Monday 4 November 2019

Memories of a ROF Apprentice


                            - MORE FROM JOHN DAY

Six months were spent in the Mechanical Engineering Department drawing office. Then I went out on my own doing installation drawings of machine tools. One installation was a large vertical slotting machine to go in the Light Gun shop, where there were already three such machines.  It seemed a good idea that the new machine should be in line with the existing three - so I did the drawing accordingly. Several weeks later I was surprised to see the new slotter was two or three feet in-front  of the older ones - not where I had wanted it  put.  The ganger told me that when they had put it where I suggested the counterweight at the back had clumped a piece of shafting so they had moved it forward. He said that he had seen my name on the drawing and, as my father was the manager of the department and the gang had had double time for moving it, it seemed silly to mention it.

 An interesting bit of plant layout that came my way was the installation of an autofrettage plant. This is a process which increases the strength of a gun barrel by subjecting it, internally, to a  hydraulic pressure which exceeds the elastic limit of the metal. It consisted two bed plates, one with the pressure generator and the other just a support and stopper for the other end. As there were two lengths of barrel to be processed, I did a drawing showing two sets of studs cemented into the floor so that the other bed plate could be picked up by the crane and set down over the appropriate studs. The chief draughtsman looked at my drawing and said “ Fine, sooner or later somebody will trip over the spare studs, put in a suggestion, get £5 and they will be sawn off”.

I was also involved in a session in the North Mill un-mothballing the gun lathes. This was a mucky job since they were coated in a thick oily varnish that had to scraped off - not one of  the modern soluble coatings and it had had twenty years to harden out. At least we were beginning to get ready for WW II in 1938!

The Tinman’s Shop made a change. I was  setting presses for stamping out ammunition containers.  The top and bottom tools had to be very accurately set, both for position and material thickness, as when the presses ran there was quite a large force involved. The presses worked with a one revolution clutch with a latch coupling  the big flywheel to the crankshaft - and controlled with a pedal.  When this was depressed the clutch engaged but  releasing this  pedal, even momentarily, meant that the flywheel did at least two revolutions for one of the crank. Unfortunately some operatives thought they were faster feeders than they actually were. This resulted in a jam - up as the second piece of metal arrived before the first had cleared. Clearing this came to me , and there was a way to rectify the tools by gently peening (hammering) the edges and then using an oil stone to restore the proper clearance.

The Tinman’s Shop was also responsible for making tin ammunition boxes such as were used to keep detonators and fuses dry in humid atmospheres. These were often nearly two feet long and it was an education to watch a seam,  the length of the tin, neatly made with one stroke of a soldering iron. The irons used were heavy copper with a blunt end; thin irons like the ones tending to be used for D.I.Y  were known as “winkle pickers “.  During my stay I made that “Brooklands” silencer from sheet steel and had it dipped in tin on the night shift for a packet of cigarettes. The neighbours of Locke King, who built the Brooklands  motor racing circuit on his land, complained about the noise, so the circuit officials designed a special silencer that was obligatory for use at the track. Needless to say a Brooklands silencer was the thing to be seen

This article apperd in the September 2000 GIHS Newsletter

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