Repair/mechanic tricks and or tips?

[Bird]

I learned one just yesterday in the grocery store.

I was getting dry ice and an old local told me he used dry ice to install rod ends in big semi trucks. He said that anytime you have to press something you can super cool the inside piece with dry ice rather than heating the outside piece at the risk of losing temper.

Now I have to find something that I need to press.

I have a cousin who owns some street sweeping trucks, and several years ago he had to replace a bearing that he simply could not get onto the shaft, so I suggested we use this trick since I had heard about it. We put the bearing in a pan of hot water and packed dry ice around the shaft it needed to go onto, waited about 5 minutes and everything went together pretty easily. So, yep, what he told you definitely works.

 

[SpringHollow]

If you have access to it, liquid nitrogen works very well for press fits you never want to be able to take apart.

Ken

 

[Danno1]

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I write the miles/hours and date on oil and air filters with a Sharpie when I change them. That way you always know when you're due.

I'm not sure if it's dry ice or liquid nitrogen that's used but there's a metal treating process called cryo-tempering that's done after conventional heat treating to improve the strenght of cutting tools (machine shop tools) and I think some of those expensive custom made knives and swords. Don't know what the ramp/soak profiles look like for that process though.

.

 

[patrick_g]

He said that anytime you have to press something you can super cool the inside piece with dry ice rather than heating the outside piece at the risk of losing temper.

I was just telling my tractor mech the same thing yesterday. His reply was that the other end of what he was working on was still in the equipment and not easily removed so he couldn't use the technique. He mentioned that he had seen guys over heat a bearing to press it on and ruined them so had dry ice been an option...

Pat

 

[BTDT]

I was just telling my tractor mech the same thing yesterday. His reply was that the other end of what he was working on was still in the equipment and not easily removed so he couldn't use the technique. He mentioned that he had seen guys over heat a bearing to press it on and ruined them so had dry ice been an option...

Pat

In that case, maybe a CO2 fire extinguisher could have been used. Just point and spray (at close range) and it will chill nicely. Just make sure you have plenty of ventilation, (don't do this in a closed garage, confined space, etc).

 

[patrick_g]

BTDT, I think the problem was that the piece was large and over 90% of it was inaccessible. The concern was the ability to cool the part sufficiently wtih means available with all the thermal mass attached.

I have used CO2 "snow" from an extinguisher before and as you say it will git 'er done. One way to get it is to discharge the extinguisher into a sock. You can pulverize some dry ice and mix it with alcohol to make a chilling bath for a part that might be shaped such that it is hard to get much contact with a slab of the dry ice.

The dry ice and alcohol is how we chill a freeze branding iron (not iron at all.)

Pat

 

[SPYDERLK]

You can pulverize some dry ice and mix it with alcohol to make a chilling bath for a part that might be shaped such that it is hard to get much contact with a slab of the dry ice.
Pat

Neat trick!
larry

 

[BTDT]

BTDT, I think the problem was that the piece was large and over 90% of it was inaccessible. The concern was the ability to cool the part sufficiently wtih means available with all the thermal mass attached.

I have used CO2 "snow" from an extinguisher before and as you say it will git 'er done. One way to get it is to discharge the extinguisher into a sock. You can pulverize some dry ice and mix it with alcohol to make a chilling bath for a part that might be shaped such that it is hard to get much contact with a slab of the dry ice.

The dry ice and alcohol is how we chill a freeze branding iron (not iron at all.)

Pat

Does this mixture still give off the smoke effect? If you light it does it go pop..pop...pop.(from alcohol lighting, and CO2 extinguishing?)

 

[patrick_g]

Does this mixture still give off the smoke effect? If you light it does it go pop..pop...pop.(from alcohol lighting, and CO2 extinguishing?)

NOt as much smoke effect as with water. Never tried to light it. To get ignition you'd have to elevate the temp to or above the ignition temp and the immediate area of the free surface of the alcohol is dense with CO2 so lighting with a flame (lighter, match, or similar) would be difficult as the alcohol vapor area would be rich in CO2 and there would not be much alcohol vapor at the temps achieved with dry ice.

For what little alcohol vapor there is, there is lots of CO2 shielding it so if you tried to light it with say a close pass with a welding torch the continuous generation of CO2 would probably put out what little of any fire you could start.

If you want pyromania type fire effects, tie knots in a few feet of Saran wrap every few inches and suspend vertically above a bucket of water. Light the lowest part. The thin unknotted plastic will flame up and heat the knot above which will catch fire and drop molten on-fire drops of burning plastic through the air into the bucket of water.

Do this in the dark. The falling droplets of burning plastic will roar as they fall and hiss as they hit the water. They will burn with a mostly blue flame. It is a nice multi-senses treat. It looks AND sounds neat. It is cheap, relatively safe for sober adults and fun.

Pat

 

[MikeD74T]

patrick g, How do you get "falling balls of fire" and "sober adults" in the same location??? MikeD74T