Clear “plastic” rod

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Clear “plastic” rod

This topic has 6 replies, 5 voices, and was last updated 2 June 2016 at 11:37 by John Allan Watson Brown.

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1 June 2016 at 21:35 #241121
michael howarth 1
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@michaelhowarth1
Does anyone know of the availability of a "plastic" material available in clear rod form. I can obviously source acrylic rod but its maximum working temperature is a bit low at 70 deg. C. The intended application is in small scale water gauges. Alternatively, does anyone know of a way to put a thread on glass tubing?

Mick
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1 June 2016 at 21:35 #29606
michael howarth 1
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@michaelhowarth1
1 June 2016 at 21:51 #241122
Jeff Dayman
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@jeffdayman43397
Are the parts you are planning to make going to be exposed to hot water or steam under pressure any higher than atmospheric?

If so, plastic must not be used. It is not safe for high temps or pressure vessels.

If the parts are for gauging cold water level at atmospheric pressure there are several types of plastic that will work. If you describe such an application I'll recommend a few. Again, these plastics must not be used at high temps or as pressure vessels.

Can you not use regular water gauge glass tubing with suitable rubber rings to seal it, and nuts to secure everything?

Threads on glass as seen on jars or pharmacy vials are usually moulded or rolled into the glass while it is hot and semi-molten. Ground-on threads in glass may be prone to cracking, even if radiused at the roots. Don't know of any commercial glass items with ground -in threads, but there may be some. JD
2 June 2016 at 06:42 #241140
michael howarth 1
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@michaelhowarth1
Thanks for that Jeff. I was hoping to experiment with "plastic" as an alternative to traditional glass tubing. I have always used glass tubing, but in the 1/32 scale models that I build not only are the bits rather fiddly to work with but the small bore of the tubing is notorious for inaccuracies in gauging boiler water level. Not quite the same thing I know, but I am sure that I have seen Mamod type boilers with "plastic" sight glasses and this set me thinking along these lines. My models work at a nominal 60psi so a working temperature of something like 140 deg.C would probably be required. I am also just starting to use electronic water level detectors but an LED is not quite the same as a water gauge.

Mick
2 June 2016 at 07:15 #241142
pgk pgk
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@pgkpgk17461
I wonder if it'd be possible to cast your parts with some of the clear resins? I couldn't find a post-set temperature range but noted that one brand recommended 60-80C for some hours as part of the cure process..suggesting they might be able to cope with expected temps???
2 June 2016 at 11:18 #241160
Tim Stevens
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@timstevens64731
One difficulty you will face at small scales is caused by surface tension. This will either draw the liquid too far up the tube, or depress it too low, depending on the properties of the tube in relation to the liquid.

It does depend, of course, on whether you want a live gauge (showing actual level) or something which looks right but does not vary.

Cheers, Tim
2 June 2016 at 11:37 #241165
John Allan Watson Brown
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@johnallanwatsonbrown
Perhaps a flat plate type gauge would suit? It gets you away from the small bore tube difficulties. A lot more work involved mostly in the clamping bolts / screws to hold the press plates together over the clear lenses. Lots of images if you search "boiler gauge glass flat plate".
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