Nitrogen use for metal contraction???

sotosberg · May 29, 2008

Hello,

Had anyone ever tried to use nitrogen to contract the crankshaft pin before install the conrod with pin and to the crank?I think that would be easier to push the pin to the crank because in so low tempertures the pin would be some microns smaller and so easier to install it and with less dammage.

What do you think about that?

Regards sotosberg

Taffy · May 29, 2008

not a good idea. the metal changes shape slightly in the flywheels to accomodate the pin. all lines and marks are across the crank while the pressure it must absorb is in a 'round' or 'twisting' motion. i therefore think that marks and lines are good for it!

also, does nitrogen change the metallurgy of the pin? what if it snapped off the next week?

regards

Taffy

sotosberg · May 29, 2008

I think that would not affect the installation that Taffy because the contraction is some microns,so the pin will be pressed to the flywheel slightly but not easylly.I think that propably that method could save some crankshaft life.My father use that technique when they made some modifications in big engines for ships.The think was that this method was required from the engine builder.The brand of that engines is Blackstone and are British,you might know them.

Hope to be articulate

Regards sotosberg

sotosberg · May 29, 2008

The word is cryogenics

FC501EAST · May 29, 2008

Hey, sotosberg....
I've used a few lumps of dry ice to accomplish the same effect. Cheap and effective...

sotosberg · May 29, 2008

Hi FC501EAST,

Nice to hear about that,was it effective?Realy,I had never thought that dry ice could do the job.I knew that they use it in F1 but only for cooling the radiators.Do you know the temperture that achived with dry ice?

Regards sotosberg

steve · May 29, 2008

Just hitting something on the outside briefly doesn't chill it all the way through, it takes time. I like to wrap bits in plastic film, aka glad wrap, and put thme in the freezer for a few hours, or even overnight. You can also put the other bit in the oven for the opposite effect.

Steve

drgnrydr · May 29, 2008

dry ice is -96f use it plenty building turbine aircraft engines

Smorgasbord · May 29, 2008

Liquid nitrogen is even colder (-196C) and more fun since you can use it to make ice cream with spectacular condensation clouds developing as the cream cools. The cooldown is so fast you don't ever get crystals in the ice cream. Some people charge money for cryo treating stuff so maybe it is good for something other than shrinking parts and for ice cream. Maybe for shrinking parts for assembly in the home garage the dry ice is more practical and economical. Unless you for some reason already have the liquid nitrogen. Regards.

sotosberg · May 30, 2008

NO!!!I dont have liquid nitrogen in my garage and from what I read in this topic I think its "a little bit" expensive.I will have to search about that localy in my country,but the dry ice seems to be very good idea.Propably the -71 C can also do the job.But I dont either know how can I fix or where can I find dry ice here,so I also have to check it.The think is that its works!!!

Thanks a lot guys!!!

Regards sotosberg

BundyBear · May 31, 2008

Liquid nitrogen is also a bit dangerous. Dry ice may rip the skin off if you touch it but nitrogen will make whole bits fall offa you that won't grow back!

If you do want to use it, be aware that cold parts will become very brittle at such low temps. Don't tap them with a hammer.

It is probably more effective to heat the outside part to as high a temp as safe. What you are after is the greatest temperature difference between the pin and its bore. Does anyone know how hot you can go before you start to mess up the heat treatment?

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