Long bed lathes affected by the tide

[John MCParticipant @johnmc39344]

Posted by mick H on 30/11/2019 06:30:35:

I was wondering why my lathe work was such rubbish…..but now I know……I live near the sea.

Mick

i don't live near the sea but its still going in my repertoire of excuses!

[BufferParticipant @buffer]

If he wasn't told that he would probably have been sent to stores for a long wait, striped paint left handed screwdriver etc.

[IanTParticipant @iant]

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…

Regards,

IanT

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Hacksaw on 29/11/2019 14:14:53:

Seeing the seismic thread reminded me …I was talking to a friend of mine , he had a decent apprenticeship with Vospers in the 70's . Their long bed lathes , really big stuff here , he said, only turned (say a propshaft for example ) accurately either when the tide was in or out ? And certain jobs would have to be fitted in around the tide .. Is that true ?

.

This page is about Vickers, but shows several long bed lathes that are probably comparable: **LINK**

https://www.gracesguide.co.uk/Vickers

In view of the proportions … I doubt if those beds could be considered stiff

MichaelG

[Mick B1Participant @mickb1]

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 yetParticipant @notdoneityet]

Posted by Mick B1 on 30/11/2019 11:30:02:

Like when long-range target rifle shooters start talking about Coriolis Effect and bullet-drift – my BS detector begins to show a persistent reading…

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 MeekParticipant @grahammeek88282]

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.

Regards

Gray,

[Mick B1Participant @mickb1]

Posted by not done it yet on 30/11/2019 12:14:46:

Posted by Mick B1 on 30/11/2019 11:30:02:

Like when long-range target rifle shooters start talking about Coriolis Effect and bullet-drift – my BS detector begins to show a persistent reading…

 

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.

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 1Participant @bobbrown1]

Bill Pudney

BHC had an issue with wing jigs for the BN Islander when they were subcontracted to make them and were setting them up, as the tide came in the concrete they were on moved throwing the jigs out of alignment.

 

FYI The main hanger Saunders Roe/BHC is now Wight Shipyard that build cats like Red Jet 6 and 7, the other site south of the floating bridge is now GKN making wing tips amongst other things and the training school is now also part of GKN. 

 

 

Edited By Bob Brown 1 on 30/11/2019 14:53:27

[Neil WyattModerator @neilwyatt]

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…

Neil

[not done it yetParticipant @notdoneityet]

Posted by Mick B1 on 30/11/2019 11:30:02

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?

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 CauntParticipant @davidcaunt67674]

Bill

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?

Dave

[Mick B1Participant @mickb1]

Posted by not done it yet on 30/11/2019 15:54:58:

Posted by Mick B1 on 30/11/2019 11:30:02

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?

 

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.

 

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 DaviesParticipant @phildavies59511]

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 1Participant @johnpaton1]

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 1Participant @alistairrobertson1]

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!

[Graham MeekParticipant @grahammeek88282]

My first project when I joined a local CD manufacturing firm in the early 1980's, was to isolate the in house designed Laser Mastering Lathe from its surroundings.

Although not heavy, the machine was in an upstairs room of an old Mansion resting on a wooden floor. The mansion stood on one side of a valley. While on the other side about a mile away was a dual carriageway. This machine would not only be affected by someone walking across the room, but also the traffic trundling down the dual carriageway.

This latter effect was not found out until after the machine was suspended on springs and fitted with oil filled dash pots. The final solution to the road noise was solved by Dr H, the Brains behind the whole mastering set-up and was done electronically. Although his initial late night fix looked more like a spiders web with dead flies in, (diodes, capacitors and the such like). When the resident Electronic's engineer came in the next morning a proper circuit board was made. The machine continued to work faultlessly afterwards and further clones were made to meet the increasing orders placed with the company

My best regards

Gray,

[Dave Shield 1Participant @daveshield1]

Worked in a hanger years ago that was very close to sea level, some states of the tide made it very difficult to open the hanger doors.

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