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Originally Posted by sapper  I am also rather amused at the statement that the pistons had been made but had become unusable while on the shelf. That’s good for a laugh. Seriously! How would alli pistons somehow change while waiting to be used? Admittedly all metals deteriate with time, Gold the “Noble metal” being for all intents and purposes free from that. But in this case we are talking about thousands of years!
As a lifetime Engineer. I am quite aware of all areas of production. The only way that "alli" will deteriate is if it oxidises! Through salt, or prolonged exposure to weather. Being the pistons (Come to that any engineered component) would be greased up for storage, (standard army practice) I completely fail to see how a high precision component machined to tight tolerances of about +-.001 could change by sitting on the shelf?
To me it sounds ridiculous, and the more that comes out, the dafter the story becomes it seems to me.
Sapper.
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I hope that the period documentation appears on this one so that we can find out if there really was a problem. In the meantime, I see that I lost track of the thread when it first appeared and have to say that I am a little uncomfortable with the suggestion that comments I had made in all seriousness were 'Good for a laugh' and making the story 'dafter'.
I realise that I made the cardinal error of not quoting sources. A case of laziness at the time. The story comes from an article on the WM20 BSA in the September 1986 issue of 'The Classic Motorcycle" by Bob Currie. After War Service as a Motorcyclist, Bob was the Midlands Reporter for 'Motor Cycle' and had probably better contacts with the industry than anyone else.
In an interview with former B.S.A. technical author Arthur Lupton, he states "...the truth was that the aircraft industry had a virtual monopoly on virgin aluminium. It was we who had to make-do with melted-down saucepans".
"...the oddest complaint of all came from Chillwell Ordnance Stores, at Nottingham, where they found that a number of brand-new M20 pistons that had been in stock a long time wouldn't fit the cylinders; we looked into it and discovered that though the pistons had been dead size when they left the works, they had been on the shelf so long that they had 'grown' and distorted - one outcome of the second-hand aluminium we were forced to use."
The article includes many references to actions necessary to remedy defects in production. I can also quote instances of Norton's Service department modifying machines already delivered to Chilwell. The point is that these quality controls generally worked but production delays would have been inevitable. I would suggest that the problem with the B.S.A. pistons would be due to impurities in the castings, perhaps zinc. Pistons are not of course pure aluminium and are not ground cylindrical so as to allow for differential expansion. Ironically, the problem is likely to have been greater for large factories with their own foundries rather than smaller plants who bought in from firms like Wellworthy or Hepworth & Grandage.
There has been a suggestion that if there were problems it was inevitably Bedfords. I don't know how far back down the supply lines these 1400 were needed but they could have been 4x2 Bedford OYs or Austin K3s rather than the 4x4s such as Bedford QLs, Fordson WOT6s (even more pistons !) or Austin K5s. Bedford incidentally supplied 52245 QLs from 1941 - 1945 according to Vanderveen.
Rich (who spends a lot of time scraping cosmolene from ex-WD components)