Aneroid barometer spring setting

Discussion in 'General Clock Discussions' started by zygo, Oct 12, 2017.

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  1. zygo

    zygo Registered User

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    Many (most?) horologists also repair BAROMETERS but as there is no obvious place to raise a question about barometers on this forum, I'll start here and if a Moderator wants to move it somewhere more appropriate, that would be great.
    My question is about setting up ANEROID barometers, and I don't just mean the calibration screw in the back. The power of the leaf spring can be adjusted by raising or lowering the two screws in the cast frame that the spring is attached to. If the screws are too far in, the spring is too strong for air pressure to compress the sealed capsule; too far out and the spring is too weak. So, short of trial and error (which could take months where air pressure does not change much), how should I set it up in the way that the factory might have done in the final stage of assembly?
    Does anyone know of a website or YouTube url that might help?
     
  2. bruce linde

    bruce linde Technical Admin
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  3. zygo

    zygo Registered User

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    Tried that first. Also tried the books by Bert Bolle, Edwin Banfield, Knowles Middleton and Phil Collins; searched YouTube, Wikipedia and the sites run by the few remaining aneroid barometer makers but and still no luck. Being the optimist, I just though that someone here might know. If that's you, Bruce, please share with the rest of us.
     
  4. bruce linde

    bruce linde Technical Admin
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    to paraphrase bob dylan, no no no it ain't me, babe. :)

    i responded with the google link because your question was so general... sounds like you're done a bunch of research but are also looking for more general tips and tricks... is that correct?

    i would challenge your assertion that 'many/most' horologists repair barometers... if that were true, there would be many more discussions of same on the message board.

    that said, try googling for:

    barometer site:mb.nawcc.org

    which will use google to search this site.

    good luck.
     
  5. zygo

    zygo Registered User

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    I didn't want to take up your challenge publicly, Bruce, but I can't see a way to PM you. I'm guessing that you probably didn't check first because there are 185 threads on this forum about barometers (none dealing with this specific point that I can find) and the very first one begins "Most clock repair persons also work on barometers" so perhaps there are more members here who repair barometers than you think. It might transpire that no one here knows, but I'd like to give them a chance.

    I'm sure you read the question before posting so I'm surprised you see it as some kind of general tip or trick; I'm seeking a better understanding of setting up a specific and vital component of an aneroid barometer that hitherto has not been raised publicly before, either on this forum or elsewhere from what I can tell. It will take someone with experience of aneroid barometer repairing to address it, although your contribution are welcome, too, all the more if they are constructive.
     
  6. JTD

    JTD Registered User
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    Hi Zygo,

    I can't answer your question myself, but I think I know someone who probably can. I see you are in UK. Try contacting Philip Collins of Barometer World. This company is in Okehampton (Devon) and the web address is www.barometerworld.co.uk which will give you a link to their contact email. Or you could phone on 01805 603443.

    Philip Collins has done a number of demonstrations on aneroid barometer repair on YouTube, though I don't know if he has covered your specific question.

    Hope this helps.

    JTD
     
  7. Bruce Barnes

    Bruce Barnes Registered User
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    #7 Bruce Barnes, Oct 13, 2017
    Last edited: Oct 13, 2017
    2222.jpg Hi, there are others that collect, repair and restore barometers and antique thermometers that are members. This is 14.5 inches in diameter and is a one of a kind.
    Are you referring to the hair spring adjustment or the diaphragm maybe a photo might help.
    Regards,
    Bruce 161616.jpg
     
  8. zygo

    zygo Registered User

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    Aha. I knew I wasn't alone! Thanks guys.
    I've spoken to Phil in the past and seen a lot of his videos but I don't think he's covered this. And there's nothing in his book.
    Here's a photo of one similar. The heavy leaf spring fixed to the casting counteracts against air pressure on the capsule and can be raised or lowered by the two bright metal bolts, one each side. Adjusting these adds to or releases the tension of the spring because the tips of the bolts just sit on the base, and when adjusted thus raise or lower the casting and spring. (The small adjusting screw in the back of the base (accessible from the back of the case) allows the opposite side to be raised or lowered, which of course affects the position of the pointer for calibrating). I just want to establish how to go about setting the position of the two adjusting bolts - ie the spring tension. It needs to be strong enough to cause the capsule to expand when air pressure falls, but not so strong that air pressure on the capsule cannot overcome. The one I've been working on for weeks rarely shows any significant movement from around 30 inches and yet when tested in a plastic bag shows movement under local pressure.

    aneroid.jpg
     
  9. Bruce Barnes

    Bruce Barnes Registered User
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    Hi, usually those are factory set and unless doing a "detail strip" normally do not need adjustment. You checked the integrity of the diaphragm and that is valid
    I live in southern California and sometimes the needle doesn't move for days.As I have moved I verify altitude and reset the needle based upon current location.
     
  10. bruce linde

    bruce linde Technical Admin
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    i'm certainly no expert, but i've been all over this forum (and additional reading material about clocks) for three and a half years and seen only a few threads about barometers... which is why i was surprised by your claim that most, etc. etc. sure, 185 threads... out of 135,000. (and, did you know/use the google trick to find those 185?)

    people ask questions all the time without providing photos. no photos tends to push questions toward general, rather the specific... no matter how detailed the words a picture is worth 1000 of them.




    if the setting up of 'a specific and vital component' hasn't been mentioned in 185 threads here (where most (supposedly) are familiar with working on barometers), and isn't covered in the essential reading you've looked into, and mr. collins at barometer world hasn't addressed it... why the optimism? why do you think it's a thing?

    isn't it more likely (as other bruce says) that those don't really get adjusted?

    maybe you should try talking to manufacturers of higher-end barometers with such leaf springs and see how they either determine material and design of the leaf springs?
     
  11. zygo

    zygo Registered User

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    I'm sorry we disagree, Bruce, but I'm not going to perpetuate this nonsense.
     
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  12. Bruce Barnes

    Bruce Barnes Registered User
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    Too bad, but over the years on this site I have seen more than a few of these "whizzing" contest over an honest question.
    Bruce
     
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  13. bruce linde

    bruce linde Technical Admin
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    gee, sorry for my part… thought I offered a couple of good suggestions. It typically takes two to communicate or not communicate :-(
     
  14. etmb61

    etmb61 Registered User
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    Adjusting the two bright bolts should change the scale length of the instrument (sensitivity to pressure change). They need to be set so that you get full scale deflection of the needle that corresponds to the pressure changes. For the best way to do that you would need a sealed chamber with a viewing window, a vacuum source, and a reference standard (water or mercury manometer or an accurate barometer) to compare with. After that it's trial and error, test and adjust to set the range.

    I worked with aircraft instrumentation for 27+ years in the Air Force.

    Eric
     
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  15. zygo

    zygo Registered User

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    Exactly it, Eric. Spot on response to the query. Thanks.
    So it's trial and error at the end of the day - the ability to control a micro-climate device just speeds up the process.

    (Sadly, there aren't any decompression chambers on eBay UK just now - ;)).
     
  16. Bruce Barnes

    Bruce Barnes Registered User
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    My question through all of this interesting conversation is, why are you sure your instrument is inaccurate? and most, unless used for scientific accuracy, are very reliable for personal use.
    Bruce(2)
     
  17. novicetimekeeper

    novicetimekeeper Registered User
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    You can buy a vacuum pump really cheaply now, around £130 will get you quite a good one. I have looked at them for school for when our ageing Edwardes speedivac finally gives up the ghost. A decent gauge would be another issue.
     
  18. etmb61

    etmb61 Registered User
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    I agree. I check my barometer almost every day but never take a reading from it. I look for high, low, and the trend.

    Eric
     
  19. Bruce Barnes

    Bruce Barnes Registered User
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    Eric, I do the same and I have five in place and set to the local altitude and sometimes the needle movement is almost miniscule. Some think because the weather news say a front is due to arrive people think their barometer should have an immediate reaction. Being an ex pilot and flying in the North West and Canada etc. it behooves one to due some studying of meteorology.
    Bruce(2)
     
  20. zygo

    zygo Registered User

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    Well, for one thing the pointer barely moves from the position of the set hand, whereas my mercury barometers are showing at least some movement in local pressure over a week or two. And yet, when placed into a sealed clear plastic bag to subject it to increased pressure, it does move, so the capsule seal seems to be OK. It might just not be able to detect slight pressure changes and in the UK where I am, there hasn't been much wild change for a long time.

    The problem is that I loosened the two screws in question while cleaning the movement and tightened them a few days later when adding a little oil after replacing the repaired chain. Now I can't see where they were originally. (Doh!) It's a repair so I was looking for a faster solution than trial and error, week by week.I thought that if someone here had who replaced a damaged capsule he will have experienced the same issue; I simply had not appreciated that a pressure chamber would be essential to set it up after replacement so I suspect very few damaged capsules are replaced. A lesson learned! Many thanks to the help and guidance offered.
     
  21. Bruce Barnes

    Bruce Barnes Registered User
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    ZYGO, you will always get a more visible and accurate reading from a mercury barometer, even the best diaphragm capsules are not as accurate.
     
  22. novicetimekeeper

    novicetimekeeper Registered User
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    People who repair barometers for a living seem to keep a Fortin as a standard. We used to have them in schools until mercury became the bogeyman.

    It does mean there are usually a few available on ebay, though you have to collect as most carriers, including Royal Mail will not carry mercury.
     
  23. etmb61

    etmb61 Registered User
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    Always tap the glass to then read the gauge.

    Eric
     
  24. Bruce Barnes

    Bruce Barnes Registered User
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    #24 Bruce Barnes, Oct 15, 2017
    Last edited: Oct 15, 2017
    If you have any photos of the instrument and the housing/case together would like to see them.
    Regards,
    Bruce (2)
     
  25. Bill Stuntz

    Bill Stuntz Technical Admin
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    #25 Bill Stuntz, Oct 15, 2017
    Last edited: Oct 15, 2017
    In the new software PM's are Conversations. Hover over your avatar up in the sticky nav bar, you should quickly see this dropdown: conv..png Conversations are like private threads, visible only to invited participants.

    P.S. I've changed the wording in that drop-down. It now reads "PM/Conversations"
     
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  26. BLKBEARD

    BLKBEARD Registered User
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    This may help, just from a mechanical point of view.
    1st....... for your reference, or others reading this thread. Screw threads are pretty accurate. When removing adjusting screws you should count & log the number of turns to remove them. To reinstall them wind them in the same number of turns as you counted on removal. This method should return you very close to the original settings.

    At this point, since those dimensions are lost. I would back them off (we'll call this the coarse adjustment) Then unscrew & screw in the calibrating screw to locate the approximate mid-point of that adjustment.(we'll call this the fine adjustment)

    Adjust the course screws to bring the needle as close as possible to the proper reading. (Using another barometer as a guide) This should give you an initial setting from which you can dial it in with the fine adjustment screw.

    You can make a simple vacuum chamber out of a jar such as this
    How to Stabilize Spalted Wood #1: Building a Pickle Jar Vacuum Chamber

    And hand vacuum pumps can be had for as little as $17.00 https://www.ebay.com/sch/i.html?
    _sacat=0&_nkw=hand+vacuum+pump&_frs=1

    Adding additional fitting will provide you a port to hook up other gauges to the chamber.

    Hope this helps, it's the best I can figure without having the unit in my hands.
     
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  27. zygo

    zygo Registered User

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    Yes, I have several, both stick and wheel type, but when calibrating a customer's after repair, I always find myself going to the Met Office website for better accuracy (partly because that's where the customer is likely to go to check my work). Interesting to read that some repairers set to local altitude; traditionally, they are set to sea level.
     
  28. novicetimekeeper

    novicetimekeeper Registered User
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    If we need a figure now for any calculations I use the local airport. I don't know the elevation there but for us it is more about the technique than the actual figure.
     
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