I have heard of those mechanical splitters - apparently they really produce but there is a slightly higher danger factor. The report I read on them was a study of a fuelwood producer and, if I remember right, they used at least two men to keep it fed. Maybe three to also clear and stack on the conveyor or truck.
If you have a backhoe, I once owned an 1,100 lb custom made six-way splitter that replaced the rear bucket of the machine. Working on frozen ground with frozen wood, the machine will split about 40 cords per day. It took four people to work it - three setting blocks on their ends within range of the hoe, and me, the guy who worked really hard pulling the levers. The splitter would be placed directly above the victim, then hoist the boom and drop the six-way on the victim. Poof - six pieces. Only blew one hose on the initial learning curve. Others said it was too hard on the machine - I say better the machine than our backs.
I'm sure commercial suppliers make a good, mass produced machine. I replaced the six-way with a splitter I made myself. Ingredients:
11 hp Honda horizontal shaft
quick coupler
10 gpm two stage gear pump
10 gpm up to 400 psi for quickness
3 gpm beyond 400 psi to 2500 psi for the work
4"x24' stroke x1.5" rod cylinder
4-way, three position open centre valve, spring return on
blow side and detent/spring return to centre on suck side
10 gallon hydraulic tank with strainer,temp/level
guage.
spin-on 10 micron filter with bypass on return line
restriction indicator on filter housing
two stage wedge - narrow at first to do the work, and
widening out to permit speed.
3-wire hydraulic hose, O-ring Face Seal (ORS)(I used these fittings to make inventory match my John Deere equipment)
It is fast, well balanced, reliable and protected with filters and relief valves. All the parts aren't necessarily cheap, but bought from a quality hydraulic shop, they also will be reliable and of good quality.
Have fun building one - April is the official month to build wood splitters - tell your wife you heard it here, it must be true, and have to go to town.