I have had a lot of experience with working with glass blowers and stuff like
that.
It seems that if you try to repair a crack in glass as soon as you start
heating the
object up the crack grows due to thermostess. It just gets worse and worse.
Also, as far as vacuum goes you need much better vacuum that you can get from a
simple mechanical vacuum pump. The break down voltage can even be less than at
atmosphere if you don't use a diffusion pump, turbo molecular pump or mag. ion
pump.
And that is usually done at a somewhat lower temperature in an annealing oven to
bake off extra gas molecules left on the surface.
73
Bill wa4lav
________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Chris Wilson
[chris@chriswilson.tv]
Sent: Monday, April 29, 2013 11:15 AM
To: Amps
Subject: Re: [Amps] Non-vacuum capacitor
> Hello all,
> My wife has a woman working for her at her art gallery that is also
> an experienced 'glass artisan', or whatever the name is, and I asked
> her about working with the glass vac variables.
> She thinks the biggest issue may be not knowing the specific glass
> composition you would be working with. The problem is the
> coefficient of thermal expansion, between the original glass and any
> glass tube (for re-evacuation) you try to melt to the capacitor.
> She has the high BTU output torch and skill working with glass,
> which are two things I don't have. If I can find a vacuum cap that
> has lost it's vacuum, she is willing to give it a try. And, we have an
> sneaking oven, as well.
> Does anyone have any mfgr documentation that may indicate anything
> abt the glass used (e.g. '... Using the highest quality Boron-Manganese
> glass...')
> 73 de Steve, NR4M
29/04/2013 16:10
The glass capsules will be pre blown and assembled and sealed up cold,
heating the glass envelope of an assembled cap to the point of
localised entry is going to knacker the seals, I am pretty sure!
Race shock absorbers (dampers) have a nitrile membrane a quarter of an
inch thick or so, through which they can be recharged with nitrogen.
They "self heal" as the hypodermic charging needle is removed. I can
see no reason why a similar sort of port couldn't be used in the
manufacture of vac variables, but holding vacuum instead of pressure.
I wonder if new ones are serviceable and can be re-evacuated at their
manufacturers, or if they just bin them if they leak?
--
Best Regards,
Chris Wilson.
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