Splitting logs the old-fashioned way can be a real hassle. Using an axe or maul can be counterproductive, time-consuming and tough on your back and arms. It can be especially aggravating when the log to be split keeps falling off the splitting stump. Tough logs with large knots in them pose another problem and sometimes just won't split the conventional way. Professionally built log splitters typically have fancy engines and hydraulics, but they can be expensive and unwieldy. It's easier to build a manual splitter using tools and items you might have lying around or can pick up easily.
Prepare the dolly/hand truck platform first. A backer board of thick, strong plywood or harder wood needs to be secured to the dolly frame. Since every dolly is different, this task may require multiple approaches. Use the U-bolt kits with straight mounting brackets if you have a pipe-style dolly. Drill holes in the backer board and metal and use bolts if you have a dolly with a square type of framing. Use common sense and sound carpentry, and consider how much wear and tear you are going to put the machine through. The backer board is the foundation of this homemade machine, so it needs to be mounted to last and should be able to sustain further framing of the jack and blade apparatus.
Bolt a 4-by-4 length near the top handle of the dolly, using a length that spans a bit more than the width of the dolly. Use large, long bolts with washers for maximum strength and durability. Drill pilot holes first in the wood and metal frame and use one large bolt on each side of the 4-by-4 to fasten this important framing piece to your new log splitter dolly. When placing this piece, consider the reach of your jack with the cutting blade attached and the size of the logs you'll be splitting.
Attach the cutting blade to the end of the jack that makes contact with the car frame during normal operation. The easiest blade to use and fit to the jack is a thick, long chisel with a fat, round handle. If the top plate of the jack is not flat, make it flat or take off the bracket at the top. Typically this is the smallest plate on the jack, so you will need to use some JB Weld (or get a professional welder) to fasten a bigger plate or mounting bracket to the jack that will allow you to secure the top plate to a short 4-by-4 block with small bolts. The block should be tall enough to be able to allow the insertion of the entire chisel handle. Use a flat wood-drilling bit first to drill a hole for the handle of the chisel to be pounded tightly into. The hole should be just slightly smaller than the handle's girth to ensure a tight fit. Once the chisel is pounded into the hole completely, the butt end of the handle should be snug to the end of the block that will be screwed to the mounting plate.
Screw the 2-by-10 wood plate to the bottom edge of the 4-by-4, centering it over the bottom metal lifting plate on the dolly. Position your bladed jack on the 2-by-10 and make pencil marks for the holes in the bottom jack plate. If there are no holes, make one on either side for bolts to pass through. Positioning of the jack should allow the cutting blade to make center contact on most of the logs you'll be splitting. You should also consider where the crank handle is and set it up for easy access and clearance.
Drill holes where you marked them for securing the jack to the wooden mounting plate. Use long, heavy-gauge bolts, nuts and washers to make sure it's a tight and solid fit. Take a couple of equal 2-by-4 lengths and make a brace for each side of the wooden plate. Cut the wood with the circular saw at the proper angles and secure one end of each brace to the top, backside corner of each side of the plate. Screw the other angled ends into the backing board. This will make sure the plate won't break under pressure.