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Discussion Starter #1
If anyone has experienced this or has any ideas please let me know.

We run two combines. Have had 6 different 7010s over the last three years and have been real pleased with them.

This year we have 7120's. There are two major changes.

1. cross augers in hopper are hydraulically driven.
2. cleaning fan is hydraulically driven

First problem is the the cross augers become overloaded very easily if shields are set too open. When they overload, the hydraulics bypass and we get cross augers which spit and sputter until finally the hopper is empty. So we closed the shields down which fixed the overloading, but now compared to the 7010's the 7120's unload very slow.

Shortly after this happened we started noticing a lot and I mean a lot of light weight trash in the grain tank. So much so that the grain began to bridge over as we were unloading. Also the yield dropped considerably.

Upon inspecting the ground to see how much grain we were throwing out the back we noticed that grain was pouring out of the fan.

Upon closer inspection we could see grain all along the lip just to the rear of the fan where the air blast moves up to the screens.

The fan shows to have the rpms needed to function properly, up to 1100. Nothing we tried as far as screens, concave, fan speed, etc., would correct the problem.

Its as if the rice is falling down the path that the air should travel on its way up to the screens, and this is either blocking the air or their isn't enough to begin with, and this is what is allowing the light trash to make it into the clean grain.

Keep in mind both combines were running fine til the cross augers drives overloaded and the bypass kicked in, and the the fan is hydraulically driven also. The two may be unrelated, but it would be a big coincidence.
There is so much trash the grain will barely slide out of the grain tank, and the yield went down almost 40%.

again if anyone has experienced this or has any ideas please let me know.
 

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Re: grain falling down in the fan on 7120's in ric

Any chance you changed the precleaner setting by accident? I'd drop the door and dump the grain out from under the fan, then check the precleaner to see that it is set where it needs to be. If it is too open, it will drop grain directly into the fan. Perhaps if the hydraulic bypass is the problem, you had a temporary drop in air speed allowing the fan to get the rice dropped in it. The 7120 should have a door under the fan that can be opened. I don't think the 10 series machines did. You had to remove a panel.
 

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Re: grain falling down in the fan on 7120's in ric

Give these settings a try. Set your unloader auger tents to the top position on the sump side of the combine (setting in seat left), both front and back. The right hand side on the second from bottom both front and back. Check you PFC pressure during unloading, it should run about 2400-2500psi, any more and you could stall your augers.
As for your cleaning system.
1. Pre Sieve- Have 3 or 4 knotches showing from top. If you open more you get grain in fan.
2. Top seive about 19-24 on settings..depends on conditions.
3. Bottom seive about 15-18 on settings..again depends on conditions.
4. Fan anywhere between 850-1000.
5. Concaves even with grates. Maybe slightly tighter.
6. Rotor speed between 730-900.
These are how most of the machines in our area are set and all seem to be doing a great job.
I'm guessing you have the small tube rotor.
Modules are round bar in LH and RH positions 1 and 2 followed by large skip wire in last 2 spots.
Vanes in mid position over concaves, and the last 4 vanes over the grates in the fast position.
Hope this helps.
 

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Re: grain falling down in the fan on 7120's in ric

Almost forgot about cleaning system tilt angle. We've been running at about .7 degrees high to on right side.
 

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Discussion Starter #5
Re: grain falling down in the fan on 7120's in ric

First let me say I was wrong about the fan being hydraulically driven being a new feature. The 7010 were also hydraulically driven.

We just never had this happen with the 7010s, but had it happen to both 7120s in the first 25 acres cut.

It appears that you guys are right about what is happening. Our mechanic came out and said he had seen it happen on one 7010, and it was because the clean grain auger could not keep the grain away fast enough and so it would build up and spill over into the cleaning fan. Once enough rice spills over, then the air flow is reduced to the point that the fan can no longer function properly.

He opened the trap doors under the fans and they were just full of rice. I think the fact that Case installed the trap doors for the 20s indicates that they knew they had a problem.

Nevertheless we could not make it happen again while he was there until he opened the pre sieve from notch 4 to 5 and within a couple hundred feet we saw a yield reduction on the monitor, stopped and the fan was full of rice again.

We put the pre sieve back in notch 4 and haven't had it happen any more after another 200 acres.

Maybe the "new" just had to get worn off the combines. But it is still concerning knowing that the combine is so close to its threshold, that one notch would make such a huge difference. And that we never experienced this with any of the 7010s.

I just hope that whatever grain we are restricting from going into the clean grain with the pre sieve is making it into the tailings before it goes out the back.

"Out driving the machine". I'm like you, how ridiculous is that. For us, it defeats the whole purpose of having these machines if the combine will not move the grain as fast it it can separate and clean it.

Thank you for the suggestions canonuser. Even though it didn't happen yesterday it doesn't mean it wont happen again as conditions change. I will keep your suggested settings in mind as I set the combines. It looks like we are running pretty close to those settings even when the problem occurred. The pre sieve settings seems to be the most critical.

Thank you all for the suggestions.
 

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Discussion Starter #6
Re: grain falling down in the fan on 7120's in ric

I also want to say this. Other than this issue which appears to have been isolated, we have been very pleased with the 7010s and 7120s.
 

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Re: grain falling down in the fan on 7120's in ric

I don't think it is that the auger can't keep the clean grain away but rather that the grain is spilling of the front of the lower sieve. I think this happens when the presieve is open too far because it directs all the material that goes through the presieve on to the front of the lower sieve. I think that this in fact overloads the front portion of thelower sieve making it more difficult to properly adjust this model of combine
 

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Re: grain falling down in the fan on 7120's in ric

You are probably right. We have been scratching our heads drying to figure out the dynamics of what was going on for the rice to wind up in the fan.

Correct me if I am wrong, but all the grain that falls through the bottom screen has to go to the clean grain? If so, then are you saying that the clean grain auger is not necessarily overloading and spilling in to the fan, but rather the grain that falls onto the front portion of the bottom screen if the screen is overload falls directly into the fan and not into the clean grain? Or are you saying it builds up and there is a space for it to spill off the front of the screen before it goes through the screen.
 

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Re: grain falling down in the fan on 7120's in ric

FYI, the new 20 series combines have the two speed clean grain elevator on them standard from the factory and the speed is set on LOW from the factory. When the machine is used in high yielding crop make sure the elevator is set on the HIGH speed (high speed is the same as the standard speed the 10 series elevators ran at). May explain the problems you are having with the 20 series versus the 10 series. High speed 6000bu/hrs capacity and the low speed 3800/4000bu/hrs so set at low it would be possible to over drive the clean grain auger.
 

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Re: grain falling down in the fan on 7120's in ric

Have to agree with all mentioned above, main reason usually is the presive too wide open. My experience however is that filling the fan with clean grain can also be caused by not correct allignment of rotor x concaves. I have seen it on few machines if the concaves are set too much to the left (related to driving direction), there is much more material throwen to the right side of the whole cleaning shoe. therefore somebody sets the SL shoe right side up to push the material back to the left. Correct would be setting the position of the concaves more to the right = more material will be throwen to the left of the cleaning shoe.
ricecutter, do the "killstop" and look into the machine and if you will see more material on one side of the cleaning then the other side, slide concaves to the side where is the more material throwen. Also make sude concaves are "in-line" with rotor and not running crocket...
The reason is if there is more trash on one side of the cleaning, the wind can not "make it through" as the trash falls from the pan to the pre-sive and the material falls over the front edge of pre-sive actually dirrectly to the fan. On the other side of the cleaning with less trash it cleans fine. More fan RPM would solve this problem on the overloaded side, but on the other side would cause grain loss over the sives.
Look into your Ops manual and this setting is mentioned, also the symptoms.

Also make sure if driving up-hill x down-hill, you should always increase x decrease fan RPM. If you do not do it, you will have grain loss going uphill and fill the fan going down-hill.
 

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Re: grain falling down in the fan on 7120's in ric

This is a nearly new combine, so I think this is not it but on our older 1688 we had the clean grain auger worn (3/4" space between auger bed and auger) to the point where it would not auger clean grain out from under the sieves fast enough in 135 bu soft wheat. It only happened when conditions where very dry and straw very brittle, so combined with high ground speed and high sieve loads we had also a lot of fines in the sample and grain pouring out of the fan housing. Slowing down indeed seemed to help the most, we tried opening the concave to have more straw stay in the rotor cage, slow the rotor down for the same purpose, but everything I did either increase losses over the back or dirtier sample.
 
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