Sierra, please don't take this as criticism, but advice from someone who's actually built a flywheel splitter that works perfectly. The 24" rack isn't nearly long enough. My Martin RA6 x 4 was cut to 42inches in order to have a 25 inch stroke. Remember, the pinion is well beyond the end of the rack in the retracted position. My Martin gear rack is 1 inch thick x 1 1/2 inches wide. SS uses a rack that is 1 inch thick x 2 inches wide. Motion Industries ,Inc. sells the Martin products. You'd need at least a 2.500 pitch dia. pinion gear ( 2.833 max OD) to bore for a 1 3/8 shaft W/ 1/4 keyway. If you weld the pinion to the shaft, you won't be able to disassamble if necessary without cutting the shaft & making a new one. SS also uses CAST flywheels that are 2 inches thick. Also not a good idea to run with just one flywheel . There's the BALANCE factor involved that requires 2 flywheels. My flywheels weigh 102 lbs. each, with the hub, and are rotating at 150- 160 rpm with just a 3 hp motor. ( running half throttle) That's 19.635 inches of travel per sec. no load speed. So far I haven't needed to ,but could speed up motor a bit if I need more splitting force. Hope this info is of some help.
Farmermike, I hope this answers some of your questions, too.
Claude