonald's pneumatics test house and had it set up for a test run. Sure enough, it was way out of limits, and clearly the problem lay in the back-lash of this spring staring us all in the face. Now I, of course, was merely a spectator dressed in a clean suit and tie, so I asked the chap running the test equipment if he could find me a pair of stout pliers, and explained what I intended to do. He nearly exploded. "You can't do that! This is aircraft equipment."  After I'd promised to throw away the spring afterwards, he found some pliers, and I bent the spring enough to remove the backlash. (The fact the spring was soft enough to bend was telling us something!)   Lo and behold, success, and the subsequent test-run saw the valve pass with flying colours.

I had been gone barely an hour, and my arrival back in the office with an explanation of my discovery did not, to my surprise, earn me universal plaudits. Quite the opposite. In addition to annoying my 'minder', who thought he had got rid of me for a week or two, I had embarrassed just about everyone who had looked at it and failed to spot the simple answer. As a young man from academia, inexperienced in office politics, it hadn't occurred to me that Clever-Clogs are not generally popular.

The next step was to get the drawing out, where it became clear that there was no requirement for the legs of the spring to be parallel when fitted. The only sensible way to do this was to supply the manufacturer with a test fixture for use by their own inspector, enabling him to check their production whilst in progress.  Sad to say, Politics reared its ugly head and the Drawing Office refused to acknowledge the omission (loss of Face, again) and fought this change for close on twelve months before it was instigated and the amended drawing and test kit reached the right place - the inspector on the production line of the spring manufacturer. Office Politics had well and truly set me up as a target, and I had to take great care not to repeat the mistake. I have no doubt that I was twice set up and caught out in the three years that I was there as a direct result of the embarrassment felt by others over that F27 valve, but I did have at least another three satisfying successes before a combination of departmental change and National Politics led me to move on.