I remember working on an ancient lathe nearly forty years ago that had a threaded-spindle chuck frozen in place. I'm thinking it was a big old LeBlond. The guy that was rebuilding the lathe made up an interesting arrangement to wrench the chuck free of the spindle.
He took two pieces of 2" x 4" or 2" x 6" CRS and drilled and tapped two big bolts (5/8 or 3/4") in the steel pieces aligned edge to edge. Two washers were slipped between the blocks and the bolts were inserted and tightened. Then a hole was bored through about 1/4" bigger in diameter than the machine's spindle. The chuck was laid face down on the shop floor with the spindle pointing straight up and this "wrench" was bolted in place around the spindle and blocked up to be level and approximately centered. The washers were still in place as spacers between the two halves. A small pot of lead was melted and then poured into the gap between the wrench and the spindle and then everything was disassembled and the lead ring was cut into halves with a small piece of sharpened brass bar stock.
You know that tough, sticky sap that runs out of pine and cedar trees? The old guy had a coffee can with a pretty good collection of the stuff. He heated some of that on a stick and smeared a little on the spindle and the bore of the wrench caps before popping the lead back in and reassembling the wrench onto the spindle without the washers separating the two halves. The bolts were then tightened until they smoked and then about a quarter turn past that that!
The big 4-jaw chuck was clamped down onto another piece of thick wall tubing lying across its face. A couple of shop rags were wrapped around the spindle's journal areas and a larger pipe was slid up over it, with the pipe being probably 8-10' long. Another pipe was slid onto the 2 x 2" tube welded to the wrench's lower cap. With a man standing on each pipe about midways along their length, the old guy mounted the piece of tubing clamped into the chuck. It sounded like a .22 rifle firing when that chuck broke loose, or at least that's how I remember it.
To help my rambling make sense, below are a couple of sketches I banged out with hopes of tying things together. First, how the wrench was configured and bolted to the spindle. Second, a combined overhead and side view, with the three football shapes representing the mens' positions while breaking the chuck free. I hope the Von Wyck doesn't require anything this aggressive but if it does...