Disc Opener Down Pressure - The Combine Forum
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post #1 of 16 (permalink) Old 06-30-2019, 12:11 AM Thread Starter
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Disc Opener Down Pressure

I've been curious how consistent the down pressure is on my drill openers through their range of travel. Finally found my crane scale so I could take some measurements. My drill is a Pillar Laser. I measured the down pressure for every inch of travel at the packing wheel. I also calculated what the disc down pressure would be at each increment. Here is how I did the measurements:


And here are the results. I typically run the drill with the opener compressed between 3.5 - 4.5 inches. Pillar states that the down pressure on the disc is 600 lbs from the factory. Looks like they were right on the money!


IMHO, I think the drill has pretty consistent down pressure for using a spring. Obviously hydraulic down pressure would be more consistent, but it adds a lot of cost and complexity.

I also experimented with adjusting the down pressure spring on the opener to see how much I could change the pressure by turning the nut on the adjustment bolt. Looks like I get about a 2.5% change in down pressure per revolution of the nut:


I'm probably going to experiment with turning up the down pressure when seeding this fall. I usually have to go fairly deep through some hard soil to get to moisture.

A friend of mine has a JD 1890, I might and see if I can take the same measurements off his drill to see how it compares.

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post #2 of 16 (permalink) Old 06-30-2019, 08:51 AM
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That is less of a change than I thought. I was always going to try this out too. But you talk to your friend about his 1890 and then I don't have to!


For downpressure I ran my pillars so the nut would just come out of my deep socket on the impact and not turn anymore. Very scientific I know!


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post #3 of 16 (permalink) Old 06-30-2019, 09:44 AM
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That's really good info to understand how the movement range and spring adjustment works. Pillar should have that in the manual. Unless I am out to lunch, I don't see a lot of variation by adjusting the springs unless you make a big change, like an inch. 4 turns I am guessing is under 1/2". When I am seeing hard soil I am thinking I am seeing 50% firmer than normal so a 4 turn adjustment really has negligible effect if changing pressure by 10%. So this is confirming my belief that shim adjustment of the cylinders is more important to get the opener to nose in more. When the drill starts pulling harder because your shim change resulted in more bite then that is ultimately putting more down force on the disc. Yes, by changing the shims you are getting the openers to go a little deeper too but I would say the angle is what is creating the added loading. I can seed at 1" and then change packer depth and seed at 1 3/4" and run similar load or I can seed at 1" and then change cylinder shims to get a similar load as if I was at a 1 3/4" setting. The difference is how much force the shape of the hoe wing has added to pull the disc into the ground.
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post #4 of 16 (permalink) Old 06-30-2019, 11:07 AM Thread Starter
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Originally Posted by kenmb View Post
That's really good info to understand how the movement range and spring adjustment works. Pillar should have that in the manual. Unless I am out to lunch, I don't see a lot of variation by adjusting the springs unless you make a big change, like an inch. 4 turns I am guessing is under 1/2". When I am seeing hard soil I am thinking I am seeing 50% firmer than normal so a 4 turn adjustment really has negligible effect if changing pressure by 10%. So this is confirming my belief that shim adjustment of the cylinders is more important to get the opener to nose in more. When the drill starts pulling harder because your shim change resulted in more bite then that is ultimately putting more down force on the disc. Yes, by changing the shims you are getting the openers to go a little deeper too but I would say the angle is what is creating the added loading. I can seed at 1" and then change packer depth and seed at 1 3/4" and run similar load or I can seed at 1" and then change cylinder shims to get a similar load as if I was at a 1 3/4" setting. The difference is how much force the shape of the hoe wing has added to pull the disc into the ground.
You are correct, it takes a lot of turns of that nut to make much difference in down pressure. I should have mentioned the adjustment bolt is 10 TPI. On mine there is about 1.75" of thread below the nut, so if I cranked it all the way down I could get about 40% more down pressure, which is significant but takes about 17 turns on the nut. For this fall I'll probably crank one side of the drill down 10 turns for a 25% increase and see if I can tell the difference in emergence.
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post #5 of 16 (permalink) Old 06-30-2019, 04:59 PM
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Ok. I could have looked at mine to gauge the amount 4 turns would do. Just thinking out loud. I haven't adjusted my springs yet. For me low areas and sand/gravel are far more common than hard dry clay hills so uncertain if I want to adjust springs. I would say that if I was in predominantly harder dry ground then tightening them up would make sense. I would have to ask the guys at Pillar how they settled on that 600# value. More so adjust them for generally harder soils of the region you are in and leave them there. I can't say I have noticed any differences in emergence in wheel tracks either so haven't done anything different to the openers behind the wheels. I do beleive my discs and boots wear faster there. It is good to have the data though, knowing how much the pressure changes is certainly good info to understand what will happen.
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post #6 of 16 (permalink) Old 06-30-2019, 10:39 PM
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Is it possible the 600# has something to do with how heavy your drill is? I have JD 750 no-till with hydraulic down pressure. The pressure gauge that came with the drill had green and red zones. I can't off hand remember the pounds of down pressure that deere assigned to hydraulic pressure. But if you ran in the red zone and the seed box was mostly empty..... it could take pressure off the rear drive wheel and cause it to slip. There are a spots to add weights to the rear of the drill if consistently runninng higher pressure either due to hard ground or more depth.
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post #7 of 16 (permalink) Old 06-30-2019, 11:27 PM Thread Starter
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Is it possible the 600# has something to do with how heavy your drill is? I have JD 750 no-till with hydraulic down pressure. The pressure gauge that came with the drill had green and red zones. I can't off hand remember the pounds of down pressure that deere assigned to hydraulic pressure. But if you ran in the red zone and the seed box was mostly empty..... it could take pressure off the rear drive wheel and cause it to slip. There are a spots to add weights to the rear of the drill if consistently runninng higher pressure either due to hard ground or more depth.
Well my drill weighs just over 30,000 lbs and has 48 openers, so that's 625 lbs per opener. However there is only going to be that much weight on the discs if the ground is so hard they don't penetrate at all. Otherwise the pressure is going to be split between the disc blade and the packer wheel. I imagine I should be able to increase the down pressure quite a bit before I would need to add weight to the frame to keep it in the ground.
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post #8 of 16 (permalink) Old 07-01-2019, 09:32 AM
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Ever have conditions where it won't penetrate? In our hard clay the Cross Slot will sometimes rattle along on top in the fall.

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post #9 of 16 (permalink) Old 07-01-2019, 09:57 AM Thread Starter
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Ever have conditions where it won't penetrate? In our hard clay the Cross Slot will sometimes rattle along on top in the fall.
Only when going through a rocky spot! Other than that I've never really seen it fail to penetrate. I have had situations where it hasn't packed as well as I'd like though since the more pressure the disc takes to stay in the ground the less pressure there is on the packer wheel.
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post #10 of 16 (permalink) Old 07-05-2019, 11:28 AM
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Your friend will be horrified when he sees the crazy range on his 1890. There's a cure for that -- hydraulic downforce.


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