A simple practical answer needed

[frozenmass]

This is a relatively simple, practical question to a backyard delima.

A friend has purchased a van with a receive hitch mounted on the rear frame.

The receiver toungue has been installed upside down, too low, and has rusted in place.

It can't be pulled out and the suggestion has been made to pack the insert in dry ice and wait until the insert has reduced in size that it may be pulled out.

The insert is 1" steel about 11" long and the receiver is about 4" deep and 3/8" thick.

The question is this: applying the dry ice to the insert will cause it to contract, but if the receiver gets cold will it shrink the square tube tighter on the insert, or will the walls of the receiver contract to make the walls thinner and threrefore increase the space between the two parts?

Also, if heat is applied to the receiver will the tube expand and tighten on the insert or expand outward to increase the opening?

All opinions accepted, considered, and appreciated.

Thanks,

Warren

 

[A.T.]

For the simple case of loosening a screw and a nut it is better to heat them up instead of cooling. Under heat the whole construct (screw + nut) expands including the gap between the two parts. It is of course more effective to heat up the nut more if possible. But even in the case of uniform temperature increase the whole construct is also uniformly scaled up, so the little gap increases as well.


This is explained well in the book http://books.google.com/books?id=k0cJAAAACAAJ&dq=thinking+physics"

 

[FredGarvin]

Usually heat in the form of torches are used to do this. The dry ice probably won't work long enough to work on the corrosion. The heat will.

It is never easy to get things like this apart. It always takes a lot of elbow grease.

 

[fleem]

Heat will enlarge a hole in the object heated.

Agree that its a LOT easier and more practical to just heat the receiver than try to keep the bar cold!

i suggest a good strong penetrating oil (the kind they sell for ceased nuts/bolts). Then heat the receiver up a LOT, then pour water on the bar, then take a sledge hammer to it, but stay away from the gas tank with that heat and that hammer!