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Re: What's the difference ?
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Posted by Terry W on August 07, 1999 at 10:19:10 from (24.29.240.87):
In Reply to: What's the difference ? posted by Randy on August 04, 1999 at 10:43:41:
Hi Randy. Dennis is right on track with this, but I can tell you a little more about draft control. The top link is connected to a pilot valve inside the three point hydraulic lift cylinder valve, and it measures the "draft", or pull on the hitch. With a tractor in motion and the three point lowered to its working depth, the pilot valve is in its "normal" or closed position. When the implement gets into stiffer soil, or other wise is harder to pull, it actuates the pilot valve to the "raise position", which starts raising the three point until the amount of "draft" or pull returns the valve to the "normal" position. As the load decreases after going through the harder soil, the pilot valve opens to the "down position" opening the lift cylinder drain, lowering the three point until the "draft" is back in the "normal" range, where it closes, holding that depth. Your depth will vary as the condition of the soil changes, but the load on the tractor, and its speed remain constant. Not good if for example you are using a blade to grade a road or landscaping a yard, but otherwise easier on the equipment. Repaired lots of these in the 70's on IH 2300's when I worked for IH in the "Payline" industrial tractor division. Usually a little piece of an O-ring would get caught in the pilot valve, causing the lift to "hickup" up and down with the lift up and no load except the weight of a landscaping box grader. Terry Welshans
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