Steve, I think you have your answer. Thanks guys.
Sock is kinda tricky. I personally have never seen it plug, but I have learned to expect anything. I have seen non-sock plugged solid with sand to the point where the water was bubbling up out of the ground, traveling overland 20' and then dropping backing down to the tile again. Dug it up, it was solid with beach sand.
Back to the stringer
Here is my original design
http://youtu.be/CX0wmON4bXw
This rig is mounted on my dozer blade now.
http://youtu.be/crniaEPL-SY
Lessons I have learned.
1) Design it in such a way that the table raises as it tilts. The table is mounted on a long arm that lifts up and over. This way, the table rail clears the ground, and you can get away from the more common folding table idea, where you have to disassemble the table to load it.
2) You need the posts to keep the tile on the table. Rather, to help it back up onto the table after it falls off. With 4 round posts at the 4 corners, the tile can un-spool lots and it will still climb back onto the table when you pull on it. Without the posts, you have to leave the cab when the tile falls off the table.
3) Tile rolls are about 8' in diameter until you cut the strings. After that, it grows to 12' in diameter pretty quick. I added 4' diameter to mine. Without that extra space, the tile falls down and quickly gets wedged into those posts.
4) Build it heavy enough so that you can set the rail into dirt, and back up. Expect to abuse the hell out of it, especially when loading.
5) I used a 8000# rated axle, actually called a tandem tube. I would go heavier the next time. Be careful how you weld it, cuz it will break at the weld if done improperly( all these points have been learned the hard way)
6) If you mount it on the front of something, expect it to be bashed around pretty good. My dozer throws it around like a flag in the wind.
7)I had good luck by using a hyd control valve that has travel stops on the spools. I have slowed the cylinder down to dead slow, so the cylinder doesn't thrash it around so much with rapid movement.
8) I used a 3" solid pivot shaft for the table to lift/tilt on. That seems sturdy enough, but the 1" pin the cylinder pushes on isn't. The connection between the lever arm and round shaft has gotten really sloppy on mine, needs to be redesigned.
9) Don't overbuild the spider on top of the pole, it is damned heavy at the end of a long day. Not having one is a huge mistake.
10) My center post is in two pcs, so i can take it off when floating. Also, make the post extra long so you have plenty of length to mount the spider. This just makes life easier in the field.
11) Building it strong will create more rotational momentum, This makes it harder to get spinning, and harder to stop. Mine uses a cylinder to push a rubber block against the flat underside of the table. Works pretty well. Any brake design that doesn't actively disengage will likely stick, creating stretched tile. Not good.
12) Although my table is a bit bowl shaped, it should likely be completely flat. I find sometimes the pipe gets pinched at the spot where the table angles up. Would be better if the table was flat. Also, mine is based on a spoke arrangement, but I find that the weight of the spool sitting on those spokes can sometimes dent the pipe a little. Mine could use a little more material to support the weight to help protect the pipe.
13) Design to keep tolerances loose, provide room for the table to flex, twist, etc. If you build it to compact, and things get a little bent during use, you will be stopped.
And just so we don't stop at 13,
14) Make sure you incorporate someplace to carry parts ( couplers, end caps, knives, string)
That should give you some things to think about anyway, have fun.
Ken
ps, The best current design uses 3pt hitch, not wheels. Tractor rides lots smoother over rough ground (tile runs) than a small wheeled trailer. Pounding over rough ground at speed is what destroys commercial tile stringers.