Without a practical way to get mechanical power to front wheels because they are mounted on long drop steering spindles to achieve the necessary crop clearance, the goal became driving the front wheels hydraulically.
This is quite an impressive makeover. I would guess there are plenty of situations where this electrohydraulic vehicle would solve problems on farms. I wonder if these folks are planning to commercialize their vehicle.
I agree it's impressive, Rob. The ag industry is known for innovative use of hydraulics and this is a perfect example. A few years ago (okay, maybe it was 25 years ago), I did a story for Design News about a farmer who developed an electrohyadulic actuation system to tip over a silo, lay it on its side, and lift it onto a flat bed trailer.
Chuck, the silo story is another impressive story about hydraulics used on the farm. Are these issolated instances of inventive solutions -- or, do some of these solutions get commercialized. I would guess the need goes beyond these individual instances.
I'm curious how they did the rear drive system on the machine.
The picture shows "crop clearance" for the rear wheels, but the article states "The normal transmission output is used to drive the rear wheels." I'm used to seeing a traditional differential rear end, but I obviously dont' see a "pumpkin" hanging down low.
Did they install some sort of bevel gear adapters on the end of the normal differential, with an equivalent set down on the wheel centers?
Given the concerns about weight and sinking into the mud, I was surprised with the relatively thin tires. Being in the mining industry for a number of years, the first thing that was done when needing "high flotation" was to increase the width of the tracks in that case. I wonder why a wider tire wasn't implemented here - or is that a farming requirement due to the width of the furrows?
A spray rig needs to be able to make extremely tight turns at the end of the field. Any normal steering axle that is also driven would be limited by the angle of the wheels because of the universal joints. Some 4 wheel drive tractors use a right angle drive at the top of the steering kingpin through a hollow kingpin down to the wheel. Problem for an application like this with extremely low production would be that the cost of machining and fabrication of the special gears and such would be prohibitive.
The rear wheels can be driven by a set of gears, or belts, or chains without a problem, but the ability to turn makes the front axle more difficult.
Don't know if you have ever spent any time on any farm equiptment, but it is normal that ag equiptment is able to have a turn radius that is little longer than the length of the vehicle. A normal 4 wheel drive truck has a turning radius larger than a comparable 2 wheel drive truck. And most 4 wheel drive axles, when engaged, require an even larger turn radius.
Consider that a field will have rows spaced 30"(or 24"). The wheels may be spaced at 120" to go down the center of the rows. That puts 4(or 5) rows under the tractor. There will be 3 rows outboard on each side. So I get to the end of the row and pick up the implement at the end of the row and as soon as it is clear of the crop I do a hard turn to clear the fence at the edge of the field (and I don't allow any extra rom because if I make the turn around area 4 foot bigger I lose a couple acres at each end of the field) and then I make a sharp turn into the sixth row over and head to the other end of the field. If I have to wrestle with a vehicle with a large turn radius I will waste a lot of time trying to get out of the currrent row and into the next. With 3500 acres to work I don't have a lot of time to spend maneuvering, as getting the current spray on the field may be a time sensitive operation.