Date: Mon, 14 Jun 2004 16:37:30 -0400

Author: sampere

Subject: Re: vacuum tube

Post:

The walls of your new tube are not concentric, nor are they circles
though they appear to be circular. So Jerry had the shop turn down the
inside surface so it was smooth and circular. Then then the circular
plugs with o-rings had a nice surface on which to seal. Make sense?

Sam

Patricia Sievert wrote:

> Jerry,
> I'm afraid I'm showing my ignorance here, but what do you mean by
> "faced on the inside surface"? I've got the thick-walled tube stock
> and was planning to have our shop produce the end caps. Your pictures
> will help there.
> Thanks,
> Pati
>
> Gerald Zani wrote:
>
>> James,
>>
>> Ours is homemade
>> http://128.148.60.98/physics/demopages/Demo/solids/demos/1c2010.html
>>
>> The tube stock polycarb or acrylic. The end caps are made with
>> double o-ring seals. The tube is faced on the inside surface. One end
>> cap has a vacuum valve connector.
>>
>> JZ
>>
>> At 11:11 AM 6/14/2004 -0500, you wrote:
>>
>>> It is an old Cenco model 76720, CP76720 is the new model that does
>>> the same job.
>>>
>>> It is glass with steel end caps that enclose the tube ends. Between
>>> the
>>> steel cap and tube is a layer of brown waxy material impregnated
>>> with ordinary cotton string (for tensile strength?).
>>>
>>> It is this material which has failed - the glass and steel parts
>>> seem to be fine. I came to that conclusion by immersing the tube
>>> and applying positive pressure, and tracking the bubbles to the seal
>>> area. The leaks all seem to occur at the glass-wax or steel-wax
>>> surfaces.
>>>
>>> The waxy seal is pretty leaky, it only holds a vacuum for about 3
>>> seconds before enough air has entered the tube to ruin the
>>> demonstration. So, it is pretty much unusable as it is.
>>>
>>> Also, I'm pretty sure that the seal material is not wax, as it
>>> flakes rather than melting under heat.
>>>
>>> Let me know what else I can tell you.
>>>
>>> Thanks,
>>>
>>> James Papp
>>>
>>> -----Original Message-----
>>> From: Wolfgang Rueckner [mailto:rueckner@fas.harvard.edu]
>>> Sent: Monday, June 14, 2004 9:42 AM
>>> To: tap-l@listproc.appstate.edu
>>> Subject: Re: vacuum tube
>>>
>>>
>>> >Hello all
>>> >
>>> >I have a vacuum tube, part of a "feather and penny" demo. Sadly,
>>> >the seals at the ends
>>> >of the tube have bad leaks, and so I want to replace them. Does
>>> >anyone have any experience
>>> >with this kind of project, or suggestions about what kind materials
>>> >I would find useful?
>>> >
>>> >Thanks ahead of time,
>>> >
>>> >James Papp
>>>
>>> Need more information about your particular tube and it's present
>>> seals to be of help. -- Wolfgang
>>
>>
>>
>> Gerald Zani e-mail: Gerald_Zani@brown.edu
>> Manager of Demonstrations phone: (401) 863-3964
>> Department of Physics FAX: (401) 863-2024
>> Brown University Providence, RI 02912-1843 USA
>>
>> http://128.148.60.98/physics/demopages/demo/
>> http://128.148.60.98/physics/userpages/staff/Gerald_Zani/index.html
>>
>> Do a little more of that work which you have confessed to be good,
>> Which you feel that society and your most Just Judge rightly demand
>> of you.
>> Cultivate the tree which you have found to bear fruit in your soil.
>> If you have any experiments you would like to try, try them.
>> Now's your chance.
>>
>> Henry David Thoreau, Journal entry, 1850.
>>
>>
>
From dimarco@physics.montana.edu Mon Jun 14 16:33:05 2004

Back