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How many tanks did you go through; one tank delivered here cost me $165 from a local company. Airgas wanted double that.

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czwalga
How many tanks did you go through; one tank delivered here cost me $165 from a local company. Airgas wanted double that.

We got 95% of the car done with one dewar, just missed out on being able to finish some stuff in the trunk area...180L I think? Grant can you confirm?

The LN was $600 something, and maybe was closer to $800 with rental and delivery.

Dave

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NoCoast
What issue of stress fractures from cold? We did break through here and there, but really, what stress fractures? Burning glue makes me feel like I'm giving myself cancer.

I'm not a material scientist, but my understanding of the issue goes like this. What allows a sheet of metal to expand and contract without acquiring small fractures is its ductility. Ductility is proportional to temp. So, when you heat a sheet of metal, it expands slightly, but the ductility of the metal "absorbs" the expansion, especially given that it is gaining more ductility as it is heated. But when you chill a sheet a metal, especially when you chill only a region of the entire sheet, it not only contracts, but loses ductility, so small fracture can be made, especially at the edge of region where you are cooling, as the chilled region shrinks inside the larger region.



Edited 1 time(s). Last edit at 11/04/2013 09:34PM by Iowa999.

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DaveK

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czwalga
How many tanks did you go through; one tank delivered here cost me $165 from a local company. Airgas wanted double that.

We got 95% of the car done with one dewar, just missed out on being able to finish some stuff in the trunk area...180L I think? Grant can you confirm?

The LN was $600 something, and maybe was closer to $800 with rental and delivery.

Dave

I think ~ 180L is what it took to do the WRX as well for all of the parts that we could get to (floor, trunk, no real underside treatment). There was some left over.

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This isn't floor mat anarchy

We used 180l dewars. Took three to do two cars due to: overnight loss from leaking valve, leaky fitting on death ray, and learning what we were doing/being wasteful. We used 320l doing Dave's BMW but only 160 or so on merkur due to practice and being ready to start right after delivery of dewar in case of another bad valve.
Best solution? Start with an STI or Evo.

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Grant Hughes

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DaveK

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NoCoast
What issue of stress fractures from cold? We did break through here and there, but really, what stress fractures? Burning glue makes me feel like I'm giving myself cancer.

Actually, I'm not sure that's a terrible guess. I sorta wonder if the freezing might've led to some of the fractures seen when the rear diff tried to remove itself from the Compact. To me it was just really strange to see factory spot welds tear in that manner...and by tear I mean clean snapping apart.

That said, agree fully with grant that heating and scraping is miserable for many reasons. I really wish there was someone locally that did acid dipping...no idea what that method costs though.

Dave

25 years ago around $1000.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

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Iowa999
Well, in defense of those who argue for heat instead of cold, there's the issue of stress-fractures in the sheet metal from being super-chilled unevenly. This is much less likely to happen with heat, because the metal is always warm enough to be ductile.

Not that I know that stress-fractures happen when using the "death ray"; just that this is the argument that I've heard against this approach. And if this point has been discussed and already ruled out, apologies for not searching enough.

This is a definite concern. You are basically cryo-treating the metal, possibly making it more brittle. I have seen a Merkur shell that was death-rayed and there were cracks and holes all over the place from the hammer. Like they froze it and hit it with the hammer and crack! It would concern me about the potential ease of cracks propagating in the future. That's my biggest reservation about LN, though I can't think of a better way to get that horrible rubberized undercoating off a Merkur shell.

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Doivi Clarkinen

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Iowa999
Well, in defense of those who argue for heat instead of cold, there's the issue of stress-fractures in the sheet metal from being super-chilled unevenly. This is much less likely to happen with heat, because the metal is always warm enough to be ductile.

Not that I know that stress-fractures happen when using the "death ray"; just that this is the argument that I've heard against this approach. And if this point has been discussed and already ruled out, apologies for not searching enough.

This is a definite concern. You are basically cryo-treating the metal, possibly making it more brittle. I have seen a Merkur shell that was death-rayed and there were cracks and holes all over the place from the hammer. Like they froze it and hit it with the hammer and crack! It would concern me about the potential ease of cracks propagating in the future. That's my biggest reservation about LN, though I can't think of a better way to get that horrible rubberized undercoating off a Merkur shell.

This is true it can happen, but it doesnt have too. One side of the car it happened probably 5-6 times in small areas, on the other side not a single time.

Just have to get the idea out of your head that you need to hit it hard. No way i'd use any kind of air tools. Really you just need to tap it and even a scraper works on the flat areas.

i have used the dry ice method in the past
but my favorite is the let the freeze for a few days in the free winter air then beat with the rubber hammer

i wonder if you could reduce the cracking issue by packing with dry ice and covering with a blanket before using the ln ?

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I would rather drive a slow car fast as a fast car slow!
first rule of cars: get what makes you happy, your the one paying for it!

For those talking dry ice vs. LN, I think we're talking different things.

Dry ice works great for tar panels on the interior and a good cold winter day can also help here...but then you have to work on the car outside too...brrr. In my experience dry ice does nothing for the rubberized undercoating.

LN can do both with ease. Just spray and listen for the crack of the coating shrinking down an loosening its bond with the metal, then tap with a hammer gently or use an air hammer at very very shallow angles.

Agree with those above who've said that using LN doesn't mean you have to mess up the metal, but if you spend too long on one area, or hit it with a hammer too hard from straight on, cracks are easy to come by.

Dave

All it requires is a little paying attention and listening.. Dave exaggerates with the "all over the place". Or, it was one done by somebody not paying attention, and being a savage. Whatever.

The point is that all around there is nothing quicker or better.

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John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

there is always the sand and gravel blasting method

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I would rather drive a slow car fast as a fast car slow!
first rule of cars: get what makes you happy, your the one paying for it!

I cleaned off all my gunk under the Civic with this:

http://www.harborfreight.com/power-tools/oscillating-tools/oscillating-multifunction-power-tool-60428.html

$20 and the thing is still going strong. I've had to buy several of the replacement scraper blades, but the tool itself keeps going. Sure, it takes a while and your hands get a bit numb from all the vibration, but it took me an evening to remove the underfloor, probably another evening or two to do the wheel wells. I was lucky and my in car sound deadening just peeled off in chunks so I just wire wheeled the seam sealer.

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BillyElliot
your hands get a bit numb from all the vibration

that's what she said!

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KF7RWG
http://www.utahrallygroup.com

It was 23f here last night.
I may embrace this cold winter weather and get the rest of the tar sound proofing off this VW shell I have here.

Edited to correct the deg C to F.

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Disappointingly not yet a Jackass



Edited 1 time(s). Last edit at 11/05/2013 11:30AM by danster.