18 thoughts on “Over Easy?

  1. When you rebuild aircraft wheels the wheel half is heated to 250F and the bearings cups are chilled with dry ice to -75F. You have to be quick or you can’t press the cup in.

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  2. I use a heat gun for bearing installs.
    What is really nerve racking is putting a new shrink fit ring gear on a flywheel. The flywheel goes in the freezer, the ring gear goes in the oven. Like Al said: You have to be quick, because you only get one shot at it.

    Whitehall, NY

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    • Had to do that on a Taurus, had the neighbor (who’s a professional welder) heat up the ring with his acetylene torch set to flame, dropped it right in – no need to cool the flywheel.
      He’d never seen that trick before, but he’s a welder and not a mechanic.
      I tried to put the pilot bearing in using a very good electric heat gun, ended up having to use the acetylene torch and slap it in with a brass hammer.

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  3. Yup, have done that old school. Used to dump the bearing and the entire motorcycle chain into a large tin can full of grease and put it over the corner of an wood fire (done outdoors, pre green nonsense) and let it boil for a while then set off to cool. Hook them out with a bit of wire, wipe and install.

    As to using dry ice and heat, should have done that on the MG head, the valve guides are about 1 or 2 thousandths interference fit. Used a press and brass hammer, damaged several in the learning process. Sadly, the original 1952 shop manual shows them hammering them in at the factory. Those Brits musta had a much better wrist than I.

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  4. Al in Ottawa has the secret. Wrist pins in some racing 2-strokes are press fit into the connecting rod, as are the crank pins into the crank cheeks I’ve gotten away with freezer and oven (-10F and +300F) on wrist pins, but I learned quickly dry ice was the right tool for the crank pins.

    And you do have to work fast – you’ve got about 5-10 seconds to make the fit and make it right the first time.

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    • In my neck of the woods we would soak (Cummins) diesel engine aluminum cylinders in hot water for maybe a half hour before installing the rods and room temp wrist pins into them.
      Different strokes different folks. Heh.

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  5. I have heated a pan of grease to 200 degrees or used the freezer depending on which way the bearings needed to go. I have also used a CO2 fire extinguisher to cool off stuff I need to shrink.

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  6. If you want to freak out your wife and quickly heat up your bearing, try using your microwave. Yep, you heard that right. wrap in water soaked paper towels and run for 1.5 minutes. Honest, see attached video…

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  7. In the air force in the 1960s and 1970s Heating up a bearing before sliding it onto a shaft was common for Jet engine repair. And we also put bearing races in the freezer for an over night before working them into place.


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