Barometer help please

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Barometer help please

This topic has 10 replies, 6 voices, and was last updated 4 March 2018 at 09:15 by john carruthers.

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3 March 2018 at 15:38 #25852
JohnF
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@johnf59703
Barometer glass replacement
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3 March 2018 at 15:38 #344224
JohnF
Participant
@johnf59703
Hi All, I have been tasked with assisting to replace the glass in an old aneroid barometer. The glass itself is not a real problem its flat plate with a bevelled edge.

However removing it from the metal bezel is a problem so wondering is anyone knows how to do this ?

It appears that the outer metal rim is rolled over the glass or the inner is pressed onto the outer thus holding the glass in place ???

The photos are of the complete glass and mount plus a closeup of the outside where you can see the rolled over edge and the inside where it seems the inner ring is pressed onto maybe an upstanding on the outer?

Any info gratefully received before I/we attempt to remove the broken glass.
3 March 2018 at 15:45 #344225
Brian Sweeting 2
Participant
@briansweeting2
In picture 3 is that round looking brass a circlip type ring holding the glass In ?
3 March 2018 at 16:19 #344228
Scrumpy
Participant
@scrumpy
Some 20+ years ago I used to work part time for a barometer restoration company their were many ways that the glass was held in place some had a brass circlip some just putty and some small clips that were fixed to the bezel and bent we used to remove glass and replace with metal putty be very careful that you Don't buckle the bezel as they are a pig to make ( I had to machine 4 in a day )
3 March 2018 at 16:43 #344230
Nigel Brown 7
Participant
@nigelbrown7
Just fixed a very similar barometer (in time to measure changes in recent weather …) given to me as "dead".

Needle had become loose on shaft. It was just a tiny brass tube pinched up so it went tight on the pin.

PO had tried 'adjusting' erratic mechanism to the limit of travel so the internal mechanism was jammed fully over one way – then the adjusting screw thread had become rusty and stuck.

Freed off adjuster (WD40).

Centralised mechanism. Reassembled.

Repinched needle and refitted at roughly correct reading as per another barometer.

Will accurately set millibars when pressure is stable over UK.
3 March 2018 at 18:33 #344251
JohnF
Participant
@johnf59703
Thanks for the reply's — Brian its not a circlip but not easy to see that in the photo, it is a rolled edge or that's what it looks like.

Scrumpy your spot on with the putty, I have now removed the broken glass — nice flat surface for the bezel and firm pressure on the glass using suitable hand protection — a thick wad of paper !! the glass popped out.

When I looked at it I guess I was over thinking it and imagined the glass under the top rolled edge and the inner ring holding it in place — close examination and Scrumpy's advice – the rest is history — Thanks gentlemen!

Down to the glass merchant next week !

Cheers John
3 March 2018 at 19:23 #344256
roy entwistle
Participant
@royentwistle24699
John Meadows and Passmore sell ready glazed bezels for barometers, you would have to fit the hand

Roy
3 March 2018 at 21:51 #344281
Scrumpy
Participant
@scrumpy
If you go down the traditional route ( I hope) and reset glass using metal putty before fixing to the barometer leave to dry for a few days and lightly colour with brown boot polish then fix
3 March 2018 at 22:17 #344282
JohnF
Participant
@johnf59703
Thanks Roy had a look there and at few others but there is nothing that suits the vintage really so will probably go down the route of a local company the owner has spoken to who say they can make one, it will need to be pretty accurate on the OD though.

Scrumpy yes we will go traditional but a little guidance on the ,metal putty will be useful, what do you recommend ?
4 March 2018 at 08:16 #344303
Scrumpy
Participant
@scrumpy
I'm so glad you are going the traditional route, as for metal putty we used one called slade100 but any putty will do as long as there is not to much oil in it , could I suggest if there is you let it air dry before using then puff some talcum powder to stop oil running then leave to harden then smear some soft/ melted brown shoe polish over the surface this is for two reasons ( covers your marks and stops reflection) hope this helps
4 March 2018 at 09:15 #344309
john carruthers
Participant
@johncarruthers46255
When I worked at the local glass works I had to do dozens for local dealers .
Check the thickness, modern 4mm float is the usual substitute but they can be from polished plate or even drawn sheet.
You will eed;
A circle cutter (can be done freehand if you are good
A '0000' alox wheel, running in water to polish the edge and bevel. (glazier speak, polish = grind)
A cork wheel or rubber & pumice wheel to buff said bevel. (can be done on a linisher running wet with a cork faced belt)
A spear point drill to drill the centre hole to fit the needle.
Slowly grind the circumference and bevel until it is a 'click' fit in the bezel, if you over cook it, start again
If the needle is a bit floppy when finished a turn or two of silk will take up the slack. Some centres have a cork washer, but 100 year old cork washers are not very robust.
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