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#1
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Barometer Dismantling
Hi all
Back again with the old baro! So I decided to take a peak last night to see if the chain was crudded up or the bellows unit shot. But fell at the (almost) first hurdle. Unscrewed three screws around the glass perimeter expecting the whole gubbins to lift out but no, just the glass lifts away and the dial etc remains housed in the wood casing. Unscrewed the screws around the dial, but that is held captive by the needle. So, how do I remove the needle - it appears to be kind of riveted to the shaft end? Before and after investigations, when the glass is tapped the needle moves 3-5mm. The needle seems fairly free to rotate, so presumably the chain gubbins is likely to be OK, but the bellows not? I have not seen the needle move more than an inch or so in either direction (from the 12 o'clock position). I guess if I can get the needle off without damaging the internals, all will be revealed. Thanks Phil |
#2
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Barometer Dismantling
On 28/06/2013 08:43, thescullster wrote:
Hi all Back again with the old baro! So I decided to take a peak last night to see if the chain was crudded up or the bellows unit shot. But fell at the (almost) first hurdle. Unscrewed three screws around the glass perimeter expecting the whole gubbins to lift out but no, just the glass lifts away and the dial etc remains housed in the wood casing. Unscrewed the screws around the dial, but that is held captive by the needle. So, how do I remove the needle - it appears to be kind of riveted to the shaft end? Before and after investigations, when the glass is tapped the needle moves 3-5mm. The needle seems fairly free to rotate, so presumably the chain gubbins is likely to be OK, but the bellows not? I have not seen the needle move more than an inch or so in either direction (from the 12 o'clock position). I guess if I can get the needle off without damaging the internals, all will be revealed. Thanks Phil Clock hands are normally "push fit" on the spindle but can get very tight. Like you, I think I'd expect the whole assembly to come out. Is it held in from the back? |
#3
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Barometer Dismantling
"thescullster" wrote in message . uk... Hi all Back again with the old baro! So I decided to take a peak last night to see if the chain was crudded up or the bellows unit shot. But fell at the (almost) first hurdle. Unscrewed three screws around the glass perimeter expecting the whole gubbins to lift out but no, just the glass lifts away and the dial etc remains housed in the wood casing. Unscrewed the screws around the dial, but that is held captive by the needle. So, how do I remove the needle - it appears to be kind of riveted to the shaft end? Before and after investigations, when the glass is tapped the needle moves 3-5mm. The needle seems fairly free to rotate, so presumably the chain gubbins is likely to be OK, but the bellows not? I have not seen the needle move more than an inch or so in either direction (from the 12 o'clock position). I guess if I can get the needle off without damaging the internals, all will be revealed. Thanks Phil You may not have left it long enough. The pressure has barely moved here for several days. I have both my aneroid and my electronic barometers set for 'local' pressure. Yesterday, both were pretty steady at around 1012 mbars. This morning, they have both dropped around 5 points. That's about a quarter inch on the aneroid dial. If you look at a current synoptic chart such as http://www.metoffice.gov.uk/weather/..._pressure.html you will see that there are high(ish) pressure systems to the east and south and south of us. To the west is a large full blown high. They are all big systems and will not be easily dislodged over - I would guess - at least the next few days, but you might well see that system out to the west nudging in over the weekend, clearing the skies, and driving your barometer up a few points. Although weather systems are quite dynamic, and those that grace us with their presence are more active than a lot due to the fact that we are sandwiched between large ocean and land masses, you should not get fooled into thinking that your barometer will dance up and down on a daily basis. At the height of summer and winter, we can get pressure systems that are static for days - or even weeks - at a time. The time to watch your barometer is when there are storms about. As the leading edges of frontal systems come across, you can sometimes watch the pressure drop like a stone over hours, or sometimes even minutes. Try having a look next time you get a sudden wind (blowing along a front) before a sudden 'stop' (the calm before the storm) followed by the rain hanging on the back edge of the front, before the storm passes. If you plot the readings, you will see a short sharp drop in the pressure, before it levels out for a short time, followed by it climbing back to around the previous level. Do you have an airfield nearby, and any kind of radio that you can listen to its arrivals / departures controller on ? Every pilot is given an accurate barometer setting for either 'local' ("QFE" ) or regional ("QNH") pressure to set their altimeter to, depending on whether they are taking off / landing, or just 'passing through' that airfield's control zone. This is done to make sure that everyone in the control zone is flying 'on the same page' height-wise and that altimeters read zero on the ground, and also that they register the same height as everyone else when they leave the control zone and join others already on a different page. Their barometers are high quality and certified, so it is a good resource for checking and calibrating your own against. Personally, I would wait at least a week and refer regularly to synoptic charts for the UK before declaring your barometer 'faulty' and trying to tear it down just to 'have a look'. They are quite delicate, and you might finish up wrecking a perfectly good instrument ... :-( Arfa |
#4
Posted to uk.d-i-y
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Barometer Dismantling
On 28/06/2013 08:43, thescullster wrote:
Hi all Back again with the old baro! So I decided to take a peak last night to see if the chain was crudded up or the bellows unit shot. But fell at the (almost) first hurdle. Unscrewed three screws around the glass perimeter expecting the whole gubbins to lift out but no, just the glass lifts away and the dial etc remains housed in the wood casing. Unscrewed the screws around the dial, but that is held captive by the needle. So, how do I remove the needle - it appears to be kind of riveted to the shaft end? It is probably a push fit, like a clock hand. There are special tools for taking clock hands off: http://www.ebay.co.uk/itm/Clock-Hand...-/400501158247 A pair of end cutters can be used, with care, instead. Before and after investigations, when the glass is tapped the needle moves 3-5mm. The needle seems fairly free to rotate, so presumably the chain gubbins is likely to be OK, but the bellows not? I have not seen the needle move more than an inch or so in either direction (from the 12 o'clock position). Which could simply be an indication of a stable pressure system in the area. I guess if I can get the needle off without damaging the internals, all will be revealed. Except where that little part that fell off and rolled away went. :-) Colin Bignell |
#5
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Barometer Dismantling
On 28/06/13 09:46, Nightjar wrote:
On 28/06/2013 08:43, thescullster wrote: Hi all Back again with the old baro! So I decided to take a peak last night to see if the chain was crudded up or the bellows unit shot. But fell at the (almost) first hurdle. Unscrewed three screws around the glass perimeter expecting the whole gubbins to lift out but no, just the glass lifts away and the dial etc remains housed in the wood casing. Unscrewed the screws around the dial, but that is held captive by the needle. So, how do I remove the needle - it appears to be kind of riveted to the shaft end? It is probably a push fit, like a clock hand. There are special tools for taking clock hands off: http://www.ebay.co.uk/itm/Clock-Hand...-/400501158247 A pair of end cutters can be used, with care, instead. I went in from the back I think Before and after investigations, when the glass is tapped the needle moves 3-5mm. The needle seems fairly free to rotate, so presumably the chain gubbins is likely to be OK, but the bellows not? I have not seen the needle move more than an inch or so in either direction (from the 12 o'clock position). Which could simply be an indication of a stable pressure system in the area. I guess if I can get the needle off without damaging the internals, all will be revealed. Except where that little part that fell off and rolled away went. :-) yes. I am worried about taking the needle off.. Colin Bignell -- Ineptocracy (in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers. |
#6
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Barometer Dismantling
On 28/06/2013 09:50, The Natural Philosopher wrote:
.... yes. I am worried about taking the needle off.. Also, how would you know where to align it when putting it back, unless you had another barometer to work from? Colin Bignell |
#7
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Barometer Dismantling
On 28/06/2013 09:10, newshound wrote:
On 28/06/2013 08:43, thescullster wrote: Hi all Back again with the old baro! So I decided to take a peak last night to see if the chain was crudded up or the bellows unit shot. But fell at the (almost) first hurdle. Unscrewed three screws around the glass perimeter expecting the whole gubbins to lift out but no, just the glass lifts away and the dial etc remains housed in the wood casing. Unscrewed the screws around the dial, but that is held captive by the needle. So, how do I remove the needle - it appears to be kind of riveted to the shaft end? Before and after investigations, when the glass is tapped the needle moves 3-5mm. The needle seems fairly free to rotate, so presumably the chain gubbins is likely to be OK, but the bellows not? I have not seen the needle move more than an inch or so in either direction (from the 12 o'clock position). I guess if I can get the needle off without damaging the internals, all will be revealed. Thanks Phil Clock hands are normally "push fit" on the spindle but can get very tight. Like you, I think I'd expect the whole assembly to come out. Is it held in from the back? Hi newshound No there is no back access except for a small hole to an adjusting screw. The way the glass and dial are fixed the internals are clearly accessed from the front only. Phil |
#8
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Barometer Dismantling
On 28/06/2013 09:19, Arfa Daily wrote:
"thescullster" wrote in message . uk... Hi all Back again with the old baro! So I decided to take a peak last night to see if the chain was crudded up or the bellows unit shot. But fell at the (almost) first hurdle. Unscrewed three screws around the glass perimeter expecting the whole gubbins to lift out but no, just the glass lifts away and the dial etc remains housed in the wood casing. Unscrewed the screws around the dial, but that is held captive by the needle. So, how do I remove the needle - it appears to be kind of riveted to the shaft end? Before and after investigations, when the glass is tapped the needle moves 3-5mm. The needle seems fairly free to rotate, so presumably the chain gubbins is likely to be OK, but the bellows not? I have not seen the needle move more than an inch or so in either direction (from the 12 o'clock position). I guess if I can get the needle off without damaging the internals, all will be revealed. Thanks Phil You may not have left it long enough. The pressure has barely moved here for several days. I have both my aneroid and my electronic barometers set for 'local' pressure. Yesterday, both were pretty steady at around 1012 mbars. This morning, they have both dropped around 5 points. That's about a quarter inch on the aneroid dial. If you look at a current synoptic chart such as http://www.metoffice.gov.uk/weather/..._pressure.html you will see that there are high(ish) pressure systems to the east and south and south of us. To the west is a large full blown high. They are all big systems and will not be easily dislodged over - I would guess - at least the next few days, but you might well see that system out to the west nudging in over the weekend, clearing the skies, and driving your barometer up a few points. Although weather systems are quite dynamic, and those that grace us with their presence are more active than a lot due to the fact that we are sandwiched between large ocean and land masses, you should not get fooled into thinking that your barometer will dance up and down on a daily basis. At the height of summer and winter, we can get pressure systems that are static for days - or even weeks - at a time. The time to watch your barometer is when there are storms about. As the leading edges of frontal systems come across, you can sometimes watch the pressure drop like a stone over hours, or sometimes even minutes. Try having a look next time you get a sudden wind (blowing along a front) before a sudden 'stop' (the calm before the storm) followed by the rain hanging on the back edge of the front, before the storm passes. If you plot the readings, you will see a short sharp drop in the pressure, before it levels out for a short time, followed by it climbing back to around the previous level. Do you have an airfield nearby, and any kind of radio that you can listen to its arrivals / departures controller on ? Every pilot is given an accurate barometer setting for either 'local' ("QFE" ) or regional ("QNH") pressure to set their altimeter to, depending on whether they are taking off / landing, or just 'passing through' that airfield's control zone. This is done to make sure that everyone in the control zone is flying 'on the same page' height-wise and that altimeters read zero on the ground, and also that they register the same height as everyone else when they leave the control zone and join others already on a different page. Their barometers are high quality and certified, so it is a good resource for checking and calibrating your own against. Personally, I would wait at least a week and refer regularly to synoptic charts for the UK before declaring your barometer 'faulty' and trying to tear it down just to 'have a look'. They are quite delicate, and you might finish up wrecking a perfectly good instrument ... :-( Arfa Hi Arfa Thanks for comprehensive response. I appreciate what you are saying about the reading remaining static for a period. What I didn't make clear is that this baro has hung on my parents' hallway wall for years and I've never seen a significant shift on the needle - maybe an inch max! Phil |
#9
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Barometer Dismantling
"thescullster" wrote in message . uk... Hi all Back again with the old baro! Before and after investigations, when the glass is tapped the needle moves 3-5mm. The needle seems fairly free to rotate, so presumably the chain gubbins is likely to be OK, but the bellows not? I have not seen the needle move more than an inch or so in either direction (from the 12 o'clock position). Two quick ways to test the diaphragm (discovered by accident): 1. Put barometer in car with windows, vents and all doors except one closed. Slam remaining car door. Needle should jump 1/2" or so. 2. Find local big hill and drive up and down, checking change in barometer reading. Can't remember what the rate of change is for inches of mercury in this metric era, but it should be noticeable in 200 feet change of elevation. NB. Doesn't work in E. Anglia as there aren't any hills. rusty |
#10
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Barometer Dismantling
On 28/06/2013 10:52, John wrote:
2. Find local big hill and drive up and down, checking change in barometer reading. Can't remember what the rate of change is for inches of mercury in this metric era, but it should be noticeable in 200 feet change of elevation. rusty At sea level is is approximately 3mb/100 ft which if my calcs are correct its 0.1inHg per 100ft. -- Chris |
#11
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Barometer Dismantling
On 28/06/13 10:13, Nightjar wrote:
On 28/06/2013 09:50, The Natural Philosopher wrote: ... yes. I am worried about taking the needle off.. Also, how would you know where to align it when putting it back, unless you had another barometer to work from? Colin Bignell That's easy. go to nearest RAF weather station. 1018.85 mb at Lakenheath right now Cambridge showing 1020 give or take. This is fairly useful also http://www.eldoradocountyweather.com...-pressure.html -- Ineptocracy (in-ep-toc-ra-cy) €“ a system of government where the least capable to lead are elected by the least capable of producing, and where the members of society least likely to sustain themselves or succeed, are rewarded with goods and services paid for by the confiscated wealth of a diminishing number of producers. |
#12
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Barometer Dismantling
If it has actually moved then surely the bellows must be working. Tapping is
often needed on these things to make them move as I'm sure you are aware. The original touch sensitive devices! You need another one to see if the readings agree, as pressure has been not hugely different in the last few days or so. You can hear the pressures on forecasts or on the web. I have an air band radio so being near an airport I can tune in to the volme, and there you can get your elevation to set the offset of courset. Brian -- From the Sofa of Brian Gaff Reply address is active "thescullster" wrote in message . uk... On 28/06/2013 09:10, newshound wrote: On 28/06/2013 08:43, thescullster wrote: Hi all Back again with the old baro! So I decided to take a peak last night to see if the chain was crudded up or the bellows unit shot. But fell at the (almost) first hurdle. Unscrewed three screws around the glass perimeter expecting the whole gubbins to lift out but no, just the glass lifts away and the dial etc remains housed in the wood casing. Unscrewed the screws around the dial, but that is held captive by the needle. So, how do I remove the needle - it appears to be kind of riveted to the shaft end? Before and after investigations, when the glass is tapped the needle moves 3-5mm. The needle seems fairly free to rotate, so presumably the chain gubbins is likely to be OK, but the bellows not? I have not seen the needle move more than an inch or so in either direction (from the 12 o'clock position). I guess if I can get the needle off without damaging the internals, all will be revealed. Thanks Phil Clock hands are normally "push fit" on the spindle but can get very tight. Like you, I think I'd expect the whole assembly to come out. Is it held in from the back? Hi newshound No there is no back access except for a small hole to an adjusting screw. The way the glass and dial are fixed the internals are clearly accessed from the front only. Phil |
#13
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Barometer Dismantling
You can get your ears to pop even going up and down the southa nd north
downs so it has to be fairly substantial. Brian -- From the Sofa of Brian Gaff Reply address is active "news" wrote in message ... On 28/06/2013 10:52, John wrote: 2. Find local big hill and drive up and down, checking change in barometer reading. Can't remember what the rate of change is for inches of mercury in this metric era, but it should be noticeable in 200 feet change of elevation. rusty At sea level is is approximately 3mb/100 ft which if my calcs are correct its 0.1inHg per 100ft. -- Chris |
#14
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Barometer Dismantling
news wrote:
At sea level is is approximately 3mb/100 ft which if my calcs are correct its 0.1inHg per 100ft. Err 100ft isn't sea level, HTH. -- €˘DarWin| _/ _/ |
#15
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Barometer Dismantling
On Fri, 28 Jun 2013 12:04:14 +0100, Brian Gaff wrote:
You can get your ears to pop even going up and down the southa nd north downs so it has to be fairly substantial. I think that depends on how often you go up and down hills. My ears don't pop when going from near sea level up to 2,000' down to 1,000 and then back up to 1,400' at home. My AWS barometer has 57 mb of correction, or 4 mb per 100' close enough to the previosly quoted 3 mb per 100' as it's non linear. 3 mb is 0.088" Hg, 4 mb 0.118" Hg. -- Cheers Dave. |
#16
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Barometer Dismantling
On Fri, 28 Jun 2013 10:13:31 +0100, Nightjar wrote:
Also, how would you know where to align it when putting it back, unless you had another barometer to work from? Not overly important provided you get it fairly close. The altitude adjustment ought to cope with a good 100 mb (3" Hg). -- Cheers Dave. |
#17
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Barometer Dismantling
On 28/06/2013 14:29, Dave Liquorice wrote:
On Fri, 28 Jun 2013 12:04:14 +0100, Brian Gaff wrote: You can get your ears to pop even going up and down the southa nd north downs so it has to be fairly substantial. I think that depends on how often you go up and down hills. My ears don't pop when going from near sea level up to 2,000' down to 1,000 and then back up to 1,400' at home. My AWS barometer has 57 mb of correction, or 4 mb per 100' close enough to the previosly quoted 3 mb per 100' as it's non linear. 3 mb is 0.088" Hg, 4 mb 0.118" Hg. I think it depends on health. A few years ago I was finding somewhere around 200 feet could be uncomfortable - now back as I always was, several hundred feet and I don't notice at all most of the time. Amazing what the right medicine does. -- Rod |
#18
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Barometer Dismantling
"news" wrote in message ... On 28/06/2013 10:52, John wrote: 2. Find local big hill and drive up and down, checking change in barometer reading. Can't remember what the rate of change is for inches of mercury in this metric era, but it should be noticeable in 200 feet change of elevation. rusty At sea level is is approximately 3mb/100 ft which if my calcs are correct its 0.1inHg per 100ft. -- Chris That's about right. My local airfield is about 300 ft ASL, and they call 9 or 10 points of difference between the QNH and the QFE Arfa |
#19
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Barometer Dismantling
"polygonum" wrote in message ... On 28/06/2013 14:29, Dave Liquorice wrote: On Fri, 28 Jun 2013 12:04:14 +0100, Brian Gaff wrote: You can get your ears to pop even going up and down the southa nd north downs so it has to be fairly substantial. I think that depends on how often you go up and down hills. My ears don't pop when going from near sea level up to 2,000' down to 1,000 and then back up to 1,400' at home. My AWS barometer has 57 mb of correction, or 4 mb per 100' close enough to the previosly quoted 3 mb per 100' as it's non linear. 3 mb is 0.088" Hg, 4 mb 0.118" Hg. I think it depends on health. A few years ago I was finding somewhere around 200 feet could be uncomfortable - now back as I always was, several hundred feet and I don't notice at all most of the time. Amazing what the right medicine does. -- Rod I think it depends on speed as well. In theory, your ears shouldn't pop at all if your eustachion tubes are clear, but maybe as you get older, they clog up, and the pressure equalisation doesn't take place as quickly. I have been in lifts that go up a long way, and had no problems, but in America, some of the lifts are very fast, and I tend to get ear popping on them. Arfa |
#20
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Barometer Dismantling
On 28/06/2013 18:06, Arfa Daily wrote:
I think it depends on speed as well. In theory, your ears shouldn't pop at all if your eustachion tubes are clear, but maybe as you get older, they clog up, and the pressure equalisation doesn't take place as quickly. I have been in lifts that go up a long way, and had no problems, but in America, some of the lifts are very fast, and I tend to get ear popping on them. Arfa You are, IMHO, quite right about speed. Makes all the difference. Suspect that if it is slow enough the ordinary way we swallow from time to time is enough. It was quite possibly the very first symptom of my deterioration about 6 or so years ago. And very glad I am not to have it any more. Living in a hilly location, I'd find even very local trips could be unpleasant at times. -- Rod |
#21
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Barometer Dismantling
polygonum wrote:
You are, IMHO, quite right about speed. Makes all the difference. Suspect that if it is slow enough the ordinary way we swallow from time to time is enough. Reminds me of the time I had a flight in a Short 330, which had the feel of being little more than a Leyland National with wings. Boiled sweets were handed round before take-off and landing, intended to promote swallowing and hence ease the discomfort on our ears. Being unpressurised they couldn't gain much height to get above the weather. The interior trim panels were covered with sticky-backed plastic, and, as the plane gained height, little bubbles appeared as it lifted off the backing. On descent, it all shrank back again. It amused me that the flight deck was so small that each pilot had his own sliding door, through which his in-flight cuppa was duly passed. Chris -- Chris J Dixon Nottingham UK Plant amazing Acers. |
#22
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Barometer Dismantling
On Friday, June 28, 2013 at 3:43:31 AM UTC-4, thescullster wrote:
Hi all Back again with the old baro! So I decided to take a peak last night to see if the chain was crudded up or the bellows unit shot. But fell at the (almost) first hurdle. Unscrewed three screws around the glass perimeter expecting the whole gubbins to lift out but no, just the glass lifts away and the dial etc remains housed in the wood casing. Unscrewed the screws around the dial, but that is held captive by the needle. So, how do I remove the needle - it appears to be kind of riveted to the shaft end? Before and after investigations, when the glass is tapped the needle moves 3-5mm. The needle seems fairly free to rotate, so presumably the chain gubbins is likely to be OK, but the bellows not? I have not seen the needle move more than an inch or so in either direction (from the 12 o'clock position). I guess if I can get the needle off without damaging the internals, all will be revealed. Thanks Phil |
#24
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Barometer Dismantling
Jet Stream ?, piggybacked on Storm Dennis ?
On 19/02/2020 07:57, Brian Gaff (Sofa 2) wrote: 2013? where did that come from? Brian |
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