gel pack question (now with hombrew enclosure pics)

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outoftune
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gel pack question (now with hombrew enclosure pics)

Post by outoftune » Tue Nov 14, 2006 11:17 am

i just purchased some gel packs to be used for an enclosure i am building. they are medical type ones. the gel packs came in ziplock bags from the store and i was wondering if it would be ok to leave them in the ziplock bags when i put them in the enclosure? i am just a bit paranoid about them potentially leaking and thought that this would be some extra backup.

also, does anyone have any idea where i could get a few silica packs to put in to absorb moisture? can they be purchased somewhere?

EDIT: i have added some pics of an alleycat style enclosure using the Hammond DFL 1590 (recommended by justblair) and some 4X5" medical gel packs.
Last edited by outoftune on Wed Nov 15, 2006 2:03 pm, edited 1 time in total.

BillTodd
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Post by BillTodd » Tue Nov 14, 2006 2:14 pm

Medical gel packs are very well sealed (I have one in front of me, as I type). As i see it, the only reasons for them to leak is A) puncture or B) bursting due to over pressure (i.e. over heating).

Punctures can be avoided if you make sure the drive and box has no sharp points or edges (component pins solder joints etc.) .

Bursting is unlikely as long as there is plenty of room in the box (i.e. dont squash the lid shut )


Adding a sachet or two of silica gel would be a good idea. If you can't get it form the local DIY shop, ask at your local computer or white goods store - silica-gel bags are often included in packing material so they might have the odd one knocking about that they could give you. You can dry the gel crystals out in a warm electric oven (not gas - combustion generates moisture) or on a hot radiator.

outoftune
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Post by outoftune » Tue Nov 14, 2006 2:47 pm

thanks for the reply. ill check there for some silica packs.

another question, the only gel packs i was able to find were quite thick, 2 couldnt fit in my enclosure. i have thought of poking a tiny hole in the corner of one, draining some gel, and then sealing the pin hole with crazy glue or melting it, then tape it up. think this is a bad idea?

i plan to do lots of testing to make sure the pack wont leak before i put it in with the HD. if i do this i was going to keep this one in the plastic zip lock, just in case. i cant see why the plastice would cause any problems, the gel packs are made of plastic too....

BillTodd
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Post by BillTodd » Tue Nov 14, 2006 3:24 pm

i have thought of poking a tiny hole in the corner of one, draining some gel, and then sealing the pin hole with crazy glue or melting it, then tape it up. think this is a bad idea?
:)
I had exactly the same thought!

I seem to remember the thought process went something like; If I puncture the bag, I'll have a problem sealing it and throw away one of the main advantages of the product. If the med-pack is too big why don't I simply make a smaller one.

The homebrew ones (see http://www.silentpcreview.com/article682-page3.html) have worked well over the years, the tiny puncture was almost certainly caused by a piece of swarf or similar (probably picked up from the workbench).

Double bagging is an obvoius safe guard. I don't think the extra layer of plastic reduces their effectiveness much, the contact area is so large that the thermal resistance overall is low.

outoftune
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Post by outoftune » Tue Nov 14, 2006 4:42 pm

i just did the hole poke/drainage to two gel packs. i put them in an enclosure with a non running hd and am going to leave it over night to see if there are any leaks. it looks like this:

top to bottom:

enclosure lid
thin layer of foam
gel pack
HD
gel pack

both gel packs are in bags. i have sealed the puncture with crazy glue, let it set, then add a bit more crazy glue and put a piece of tape over that. then put it in a ziplock bag. the fit is fairly tight (nothing moves around, ive got some extra foam in there on the sides) but the gel packs are being squeezed too tightly.

think there is anything else i should do to the enclosure?

i will post back with my results and maybe some pics too. i wont be setting up the system these will be going in for a few weeks but this should work fine considering others previous experiences.

BillTodd
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Post by BillTodd » Wed Nov 15, 2006 1:30 am

leave it over night to see if there are any leaks.
A worth-while check (I left mine a year and a half :) )

If, as I suspect, the gel is methyl cellulose like my homebrews then they tend to self seal to a degree. As the water evaporates, the gel crystalises and seals the hole; It's just a pity the stuff is slightly corrosive.
enclosure lid
thin layer of foam
gel pack
HD
gel pack
Do you need the foam layer? It'll insulate the gel pack from the lid.

If the enclosure is mounted on either the long or short edges, the gel will flow down, expand the bag and fill the gaps between case and HDD.


I look forward to seeing the pictures.

outoftune
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Location: canada

Post by outoftune » Wed Nov 15, 2006 9:05 am

i thought of putting the foam in just to make sure it fits tight but you are right about it insulating it from the lid. ill make sure it has good contact. thanks.

outoftune
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Post by outoftune » Wed Nov 15, 2006 2:02 pm

here are some (kinda blurry)pics....

medical gel pack (purchased at drug store for $1.99 canadian): notice in the top left corner is where i made a tiny opening to drain out some of the gel. it has been sealed with crazy glue, then tape, then more crazy glue, then put in a ziplock bag.
Image

here is the enclosure (hammond 1590 DFL, recommended by forum member justblair, purchased from mouser for $20 canadian) with a gel pack in it and a bit of foam, no cables right now but we all know what those look like. also i have filed out a small notch for the cables to fit through.
Image

added the samsung HD.
Image

added another gelpack on top (the masking tape is holding the excess ziploc bag nice and tight).
Image

piece of foam for the top (not sure if i am going to go with this for sure, it helps things fit tightly but also inhibits the gel pack to box heat transfer. the top gel pack doesnt touch the box but its pretty close)
Image

with the lid on (those are extra screws taped to the enclosure so i dont lose them)
Image

i haven't put this in my system yet but will reply with some results concerning noise and temperatures. feel free to ask any questions.

BillTodd
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Post by BillTodd » Wed Nov 15, 2006 3:41 pm

Looks good to me :)

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