Why did they do this??

[DrRod]

In Maryland, lots of Interstate is planted with wild flowers and even daffodils. It really is an impressive sight.

As for other uses of the median strip, I always thought it would be a good place to dump leaves. We have large facilities dedicated to holding residential leaves in the fall and there might be stretches of median where they could be dumped or spread to eventually rot away. Probably some drainage issues plus the risks of trucks working the median, but there are parts where this could be done.

 

[HuskerInVA]

I use to erect/repair/move center pivot irrigation systems back in Nebraska during the summer while in high school. The standard system was 1/4 long and could go longer or shorter. Longest one I worked on was 1/2 mile long.

One option on these systems was that they can be moved. We installed a lot of these in fields that were 1/2 mile wide x 1 mile long with 2 wells, each centered on an end. The drive shafts at each tower could be disconnected and the wheels rotated parallel with the system. Farmer would rotate wheels, disconnect the center pivot from power and well, hook up a tractor much larger than I currently own /forums/images/graemlins/wink.gif, and the 'tow' the system to the other well head in the field.

It was a fun job in late July - 7ft tall corn, 105 degrees, 75% humidity. Let's just say I was in much better shape back then -- now I just keep telling my wife, "Round is a shape. "
/forums/images/graemlins/grin.gif

 

[MossRoad]

You mentioned a drive shaft. What does it drive?

Around here, it appears that there are individual motors on each wheel set. Don't know if they are driven by water or electric. Never looked. However, I did figure that each would have to be geared differently or driven at a different rate since the farthest out wheels have to travel the fastest, then the next set inwards would have to travel slower, etc... except for that corner thingy, when everything changes and those wheels pivot as well as drive. YIKES! Timing nightmare.

Also, the inner sprinkler heads put out only a trickle and they get progressively more powerful as they work out toward the end or the center would flood. Pretty neat systems. A mechanical masterpiece if I do say so myself. /forums/images/graemlins/cool.gif

 

[HuskerInVA]

</font><font color="blue" class="small">( You mentioned a drive shaft. What does it drive? )</font>

On each tower there is an electric motor mounted on the base. Two drive shafts (looks more like a pto shaft) extend to each side of the tower connected to a worm geared gear box which drives the wheels. A 10 tower system is 20 wheel drive. /forums/images/graemlins/wink.gif The gear boxes are mounted on a pivot so the drive shaft would be disconnected and the entire gear box/tire can be rotated 90 degrees to tow the system in a straight line.

On the old systems, I'm sure they changed them to all computer controlled rain gage by now, you would set the percent of time you want the outside tower to run. At 100% it was continually moving, but at full on it would leave very little water on the field. Typical setting was around 20% - move for 6 seconds and shut off for 30 seconds or some proportion of that.

All motors and wheels turn at the same speed -- the inside ones just don't run as much. The movement of the inside towers are controlled via microswitches. When the outside tower got a little bit ahead the switch would get activated and the tower will run until it catches up to the outside and then shut the tower down again. This switch on/of would continue all the way back thru each tower the system so it keeps the entire center pivot straight and synced to the outside tower.

Here's a link to the movable Zimmatic systems I use to install.

http://zimmatic.com/zim_agsysystem_mobile.asp

 

[jimg]

OK, thats was interesting! I wondered how it kept from tearing itself apart. A few of the longer systems (> 1/2 mi I think) in NE were quite impressive. It seemed that if they werent controlled properly they become noodle shaped. I dont think of large pipe being flexible but at that length it look pretty bendy.

 

[HuskerInVA]

It's not one large piece of pipe. A 'flex coupling' is installed between the pipe sections at each tower which allows a certain amount of bending and flex. The pipe between the towers is rigid bolted sections. If you get a bend in the middle of the section this is usually because of something bad happening.

It was always fun after a tornado took one out. Lots of blue wrench work to get the things apart so it can be repaired.

 

[jimg]

Right. I understand its not a single section but from the road it did look somewhat flexible. In fact the sections looked pretty long from the road so upclose Im sure they were.

Did you ever work on the type of system that runs on large wheels very low to the ground? The type Im thinking of has the irrigation pipe running thru the middle of the wheel. I hope thats clear...

 

[HuskerInVA]

Nope didn't touch those. I only worked on the tower center pivots. The one you are describing would most likely not pivot, but move laterally through the field.