[time-nuts] OXCO insulation

Dave M dgminala at mediacombb.net
Sun Feb 22 14:56:47 EST 2015


Yes, I'm aware that the newer OXCOs don't have any insulation other than air 
inside the package.  I failed to mention that in my post.  I am primarily 
interested in the older OXCOs that have foam insulation inside.  I have a 
couple of them, including the crystal oven from an old HP 5245L counter that 
needs new insulation.  The old foam was destroyed by a heater that ran wide 
open for a while, burning a large portion of it to a crispy mess.

Thanks for your response,
Dave M


Bob Camp wrote:
> Hi
>
> A lot of modern OCXO’s no longer use insulation…. the gaps inside are
> now so
> small that you get very little benefit from it.
>
> On the older parts that do use insulation 2 to 4 pound per cubic foot
> density
> urethane foam is a typical choice. You can buy it from most plastics
> suppliers. It
> can be machined with just about any tooling out there. The dust is a
> mess, but
> it’s not normally considered hazardous.
>
> Bob
>
>
>> On Feb 21, 2015, at 7:09 PM, Dave M <dgminala at mediacombb.net> wrote:
>>
>> What kind of foam insulation is generally used inside an OXCO?  Do
>> all manufacturers use the same kind?  Is it available in small
>> (hobbyist) amounts?
>>
>> I've read that some folks have used Great Stuff polyurethane-based
>> insulating foam to repair an OXCO.  I've used it to fill gaps around
>> pipes in my home, but it's nor subjected to the high heat
>> encountered in an OXCO. According to Dow's web site, it could
>> present a fire hazard if subjected to temperature of 240F (115C).
>> There is a "Fireblock" variety, but it appears to have pretty much
>> the same formulation as the other varieties, so I can't see any
>> advantage to it.
>> Has anyone experienced any long term problems with Great Stuff in an
>> OXCO?
>>
>> Dave M




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