Compression fitting using Liquid Nitrogen

[Inferno]

You don't have to do anything with it. Like President Trump said about Covid. "One day it will all just go away" With LN2 that day will be coming up in a day or two at most.

You're not completely incorrect. The dewars I have will hold LN2 for up to 60 days. More if kept in a freezer.

 

[rwm]

I used to get liquid nitrogen from Airgas in a metal thermos and kept the lid cracked in the trunk of may car. I doubt they will still allow that these days? Does anyone know? Has anyone done this recently? Are there other new requirements?
Robert

 

[Inferno]

I used to get liquid nitrogen from Airgas in a metal thermos and kept the lid cracked in the trunk of may car. I doubt they will still allow that these days? Does anyone know? Has anyone done this recently? Are there other new requirements?
Robert

The local air gas supplier td me they have loaner dewars and said that a vacuum insulated container is all you need. He mentioned something about Styrofoam but by then I saw a squirrel.

 

[pacifica]

You need to find out how much press fit on the outer ring the manufacturer of the bearing recommends. The bearing ring is thin and most of the interference in the press fit just translates into a shrinking of the ID of the ring.
Bearings are made with a bit of clearance between the rings and the balls. something like .0002-.0005 inches.
A two thousandth press will close up all the clearance and the bearing will NOT turn freely, it will go bump, bump, bump

Using temp extremes to make up for lousy machining tolerances will not get you a well running machine.

I agree, press fits can be problematic.Not only must tolerances be very accurate, you need to know the metals you're working with and if bearings are involved one more difficult variable is added.

 

[Inferno]

Proof of concept, step one.

I got the bearings in today and, rather than start the LN2 experiment now, I simply pressed one in to the wheel.
It went in nice and smooth. Smoother than the piston wrist pins I bought the hydraulic press for.
I have no doubt that this will work with Liquid Nitrogen also.

The bearing is shown flush but it's protruding about .012" on the other side. If this makes it all the way to a functioning system, I'll center the bearing in the wheel. Having a .006" clearance will be pretty good.

BTW, the "rusty" looking stuff is just the cosmoline I haven't cleaned yet