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Post by districtgrandmaste on Apr 26, 2007 10:06:07 GMT
Back in 1953 (I remember it well!!) LBSC published the design for a Steam Crane in ME.
Having three Grandchildren I decided to make this and to give them a bit to think about I'm including a Water Gauge (LBSC didn't bother as it is just a pot boiler and could be run dry without risk - he says!).
In Shop, Shed and Road there is a published design for a Water Gauge that will do fine - but what would the packing round the glass be? I'm thinking of O rings but a 3/16" water tube fitted with O rings has an overall diameter of about 0.290". Thus the retaining nuts (9/32" x40 TPI) are likely to be too small - or am I worrying over much?
Opinions awaited!
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Post by alanstepney on Apr 26, 2007 11:02:02 GMT
Some PTFE tape twisted into a braid will do well.
Or, some string will work.
At those low pressures, and given a small gap, it isnt critical.
Thin string commercial packing is available, or a sliver of rubber tube could be used.
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Post by Laurie_B on Apr 26, 2007 12:31:15 GMT
The PTFE string should work fine.
Both Reeves and Polly Model Engineering (Bruce Engineering) list gauge glass O rings in their catalogues.They are for metric size glass tube,the nearest size for your crane would be 5mm.The O ring section diameter is 1.0 mm.
I have these O rings fitted to my loco gauge glasses and they seal perfectly,and the loco passed a steam test recently at 100 psig.
(Sorry about the mixed units!)
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Post by gilesengineer on Apr 26, 2007 12:41:27 GMT
Nowadays, our standard trick is to put a bead of silicone mastic round the glass, and screw the gland nut down on top of that. It gives an easy and reliable job ......... self-adjusting, as it were...
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Post by baggo on Apr 26, 2007 13:10:45 GMT
I've just made a water gauge for a 2½" loco which uses 5/32" dia.(4mm) glass. For the seals I've used square section rings cut from some 5/32" I.D. silicon tubing that I happened to have. (I think it's used for air lines in fish tanks etc.) To make the rings push a length of the tube onto a mandrel (e.g. drill), put it in the lathe and part off 1/16" lengths with a sharp knife. Make a load of spares while your at it! The wall thickness is about 1mm and, in my case, it fits nicely inside 1/4"x40 nuts, so you would be ok with your 3/16" glass and 9/32"x40 nuts.
John
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Post by ron on Apr 26, 2007 19:38:01 GMT
I've used both O-rings and Baggo's method in small gauge glasses with good results, I found Reeves' O-rings rather too small in cross section, proprietary ones of about 1/16" X section were better.
Ron
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Post by chris vine on Apr 26, 2007 21:13:53 GMT
Hi,
You can always use an old method of a bit of graphite yarn. I have used that in the past and, apart from getting your digits dirty, it works fine.
Although I am sure that PTFE tape twisted up as Alan suggests will be fine or rather better.
Chris.
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Post by districtgrandmaste on Apr 27, 2007 9:03:49 GMT
Many thanks for all these suggestions. It'll be some time before I get to fitting packing but when I have I'll add to this thread to say how I got on!
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