Re: Babbitt

Posted by Joe on March 18, 1998 at 07:49:18

In Reply to: Babbitt
posted by Jim Hansell on March 17, 1998 at 12:14:45

Jim
You're a fortunate Model A mechanic!I would dearly love to own the tools necessary to rebuild a Model A engine myself but the "price of admission" prevents it.
I have rebuilt many other machines over the years having an affinity for 19th century flat belt driven machine tools that typically require a babbited bearing.
The best article I have seen was written in "Fine Woodworking" in the late 1980's and has since been reprinted in one of their "Fine Woodworking On" series of books entitled "Making and Modifying Machines."This article is much like having a seasoned professional millwright looking over your shoulder as you pour your first pour.This book sells for $9.95 and is available from Taunton Publications.See for more info on aquiring the book.
As to the properties of the babbit itself, the best available babbits are tin based and in particular "POWER" brand babbit as sold by McMaster Carr is probably the best.In my view the thing most important is that your supplier can provide a "certificate of compliance" assay to verify that babbit provided is formulated to some SAE or ASTM number.There is a lot of "junk" babbit around just sitting on shelves waiting to be sold.
Babbit formula is literally a science unto itself.The best modern description including ASTM numbers can be found in "Machinery's Handbook".Mine is the 19th ed. and pages 581-582 give a wide description.The best historical description of babbits I have is "Marks Mechanical Engineer's Handbook" of which my most treasured is the 1ed. from 1916 but any edition is basically the same up to at least the 7th.
Babbit pouring technique is largely a matter of practice.Making sure you have adequate heat resistant "forms" and "dams" is the key to a succesful babbit pour.Lots of heat available and adequately preheating the bearing cavity prior to pouring is essential too.An acetylene torch is pretty much required here.
Having the Model A pour shells will make it a lot easier.That was the beauty of the various "rebabbiting kits" that were sold by KD and others.
Once having the babbit poured is only half the battle, however.Now you have to machine it to size and in alignment.And this includes all the required radii, oil grooves, and end to end clearances as well.
Maybe this is why I left this portion of my Model A engine rebuild to others?
Still, I'm envious - it sounds like a grand project.
Let us know how you make out.
Best regards,
Joe

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