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Purging a scope

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Purging a scope

Postby hungryrob » Mon Jul 27, 2009 11:41 pm

I treid purging my old ZRAK scope tonight. Didn't have any nitrogen so I used CO2 from an airgun cartridge.. Emptied it into a large square box and assembled cleaned scope inside the box...

I'll let y'all know then next time it rains if I get misted up :grin:

What's my chances?
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Re: Purging a scope

Postby Beer Hunter » Tue Jul 28, 2009 12:08 am

Isn't CO2 used to create fog at lower temperatures - e.g. dry ice?

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Re: Purging a scope

Postby Born Again » Tue Jul 28, 2009 12:32 am

Some performance bike tyre fitters offer a dry nitrogen fill. Worth a look.
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Re: Purging a scope

Postby RichardH » Tue Jul 28, 2009 12:45 am

hungryrob wrote:I treid purging my old ZRAK scope tonight. Didn't have any nitrogen so I used CO2 from an airgun cartridge.. Emptied it into a large square box and assembled cleaned scope inside the box...

I'll let y'all know then next time it rains if I get misted up :grin:

What's my chances?


I predict not great :grin:

CO2 and Nitrogen are very different, still it doest sound like an expensive scope, think of it as one of those snowstorm domes..........

People pay a fortune for those :grin:

Rich :grin:
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Re: Purging a scope

Postby jeff » Tue Jul 28, 2009 1:58 am

There must be a reason they don't use nice cheap CO2.....but I am interested in the results. :grin:
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Re: Purging a scope

Postby humperdingle » Tue Jul 28, 2009 7:18 am

hungryrob wrote:.. Emptied it into a large square box and assembled cleaned scope inside the box...



What lengths will you go to, to achieve the perfect result?


Fab! :grin:
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Re: Purging a scope

Postby URX » Tue Jul 28, 2009 8:01 am

I've heard of this being done before.
Basically the co2 is used to displace moisture laden air ... the theory being that the co2 is drier.
Nitroge or argon or similar with nil or v low moisture content would be better than room air.
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Re: Purging a scope

Postby hungryrob » Tue Jul 28, 2009 8:18 am

Born Again wrote:Some performance bike tyre fitters offer a dry nitrogen fill. Worth a look.

Sounds like a good idea!

Must look for them locally :)
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Re: Purging a scope

Postby jeff » Tue Jul 28, 2009 8:35 am

hungryrob wrote:
Born Again wrote:Some performance bike tyre fitters offer a dry nitrogen fill. Worth a look.

Sounds like a good idea!

Must look for them locally :)


You'll get Argon from a decent technical-biased dive shop (Especially up there in dry suit land) too, but I have no clue if it's heavier than air, or better/worse than CO2 or Nitrogen.

If you really wanted to get silly, you could probably make yourself a box with rubber gloves sealed into it (Like for grit blasting, etc.) and have it pressurised off a cylinder enough to displace air and then do the scope back up while inside it....
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Re: Purging a scope

Postby Fenrir » Tue Jul 28, 2009 8:48 am

Just goes to show that there is always room for reducing your CO2 emmisions.
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Re: Purging a scope

Postby jeff » Tue Jul 28, 2009 9:30 am

Fenrir wrote:Just goes to show that there is always room for reducing your CO2 emmisions.


With Robbie and Bruno sharing a house, I doubt the scope will be the main source.... :grin:
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Re: Purging a scope

Postby Beer Hunter » Tue Jul 28, 2009 9:36 am

jeff wrote:
Fenrir wrote:Just goes to show that there is always room for reducing your CO2 emmisions.


With Robbie and Bruno sharing a house, I doubt the scope will be the main source.... :grin:

I guess he could use methane purging :D

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Re: Purging a scope

Postby The_Dogge » Tue Jul 28, 2009 10:42 am

jeff wrote:
hungryrob wrote:
Born Again wrote:Some performance bike tyre fitters offer a dry nitrogen fill. Worth a look.

Sounds like a good idea!

Must look for them locally :)


You'll get Argon from a decent technical-biased dive shop (Especially up there in dry suit land) too, but I have no clue if it's heavier than air, or better/worse than CO2 or Nitrogen.

If you really wanted to get silly, you could probably make yourself a box with rubber gloves sealed into it (Like for grit blasting, etc.) and have it pressurised off a cylinder enough to displace air and then do the scope back up while inside it....

Hmmm, could a "sealed" box with plenty of dry air from a dive cylinder blown through it work? I dont think you need a fancy gas mix (though an oxygen free environment may make scope internals last longer I suppose) just a lack of water to condense out is what youre after isnt it?

Remember that argon and nitrogen are used commercially to gas poultry, and CO2 works too, it's just more unpleasant to be gassed with, so working with these gases isnt risk free, do so in a well ventilated area etc etc.
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Re: Purging a scope

Postby Born Again » Tue Jul 28, 2009 11:57 am

I think if I was trying to purge a scope I would fix a balloon full of nitrogen / argon over one end. Then carefully loosen the lenses either end until the balloon had deflated through the scope and nip them up again.
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Re: Purging a scope

Postby hungryrob » Tue Jul 28, 2009 12:04 pm

If I stick the scope in the freezer for five minutes, I suppose I'll find out if it has worked won't I??

I'm pretty confident it if full of dry CO2..
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