3-Point Hitch L-series Jerky 3PH - Jeff's homebrew repair.

[Gordon Gould]

I am not a hydraulic engineer but from your explanation I can understand your fix, and how it works, and why you are criticizing the original design. Thank you very much for taking the time to post this. The thing that bothers me is why Kubota won't take care of this.

 

[Harvest Moon]

Nice! Thank you!

All that's left is put together an after market kit with the valve, bracket, hardware, hoses and instructions and I bet there will be a lot fewer up sells at Kubota! Shame on them for letting it go on this long.

Great tractor, lousy hitch function.

 

[J252]

Nice! Thank you!

All that's left is put together an after market kit with the valve, bracket, hardware, hoses and instructions and I bet there will be a lot fewer up sells at Kubota! Shame on them for letting it go on this long.

In my mind, there's no real need for a kit - Other than the bracket (something suitable can be made with a drills and tap), pretty much everything else is right on the shelf at your local surplus center/princess auto/misc hydraulic store. Should be well within the scope of the average owner.

 

[Chilly807]

This looks like a pretty good fix to me. We had talked about adding a restriction before the 3 point hitch, but the problem was that without giving the excess fluid somewhere to go, it ends up going over the relief valve. This type of valve was discussed, I think, but nobody had taken the plunge and tried it.

Reducing the flow rate to the lift cylinder will certainly help, I've noticed that if the loader is lifted at the same time (feathering it is enough) the hitch is much smoother.

Mine will be a little bit different, since I have the remote valve in between the loader valve and the 3 point valve. There may be enough room to one side of the seat to mount the flow divider.

Mine has a newer version of the PCV, I may try checking the adjustment on that before I go this route, but it sure does look like an improvement over mine.

Thanks, Jeff, for both trying this and also taking the time to show us the results. I assume you're in Canada (Princess Auto), but I don't suppose you're in NS??

Sean

 

[canoetrpr]

I am very much a hydraulic newbie so you will have to explain to me how modifying the flow to the 3PT cylinder does not impact the lift capacity.

Also, do I understand correctly that in order to change the lift increment to being more granular, you had to change the physical linkage of the 3PT control arm in some way?

 

[k0ua]

I am very much a hydraulic newbie so you will have to explain to me how modifying the flow to the 3PT cylinder does not impact the lift capacity.

Also, do I understand correctly that in order to change the lift increment to being more granular, you had to change the physical linkage of the 3PT control arm in some way?

Here let another hydraulic noob, try to help, since the cylinder is still the same, and the relief valve is still set at the same, it will just take a little longer to develop the full pressure in the cylinder as the flow rate is lower. So the 3pt lifts slower but will still have the same ability to lift the same load. I learned about pressure and volume about 40 years ago. from trading for a 200 PSI air pump that ran on 12 volt DC. Yes it will develop 200 PSI, but it would take a minute to do that in just filling up its own little 1 foot hose. let alone a tire. the Volume of air it can compress and deliver to anything is miniscule. On the other end of the spectrum is an air pump designed to inflate toys and air mattress etc. It is very low pressure, (PSI) and high volume (Cubic Foot/ Minute)
hopes this helps.

James K0UA

 

[canoetrpr]

Makes perfect sense.

I will try to get a video of my L3400 3PT before it gets traded in next week. I am one of the lucky few to have gotten it changed to the valve from the L3010 so it is 'relatively' smooth. I would say equivalent to what we saw in this thread.

I'm expecting that the 3PT on my new to be M7040 is gonna be smooth!

 

[J252]

Thanks, Jeff, for both trying this and also taking the time to show us the results. I assume you're in Canada (Princess Auto), but I don't suppose you're in NS??

Sean

No problem, I've been meaning to post this up for months.

I'm in the rainy Fraser Valley in BC.

 

[J252]

I am very much a hydraulic newbie so you will have to explain to me how modifying the flow to the 3PT cylinder does not impact the lift capacity.

So the 3pt lifts slower but will still have the same ability to lift the same load.

Yea, Koua got it. The maximum lift force is limited by the system pressure (which we are not changing). The rate of cylinder extension is determined by the flow rate.

Also, do I understand correctly that in order to change the lift increment to being more granular, you had to change the physical linkage of the 3PT control arm in some way?

Actually, I did look into that, but any changes would have to be made to the error mechanism inside the casting near the control valve, and there wasn't clearance to do it.

What I actually did is took apart the control valve and modified the actual spool slightly. I'll post up what I did there later. That said, its a bit of a hassle, and if one can live with non-jerky but low resolution control, just add the flow control.

 

[Chilly807]

The video you posted was at 2000 rpm, and was pretty smooth. How does the flow divider valve work at lower speeds (and pump flow rates), at idle for example? Does it scale the delivery from the CF port to be the same volume (provided the pump still produces that much flow at the lower speed, of course), or is the lift proportionally slower?

Sean