My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

[Reg]

Re: My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

Hi EE_bota. I don't know what a sliding friction disk is unfortunately. Not quite sure how to get my printer to scan. I think it has the functionality so I will take shot at it soon and try to scan in the page from the service manual that explains the workings of the position control valve.

I'll try to describe but its bound not to do much good.

- The position control lever turns a shaft which is connected to the a control on the valve which causes the valve to open thus moving the hitch.
- The feedback linkage from the hitch arms is also connected to the same control on the valve and as the hitch moves into position, the feedback linkage arm closes the control on the valve which causes the valve to close.
- The delta between the position of the position control lever and the feedback arm is what causes the valve to open. Once the hitch moves (or drops) because a delta is created by moving the position control, the feedback lever moves into place to close the delta.

It is all a simple mechanical feedback mechanism. No rocket science to it whatsoever.

Yes, this is what I said VERY early on.
The thing I don't (yet) know is whether the delta is regarded as a binary quantity, i.e. ON or OFF, MOVE or STAY, LIFT or STOP.
Slack in the linkages could/might introduce jerkiness and/or dampen it, it is POSSIBLE that a defined amount of slack is part of the design.

My MAJOR point all along has been that there is almost certainly a set-up procedure for the linkage(s) and it is AS LIKELY that this is being overlooked at the factory - as likely as bad/inappropriate parts.

Design, design for manufacture, manufacture WITH set-up if/when needed by the design, etc.

So, anyone have the shop manual with the set-up for this ?

 

[Harvest Moon]

Re: My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

Yes, this is what I said VERY early on.
The thing I don't (yet) know is whether the delta is regarded as a binary quantity, i.e. ON or OFF, MOVE or STAY, LIFT or STOP.
Slack in the linkages could/might introduce jerkiness and/or dampen it, it is POSSIBLE that a defined amount of slack is part of the design.

My MAJOR point all along has been that there is almost certainly a set-up procedure for the linkage(s) and it is AS LIKELY that this is being overlooked at the factory - as likely as bad/inappropriate parts.

Design, design for manufacture, manufacture WITH set-up if/when needed by the design, etc.

So, anyone have the shop manual with the set-up for this ?

I took a closer look at this after reading your earlier post and what I concluded at the time was that adjusting the feed back rod only results in a different final stop for the lift arm. Like Rockyridge discovered:

I did learn that the 3ph is not going all the way to the top though. I should be able to get an additional inch or so higher at the top arm by adjusting the feed back rod.

I'm taking the linkage suggestions very seriously but there are three questions I haven't been able to answer just yet and I didn't find them in the WSM.

1) Is there anything else to adjust other than the rod in this linkage. Or modify?
2) What purpose do the 10 nut's washers and other that are on the shaft (#20 seen in post 116) that connects the position control lever to the valve serve
3) What would be the reason the nearly same assembly on the L3010 would have a different effect?

 

[GMtb42]

Re: My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

Had to go out of town for a few days , ordered parts today , will put in as soon as they arrive .

 

[EE_Bota]

Re: My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

I will make two posts. They are long and bothersome, but they could answer many very good questions on this page.

Reg---you asked "Is the valve binary."
The answer is no. But the system is binary.
At least that's my theory, and here's how I figure it.

If you have strict control of the spool, through some slop-less linkage, it would be proportional to your hand movement.
You could control the speed of movement of the lift cylinder as precisely as you can move your hand.

But the linkages have at least 6 points of slop (looseness.)

Valve spools can be cut in different ways.
As the spool slides, we must connect pressure to the cylinder, but block flow to the tank. Lets design a spool:
We can cut the spool (our choice):
A)So when our hand pushes on the spool, it will push back against our hand at all times.

OR..

B)We can cut the spool so when our hand pushes, the spool pushes against us at first, but then pulls inward instead of resisting our push. This will cause the spool to go full open. This is due to the spool acting link a tiny hydraulic cylinder.

A)IF: I cut the spool to go to the cylinder first*, and pinch off the tank last, I can do proportional control by pinching off the tank to varying degrees. And the spool reaction force will push back against me, taking up all the slop in my linkage. If I make it so that the path to the cylinder is very open before I pinch off the tank, there is no "spool tiny hydraulic cylinder" effect.
Technically, if I push it far enough, it will stop pushing back, but the spring will keep pushing back. SO EITHER WAY, the linkage slop is taken up, and movement of the spool is proportional to our hand movement.

B)IF: I cut the spool to block off tank first, pressure will build in the valve immediately, and upon the spool moving slightly further oil will blast into the cylinder, and simultaneously push the spool open further (in effect, the spool is acting like a tiny hydraulic cylinder and will move on it's own to open the oil path larger until it is either full open, or has firmly compressed the centering spring.) This will continue until either our hand or the feedback linkage returns the spool to center OR until the lift is full up, dead heading the "tiny spool hydraulic cylinder" flow, making the return spring (if present) able to return the cylinder to center.
A man with a strong hand and a tight linkage can prevent this from happening. The linkage in these tractors is too sloppy though, so the valve blasts close to full open.

I suspect the spool on these tractors is cut slightly wrong (B type), and the replacement spool is closer to an (A Type).

So what should be proportional is binary due to the slop of linkages and the way the spool was cut. Can't swear to it, but it's certainly a sound possibility. I have spools cut in various ways for our valves at work so I know this can be done.


*I CAN do this, so long as there is a check valve, or a pilot operated check valve in the system, such that oil cannot spill from the cylinder to tank. The tractor model that I show the linkage for has such a check valve.

 

[EE_Bota]

Re: My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

Warning...this post is not fit to read, and if you choose to not waste time on it, I understand. But the one above is worthwhile, so please consider reading it.

General ideas...I could be wrong, and if so, I don't understand this machine.
Call up the post #116 drawing in a separate window. Do you all agree that:
#240 can rotate in #10, else the spool will be ruined by side loading. #250 attaches to the spool valve.
The tips of #10 can wobble in the doglegs of #20 and #100.
When the dogleg of #20 moves one way, the center of shaft #10 moves in that same direction, the lift moves causing the linkage to move the dogleg of #100 the opposite direction, which moves the center of shaft 10 to the center position again.

Roll-pin #150 is adequate to retain #100, therefore #120 is probably made of spring steel and controls axial movement of #100, pushing inward to make sure #10 cannot jump out of the dogleg, also limit the slop a bit.
Same is true for other side, but collar #320 and bolt #50 act on #40 to make sure #40 cannot rotate, such that all of the other outboard plates and washers can make a friction assembly to make sure the control lever does not move due to bumps in the road, rather it only moves when the operator (person) moves it.

I have little doubt that reduced flow would help..but it makes me wonder if when people change the valve and get success...whether it's actually the valve or is it subtle improvements to all the linkages during the re-installation!
I have explained that the spool can be cut to cause the problem.

 

[Rockyridge]

Re: My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

Great information and well explained EE_Bota.

One more piece of the puzzle that has not been discussed is the 電raft control function.

Draft control works by lifting the 3ph when it senses pressure on the top link of the 3ph. This pressure on the top link is created when using 3ph ground working equipment, for example, a field plow. The harder it is to move the plow through the ground, the more pressure created by the top link. On tractors with draft control, the tractor end connection for the top link is hinged on the bottom so it can move in response to the load encountered and control the draft link control valve. As the top link senses more pressure from resistance from ground equipment, it activates the draft control valve putting more upward pressure on the 3ph which in turn provides more traction for the tractor. As the additional resistance is reduced the top link goes back allowing the 3ph to move back down to the original position.

That much I am comfortable is correct, the rest, not as sure about.

Possibly the play or slop in the linkage is necessary to allow the 3ph to move up some in response to the draft control valve without being over ridden by the position control valve. If that is true, is there an upgrade to the position control valve for tractors that will never install the draft control function?

The other thing that I have not figured out yet is how the counter-pressure is developed on the hinged top link holder. On the old Ford 8N there is a large spring where the top link attaches to the tractor to provide this counter-pressure. The pressure on the top link has to over ride that spring before draft control functions to lift the 3ph and as the pressure decreases it returns to the level it was set at. I do not see anything like that in the L2800 parts list though.

It looks like main control valves were updated to allow for the draft control functionality starting with serial # 53277. If you look at the parts list from Kubotabooks.com for the L2800, toward the bottom of the bookmarks on the left side of the page, you will see the parts list for draft control, including draft control valve, and the top link holder.

It is my guess that the main control valve was updated to allow draft control functionality on all tractors but the extra valve and feed back system is optional and installed only on tractors that were ordered with the draft control option.

I would be interested to know the 3ph works for any tractor with serial number less than 53277. Is it smooth or is that still jerky?

 

[Harvest Moon]

Re: My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

I have explained that the spool can be cut to cause the problem.

Wow EE_Bota, I always suspected if we took our valve to a qualified hydraulic shop or an engineer, someone could modify a component or two to improve things.

After learning more about spools, it seems like its just a lathe cut rod and if I read all that you wrote right... you are saying, if you had a valve and a machinist you could get it right!

That's exciting. I bet if you put the formula together, some of us would send you cash for a specification/CAD to take to a local machine shop shop!

What you said in your second post above made sense to me.

 

[Harvest Moon]

Re: My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

Here it is, I got my tractor back today. I'm pleased but it's not at all the miracle that I'd hoped for.

YouTube - L3400 3 point New LSV New PCV one
YouTube - L3400 3 point New LSV New PCV two

I really don't get it. When I changed the LSV, it seemed that my hitch got jerkier but more responsive. Now that I have the new PCV, I've lost the responsiveness that I'd expected to carry through. I have to move the lever about 1/4" before the hitch moves. Some may suspect the "slop" EE_Bota has been referring too and may be right but before my LSV change my lever was responding in 1/4 inch increments, after it was responding almost instantly. Or at least it seemed that way.

The new PCV is much smoother than the old one, it doesn't necessarily appear that way in the video but if you focus on the fender you'll note that with the new PCV the tractor is pretty still even though there is some bounce with the BB. In the previous videos the entire tractor is shaking violently.

At this point I'm wondering if the LSV change has helped, hurt or is insignificant. I'm not ready to change it back though. If GMtb42 is still willing to go through with his test in spite of my lacking results, we may learn more. Although, I wouldn't blame him if he decided to mail those parts right back.

As for the PCV change, the mechanic said he spent most of his time removing and replacing all the shields. That it wasn't a big deal for him to replace the valve.

Still, more questions:

Why, is my tractor, with the same LSV, PCV and feed back linkage still jerky compared to the L3010?
Why did the extra sensitivity I seemed to gain with the LSV change go away with the new PCV?

The obvious answer would be the last remaining components of the system.
If I up my system pressure to 2400 psi, then I'll have a similar pressure to the L3010 (and a stronger loader). According to TractorData.com the L3010 has 7 gpm and the L3400 has 6.3 (My WSM says 6.31). I don't yet see how that works against me, a big part of our discussion has been about reducing flow. So, that covers the pump, I would think. The only other component that I can think of that would cause the L3400 to behave differently than the L3010 is the cylinder.

At this point we need more info. from someone with a WSM for the L3010. We need to know what size the L3010 3 point cylinder is, I think that means something to this puzzle. I'm close to duplicating the L3010's system in my L3400 and I need to know what's missing to make sense of this.

The L3400 Cylinder Bore is: 75mm/2.9528 inches.

 

[teg]

Re: My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

I had my valve changed out to be somewhat smooth... I can open the LSV and see what is in there, if it's not too hard to do. You said a couple of bolts and 5 minutes? (I'll go back a re-read that post). The problem is that it might be a couple of weeks before I get to see my tractor again

Since the new LSV was more jerky, I would swap the old one back in and give it a try. If I remember correctly, you said it was a 5 minute swap.

 

[canoetrpr]

Re: My quest for "Grand" 3 point performance from my "economy" tractor. The L3400

Harvest - yes your new setup seems to be about as smooth as mine is - it is now a 1/4 inching valve instead of a 1 inching valve.

As per earlier discussion, I think it is cylinder size relative to the flow. As you point out, our flow is similar to L3010. I'm sure the L3010's cylinder is bigger and hence it must take longer to raise the hitch and it is smoother as a result.

Still only a theory. As far as I can tell you have done more work than anyone else to solve this mystery. I appreciate your effort.