Does your 3-point take a hydraulic beating

[sneaky_pete]

</font><font color="blue" class="small">( I have adjustable chain drop limiters on my tractor. Works great, supports my 3/4 ton counter weight well and I can set how low I want the front of my cutter to drop and not worry about it.
The chains hook to the top pin ends on the tractor rear and on the lift arms.
)</font>

Me too. The poor man's position control, but it's simple and easy to use.

Pete

 

[SPIKER]

hi guys thought I toss in my 2 cents:

My JINMA has the same LOCK / LOWER SPEED CONTROL KNOB. anyhow the thing is each HYDRAULIC circuit may be different so making universal quotes won't work. the 3pt pressure relief valve is only in the circuit WHEN YOU ARE LIFTING, and is locked out by the valve I believe, same with a FEL valve, the relief valve is set more or less upstream of the hydraulic control valve for most applications, and usually will only save the pump not the hoses etc down stream of the valves.) I went digging for more info a while back about this, some valves come with LOCK/CHECKS on the valves so that when the valve is set the load can not move. these are more$ so not used very often, way manufactures get around adding the load locks is to make the spool valve the load lock, so that it basically lOCKS the load when the spool is centered.

on 3pt valves, you're relief is on mine again) is upstream / inlet side of the 3pt valve, this will let pressure build in side the tractor lines to it;s relief setting and if it has not yet been reached when pushing the spool valve over to one side the fluid goes through the spool valve once you try to lift too much weight, the relief then opens, and fluid is going through the relief and still to the spool (if it is still being pushed over.) once the spool returns to center then the fluid stops going through the relief and goes through the OPEN CENTER valve.

if you have a CLOSED CENTER SYSTEM (hyd pump is a variable vain pump which always has X000 PSI on it and only adjust the amount of FLOW OUT of the pump then you do not have the open center part of the valve) , but pressure is always on the spool, in these cases then relief valves (if equipped) are more than likely down stream of the spool so that each spool can be adjusted to different max PSI settings.

this means that if you have top & tilt on a closed center system you can have different relief valve settings for each spool... these usually have a center spool mounted spring relief valve, which can be adjustable or non-adjustable or uses shimms... the system can also have a single relief valve for multiple spools but then that goes back to the usually upstream side of the spool...

every valve manufacture is a bit different as they have to be to avoid patent liabilities etc. many ways for many systems :

anyhow hope this muddies up the waters some more /forums/images/graemlins/blush.gif

 

[BillyP]

I've really never thought about it. I just raise the implement and transport on. I've never had any problem with the 3pt hydraulics not holding the implement up during transport.

Seems the leak down on the 3pt system is non existent?

 

[JerryG]

I have never said that you couldn't lock it with the knob, but it is dangerous to the system during transport. The only compact tractor that I can see as maybe being different might be the Grand L's with their external cylinders.

 

[TWINKLE_TOES]

"check chains'

 

[ZJ_HR]

If mentioned tractors have position control, any dropping of lower links, caused by internal hyd leaking will be corrected automatically. When internal leak is strong (worn out o ring on lifting cylinder) 3pt lift jumps often.
Just a stupid question; why you need to lock hyd valve for transport???

 

[MMM]

Not sure if it's available for CUT's, but my Case has a "cushion valve " for 3pt shock loads. My HD cutter also has a set of chains, yoke and it's own notched top link that allow the load to be carried by top link instead of the lift arms while mowing. The cutter is set up with tail wheel and front chain/yoke, then lift arms are lowered completely. The only stress is on sway limiters.

 

[KiotiJohn]

I'm going to have to read this again tomorrow after I've had many hours of sleep!!! I read it over and over until I was more cross-eyed than I was when I got home and it takes some following /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif G'night! John

 

[OkieG]

<font color="blue">... that allow the load to be carried by top link instead of the lift arms </font>

I wish I could visualize that. The top link in my conventional system maintains front-to-back alignment of an implement. It can only be in tension or compression, ie have stretch and squish forces placed on it, and that's about it. It carries a load in the sense that it limits how far an implement can pivot around the lift arm pins. Can you post a picture to show how the toplink carries the load? Thanks.

OkieG

 

[RoyJackson]

"Just a stupid question; why you need to lock hyd valve for transport???"

Not a stupid question...

I can see locking the hydraulics to prevent an accidental lowering of the implement during transport since you cannot lock the rockshaft lever (at least not on my 790).
Also, although the manuals (and common sense) tell you to lower any implements when the tractor is shut down, there may be occasions the implement must be left in the raised position (can't think of any reason though), again to prevent an accidental or inadvertent lowering.
Just remember that even with that hyraulic lock, you don't want to get under that implement!!

However, the lock in conjunction with an adequate number of jackstands may be a reasonable way to work under the implement...not sure I'd do it that way, but I don't make my living on tractors.

 

[JerryG]

If I may, I believe that he is referencing to the third arm bracket on the tractor end, as carrying the load. The chains attach to the 3/4" pin on the tractor and then, the 7/8" pins on the implement. (Cat 1)

 

[PineRidge]

OkieG I'm with you, I would like to see a picture as I can't make a visualization of the set up.

 

[MMM]

I could cut quite a few acres in the time it took to figure this image deal out! /forums/images/graemlins/grin.gif

 

[JerryG]

<font color="blue">I would like to see a picture</font>
Picture Above.

 

[MMM]

Well, the image showed up in the preview? Try it another way-
http://www.hpphoto.com/servlet/com.hp.HPGuestLogin?username=mnmmayhaw&password=38554331

 

[OkieG]

MMM,
Please excuse my ignorance, but what a peculiar looking set-up. Somebody put a lot of time in to figure that out. Does the bar with the pins on top connect to the toplink tractor mount?

Just when I think I'm starting to get a handle on things, something comes along that throws me. I appreciate the picture (and yours too Jerry). I think I have a little better idea of what you're talking about, but I've never seen anything like that at the tractor stores I've been to.

Remind me,...what does that set-up do for you?? Thanks again.

OkieG

 

[MMM]

You won't see it in stores as it's an industrial cutter used in maintaining utility, etc, right of ways. Closest thing I've seen is BH406. The beast is rated for 4"dia, has 165hp gearbox and has 1/4" deck.
It is very heavy, hence the need for the lower link relief. The front of cutter is essentially carried by the chains instead of lift arms while mowing.

 

[jinman]

OkieG, I'm attaching a photo of my old Ford Jubilee with the setup Jerry showed. In principle, it works just like the one MMM posted. MMMs setup is adjustable in height by moving up and down the toplink whereas the chain setup is adjustable by taking up more or less links in the chain on each of the sidelinks.

In this photo I was also experimenting with using chain instead of a toplink because I was mowing on some very tough terrain. Some folks say this is dangerous if you hit something with the front lower lip of the mower and cause it to flip forward. /forums/images/graemlins/shocked.gif I never had that problem. /forums/images/graemlins/grin.gif

Both of these setups are especially good if you have a 3PH that leaks down and you constantly have to correct for that leakage during mowing. It can also be used to relieve any pressure on your 3PH during mowing.

On my new tractor (NH TC45D) I never use this setup for mowing because the cutter is so light and the 3PH probably only has abotu 350# of load on it from my 5' cutter. I'd bet it is never over 500# even with the heaviest cutter as long as the tail wheel is on the ground. For long transports down a gravel road, I always just let my tailwheel ride on the road, and that also keeps more weight on the front wheels anyway.

PineRidge initially asked about his tractor's ability to lock the 3PH and I have checked my Repair Manual and have an answer for him. I'll do another post with the hydraulic circuit to discuss this issue separately.

 

[jinman]

PineRidge's original question related to not having a physical lock feature for his NH TC40D. The attached hydraulic diagram should clear up this issue for our specific model of tractor, but there are no guarantees any other tractor is the same. My guess is that there are several with similar designs, but I'm the kind of person who wants to see the actual schematic and make my own personal decisions about my comfort level with the design.

In the attached diagram, the hydraulic pump and filter are shown on the left and immediately after the high pressure fluid leaves the pump, it goes to a relief valve. Therefore, the pumps outlet pressure is always limited by this relief valve (150 bar, 2135 lb) on our Boomers.

The fluid continues into the HPL control valve that provides position control to our 3PH. Inside the HPL valve, there is no pressure relief valve. Any pressure feedback from the lift cylinder assembly (ref no. 7 & 8) is felt by the HPL valve components. The pump relief valve will only be in the circuit while the 3PH is actively lifting a load. When the position control nulls out the control handle input, the lift cylinder becomes isolated from the pump circuit because the unloading valve opens and directs input fluid back to the reservoir.

There is, however, a pressure relief that is always in the system. That is a high pressure relief valve that is an integral part of the hydralic lift cylinder. That valve relieves pressure at 3650 psi (250 bar). It's function is to relieve extreme shock loads from the lift cylinder.

When the flow valve (ref no. 8) is fully closed, the shock pressure is relieved from the HPL valve and is only felt by the lift cylinder. The flow valve effectively isolates the entire HPL valve circuit from the shock. If there is damage, it will be limited to the lift cylinder only. Therefore it is my contention that this valve could be useful for locking the 3PH position because ultimate protection is still supplied by the high pressure relief valve and the HPL valve is completely protected. /forums/images/graemlins/cool.gif

 

[OkieG]

<font color="blue"> third arm bracket on the tractor end, as carrying the load. </font>

Is that a bracket that's not on a small tractor like mine? Is the toplink connector so strong that it's better to chain implement weight to it, rather than allow the lift arms to carry the load?

I can see the utility of the chains to limit drift down on a 3PH w/o position control.

Jerry, MMM and Jinman, thanks for your patience. I appreciate the education.

OkieG