I wish I'd had this machine last year, when I used my Bridgeport mill to slot out six hundred sleepers to take steel rails (and it took about a week to get rid of all the wretched sawdust). Somebody has done a very nice job of making a gang-milling sleeper-slotter here, with a ball-race mounted arbor running above a "sledge" into which are clamped ten sleeper blanks. The sledge is simply pushed under the cutters, producing ten finished sleepers per pass. The sledge is on tough polyurethane wheels which run along a pair of guide bars, it is equipped with a guard at the handle end.
I was going to say something about this gadget probably not meeting modern safety standards but, having thought about it, it probably didn't meet any safety standards when it was built either. You will need to fit a motor and V-belt to drive it, whereupon you will have three very sharp cutters whipping round with little or no guarding. It will be dangerous, there will be unguarded belts, cutters, blah blah blah. You have been warned.
Baseboard 14 x 42 inches
Guide rails 36 inches long
Slots 3/8 inch wide x 1/2 inch deep, 3 1/2 and 5 inch gauge