I have seen old photos of cast iron steam engines being repaired.  The
technique involved an asbestos tent and a charcoal fire to preheat the
entire casting to around 500 degrees.  Then the previously ground-out
crack was brazed with an acetylene torch, peened, and allowed to cool
_very_ slowly.

I saw (and maybe Jody did, too) the welder at the machine shop at the
University of Illinois Civil Engineering Department repair a crack in
a cast iron pump from one of the University's fire engines.  There were
two pumps fabricated in the same casting, with a common shaft holding
two impellers.  With the pump disassembled, we could see that the two
scroll cases were Siamesed back-to-back with a common web between them.
This web was bored to hold a bearing for the common shaft, and had
cracked radially from the bearing hole about halfway to the edge of the
scroll cases.

Our welder ground out the crack, heated the whole casting in an electric
furnace, filled the crack with some kind of brazing rod, probably
nickel, put it back in the furnace, and cooled it off over a number of
days.  When it was cool, he cleaned up the weldment to restore the
internal clearances between the impeller and the scroll case, and back
into service it went!

This experience gave me the courage to try to repair a 14 inch cast iron
pulley.  It was on my cement mixer, which tipped over while being towed.
A couple of the spokes fractured, but two were undamaged and held the
hub in place, so I went for it.  I ground out a bevel on the broken
spokes, put the whole thing in my grill, and heated it up.  I filled
the beveled areas with nickel rod, closed the lid on the grill, and
over a few hours slowly turned down the heat.

The pulley warped during the process -- the axis of the shaft is no
longer exactly perpendicular to the V-belt groove, so it wobbles about
a half inch, but it still works!

Steve McCollum