Temperature gauge preservation

[AZJeepNut]

You guys seem pretty professional and I'm impressed with the skill and attention to detail in this project. I'm sure you already know this, but just for safety's sake, keep in mind that diethyl ether is extremely flammable and can be explosive under certain conditions. Would hate to hear that all your work went up in flames! Again, I expect you already knew this and I am probably just adding unnecessary info here, but safety first, eh . . .

[stony]

Thanks AZ, yeah already have my safety goggles and flame retardant suit ready.� Filling and soldering will be an outdoor job.� Drilled it this morning and it looks like there was a plug in there.� Looks thick enough to thread for a brass screw.  Professional???  Nope, just stubborn old farmer who would rather fix than replace.  The challenge is fun.

[calvinhunt]

I love it! A fun thread to follow! Thanks!

[PaulS]

Very cool effort here!  I'm pretty sure mine has an electric gauge in it right now, but the original style is nice.

I think you'll have to be careful not to get any air in there with the ether.  The presence of air will affect the phase behaviour of the ether, and you won't get the same pressure/temperature relationship.  Meaning, the gauge won't read right.  If it's just a small amount of air, the error may not be large, though. 

You should check the calibration when you're done.  Easiest way to do that is to put the sensor end in boiling water.  Just remember that water boils at 212�F only at sea level--the actual temperature gets lower as you increase in altitude.  Where I live, it's more like 208�F.

-Paul

[stony]

Thanks guys.� The hole is drilled, and it does appear that there was a little plug there.� Interesting thing is the capillary tube appears to extend about 3/4 of an inch into the bulb.� I don't think the air will make much difference, because it is compressible and the vapor pressure of ether is so high the gauge should be reasonably accurate as long as some liquid ether remains in the bulb.� Ether should be here tomorrow and still have to find my heavy duty soldering iron.� As for calibration, since the back of the gauge is inaccessible because the bezel is crimped on, there is no way to access the Bourdon tube or linkage to adjust it, will have to live with whatever I get.� I'll be happy if it moves at all LOL.�

Update the diethyl ether just showed up.  500 ml was the minimum I could order, so will have enough left over to do approximately 99 more LOL.  No puttin it off now.

[PaulS]

I don't think the air will make much difference, because it is compressible and the vapor pressure of ether is so high the gauge should be reasonably accurate as long as some liquid ether remains in the bulb.� ...� As for calibration, since the back of the gauge is inaccessible because the bezel is crimped on, there is no way to access the Bourdon tube or linkage to adjust it, will have to live with whatever I get.

The air will not just be inert--it actually affects the pressure of the ether at a given temperature.  The software I have that can do these calculations doesn't work for the diethyl ether - air mixture, so I can't tell you by how much.  I entered a pentane-air mixture (pentane has a similar boiling point to diethyl ether), with 1% air by mass, to see what would happen, and for that mixture, it gave an error of about 3�F at 212�F (relative to the pure pentane).  Not a big error, but perhaps noticeable.

Even though you can't change the calibration of the gauge, you can check how far off it is by putting it in boiling (or very hot) water with an accurate thermometer for comparison and then make a note of how far off it is.

-Paul

[stony]

True for a gas mixture (Boyle's law right?), but the thermometer reading will depend on the vapor pressure of the liquid ether.� As the gas pressure inside the reservoir raises, the boiling point of the ether will rise, so at 212F the pressure is about 100 PSI.� So as long as there is liquid ether in there the pressure will rise as a function of the vapor pressure.� �Once the temperature has reached the point where all of the ether has boiled off the change in pressure will be a function of temperature on the expansion of a gas.� So if the boiling point of the ether continues to rise with increased pressure it shouldn't make any difference what the gas mixture above the ether is.� I think that is why ether was chosen, it's BP is 34C (about 100F) and it has a relatively high vapor pressure.� Of course I may be wrong, physical chemistry is a long way in the rearview mirror.

Update 2:  Tried a couple of times tonight.  No luck   my plugs were not tight enough, and my wimpy soldering gun took too long to melt the solder.  Things got too hot, built up too much pressure and the ether escaped.  Have some other ideas, mostly unconventional LOL.  Have to keep the ether cold and hit it quickly with a big soldering iron. One good thing I put some pressure on it from the air compressor, seems to work fine.  Try again in a couple of days.

[Jesse]

Just thinking out loud here, but could you drill a hole through a piece of dry ice and put the bulb through? That would leave the end open to solder but would keep the bulb and ether very cold. Still probably isn't going to work without a high temp iron though.

-Jesse


Don't mind the grade school illustration, you are getting what you pay for with this advice anyhow.

[stony]

Thanks, yeah I have thought about that, problem is you would need a VERY hot iron to seal it, I have already thought about using epoxy, but it would never cure at low temp.   I am leaning toward soldering in a copper capillary tube and filling through that and crimping it shut, then soldering or epoxying. 

[1955CJ-5]

The gauges can be dis-assembled. The bezel ring is very soft steel. If I had thought to round the sharp edges on the screwdriver it would have been a smoother operation..as it is I marked the case a little, but not bad...

[stony]

CJ, yeah I have taken them apart before, did not want to except as a last resort.  I have some syringes coming so in theory I could fill it from the gauge end but would take forever.  Beginning to think it was originally filled and sealed cold and the solder was added to strengthen the seal.  Right now I am looking at two options: soldering in a small copper tube and crimping to seal or a small machine screw with a O ring to seal.  Will reenforce with epoxy rather than solder.  Anyway will figure something out .  BTW my first jeep was a 56 CJ5

[1955CJ-5]

My gauge was stuck right where the picture shows, so I figured that I might as well take it apart. I bent the Bourdon tube, and to my surprise it worked.....calibrated it with a candy thermometer and a coffee cup..

For that Bourdon tube to get bent/straightened to the point where the needle was pegged, the engine must have gotten pretty hot....

That old 55 CJ has been in the family since I was 8......

[Matto]

If you need to fasten a plug in a hurry, there is a product called 2P10 which is basically Crazy glue on steroids. Apply adhesive to the base and spray a shot of accelerator to the plug. When the two parts meet, you will have a high strength bond in about 3 seconds. Good luck, interesting thread.
Matt

[stony]

Matt:  That is a good idea, however CA glues are soluble in acetone, so I am pretty sure that they will not stand up to ether, which is an even better solvent.   Right now I am leaning toward soldering on a brass 6-32 nut and using a machine screw and an "O" ring for a physical seal then overcoating with epoxy.  I WILL make this thing work somehow!

[1955CJ-5]

Stony,

When the gauges were new, would the entire capillary tube, Bourdon tube and bulb be filled with liquid ether?

Or would the bulb only be filled with liquid ether and the remainder ether vapor?

I suppose there needs to be room for vapor as that provides the pressure to expand the Bourdon tube...� I found a write-up on Bourdon tubes..interesting...