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Comment by refurb

2 years ago

You’d be surprised how little glass is needed to be strong enough to withstand a near perfect vacuum.

I worked in a lab where we routinely held a few micro-torr of vacuum, which is about the limit for mechanical pumps. Cathode ray tubes are typically thousands or tens of thousands higher pressure.

We ran 1/4” wall thickness glass even in large flat stretches without issue.

I’m guessing the weight of large cathode ray tubes are more for durability than need for the vacuum inside.

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refurb

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Karliss  2 years ago

That's a bit misleading the level of vacum might differ by factor of 10000, but most of the force is still coming from atmosphere. For overall mechanical strength it doesn't matter that much if its 0.99 or 0.99999999999 atmospheres of pressure difference, temperature and other wheather changes are probably causing much bigger change in force applied to glass.

  • willis936  2 years ago

    I don't think it's that misleading. At the end of the day you need a 14.696 psi negative pressure vessel. That isn't very dramatic. If you can confidently make something that works to 14.696 psi then you can be confident it will work at 14.65 or 14.5 psi.

    The meat of the comment is that you don't need much material to withstand Earth's atmosphere compared to pressure vessel. It's a common misconception for folks who don't work with vacuums.

    Having carried my share of heavy CRTs I can share that most of the weight is in the front glass. It needs to support the phosphor wire mesh and withstand the pokes and stabs of the world while not compromising the fragile thin-walled neck.