I originally designed the carts for hauling harvest and supplies around the farm, but very quickly I realized that the frame could be used to carry tools, almost like a cultivating tractor, or what is now sometimes called a tool carrier in Europe.
The first tool I set up for the cart was a rolling bed marker and the first photo in my blog post Early Photos shows the rolling bed marker that resulted from the above sketch. There are more photos of that marker in action over at my joshvolk.com site here. That early cart was fixed and designed for 36″ centers, relatively tight beds. The bed marker marks out the planting rows, but even slicker, on a field that’s tilled completely flat, by walking behind one of the cart wheels, the other cart wheel marks out the next pathway while the bed marker is marking the planting rows and in line spacing. This is a huge time saver and is much easier than using flags and a tape measure.
The above sketch shows most of the basic parts of the marker. The rollers are made from plywood rounds, thicker is better for the right balance of float and weight, 3/4″ is great, but 1/2″ is fine, or you can sandwich two rounds together. You can see my notes on possible diameters for the rounds. You can probably tell that I went with the 4′ circumference, with four 1×1″ hardwood cross pieces (I think I used oak – a common material for tomato stakes in some areas of the country). To attach these I notch a V into the rounds for the cross pieces and then drill a pilot hole and drive a long screw through the cross pieces and into the plywood. This isn’t a super strong/stiff connection, but it will work for a number of years if the tool isn’t abused before it gets loose, or you could spend some time making a gusset to support the connection. Maybe using wider 1x boards on edge would also work, notched to the center round and screwed through the plywood into the ends of the 1x.
For the axle I used 1/2″ black pipe nipples, 4-6″ is good with a flange to hold them to the rounds. A larger, 3/4″ (I think, check this) black pipe T slides over the 1/2″ nipples making a very crude but effective bearing. That is screwed into more pipe in the shape of a U using two additional elbows. 30 or 36″ is good for the length of the legs of the U.
Pay attention to what order you screw all of the pipe together, it’s basically backwards from what I describe above. The center of the U has to slide into the brackets first, then you can put that together. The axles are the last thing as they have to fit through the T’s.
I cut plywood brackets to hold the u to the cross bar on the cart. I found the pins in the sketch are completely unnecessary and it will hold itself on just with gravity. I make the slot for the cross bar long enough to also hold a 1×2, or similar sized piece of wood that spans the full width of the inside of the cart frame. This automatically centers the marker when it sits in the frame. Shown are gussets to hold that piece of the wood to the plywood; what I found works better is another piece of 2×4 that sits on top of the cross bar between the two brackets that you can screw the brackets to from the outsides. For the plywood brackets, make sure to leave a decent amount of material to keep them from splitting apart; cut them a bit oversized and consider also cutting handle slots for lifting the whole thing into place.
There are many other possible ways to make this and I’m working on a metal adjustable version to offer for sale. I encourage folks to build their own versions but if you want me to build one for you let me know and I can customize it to your cart and spacing needs.
One note on using the marker: I set them up so that they mark three rows and roughly 1′ hash marks. I plant most things on either 1, 2 or 3, or sometimes 5 rows, so this works for all three of those options. With 12″ (1′) hash marks I can easily plant at 12″ spacing, but also 4″, 6″, 8″, 9″, 18″, 24″, etc. With very little training most folks can get this and essentially all it is is eyeballing halves or thirds. You can set it up however you like of course.