Precision air cart metering discrepancy - Page 3 - The Combine Forum
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post #21 of 25 (permalink) Old 05-13-2019, 09:21 AM
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We are having the exact same issue on a new to us 4350 FC. We are now building in a 10% error factor and it seems to be more consistent. I thought we should start over and do a distance calibration again. We have also found we have to work quite hard to squeeze 400 bushels of inoculated peas into a 430 bu tank. We never know densities and with the old 2320, we always used the average density and was usually pretty close. Never liked calibrating and guessing at tank levels. Always nerve wracking whether you will have enough to finish the field. We grow a lot of different crops so go through that every second day or so. Good luck!

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post #22 of 25 (permalink) Old 05-13-2019, 10:01 AM
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Originally Posted by stsdavew View Post
So what do you do? Is calibrating while driving around more accurate?

We have the added complication that our seeds and fertilizers are different to NA so we use the charts etc that come with the equipment as a starting point. Put a known amount into tank then go seeding, when it runs out calculate the rate achieved. The bigger the weighed amount the more accurate your calculation will be. We use both in bin cameras and blockage sensors to know when the meters are nearly running dry. There is no more accurate method IMHO

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post #23 of 25 (permalink) Old 05-14-2019, 08:15 AM
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I have a BG mechanical cart so can't talk specifics, but the only time I do a weight test is when trying something I have no history on such as a new crop or a new fertilizer. In those cases I drive 400ft (or whatever), weigh the sample captured from the metering auger and adjust my gear ratio. Once I have that close then I fill the tank full and drive till it runs out. Product density x tank volume acres shown on GPS. Then that calculation tells me how close my ratio is. I have not plugged a "cal factor" into the monitor for many years. The monitor is used for shaft and fan rpms as well as bin level alarms.

Once you have a history (ie notebook from past years) the calculation for changing driven gear to adjust rates works pretty well:
Known lbs/ac x used driven teeth desired lbs/ac = required driven teeth

The BG cart is pretty darn accurate. I watch the GPS acreage and, once set, I know within an acre when the tank alarm will be going off. But whenever I have done a setup by driving and capturing the product to weigh I am usually out a lot, maybe 20%. I can't figure out why, maybe because the fans aren't on. So ultimately, for me, the best setting accuracy is from running a full tank out.
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post #24 of 25 (permalink) Old 05-14-2019, 09:38 AM
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Once you have a history (ie notebook from past years) the calculation for changing driven gear to adjust rates works pretty well:
Known lbs/ac x used driven teeth desired lbs/ac = required driven teeth


Do you ever go back and look at some of the pages from a year or two ago and wonder what the he!! was I trying to figure out there!!! Sometimes it looks like I was trying to land a ship on the moon!

We have a mechanical Bourgault tank also and like you said, can pretty much go with the same sprockets from year to year. They are very accurate. We put 46 down with an older Bourgault drill, and have to keep fiddling with the settings a bit because the coarseness of the product changes load to load.

Like you said, the best way to get it set right is to fill it right up, that way you know how much is in it with the cubic densities of the products. I know people say doing it by bushels is old school, but if you use bushels by volume and not weight, it is pretty much bang on for plant densities. I tried the 1000 kernal seed way a few times, and worked out to the exact same settings anyway, so I will keep rockin' it old school!

It's easy enough to be pleasant, when life goes by like a song. But the man worth while, is the man with a smile, when everything goes dead wrong!
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post #25 of 25 (permalink) Old 05-15-2019, 09:27 AM
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Ya, I keep it simple. Drove myself crazy a few years ago setting it up for flax the first time. Did the weigh of product by driving 500ish feet, then 1000 ish feet, did it driving through the field, down the road, and each time I was changing sprockets based on weight collected the numbers were drifting all over the place. Was shooting for 35 lbs an acre and had sprocket ratio of around 33:25 based on weigh process. By the time I was done the 160 acres I was closer to 64:21 and still under 30 lbs/ac. That was the last straw for me, I have given up trying to figure out what was wrong in my procedure of simply getting a weight on a 0.5 ac or 1 acre sample to match what a full tank does. Trying to adjust a monitor to display application rate on top of this would make me think I need a $70,000 upgrade. So I rely on what is written in my $5 notebook and that serves me well enough for now.

Having the fans running and a pressurized tank when taking a sample with the BG cart would probably improve things but there is no easy way to collect a sample. We used to collect a couple samples from the seed boots but you are victim of air flow distribution so that is flawed too.

In the end, get ratios close, run out the full tank, make notes, adjust accordingly, and keep those notes.
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