DIY manometer

For some reason, I feel unduly proud of myself for having constructed a manometer for soundness-testing my recent gas installation. Total time - just over an hour.
In case anyone wants to do the same (as they cost about 25 quid in the shops) this is what I did. As I had the materials lying around anyway, this cost me nothing.
Materials:
White contiboard offcut - about 60cms by 5 cms
Clear plastic flexible tube - about 1.5 metres long - I used 3/8ths of an inch outside diameter, but this was a bit narrow
Some wire like you would use in the garden for tying back plants
A 30 cm school ruler
Tools
Small drill
Pair of pliers
Warm the end of the tube in hot water and expand one end of the tube to about 3/8ths of an inch inside diameter and shove something in to stop it shrinking back - you might be better off with wider tube but this is what I had lying around.
Arrange the tube on the contiboard in a U-shape, with about a foot of the expanded end loose. Drill holes in the contiboard and secure the tubing in place with the wire. It does not matter what is happening at the U-shaped end, as long as the two straight parts of the tube are parallel to each other. I arranged them so they were side by side, rather than leaving a gap between them. I screwed the ruler to the contiboard with the centimetre scale next to one of the straight bits of tubing - in fact tucked slightly under for accuracy of measurement.
Use a hook in the end of the contiboard or a loop of wire, so that the whole thing will hang vertically.
Add water to fill the bottom of the U and bring the water level up to the bottom of the ruler. If you are being feisty, you could cut slots in the ruler for the fixing screws, so it can be moved up and down to zero it. Otherwise, you just have to make a note of the starting level, so that you can subtract this from the ending level. I found no need to add ink to the water but you could add this if you want the fluid to be more visible.
You can read the pressure in millibars off the ruler - 1 cm = 1 mb. This is accurate to 3%, ie the correct conversion is 1.03cm = 1 mb.
I measured the movement in the water of just one of the sides of the manometer. In other words I just measured the rise in the water in one half of the U. I assumed that the other side had dropped by an equal amount but did not measure it. This means that I needed to double whatever difference in level I found.
HTH
Geoff
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GB wrote:

<snip>
Full marks for making your own, mine was only 9.99 in the plumbers merchant so ICBA myself :-)
Lee
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On Sun, 28 Sep 2003 12:29:03 +0100, Lee Blaver

ICBA?
.andy
To email, substitute .nospam with .gl
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Andy Hall wrote:

"I couldn't be a*sed", I thought it was a common abbreviation, obviously not then. Sorry :-)
Lee
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On Sun, 28 Sep 2003 12:29:03 +0100, Lee Blaver

Did I hear someone's ego just deflate rapidly? ;)
PoP
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PoP wrote:

Oh I dunno ;), he's still made something that works and saved at least a tenner. A lot of people make things becuase they like to and it ends up costing more than it would have to buy them... <grin>
Lee
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wrote:

Hi PoP
I looked in the BES catalogue where manometers are 25 quid. If I had found a ready-made one locally at 10 quid, I too would not have bothered.
I have just fitted a new gas boiler and I wanted to pressure-test the system to check it's all ok. I'll only use the manometer this once probably.
I was quite happy pottering around making it. It was easy, and I wanted to point out to other people that it is easy, in case it was of help to them. I guess it was a bit egocentric of me to think that anyone would be interested, but these NGs are archived and maybe some day someone else will need to build their own manometer and this could be of use to them.
I am not quite sure why I got pleasure in making it. Silly really, but I did a degree in physics 30 years ago, and I hardly get a chance to use it these days. Doing the conversion from millibars to cms of H2O was quite interesting and took me back a bit.
Geoff
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On Sun, 28 Sep 2003 16:38:33 +0000 (UTC), "GB"

Must admit there's a certain amount of pleasure from making your own jigs and things. I keep thinking about making hinge and doorbox jigs for my router. Latest idea is to make a couple of those long router clamps, haven't bothered yet but I can't see me rushing out to buy the real mccoy at 40 quid plus anytime soon :)
PoP
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On Sun, 28 Sep 2003 21:12:59 +0100, PoP

Not sure I've seen them, what are they about then?
Take Care, Gnube {too thick for linux}
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wrote:

Here you go:
http://tinyurl.com/p0vv
Basically a bit like a sash cramp in operation, can be acquired in multiple widths (up to 50 inch I've seen). Provides a straight edge to rip or route against, so you could feasibly chop up a large 8x4 ft board accurately.
It's basically a simple replacement for clamping a piece of wood onto the workpiece to run against with the router.
These things seem a bit overpriced for my liking. Another one of those areas where you could make a killing if you could manufacture something simple to take its place.
PoP
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On Mon, 29 Sep 2003 11:22:28 +0100, PoP

Ah, right, know what you mean now - that one's a bit pricey though; Axminster do a pair for not much more than he's asking for that one!
I guess that one might be a super duper special, but he made no mention of it! (in fact it looks like the description from the axminster catalogue!)

Yeah, I wanted one at about 2M this very weekend! They don't make them that size (of course!) unless you know different that is? (hopefully!)

I like that they clamp back to back to each other too - could be well handy I would guess.

I don't have a car anymore, but I do have a couple of those square section roof clamps (part roof rack sort of pair of things from the "Nordic" countries that let you clamp Luxembourg to your car roof) that have hardly been used at all in the attic, I better go investigate soon I think! It might feature a straight edge amongst it all too with luck. Thanks for the info.
Take Care, Gnube {too thick for linux}
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wrote:

Sorry, no further information available.
I first came across these clamps in the Reading B&Q a couple of months back - they are hung on the wall in the far corner of the power tools section (immediately adjacent to the checkouts). Took a look at one and thought "hmm, yes, useful". Price tag gave me another message though.
PoP
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On Tue, 30 Sep 2003 08:18:19 +0100, PoP

OK, thanks, just for your info, Axminster do about 3 sizes, and also offer discounted "pairs" of each size. The dearest "pair" is a little shy of 40 from memory. Dearest single was about 20 I feel. Not too unreasonable to be honest.
Take Care, Gnube {too thick for linux}
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That looks like a Useful Thing.
I make up my own "sawmizer" jigs for routing, accurate cutting with circular saw, drilling shelf holes, etc etc (the jigs start off simple and evolve as necessity dictates) but one of the problems is to get the reference straight edge in the first place.
Usually this means ripping the machined straight edge off a sheet of 12mm or 18mm MDF using the circular saw's rip fence, but you only get two long straight edges per 8' board, and sometimes the machined straight edge isn't quite as accurate as I'd like.
One of these might be just the ticket...
-- Richard Sampson
email me at richard at olifant d-ot co do-t uk
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Hi
There are many tools one can make: level, bevel, my brains gone blank, what are those L shaped things called? Anyway, ladders, board carriers, sheet metal benders, various stuff.
Regards, NT
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snipped-for-privacy@meeow.co.uk (N. Thornton) wrote in message

Buying a new level recently I came across one with a notice attached to the effect it had to be calibrated first! What use is that?
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Not a problem! Simply put it on a *flat* surface (doesn't have to be dead *level*) and adjust the bubble so that it reads exactly the same when you turn the level through 180 degress in plan view.
Roger
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That's odd, but it's possible to calibrate it without having a horizontal level to check it against.
Geoff
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If you don't check, you'll end up with very odd shelves!
I *always* check and re-calibrate my spirit level before use:
1. Place on any flat nearly-level surface (doesn't have to be level). Note position of bubble. 2. Rotate level through 180 deg. and replace in same position.
If your level is correct, bubble will be in the same place as before. If not, it'll need adjusting. Adjust, then iterate until you get the same reading both ways round.
It's amazing how many 'maintenance free' levels in shops are badly out. Always check, even for the circular bubble-in-centre type. It's also amazing how easy it is to knock the adjustable type off true, especially in the toolbox.
Regards,
Simonm.
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SIMON MUIR, UK INDEPENDENCE PARTY, BRISTOL www.ukip.org
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I think I've still got the one I made about 30 years ago out of an old piece of floorboard with a strip of graph paper stuck on it and a length of clear plastic tube bent into a U and held on with staples - very similar in pinciple!
Roger
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