|Clive Hartland||29/11/2019 22:24:23|
2493 forum posts
One of the helicopter companies had problems measuring the jig they made the helicopter body in. Using a Leica N3 level for measuring, it came back 3 or 4 times to me for calibration and was withing the fine tolerance we had. More complaints and the Tech rep. visited and found the shop on the bank above a tidal estuary and stayed long enough to prove that as the tide came in it heaved the concrete base and affected the jig and levelling. They would level before lunch and come back and find all levels and measuring points all over the place as the tide receded.
|Nigel McBurney 1||29/11/2019 22:25:06|
631 forum posts
Believe Vospers were located in Gosport,west side of Portsmouth harbour, On the north eastern side of Portsmouth,around the old airfield area, close to Farlington marshes the tide was also known to affect the stability of machine tools,I believe it was Marconis & De Havilands factories. I dont remember which type of machines were affected,as most high precision machines are built with only three mounting points ie grinders,jig borers etc so they should not been affected ,where I worked a few miles along the coast the large Cincinatti cnc mill sat on a 4 ft deep block of concrete, Searching the net a while ago in Vickers archives,there were photos of the foundation of a very large long bed lathe ,probably for prop shafts, the excavation was 20 ft deep and around 100 ft long and then filled with concrete.Its well known that heavy presses and other tools eg drop forging stamps were know to upset other machine tools,and in more recent times electrical supplies to cnc sheet metal punches have been affected when spot and arc welders were in use.
|Bill Pudney||30/11/2019 00:40:18|
|429 forum posts|
1/ Where I did my apprenticeship, at Saunders Roe (later became BHC) East Cowes IOW. The machine shop was about 25...30 feet away from the sea wall. The company designed and built a large mill to machine the wing spars for the Princess flying boat, the mill had a bed 60 odd feet long, but only about two feet wide. This machine was installed in the corner of the building nearest the sea wall. When I was in the Millwrights dept I had to do some work on some equipment adjacent to this mill. My curiosity was aroused by the tide tables on the wall near the machine. I asked my boss, George the full time machine shop maintenance man about the tide tables and he explained....due to the proximity of the sea the machine bed moved up and down dependant on the tide state, there was only one guy who knew how to make accurate parts. He depended on the tide tables, and as the cutter traversed the bed, the cutter height had to be adjusted to suit the tide state. He did this with chalk marks on the bed with arrows to indicate "up" or "down" and a number to indicate dimension change. The expert had retired before my time, but was called back when there was a need. The last job was Vickers Valiant wing spars, apparently there was a giant corporate sigh of relief when the Valiant was scrapped!!
2/ I also worked at Vosper Thornycroft at their Southampton yard. The yard was established in the 1870s, the centenary of the yard was celebrated whilst I was there. In the machine shop the was a huge lathe designed purely to machine propeller shafts for destroyers. The whole yard knew when this machine was being used as there was a very low frequency rumble which could be heard and felt all over the yard
The Saunders Roe/BHC and Vosper Thornycroft sites where I worked are now pretty much closed. They both seem to be car parks......
|mick H||30/11/2019 06:30:35|
|703 forum posts|
I was wondering why my lathe work was such rubbish.....but now I know......I live near the sea.
|John MC||30/11/2019 07:38:52|
227 forum posts
i don't live near the sea but its still going in my repertoire of excuses!
|122 forum posts|
If he wasn't told that he would probably have been sent to stores for a long wait, striped paint left handed screwdriver etc.
|1386 forum posts|
Maybe hanging a chart of the Lunar Phases by my lathe would help improve my work?
I seem to vary more than my lathe I'm afraid...
|Michael Gilligan||30/11/2019 10:39:52|
14624 forum posts
This page is about Vickers, but shows several long bed lathes that are probably comparable: **LINK**
In view of the proportions ... I doubt if those beds could be considered stiff
|Mick B1||30/11/2019 11:30:02|
|1284 forum posts|
Like when long-range target rifle shooters start talking about Coriolis Effect and bullet-drift - my BS detector begins to show a persistent reading...
|not done it yet||30/11/2019 12:14:46|
|3797 forum posts|
Perhaps not your long range air rifle, but just calculate the displacement of the target, for a sniper, at a range of over a kilometre - perhaps two.... Average bullet velocity over that sort of range is rather less than muzzle velocity. Same for drift - it will be known for that particular combination of weapon, projectile and range; it will be more than the coriolis effect. Against this, the target shooter will likely have zeroed in his ‘scope at some considerable distance already, which will take out any of these two effects at that range.
Agreed, windage is likely a larger correction and is more variable, but they all need to be taken into account. I would think snipers like really still days for long range hits in east-west directions.
|Graham Meek||30/11/2019 12:17:46|
|141 forum posts|
As an aside, and to illustrate the effects of soil substrates. My last employment was involved in the maintenance of Linear Accelerators. (Radiotherapy treatment machines), at a local Oncology centre. These machines are housed in reinforced concrete bunkers, the walls, floor and roof being an average thickness of 1 m. With 25 mm steel plates in-bedded in the walls at strategic places.
In the walls at right angles to the machine centre line and in the roof were lasers. These lasers had to meet at the ISO centre of the beam, which was also the pivot point for the rotating gantry. While routine morning checks are carried out on these lasers using a specially made in-house checking device there would always be a cry for help to the workshops during the run up to winter and late spring. This did not affect just one particular bunker, as all machines required re-calibrating.
The reason, the water table was not far under the foundations and the whole structures settled during the autumn, (the rainy season) and then moved again as the ground dried out during the spring and summer.
|Mick B1||30/11/2019 13:30:45|
|1284 forum posts|
No need to make assumptions. I can remember shooting at 1000 yards on Stickledown at Bisley in a 19-minute wind. We calculated that the bores were aligned roughly above the next target but one. Nobody was talking about Coriolis - its effect was maybe somewhere in the 0.1 MoA range?
Edited By Mick B1 on 30/11/2019 13:33:30
|Bob Brown 1||30/11/2019 14:48:41|
993 forum posts
Edited By Bob Brown 1 on 30/11/2019 14:53:27
|Neil Wyatt||30/11/2019 15:28:26|
16959 forum posts
I've read the detailed story about the tidal state affecting Vicker's machines somewhere in the past.
Machines are very sensitive to weight distribution, I can put them out of adjustment just by being in the same room...
|not done it yet||30/11/2019 15:54:58|
|3797 forum posts|
Better to write in proper mechanical units on an engineering forum? I would understand millimetres. Don’t understand a 19 minute wind - is that how long it took to get from one end of the range to the other?
Coriolis will depend on other factors than the range - average velocity of projectile and direction (as well as latitude, if not east-west direction of fire?) - as the rate of lateral displacement might be at anything from zero to ~1000mph. No point in quoting figures unless the pertinent conditions are all provided.
|David Caunt||30/11/2019 16:07:34|
4 forum posts
Your comments on the relief when the Valiant was scrapped.
I worked on the Valiant at Marham in the 60's and the "excuse for scrapping them" was that low level flying was cracking the main spares.
I wonder was that the chickens coming home to roost?
|Mick B1||30/11/2019 16:36:52|
|1284 forum posts|
Better to understand the terminology and units used, along with their likely relative magnitudes, in the subject area you choose to comment on, and avoid patronising quips.
I'm out of this thread now.
Edited By Mick B1 on 30/11/2019 16:38:55
|Phil Davies||05/12/2019 15:20:28|
|3 forum posts|
Anecdotal of course, but I know of at least one place where this has happened, though of course it is based on hearsay. I do know a place where I used to work as an apprentice, on one of the machines there was a large trumpf CNC punch press, and it used to play havoc when you were trying to clock in jobs, with the dial indicator bouncing all over the place. They did eventually move it into an adjoining building, and set it into a rubber lined foundation. (Which, they soon discovered, had an underground stream under it....)
|John Paton 1||05/12/2019 17:23:34|
|189 forum posts|
When I worked in Essex our surveyors were working on the Fre Station site in Tilbury and having difficulty 'closing' the survey to the local datum anything like the required accuracy.
After some investigation they found that the land was rising and falling appreciably with the tide. I am sorry that I cannot recall the actual amounts but I seem to recall that it was afactor closer to inches than thous.
|Alistair Robertson 1||05/12/2019 17:42:00|
|69 forum posts|
A factory where I worked had an internal rail siding (Long gone when I was there) it was only about 100 yards from the beach and built on basically sand.
During the war, parts were made for aviation engines and some machines could only be used when the loaded wagons were either in or out of the works as the whole building sunk with the weight. I never heard them mention the tide but in a heavy storm the dust used to come off the rafters so that could have been a factor as well!
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