Here's one I made for my horses. I used old conduit reels for the round rings. They were like 8', but I cut them down, and rolled them down to 6'. I made my own bender from scrap, an IH combine header lift hyd. pump, and a Cub Cadet hydraulic cylinder, and control. Took longer to build the bender than it did the feeder, LOL..
I used the center spokes of the reel's for my straight pieces. Some had to be doubled for the tops of the end gates. I rolled a 6 footer for the ends, and cut it in half. Also used straight pieces for the legs under each ring.
I capped the legs with 1" angle iron pointing up. The rings laid in this cradle, and I welded them in place.
Sheet metal for a top, and expanded metal in the bottom so as not to hold water.
There is a piece of 1 X 3 tubing running longways down the bottom center to carry the rings too. At the ends I extended it out past the last ring wide enough to hold the end gates... On the end of the bottom tubing, I put a piece of 3/8" rod sticking up, maybe 3/4" rounded off, as a pin to hold the bottom of the ring. The ring was drilled, so as to drop over the pin.
Tops of the end gate was drilled on the top, and angle iron swivel tabs were just above it, and drop pins to hold the gates in place. I put pieces of swing chain on the pins, to keep from losing them.
After some use, and my filly testing it... I modified it some, and made the tabs on top of the gate spring loaded, as my filly playing with the chains holding the pins, would pull them out, and drop the gate... You need to swing the tabs out of the way, to aloow to lift off the bottom center pin.
I also added 3/8" rod full length of the sheet metal on top, and expanded metal at the bottom, as edge guards, to keep them from getting cut on the sharp edges...
Also note in the picture with my boy Percy eating out of it, I put expanded metal on the bottom sides. The horses would get down, and reach underneath to get the fine stuff... I was afraid they may get stuck, or possibly get some moldy stuff...
I mounted it on 4X6's w/tapered ends for skids. On the bottom crossbar tubing, I cut a 1" hole underneath. I made a 3 pt. towbar with a 3/4" pin to tow it where ever..
The wasted hay you see laying around, is from my spoiled gelding. Had him used to eating only second & third cutting. With getting 4 more horses, and keeping my first cutting, he picks through to get the good stuff, and drags the rest out...
I had high hopes of building some of these to sell. A neighbor even suggested getting a patent... I went to the patent office online, and there are more than several patents on similar feeders... Steel prices rocketing was the main reason I haven't persued it... At the time in '05, I figured with my time and materials I would need to sell them for about $500.00.
This has held up fine with the horses. Not sure the light tubing would hold up for cattle... Just heavier tubing would work I guess... Maybe try one from this type of material, and experiment.