Author Topic: How to Refill a Scope with Nitrogen (Read 4093 times)

woodchukhntr · « **on:** December 25, 2009, 08:13:14 AM »

Does anyone know how to fill a scope with nitrogen? I was given a 2-7 X Cabella's scope that either leaked or somebody unscrewed the rear lens housing off enough to break the seal so air got inside. It is not under warranty because I am not the original owner and the warranty is not transferrable (I called them). I was thinking about taking it to a tire shop that fills tires with nitrogen and purging it with nitrogen while I screwed the housing back on. If it leaks afterwards it is no loss since I don't have anything invewsted and I can take it apart to see how it works.

Graybeard · « **Reply #1 on:** December 25, 2009, 10:08:11 PM »

YOU do not. You'll have to send it to a facility that works on optics. If it has been unsealed it will fog internally and is now for all practical purposes useless.

torpedoman · « **Reply #2 on:** December 26, 2009, 03:36:18 PM »

nitrogen is heavier than air all you need to do is check if the tire shop uses dry nitrogen (should be on bottle) if so open the scope up and hold it pointed down allow enough nitrogen to get in to displace all the atmosphere and screw it back together. salvaged several scopes that way when i had access to the nitrogen. (torpedoes are filled with dry nitrogen after repair)

john keyes · « **Reply #3 on:** December 26, 2009, 09:56:45 PM »

Quote from: Graybeard on December 25, 2009, 10:08:11 PM

If it has been unsealed it will fog internally and is now for all practical purposes useless.

I lost a deer sunday because of this. It has been very wet in the southeast as some of you may know. On this particular day it was nice and sunny..beautiful....but little did I know while 20' up in my climber that my little Weaver 6X (that I have been very proud of since I bought it for sixty bucks from a pawn shop a couple years ago) was full of condensation.

I had promised to get down at noon. At 1100 I said to myself what the heck am I still doing here, why not get down. But I told myself, no, stay till noon and then go. Sure enough at 11:15 here come the deer. Nice does with some young ones. I picked out the biggest one...could not find it. put the rifle down, picked up the binoculars....hmmm its right there... looked through the scope again...no deer...back to the binoculars...

repeated this scenario...later I saw all of the condensation in the scope....I think now the grey doe was blending in and the condensation was obscuring it...I could see the trees and the cut in the woods but the deer was invisible

so I promised myself I would chunk the scope ASAP but I'm still thinking I can dry it out so yes I'm still a dumba$$ whether I choose to believe it or not. talk about false economy.

but I have two bushnell banners on the way anyhow that will be pressed into service asap and I will throw away that leaking scope for sure.

Graybeard · « **Reply #4 on:** December 27, 2009, 03:06:08 AM »

Throw it away and get a new scope. Been there done that and it ain't worth the trouble.

Reverend Recoil · « **Reply #5 on:** December 28, 2009, 07:01:11 AM »

Never pay to have your tires filled with nitrogen. There is nothing to be gained. It's a scam.

charles p · « **Reply #6 on:** December 28, 2009, 09:25:11 AM »

I think the pneumatic wrenches used to change race car tires are driven off compressed nitrogen

ShadowMover · « **Reply #7 on:** December 28, 2009, 10:06:11 AM »

Let's try to get some facts here. First of all, Nitrogen is not heavier than air, it's lighter. It makes up 78% of the air with Oxygen at 21% making up most of the remainder. The atomic weight of N2 is 28 grams per mole and that of O2 is 32 grams per mole. The air mix is heavier than Nitrogen alone. I won't waste time with the math unless anyone wants to. Secondly, the reason it's put in scopes is to keep out that little trace of water vapor that causes the condensation or ice.

Argon is heavier than air with an atomic weight of 40 per mole. A mole is 6.022x10^23 atoms ( 6 with 23 zeros after it). This many atoms of any gas at normal temperatures and pressure will take up the same amount of volume of 22.4 liters, (About a 5 gallon bucket) So a mole of N2 will weight 28 grams, or about an ounce per 5 gallon bucket full, Oxygen about 32 grams, and CO2 about 44 grams.

Argon would work well in a scope too.

If it was my scope, I'd open it up and put it in a transparent plastic bag with two latex gloves taped onto either end. A bag like I get my newspaper in would be fine. I would attach a small 1/4 size hose to a tank of dry Nitrogen and flush the bag by letting a very slow stream of N2 flow into the bag. Duct tape will do the sealing job. Then put the scope and bag in a warm room and wrap it up in a heating pad while the N2 is very slowly flowing into the bag. Don't waste the N2 by flowing too fast, just enough to keep air from coming in. After a few hours put your hands in the gloves and put the scope together. The heated pad should vaporize any moisture, and the dry N2 should push it out of the bag.

Another low tech method would be to use the same bag trick, but put a container of Dry Out, Damprid, Damp Check, or freshly baked silica gel in the bag and put the scope in a warm end with a heating pad and leave the moisture absorbent in the other. Let it work for a few days and reassemble in the bag with the gloves you taped in. This method is cheaper and may introduce calcium chloride dust into the scope.

After reassembly let it come to room temperature and then put it in a fridge or freezer and see how it works. It sure beats throwing it out. If the scope gets all fogged up in the freezer, you can either repeat the procedure, being more careful and using more heat and time, or toss it.

I'm just a poor boy, and don't have all the money you guys do, so I try to work around some of the easier more obvious solutions. It sure is nice when it works out.

john keyes · « **Reply #8 on:** December 28, 2009, 11:15:44 AM »

so you are talking about purging the moisture out and refilling with dry, inert gas....

and I assume you screw the front eyepiece off to do all of this...

but don't you need some new gaskets or O-rings or something to seal it all up when you put it back together?

uh oh, my coffee has 1,3,7-trimethyl-xanthene in it...

ShadowMover · « **Reply #9 on:** December 28, 2009, 03:09:50 PM »

You have it exactly right on what I was talking about. I don't know how your scope comes apart. New gaskets or O rings would be a nice thing if you knew where to get them. If the old one was in one piece, I'd give it a real good looking over and wipe down with isopropyl alcohol. If they just took off one end of the scope and looked at it without breaking or nicking the O ring, maybe you can reuse it. I got the idea you knew how the thing got opened up. Some scope eyepiece adjustments have a very heavy silicone grease in their threads. Is the condensation on the front lens or the eyepiece, or both?

rex6666 · « **Reply #10 on:** December 29, 2009, 10:17:14 AM »

Quote from: Reverend Recoil on December 28, 2009, 07:01:11 AM

Never pay to have your tires filled with nitrogen. There is nothing to be gained. It's a scam.

Would you care to elaborate on this?
Since most all tire stores have it.

drdougrx · « **Reply #11 on:** December 29, 2009, 10:52:25 AM »

I just can't believe we're having this discussion. Ditch the scope and get another. You're asking for trouble.

Reverend Recoil · « **Reply #12 on:** December 29, 2009, 11:23:38 AM »

"Would you care to elaborate on this? Since most all tire stores have it."

Several claims are made of its benefit. All have been scientifically de-bunked. Do a Google search on nitrogen filled tires. Its all there.

Examples:

The nitrogen molecule is larger than the oxygen molecule so you will have less leakage. Yes there is a difference in molecular size but not much. You will never know the difference by checking tire pressure with a stem pressure gauge.

Nitrogen is inert so you will have no oxidation of the rubber or wheel material. What about the outside of the tire that is exposed to air? Besides, the air we breath is 79% nitrogen and it’s free. What will paying for another 21% do for your tires? Nothing.

There are a few other stupid claims but the best reason to pay money to have your tires filled with nitrogen is because Navy fighter jets and NASCAR racers have their tires filled with nitrogen. Wouldn’t it be cool to have the same gas filled in your tires as they do? Its your money.

The main reason Navy fighter jets and NASCAR racers fill their tires with nitrogen is one of convenience. In some cases a bottle of compressed nitrogen is easier to use where its needed than an air compressor, power supply, receiver vessel, air dryer, and oil separating system. Nitrogen may be slightly better than air for high temperature tire service but it will make no difference to the way we operate our vehicles.

ShadowMover · « **Reply #13 on:** December 29, 2009, 02:42:41 PM »

Quote from: drdougrx on December 29, 2009, 10:52:25 AM

I just can't believe we're having this discussion. Ditch the scope and get another. You're asking for trouble.

What's the problem? We can tell you don't approve of trying to fix a scope, but if it's not a critical component, why not? People who don't have a lot of money to spend can improve their standard of living, the standard of their toys, and actually learn something. Believe it or not, some people don't have enough money to buy a new scope.

Savage .250 · « **Reply #14 on:** December 30, 2009, 01:14:07 AM »

Keep us posted on how that project turns out.

drdougrx · « **Reply #15 on:** December 30, 2009, 12:59:05 PM »

Shadow...fix what you want...the price of a new scope is immaterial. It's not about money. Heck a Bushnell banner or a scope from one of the GB sponsors isn't going to break anyone's bank. I'm not suggesting Leupold BTW. Just an inexpensive and reliable scope. By the time you buy the supplies and figure out how to do it and possibly have to do it again...what's the point. OK...if a guy wants to play..have at it.

ShadowMover · « **Reply #16 on:** December 30, 2009, 02:42:47 PM »

Quote from: drdougrx on December 30, 2009, 12:59:05 PM

Shadow...fix what you want...the price of a new scope is immaterial. It's not about money. Heck a Bushnell banner or a scope from one of the GB sponsors isn't going to break anyone's bank. I'm not suggesting Leupold BTW. Just an inexpensive and reliable scope. By the time you buy the supplies and figure out how to do it and possibly have to do it again...what's the point. OK...if a guy wants to play..have at it.

I get your point. Sometimes the satisfaction of fixing something is worth the extra time. Like getting 3 holes close together on a piece of paper. It may actually cost more than doing it the easy way :-) Some DIY types have many of the supplies it would take to do the job already. How many of GBO members have a MIG welder with an Argon tank? I'll bet there are at least 1000 of them out there. If this was a 'critical mission' component like the battery in your truck, wet primers, or a leaky radiator; I'd say toss it and spend the money. Maybe I'm a little more hands on with the optics because I'm into astronomy, and go to a telescope makers meet every year. It ain't magic, or brain surgery. It's a metal tube with some glass in it. I sent a GBO member some .001 wire to redo his cross hairs a year or two ago.

It's all about fun, and if it works so much the better. If not there is always the trash can.

drdougrx · « **Reply #17 on:** December 30, 2009, 03:16:03 PM »

I can't disagree really...all I suggest is that a fogged scope can mean a ruined hunt, that's all ... really. I'm hearing you about DIY...GL.

yooper77 · « **Reply #18 on:** December 30, 2009, 03:32:52 PM »

Quote from: Reverend Recoil on December 29, 2009, 11:23:38 AM

The main reason Navy fighter jets and NASCAR racers fill their tires with nitrogen is one of convenience. In some cases a bottle of compressed nitrogen is easier to use where its needed than an air compressor, power supply, receiver vessel, air dryer, and oil separating system. Nitrogen may be slightly better than air for high temperature tire service but it will make no difference to the way we operate our vehicles.

Nope the main reason for the use of nitrogen in aviation is to prevent corrosion and its not just for tires. I don’t know why NASCAR uses it maybe it’s also a water = corrosion.

yooper77

squirrellluck · « **Reply #19 on:** December 30, 2009, 04:06:50 PM »

Have heard the reason for using nitrogen in tires is because it is more stable? 32# is 32# regardless of temp. Air can fluxuate due to temp more than nitrogen. If you ever look at tires in different temps they my look lower at times. Nitrogen supposedly does not do that. I believe all gases do this I use refrigerant as an extreme example. This is supposed to be a benefit as tire pressure affects fuel mileage.

Graybeard · « **Reply #20 on:** December 30, 2009, 06:11:26 PM »

Since nitrogen is the primary component in air how can you believe such wild claims? Gas is gas and no matter which gas it expands as temperature rises and as it cools it does the opposite and pressure goes as the expansion or contraction goes. Simple law of physics.

briarpatch · « **Reply #21 on:** December 30, 2009, 06:41:48 PM »

If you have ever run a car on the oval. You start out with sizeing the tires. I would pull a tape around the tire and use the size to help with a tight car or a loose car. When you use nitrogen the tire will stay the same size. or closer to the same size. When you use air the moisture in the tire would heat up and change the size of the tire. The handling would change with it. When the car comes off the track after a run. I check the temps of the tires, they will be well above 200 degrees. It does not take much change to make a good car that will win or a bad car you cant get around the track with.
That is the reason nascar will use tire pressure to change the handling of a car. Half a pound will make a big difference. It changes the size of the tire.
P.S. This does not have anything to do with scopes or filling scopes. Just a reason why nitrogen is used in tires.

jcn59 · « **Reply #22 on:** December 30, 2009, 07:07:42 PM »

HERE'S A THOUGHT. Our local wine shop sells an aerosol can of gas that you spray into your half empty bottle of expensive wine to displace the air, ( so your wine doesn't rot). It's heavier than air. It may be argon, & costs ten bucks.

I think I remember reading that the nitrogen they use in a scope goes away after a period of time ~ it's just used to get rid of the moisture.

When I sent my Redfields to ABO repair in Florida they gave me a choice of nitrogen or another process involving heat to get rid of the moisture. I passed on the nitrogen and it's never fogged up yet. I would add that I don't use it much.

SteveHawaii · « **Reply #23 on:** December 30, 2009, 09:13:53 PM »

Nitrogen is used in aircraft tires primarily to prevent explosions. Here's an article from Boeing:

http://www.boeing.com/commercial/aeromagazine/aero_05/m/m03/index.html

It's also required by an Airworthiness Directive issued by the Federal Aviation Administration which states in part: "To eliminate the possibility of a chemical reaction between atmospheric oxygen and volatile gases from the tire inner liner producing a tire explosion."

You can find the AD at:

http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/55850E6389EFBA3C8625695B006723A3?OpenDocument&Highlight=87-08-09

Hope this helps,

Steve

ShadowMover · « **Reply #24 on:** December 31, 2009, 07:41:55 AM »

What the Original Poster (OP) asked, was if there was a way to do it, not if it was the only thing to do. Well, there is a way. If you have a planned hunt or some other critical situation I wouldn't recommend a untested repair job as a main tool. I recommended putting the unit in a fridge or freezer after to test for condensation. Another test would be to take it out and use it for a while and see how it holds up and performs.

Let's face it, we all use repaired equipment from our cars, our reloaded ammo, to our selves. After you put in a new set of brakes, you take the car on a test ride. I think with the economy the way it is, we will all be a little more hands on and DIY. If the emphasis and philosophy is just 'get 'er done' then by all means get out the credit card and get that scope. Maybe the old junk can be donated to as a gift to some of the other GBO members who have more time and patience than money. Everybody has a viewpoint, and all expressed here have valid points.

A Happy New Year to you all.