Re: [time-nuts] Thermal insulation choice?

[shalimr9]

You could make a form (a mold) with cardboard and use a can of polyurethane 
insulation to fill it with your OCXO inside (protected by a plastic bag) like 
the "foam-in-place" principle. It will be exactly the size you want, pretty 
stiff, strongly bonded to the cardboard, so it will be easy to mount things on 
it if needed and with a minimum number of seams.

It may be more work than cutting sheets of styrofoam though.

Didier KO4BB

--Original Message--
From: John Ackermann N8UR
Sender: time-nuts-boun...@febo.com
To: Time-Nuts
ReplyTo: Time-Nuts
Subject: [time-nuts] Thermal insulation choice?
Sent: Jan 6, 2012 1:39 PM

I am looking for a readily available (from Home Depot or other local 
source) insulating material to use in a chassis that's housing a 
sensitive OCXO.  My goal is just to slow down any external thermal 
transients so the oven loop has time to react gracefully.

I'm thinking of something in sheet form that I could glue to the inside 
bottom and side of the metal chassis.  The trimmed sheet sizes will each 
probably end up being around 4 x 8 inches.  I have enough clearance for 
a thickness of a half inch or so.  I'd like to avoid a bat material as 
that would be hard to mount neatly.

Long lifetime (ie, not getting all crumbly after a few years) is 
important as I don't expect this oscillator to get cold until I do.

Any suggestions of a material to look for?

Thanks,

John

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Sent from my BlackBerry Wireless thingy while I do other things...
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[time-nuts] Thermal insulation choice?

[Mark Sims]

How about using Hostess Twinkies?   They look like they would have good 
insulating properties and are well known to never, ever decompose ;-)

  
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Re: [time-nuts] Thermal insulation choice?

[Poul-Henning Kamp]

In message , "Tom Van Baak" writes:

>What I did instead was to buy a bunch of cement paving blocks
>from Home Depot and made an air-tight sarcophagus (Egypt or
>Chernobyl-style). Lots of thermal mass.

My personal best was an old fridge, and if you _really_ want execellent
preformance, you circulate a constant temperature liquid in the
cooling circuit using a little pump and a peltier.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Thermal insulation choice?

[Charles P. Steinmetz]

Rick wrote:


We also tried mounting the modified 10811 in Hammond metal box.
Initially, we mounted the 10811 to the box using the
two standoffs that come with the 10811.  However, this
degraded the performance somewhat.  We removed these and
had the 10811 supported mechanically only by the edge
connector.  With that change, it was as good as the cardboard
box.


I often mount OCXOs inside metal boxes with nylon or teflon standoffs 
(or resilient mounts, for some vibration isolation), with excellent 
results.  If tighter temperature control is needed (IME, it often is 
not), mount that box inside another box on thermally insulating 
standoffs and control the air temperature in the larger box with a 
thermostatically-controlled fan.  (The control should be set to no 
more than the maximum expected ambient temperature, or perhaps a bit 
lower, to preserve as much thermal differential for the oscillator 
oven as possible.)


Best regards,

Charles







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Re: [time-nuts] Thermal insulation choice?

[Rick Karlquist]

Neville Michie wrote:

> I wonder if TVB knows what the brown foam in 10811 is? Does it have a
> radiation absorbing powder in it?
>
> cheers, Neville Michie
>

Various foams were tried and or used in the 10811.  The main
concerns with foams had nothing to do with insulating qualities
and certainly no one worried about radiation absorbing powder.
They wanted a foam that would not fatigue or disintegrate
mechanically.  It had to have good castability in the mold,
as the dimensions are fairly critical and the shape is intricate.
It could not outgas hazardous substances under normal oven
temperatures.  There was also an issue about what it would
do if the oven ran away.  It could not catch on fire, etc.
There are the usual manufacturability issues like cost, availability,
whether the vendor was "approved", etc.

In the E1938A, with a demonstrated thermal gain of over 1 million,
it was still the case that any foam or no foam worked fine thermally.
The most the foam could do is possibly change the ratio of heat
between the main surfaces and the rim.

There are minor differences in the amount of oven power for various
types of foams.  In general, it is fairly difficult to screw up
an oven oscillator by choosing the wrong foam.

Rick Karlquist
N6RK


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Re: [time-nuts] Thermal insulation choice?

[Hal Murray]

> I wonder if Balsa wood would be suitable?  Like polystyrene foam,  only
> stronger and easy to glue. 

Another option would be cardboard.

Readily available, easy to cut.


-- 
These are my opinions, not necessarily my employer's.  I hate spam.




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Re: [time-nuts] Thermal insulation choice?

[Neville Michie]

"Insulation" of an object to reduce heat transfer has three main  
components.
Convection, the movement of air which carries heat from place to  
place, this is easily reduced by
small cell (less than 5mm) structures, below this size thermal  
convective circulation does not occur.
Conduction, this is reduced by making the cross-section of any solid  
material very small, the length great

and by choosing a low conductivity material.
Thermal Radiation is very significant, and as many materials are  
transparent to long wave (10 micron)
radiation it is important to design for it. A low emmissivity (very  
shiny) surface reduces radiative transfer,
but shiny surfaces usually tarnish with time. A non transparent  
barrier, like metal foil, will stop radiation,
but the foil will heat up and re-radiate. If you have a setup with  
two parallel metal plates, a certain
amount of heat is transferred which does not change with increasing  
distance. If you add an intermediate
plate, it will heat to half the temperature difference,and as each  
plate sees half the temperature difference
only half the heat is transmitted. So on to 10 layers where only one  
tenth of the heat is transmitted.
So if you want to use polymer foam, make it in thin layers with a  
very thin layer of foil between each layer.
Balsa wood sounds as if it could be good, because it will have  
distributed absorbers of radiation
throughout it, equivalent to many layers of foil, and its conduction  
is low because it is mainly air.
I wonder if TVB knows what the brown foam in 10811 is? Does it have a  
radiation absorbing powder in it?


cheers, Neville Michie


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Re: [time-nuts] Thermal insulation choice?

[Chris Albertson]

On Fri, Jan 6, 2012 at 2:50 PM,   wrote:
>  My goal is just to slow down any external thermal
> transients so the oven loop has time to react gracefully.
>
> Are you sure it is not thermal mass that needs to be increased and not just
> insulation?

The trouble is that if your insulation is good, the temperature will
raise without limit.  Some how you have to let the heat out.  Either
use poor insulation like the cardboard box or the pile of concrete
blocks.

Chris Albertson
Redondo Beach, California

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Re: [time-nuts] Thermal insulation choice?

[David]

On Fri, 6 Jan 2012 19:08:18 -0500, Joe Gwinn 
wrote:

>At 10:15 PM + 1/6/12, time-nuts-requ...@febo.com wrote:
>>Date: Fri, 06 Jan 2012 14:41:13 -0600
>>From: David 
>>To: Discussion of precise time and frequency measurement
>>  
>>Subject: Re: [time-nuts] Thermal insulation choice?
>>Message-ID: 
>>Content-Type: text/plain; charset=us-ascii
>>
>>I completely forgot about those two.  [Balsa wood and foam-in=place 
>>urethane foam]
>>
>>I have a good local hobby shop
>>with large pieces of balsa wood but I suspect it would be more
>>expensive than good quality expanded polystyrene bead sheet.  I will
>>have to check out foam board next time.  Both would be more difficult
>>to cut without a hot wire knife.
>
>Balsa wood cuts very easily with a sharp knife, glues very well with 
>carpenters' glue, and will not degrade over time.
>
>Joe Gwinn

My fault there.  I meant "with" obviously and my spell checker does
not check logic. :)

A hot wire knife makes it easy to cut and shape irregular curves and
surfaces without being inundated with sanding debris.

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Re: [time-nuts] Thermal insulation choice?

[lists]

Maybe support the osc on beads of RTV. That would both break the thermal path 
and provide a little shock (vibration) isolation. 

Some notebook PCs mount the hard drive in gel for shock. 

-Original Message-
From: Malcolm 
Sender: time-nuts-boun...@febo.com
Date: Fri, 6 Jan 2012 19:34:37 
To: 
Reply-To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] Thermal insulation choice?

I would recommend and have used 1/4 inch polystyrene foam that is available in 
roll form from DIY stores and either glue or double sided tape.  It is easily 
workable and cheap and achieves what you want.  There is a caveat in that you 
should also use nylon or other (heat) insulating washers and nylon nuts and 
bolts to attach the oven to the case.  Otherwise you will loose heat through 
conduction and introduce cold spots to the oven

Regards

Malcolm
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Re: [time-nuts] Thermal insulation choice?

[Malcolm]

I would recommend and have used 1/4 inch polystyrene foam that is available in 
roll form from DIY stores and either glue or double sided tape.  It is easily 
workable and cheap and achieves what you want.  There is a caveat in that you 
should also use nylon or other (heat) insulating washers and nylon nuts and 
bolts to attach the oven to the case.  Otherwise you will loose heat through 
conduction and introduce cold spots to the oven

Regards

Malcolm
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Re: [time-nuts] Thermal insulation choice?

[Bob Smither]

John Ackermann N8UR wrote:
> I am looking for a readily available (from Home Depot or other local
> source) insulating material to use in a chassis that's housing a
> sensitive OCXO.  My goal is just to slow down any external thermal
> transients so the oven loop has time to react gracefully.

A friend is diabetic.  He gets his insulin mailed to him in foam "ice boxes"
that are 9"x11" outside, 6"x8" inside, with a lipped lid that fits snugly.

I have an OCXO in one such box.  The FE-5680A would fit, but as I don't really
know what the case temperature should be I am hesitant to try this.  Maybe if I
get a spare ...

-- 
Bob Smither, PhD   Circuit Concepts, Inc.
=
  "The world is a dangerous place, not because of those who do evil, but
  because of those who look on and do nothing".
-- Albert Einstein
=
smit...@c-c-i.com  http://www.C-C-I.Com  281-331-2744(office)  -4616(fax)
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Re: [time-nuts] Thermal insulation choice?

[Joe Gwinn]

At 10:15 PM + 1/6/12, time-nuts-requ...@febo.com wrote:

Date: Fri, 06 Jan 2012 14:41:13 -0600
From: David 
To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] Thermal insulation choice?
Message-ID: 
Content-Type: text/plain; charset=us-ascii

I completely forgot about those two.  [Balsa wood and foam-in=place 
urethane foam]


I have a good local hobby shop
with large pieces of balsa wood but I suspect it would be more
expensive than good quality expanded polystyrene bead sheet.  I will
have to check out foam board next time.  Both would be more difficult
to cut without a hot wire knife.


Balsa wood cuts very easily with a sharp knife, glues very well with 
carpenters' glue, and will not degrade over time.


Joe Gwinn

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Re: [time-nuts] Thermal insulation choice?

[Mark Spencer]

As an additional data point..

When experimenting with various forms of insulation for a thunderbolt board I 
found that a corrugated carboard box provided a noticeable decrease in 
temperature fluctuations while limiting the overall temperature rise.   Even 
small ammounts of additional insulation (ie. a few layers of thin flexible foam 
sheets maybe 2 mm thick used for wraping items for shipment) caused the 
temperature as reported by the thunderbolt to increase signficantly.  (Maybe 15 
Deg C IIRC ?)




--- On Fri, 1/6/12, Magnus Danielson  wrote:

> From: Magnus Danielson 
> Subject: Re: [time-nuts] Thermal insulation choice?
> To: time-nuts@febo.com
> Received: Friday, January 6, 2012, 6:10 PM
> Rick,
> 
> On 01/06/2012 10:14 PM, Rick Karlquist wrote:
> > John Ackermann N8UR wrote:
> >> I am looking for a readily available (from Home
> Depot or other local
> >> source) insulating material to use in a chassis
> that's housing a
> >> sensitive OCXO.  My goal is just to slow down
> any external thermal
> >> transients so the oven loop has time to react
> gracefully.
> > 
> > Before making this into a science project, consider
> this data
> > point:  We converted the oscillator in a 10811 to
> run in mode
> > B at 10.95 MHz.  The tempco in mode B is about 30
> ppm per degree
> > C.  Needless to say, the converted 10811 was
> extremely sensitive
> > to crystal temperature.  I could wave my hands
> around it and notice
> > the temperature change from the air currents. 
> However, simply
> > putting the 10811 into a small empty cardboard box
> completely
> > solved this problem.  No rocket science
> necessary.  So in the
> > short term, this simple box was like a double
> oven.  Of course,
> > in the long run, the 10811 thermal gain is only 1000
> or so and
> > you can see the effect of the HVAC shutting down at
> 7PM, etc.
> 
> This is essentially what I've found quite useful at many
> times, quick air fluctuations affects crystals pretty good
> but just blocking the air helps to slow down things.
> Long-term creeps through but is not on the same scale.
> 
> A large enough cardboard box will leak over-temperature
> such that the oven keeps working.
> 
> Cheers,
> Magnus
> 
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Re: [time-nuts] Thermal insulation choice?

[Magnus Danielson]

Rick,

On 01/06/2012 10:14 PM, Rick Karlquist wrote:

John Ackermann N8UR wrote:

I am looking for a readily available (from Home Depot or other local
source) insulating material to use in a chassis that's housing a
sensitive OCXO.  My goal is just to slow down any external thermal
transients so the oven loop has time to react gracefully.


Before making this into a science project, consider this data
point:  We converted the oscillator in a 10811 to run in mode
B at 10.95 MHz.  The tempco in mode B is about 30 ppm per degree
C.  Needless to say, the converted 10811 was extremely sensitive
to crystal temperature.  I could wave my hands around it and notice
the temperature change from the air currents.  However, simply
putting the 10811 into a small empty cardboard box completely
solved this problem.  No rocket science necessary.  So in the
short term, this simple box was like a double oven.  Of course,
in the long run, the 10811 thermal gain is only 1000 or so and
you can see the effect of the HVAC shutting down at 7PM, etc.


This is essentially what I've found quite useful at many times, quick 
air fluctuations affects crystals pretty good but just blocking the air 
helps to slow down things. Long-term creeps through but is not on the 
same scale.


A large enough cardboard box will leak over-temperature such that the 
oven keeps working.


Cheers,
Magnus

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Re: [time-nuts] Thermal insulation choice?

[Rick Karlquist]

Bob Camp wrote:
> Hi
>
> A metal shell inside a metal shell pretty well takes care of everything.
> Gradients, transients, drafts, what ever. You don't need super thick
> stuff.
> Bud chassis, Hammond boxes, copper pipe, PC board material, or soldered
> brass flashing all will do the trick.

We also tried mounting the modified 10811 in Hammond metal box.
Initially, we mounted the 10811 to the box using the
two standoffs that come with the 10811.  However, this
degraded the performance somewhat.  We removed these and
had the 10811 supported mechanically only by the edge
connector.  With that change, it was as good as the cardboard
box.  Remember that my modified 10811 is orders of magnitude
more sensitive that an ordinary oscillator, so if I don't see
a change, you definitely won't.

During E1938A development, we compared foam to still air.
We could see no difference.  It's just an implementation choice.

Rick Karlquist
N6RK


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Re: [time-nuts] Thermal insulation choice?

[Chris Albertson]

I'm planning to do it a little different.  I'll mount the FE5680 on a
heat sink and put that inside a metal box.  The I drill a hole in the
center of the heat sink and epoxy in a temperature sensor.  These
produce a voltage proportional to temperature and will control a small
fan.   The moving air will be in the lower part of the box separate
from the Rb oscillator


Once for another project I use  a TEC (aka Peltier Device)  The
peltier did the fine tuning.  They are not hard to use at all.  But
you need a few amps of DC current and a controller.   You can get to
0.1C this way.

-- 

Chris Albertson
Redondo Beach, California

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Re: [time-nuts] Thermal insulation choice?

[phil]

  My goal is just to slow down any external thermal
transients so the oven loop has time to react gracefully.

Are you sure it is not thermal mass that needs to be increased and  
not just insulation?


Phil

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Re: [time-nuts] Thermal insulation choice?

[Jim Lux]

On 1/6/12 11:39 AM, John Ackermann N8UR wrote:

I am looking for a readily available (from Home Depot or other local
source) insulating material to use in a chassis that's housing a
sensitive OCXO. My goal is just to slow down any external thermal
transients so the oven loop has time to react gracefully.

I'm thinking of something in sheet form that I could glue to the inside
bottom and side of the metal chassis. The trimmed sheet sizes will each
probably end up being around 4 x 8 inches. I have enough clearance for a
thickness of a half inch or so. I'd like to avoid a bat material as that
would be hard to mount neatly.

Long lifetime (ie, not getting all crumbly after a few years) is
important as I don't expect this oscillator to get cold until I do.

Any suggestions of a material to look for?



There are a variety of foams available. Expanded Polystyrene (EPS) foam 
(styrofoam) is one,and readily available, but typically fairly low 
density (sort of like big cottage cheese blobs). Also called "beadboard" 
(which name is obvious if you've seen degraded styrofoam icechests). 
It's got tiny passages which let water migrate through, so in commercial 
insulation, you need impermeable face sheets.


Extruded Polystyrene foam (aka XPS or XEPS) is blue or pink board.  It's 
what's used in construction a lot. It's a higher density (in a kg/liter 
sense) than EPS with more uniform smaller bubbles.  Easily sawed, 
sanded, etc. (an electric carving knife works great).


Polyisocyanurate and Polyurethane.  Polyisocyanurate is the stuff with a 
foil backing layer.


For the same thickness, the latter foams have a higher R-value (maybe 
50% higher).



Lowes has insulfoam R-tech 1"x2'x4' for $3 according to the web (with 
poly, not foil, face sheets) .  That's a expanded polystyrene.


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Re: [time-nuts] Thermal insulation choice?

[Tom Van Baak]

I am looking for a readily available (from Home Depot or other local 
source) insulating material to use in a chassis that's housing a 
sensitive OCXO.  My goal is just to slow down any external thermal 
transients so the oven loop has time to react gracefully.


Hi John,

Once I used several inch thick polystyrene sheet from Home Depot
for this very purpose, sealed it up all nice with tiny holes for the
power and RF wires. It turns out I nearly burned out the oscillator
because the insulation was so good. The temperature stabilized
somewhere between the crystal set point and the melting point of
solder.

So the lesson is good insulation is not necessarily what you want.
How many watts does your OCXO put out?

What I did instead was to buy a bunch of cement paving blocks
from Home Depot and made an air-tight sarcophagus (Egypt or
Chernobyl-style). Lots of thermal mass.

This was all placed on the concrete basement floor to reduce the
effects of vibration and shock on the oscillator; something else
you may want to consider for best long-term performance.

/tvb


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Re: [time-nuts] Thermal insulation choice?

[Bob Camp]

Hi

A metal shell inside a metal shell pretty well takes care of everything.
Gradients, transients, drafts, what ever. You don't need super thick stuff.
Bud chassis, Hammond boxes, copper pipe, PC board material, or soldered
brass flashing all will do the trick.

Simply tossing a fluffy towel over the unit works amazingly well if drafts
are the only real concern. 

Bob

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Rick Karlquist
Sent: Friday, January 06, 2012 4:15 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thermal insulation choice?

John Ackermann N8UR wrote:
> I am looking for a readily available (from Home Depot or other local
> source) insulating material to use in a chassis that's housing a
> sensitive OCXO.  My goal is just to slow down any external thermal
> transients so the oven loop has time to react gracefully.

Before making this into a science project, consider this data
point:  We converted the oscillator in a 10811 to run in mode
B at 10.95 MHz.  The tempco in mode B is about 30 ppm per degree
C.  Needless to say, the converted 10811 was extremely sensitive
to crystal temperature.  I could wave my hands around it and notice
the temperature change from the air currents.  However, simply
putting the 10811 into a small empty cardboard box completely
solved this problem.  No rocket science necessary.  So in the
short term, this simple box was like a double oven.  Of course,
in the long run, the 10811 thermal gain is only 1000 or so and
you can see the effect of the HVAC shutting down at 7PM, etc.

Rick Karlquist
N6RK


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Re: [time-nuts] Thermal insulation choice?

[David]

On Fri, 06 Jan 2012 16:33:19 -0500, John Ackermann N8UR 
wrote:

>On 1/6/2012 4:14 PM, Rick Karlquist wrote:
>
>> Before making this into a science project, consider this data
>> point:  We converted the oscillator in a 10811 to run in mode
>> B at 10.95 MHz.  The tempco in mode B is about 30 ppm per degree
>> C.  Needless to say, the converted 10811 was extremely sensitive
>> to crystal temperature.  I could wave my hands around it and notice
>> the temperature change from the air currents.  However, simply
>> putting the 10811 into a small empty cardboard box completely
>> solved this problem.  No rocket science necessary.  So in the
>> short term, this simple box was like a double oven.  Of course,
>> in the long run, the 10811 thermal gain is only 1000 or so and
>> you can see the effect of the HVAC shutting down at 7PM, etc.
>
>That's interesting, Rick.  I was also thinking that just still air was 
>most of the battle, but since I have the opportunity to do it "right" 
>within reason and this is a fairly major project, I thought that adding 
>some additional thermal isolation couldn't hurt, so why not? 
>(time-nuttery, etc.)

Still air certainly matters for thermocouple effects which can be
difficult to distinguish from 1/f noise but that is what Dixie cups
are for.  I have seen voltage noise improvements of more than 10 times
in some cases but I am not sure how that would apply to the voltage
control signal of an OCXO or the OCXO itself yet.  There must be some
improvement to be gained since double oven OCXOs do exist.

Like you say, the added insulation can not hurt.  I suspect it would
be more effective either mounted directly around the OCXO (probably
difficult) where the surface area would be smaller or mounted on the
outside of the enclosure (impractical) so the added thermal mass of
the enclosure itself would buffer the temperature changes.  The inside
of the enclosure seems to be an easy compromise and would dampen
convection.

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Re: [time-nuts] Thermal insulation choice?

[lists]

I don't see how the foil is useful here. The metal box takes care of radiation. 

-Original Message-
From: Graham / KE9H 
Sender: time-nuts-boun...@febo.com
Date: Fri, 06 Jan 2012 14:26:46 
To: Discussion of precise time and frequency measurement
Reply-To: Discussion of precise time and frequency measurement

Subject: Re: [time-nuts] Thermal insulation choice?

John:

The solution that will last longer than you will, is alternating
layers of aluminum foil (kitchen variety) and (dry) fiberglass cloth
(sold as "roven woven" anywhere they sell fiberglass supplies,
looks like white cloth, you can cut with scissors.)
Good to cryogenic temperatures, no crumbling mechanisms like
foams. Just seal the edges of the stackup with tape, so air can not
move in and out of the stack by convection.

--- Graham / KE9H

==
On 1/6/2012 1:39 PM, John Ackermann N8UR wrote:
> I am looking for a readily available (from Home Depot or other local 
> source) insulating material to use in a chassis that's housing a 
> sensitive OCXO.  My goal is just to slow down any external thermal 
> transients so the oven loop has time to react gracefully.
>
> I'm thinking of something in sheet form that I could glue to the 
> inside bottom and side of the metal chassis.  The trimmed sheet sizes 
> will each probably end up being around 4 x 8 inches.  I have enough 
> clearance for a thickness of a half inch or so.  I'd like to avoid a 
> bat material as that would be hard to mount neatly.
>
> Long lifetime (ie, not getting all crumbly after a few years) is 
> important as I don't expect this oscillator to get cold until I do.
>
> Any suggestions of a material to look for?
>
> Thanks,
>
> John
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
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Re: [time-nuts] Thermal insulation choice?

[John Ackermann N8UR]

On 1/6/2012 4:14 PM, Rick Karlquist wrote:


Before making this into a science project, consider this data
point:  We converted the oscillator in a 10811 to run in mode
B at 10.95 MHz.  The tempco in mode B is about 30 ppm per degree
C.  Needless to say, the converted 10811 was extremely sensitive
to crystal temperature.  I could wave my hands around it and notice
the temperature change from the air currents.  However, simply
putting the 10811 into a small empty cardboard box completely
solved this problem.  No rocket science necessary.  So in the
short term, this simple box was like a double oven.  Of course,
in the long run, the 10811 thermal gain is only 1000 or so and
you can see the effect of the HVAC shutting down at 7PM, etc.


That's interesting, Rick.  I was also thinking that just still air was 
most of the battle, but since I have the opportunity to do it "right" 
within reason and this is a fairly major project, I thought that adding 
some additional thermal isolation couldn't hurt, so why not? 
(time-nuttery, etc.)


John

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Re: [time-nuts] Thermal insulation choice?

[Rick Karlquist]

John Ackermann N8UR wrote:
> I am looking for a readily available (from Home Depot or other local
> source) insulating material to use in a chassis that's housing a
> sensitive OCXO.  My goal is just to slow down any external thermal
> transients so the oven loop has time to react gracefully.

Before making this into a science project, consider this data
point:  We converted the oscillator in a 10811 to run in mode
B at 10.95 MHz.  The tempco in mode B is about 30 ppm per degree
C.  Needless to say, the converted 10811 was extremely sensitive
to crystal temperature.  I could wave my hands around it and notice
the temperature change from the air currents.  However, simply
putting the 10811 into a small empty cardboard box completely
solved this problem.  No rocket science necessary.  So in the
short term, this simple box was like a double oven.  Of course,
in the long run, the 10811 thermal gain is only 1000 or so and
you can see the effect of the HVAC shutting down at 7PM, etc.

Rick Karlquist
N6RK


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Re: [time-nuts] Thermal insulation choice?

[David]

I completely forgot about those two.  I have a good local hobby shop
with large pieces of balsa wood but I suspect it would be more
expensive than good quality expanded polystyrene bead sheet.  I will
have to check out foam board next time.  Both would be more difficult
to cut without a hot wire knife.

On Fri, 6 Jan 2012 15:21:48 -0500, "jmfranke" 
wrote:

>Balsa wood is good and is readily available from Hobby Shops. Or Gator board 
>(paper laminated on foam) also called foam board from Art's and Craft 
>stores.
>
>John  WA4WDL
>
>--
>From: "John Ackermann N8UR" 
>Sent: Friday, January 06, 2012 2:39 PM
>To: "Discussion of precise time and frequency measurement" 
>
>Subject: [time-nuts] Thermal insulation choice?
>
>> I am looking for a readily available (from Home Depot or other local 
>> source) insulating material to use in a chassis that's housing a sensitive 
>> OCXO.  My goal is just to slow down any external thermal transients so the 
>> oven loop has time to react gracefully.
>>
>> I'm thinking of something in sheet form that I could glue to the inside 
>> bottom and side of the metal chassis.  The trimmed sheet sizes will each 
>> probably end up being around 4 x 8 inches.  I have enough clearance for a 
>> thickness of a half inch or so.  I'd like to avoid a bat material as that 
>> would be hard to mount neatly.
>>
>> Long lifetime (ie, not getting all crumbly after a few years) is important 
>> as I don't expect this oscillator to get cold until I do.
>>
>> Any suggestions of a material to look for?
>>
>> Thanks,
>>
>> John
>>
>> ___
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>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
>
>
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Re: [time-nuts] Thermal insulation choice?

[Joe Gwinn]

I wonder if Balsa wood would be suitable?  Like polystyrene foam, 
only stronger and easy to glue.


I think commercial OXCOs use polystyrene foam that's expanded to 
shape, which is fine in production, but making the mold for one use 
is not efficient.  However, there are lots of expand-in-place 
urethane foams available from building supply houses.


Joe Gwinn

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Re: [time-nuts] Thermal insulation choice?

[John Ackermann N8UR]

On 1/6/2012 2:54 PM, Chris Albertson wrote:


Can you put something that uses power inside an insulated box? I'd
think it might over heat.


Thanks, all, for the numerous and helpful responses!

To answer Chris' question, putting insulation all the way around the 
oscillator might cause problems as you suggest.  I'm only planning to 
put the insulation on the two surfaces that are only a couple of inches 
from the OCXO (chassis bottom and one side), and maybe on the top cover. 
 There will be several inches of interior space on the other sides; 
enough, I hope, to smooth any thermals coming from the other exterior walls.


John

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[time-nuts] Thermal insulation choice?

[ed breya]

Yes - especially don't rub any cats on it or it may damage some electronics.

BTW for machining, any fine-toothed saw blade works well for straight 
cuts. A metal hacksaw blade is usually stiff enough by itself to make 
accurate, clean finish cuts on "quality" styrofoam. For drilling 
round holes use paper drills - you can make your own custom sizes 
from any soft metal tubing with a chamfered slicing rim formed by 
running a larger drill bit into the end until the rim is sharp.


Ed


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Re: [time-nuts] Thermal insulation choice?

[Graham / KE9H]

John:

The solution that will last longer than you will, is alternating
layers of aluminum foil (kitchen variety) and (dry) fiberglass cloth
(sold as "roven woven" anywhere they sell fiberglass supplies,
looks like white cloth, you can cut with scissors.)
Good to cryogenic temperatures, no crumbling mechanisms like
foams. Just seal the edges of the stackup with tape, so air can not
move in and out of the stack by convection.

--- Graham / KE9H

==
On 1/6/2012 1:39 PM, John Ackermann N8UR wrote:
I am looking for a readily available (from Home Depot or other local 
source) insulating material to use in a chassis that's housing a 
sensitive OCXO.  My goal is just to slow down any external thermal 
transients so the oven loop has time to react gracefully.


I'm thinking of something in sheet form that I could glue to the 
inside bottom and side of the metal chassis.  The trimmed sheet sizes 
will each probably end up being around 4 x 8 inches.  I have enough 
clearance for a thickness of a half inch or so.  I'd like to avoid a 
bat material as that would be hard to mount neatly.


Long lifetime (ie, not getting all crumbly after a few years) is 
important as I don't expect this oscillator to get cold until I do.


Any suggestions of a material to look for?

Thanks,

John

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Re: [time-nuts] Thermal insulation choice?

[jmfranke]

Balsa wood is good and is readily available from Hobby Shops. Or Gator board 
(paper laminated on foam) also called foam board from Art's and Craft 
stores.


John  WA4WDL

--
From: "John Ackermann N8UR" 
Sent: Friday, January 06, 2012 2:39 PM
To: "Discussion of precise time and frequency measurement" 


Subject: [time-nuts] Thermal insulation choice?

I am looking for a readily available (from Home Depot or other local 
source) insulating material to use in a chassis that's housing a sensitive 
OCXO.  My goal is just to slow down any external thermal transients so the 
oven loop has time to react gracefully.


I'm thinking of something in sheet form that I could glue to the inside 
bottom and side of the metal chassis.  The trimmed sheet sizes will each 
probably end up being around 4 x 8 inches.  I have enough clearance for a 
thickness of a half inch or so.  I'd like to avoid a bat material as that 
would be hard to mount neatly.


Long lifetime (ie, not getting all crumbly after a few years) is important 
as I don't expect this oscillator to get cold until I do.


Any suggestions of a material to look for?

Thanks,

John

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Re: [time-nuts] Thermal insulation choice?

[Poul-Henning Kamp]

In message <201201062016.q06kg3vj016...@mail32c40.carrierzone.com>, ed breya wr
ites:

>That stuff at Home Depot is the way to go. You can use regular 
>styrofoam [...]

Just remember that clean styrofoam is great at static electricity...


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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[time-nuts] Thermal insulation choice?

[ed breya]

That stuff at Home Depot is the way to go. You can use regular 
styrofoam from coolers and cold shipping boxes, but there are a lot 
of grades, ranging from crappy to great, and some are even 
biodegradable - not good for this application. The construction types 
are made to last, but also may have fire retardants and preservatives 
that could cause problems. I think the smallest standard sheets will 
be 4' x 8' in the US, in various thicknesses. If you are near any 
construction sites you can sometimes find cutoffs for free in the 
dumpsters - perfect for small projects. I recently scrounged a few 
pieces of the pinkish type - very strong, good stuff, with fine foam, 
it machines nicely, and seems to be chemically inert.


Ed


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Re: [time-nuts] Thermal insulation choice?

[Eric Garner]

I mostly like it because it's easy to use, and _doesn't_ insulate too
well. you can add/subtract what you like to find the performance you
are happy with.

it also has the advantage that it doesn't degrade into garbage like
some closed cell foams do, and is really easy to work with

-Eric

On Fri, Jan 6, 2012 at 12:00 PM, Poul-Henning Kamp  wrote:
> In message 
> 
> , Eric Garner writes:
>
>>I've used "Reflectix" duct insulation in applications like this. it's
>>essentially bubble wrap with a reflective layer, you can layer it
>>pretty easily to add/subtract from the insulation value. plus is comes
>>in small, cheap rolls
>
> Be aware that most of the (claimed!) insulation in these kind of
> materials come from the radiation reflection and is contingent on
> there being a huge-ish temperature difference between the two sides
> *and* that the material is not in contact surfaces, certainly not
> on the hot side.
>
> Where this material really wins is under roofs, which can become 100C or
> warmer, while you want to maintain 20C inside the house.
>
> They suck if you have 20C on one side and 32C on the other.
>
> Compared to bubble-wrap, it is unlikely to perform any different
> in an application like this, because of the low temperature differences.
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> p...@freebsd.org         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
>
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-- 
--Eric
_
Eric Garner

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Re: [time-nuts] Thermal insulation choice?

[George Dubovsky]

There is a closed-cell foam,  aluminum foil clad on one or both sides that
is used as HVAC ductwork - they score it with a knife, and fold it to size
- that should withstand the temperatures you are contemplating, for a long
time. I have seen some approximately 1/2 to 5/8 inch, and the quantities
you need should be available free from your local HVAC shop.

73,

geo - n4ua

On Fri, Jan 6, 2012 at 2:39 PM, John Ackermann N8UR  wrote:

> I am looking for a readily available (from Home Depot or other local
> source) insulating material to use in a chassis that's housing a sensitive
> OCXO.  My goal is just to slow down any external thermal transients so the
> oven loop has time to react gracefully.
>
> I'm thinking of something in sheet form that I could glue to the inside
> bottom and side of the metal chassis.  The trimmed sheet sizes will each
> probably end up being around 4 x 8 inches.  I have enough clearance for a
> thickness of a half inch or so.  I'd like to avoid a bat material as that
> would be hard to mount neatly.
>
> Long lifetime (ie, not getting all crumbly after a few years) is important
> as I don't expect this oscillator to get cold until I do.
>
> Any suggestions of a material to look for?
>
> Thanks,
>
> John
>
> __**_
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/**
> mailman/listinfo/time-nuts
> and follow the instructions there.
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Re: [time-nuts] Thermal insulation choice?

[lists]

Heat is transferred via convection, radiation, and conduction. A sealed metal 
box takes care of radiation and convection, so as you correctly point out, 
conduction is the next frontier. 

I'd say foam board , but I don't know specifically what kind of foam. 

--Original Message--
From: John Ackermann N8UR
Sender: time-nuts-boun...@febo.com
To: Discussion of precise time and frequency measurement
ReplyTo: Discussion of precise time and frequency measurement
Subject: [time-nuts] Thermal insulation choice?
Sent: Jan 6, 2012 11:39 AM

I am looking for a readily available (from Home Depot or other local 
source) insulating material to use in a chassis that's housing a 
sensitive OCXO.  My goal is just to slow down any external thermal 
transients so the oven loop has time to react gracefully.

I'm thinking of something in sheet form that I could glue to the inside 
bottom and side of the metal chassis.  The trimmed sheet sizes will each 
probably end up being around 4 x 8 inches.  I have enough clearance for 
a thickness of a half inch or so.  I'd like to avoid a bat material as 
that would be hard to mount neatly.

Long lifetime (ie, not getting all crumbly after a few years) is 
important as I don't expect this oscillator to get cold until I do.

Any suggestions of a material to look for?

Thanks,

John

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Re: [time-nuts] Thermal insulation choice?

[Brooke Clarke]

Hi John:

Michaels has Styrofoam, hot wire cutter and glue.

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Brooke4Congress.html


John Ackermann N8UR wrote:
I am looking for a readily available (from Home Depot or other local source) insulating material to use in a chassis 
that's housing a sensitive OCXO.  My goal is just to slow down any external thermal transients so the oven loop has 
time to react gracefully.


I'm thinking of something in sheet form that I could glue to the inside bottom and side of the metal chassis.  The 
trimmed sheet sizes will each probably end up being around 4 x 8 inches.  I have enough clearance for a thickness of a 
half inch or so.  I'd like to avoid a bat material as that would be hard to mount neatly.


Long lifetime (ie, not getting all crumbly after a few years) is important as I don't expect this oscillator to get 
cold until I do.


Any suggestions of a material to look for?

Thanks,

John

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Re: [time-nuts] Thermal insulation choice?

[Poul-Henning Kamp]

In message 
, Eric Garner writes:

>I've used "Reflectix" duct insulation in applications like this. it's
>essentially bubble wrap with a reflective layer, you can layer it
>pretty easily to add/subtract from the insulation value. plus is comes
>in small, cheap rolls

Be aware that most of the (claimed!) insulation in these kind of
materials come from the radiation reflection and is contingent on
there being a huge-ish temperature difference between the two sides
*and* that the material is not in contact surfaces, certainly not
on the hot side.

Where this material really wins is under roofs, which can become 100C or
warmer, while you want to maintain 20C inside the house.

They suck if you have 20C on one side and 32C on the other.

Compared to bubble-wrap, it is unlikely to perform any different
in an application like this, because of the low temperature differences.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] Thermal insulation choice?

[Chris Albertson]

They sell 4x8 foot sheets of aluminum foil faced foam insulation at
Home Depot.  The thinnest is maybe just under one inch.  Thickest is
about 4" thick.  The other thing is just to make the cabinet out of
wood rather then sheet metal.  Finally in stores that sell camping
equipment you can get roll up pads that are used under sleeping bags.
This stuff is very durable and is designed for insulation.  It will be
a closed cell flexible foam.  I use this stuff inside Pelican type
cases and you can attach it with contact cement.

Can you put something that uses power inside an insulated box? I'd
think it might over heat.



On Fri, Jan 6, 2012 at 11:39 AM, John Ackermann N8UR  wrote:
> I am looking for a readily available (from Home Depot or other local source)
> insulating material to use in a chassis that's housing a sensitive OCXO.  My
> goal is just to slow down any external thermal transients so the oven loop
> has time to react gracefully.
>
> I'm thinking of something in sheet form that I could glue to the inside
> bottom and side of the metal chassis.  The trimmed sheet sizes will each
> probably end up being around 4 x 8 inches.  I have enough clearance for a
> thickness of a half inch or so.  I'd like to avoid a bat material as that
> would be hard to mount neatly.
>
> Long lifetime (ie, not getting all crumbly after a few years) is important
> as I don't expect this oscillator to get cold until I do.
>
> Any suggestions of a material to look for?
>
> Thanks,
>
> John
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
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> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



-- 

Chris Albertson
Redondo Beach, California

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Re: [time-nuts] Thermal insulation choice?

[Eric Garner]

I've used "Reflectix" duct insulation in applications like this. it's
essentially bubble wrap with a reflective layer, you can layer it
pretty easily to add/subtract from the insulation value. plus is comes
in small, cheap rolls

here is a link to the amazon item, but it's in most hardware stores too:
http://www.amazon.com/Reflectix-6X25-Foil-Insulation-Lpw0602506/dp/B000BQNYSI/ref=sr_1_5?s=hi&ie=UTF8&qid=1325879277&sr=1-5


-Eric

On Fri, Jan 6, 2012 at 11:39 AM, John Ackermann N8UR  wrote:
>
> I am looking for a readily available (from Home Depot or other local source) 
> insulating material to use in a chassis that's housing a sensitive OCXO.  My 
> goal is just to slow down any external thermal transients so the oven loop 
> has time to react gracefully.
>
> I'm thinking of something in sheet form that I could glue to the inside 
> bottom and side of the metal chassis.  The trimmed sheet sizes will each 
> probably end up being around 4 x 8 inches.  I have enough clearance for a 
> thickness of a half inch or so.  I'd like to avoid a bat material as that 
> would be hard to mount neatly.
>
> Long lifetime (ie, not getting all crumbly after a few years) is important as 
> I don't expect this oscillator to get cold until I do.
>
> Any suggestions of a material to look for?
>
> Thanks,
>
> John
>
> ___
> time-nuts mailing list -- time-nuts@febo.com
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--
--Eric
_
Eric Garner

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Re: [time-nuts] Thermal insulation choice?

[David]

I just did this search for similar application.  The cheapest stuff
they have is expanded polystyrene bead sheet which is easy enough to
work with but may be too thick (3/4") or not as durable as you want. I
made a hot wire cutting element for my Weller soldering gun out of a
length of 10 gauge copper wire to cut out and trim the shapes I
wanted.

They also have a bunch of thinner (about 3/8") closed cell insulating
foams (I didn't check but would guess real Styrofoam) which are
probably more than durable enough but more expensive because of the
sheet size.

On Fri, 06 Jan 2012 14:39:05 -0500, John Ackermann N8UR 
wrote:

>I am looking for a readily available (from Home Depot or other local 
>source) insulating material to use in a chassis that's housing a 
>sensitive OCXO.  My goal is just to slow down any external thermal 
>transients so the oven loop has time to react gracefully.
>
>I'm thinking of something in sheet form that I could glue to the inside 
>bottom and side of the metal chassis.  The trimmed sheet sizes will each 
>probably end up being around 4 x 8 inches.  I have enough clearance for 
>a thickness of a half inch or so.  I'd like to avoid a bat material as 
>that would be hard to mount neatly.
>
>Long lifetime (ie, not getting all crumbly after a few years) is 
>important as I don't expect this oscillator to get cold until I do.
>
>Any suggestions of a material to look for?
>
>Thanks,
>
>John

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Re: [time-nuts] Thermal insulation choice?

[Poul-Henning Kamp]

In message <4f074dd9.5070...@febo.com>, John Ackermann N8UR writes:

>I am looking for a readily available (from Home Depot or other local 
>source) insulating material to use in a chassis that's housing a 
>sensitive OCXO.  My goal is just to slow down any external thermal 
>transients so the oven loop has time to react gracefully.

>I'm thinking of something in sheet form that I could glue to the inside 
>bottom and side of the metal chassis.  The trimmed sheet sizes will each 
>probably end up being around 4 x 8 inches.

Buy a foam camping-matress of the kind you put under your sleeping bag ?

They're cheap, and usually impregnated against anything that might
conceiveably try to eat them.


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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[time-nuts] Thermal insulation choice?

[John Ackermann N8UR]

I am looking for a readily available (from Home Depot or other local 
source) insulating material to use in a chassis that's housing a 
sensitive OCXO.  My goal is just to slow down any external thermal 
transients so the oven loop has time to react gracefully.


I'm thinking of something in sheet form that I could glue to the inside 
bottom and side of the metal chassis.  The trimmed sheet sizes will each 
probably end up being around 4 x 8 inches.  I have enough clearance for 
a thickness of a half inch or so.  I'd like to avoid a bat material as 
that would be hard to mount neatly.


Long lifetime (ie, not getting all crumbly after a few years) is 
important as I don't expect this oscillator to get cold until I do.


Any suggestions of a material to look for?

Thanks,

John

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