I'm making some progress on the hydraulic reconfig.
Because the main pressure feed line will be redirected, it's essentially a complete redesign of the system.
In the old design there are three lines connected to the TCV: the high pressure feed line from the pump, the big low pressure return-to-tank line heading up to the oil cooler, and lastly a small low pressure line from the power steering valve connected to the TCV at the point marked, "PB" where it dumps the ps valve's return-to-tank oil into the low pressure side of the TCV, sort of using the TCV as a tee. From there that oil joins the other low pressure oil heading off on its way, first through the oil cooler, then through the oil filter, and finally into the tank.
I can use the magic of Gimp to illustrate:
In the new design, there will again be 3 lines attached to the TCV: The high pressure feed line from the pump, as before. A new high pressure feed line leaving the TCV's new power beyond port, heading outboard to underneath the right side foot rest. And a new low pressure line leaving from the old return to tank port, heading up to join into the newly created return-to-tank manifold.
At rest position, the high pressure oil entering the TCV will all pass through and exit via the new power beyond port, where it will make its way underneath the right hand footrest and ultimately arriving at a quick disconnect of in front of it.
With the travel spool activated, the high pressure oil will head from the TCV to the travel motor and cause the tractor to move. The return oil from the motor will then make its way out the power beyond port. So whether the tractor is in motion or not, there is always flow out of the power beyond port and therefore always some pressure available at the quick disconnect in front of the right footrest. Using the loader while the tractor is in motion will cause the pressure to be split between the two functions. So the tractor will slow down while the bucket raises or whatever, but neither will be completely starved of flow.
With the lift spool activated, the oil heads out of one of the lift ports, through the lift cylinder, back into the other lift port, and is then dumped into the new return to tank line. So the new return to tank line can be much smaller than before, because it only has to handle oil coming from the lift cylinder, and only when the cylinder is actually moving. Most of the time there will be no flow in that line at all.
So we now have two small lines and one large line that all need to be connected to return-to-tank: The original small return line from the power steering valve, the new small return line from the TCV, and large line that will be coming, via a second quick disconnect, from the loader valve.
Due to space constraints and the way things are arranged in the tower, I have changed the return oil flow a little bit. All return oil will enter a half inch NPT pipe built-up manifold at the forward edge of the right side tower access panel. From there it will pass through the oil filter, and then through the oil cooler before turning to go straight up into the bottom of the tank.
It seems to me that there's a lot more space to work and better access in the tower with this new configuration than there was before. So that's a big plus.
In the original config, the hot return oil went through the cooler before it passed through the filter. Now it will now go through the filter first and then through the cooler. I think that's a better situation, because the oil is less viscous when it's hotter, allowing it to make its way through the filter that much easier. Due to the combined effects of pre-cooled oil passing through an undersized filter head, I strongly suspect that in the factory configuration a lot of the oil is actually bypassing the filter itself and just dumping through the filter head's relief valve straight into the tank. I documented elsewhere that I've increased the size of the filter head and increased the GPM capacity of the filter itself. So I really do think that the majority of the oil will now actually pass through the filter elements, which should be a benefit to the system overall.
The built-up manifold consists of a regular half inch NPT tee that will be connected to the new return side quick disconnect, and a small pipe nipple onto which I've welded two JIC6 male stubs.
(If you want welds that look THIS good, you'll have to hire me!
)
The two smaller return lines will screw onto those JIC 6 fittings, and the half inch line with the quick disconnect will just stick out of the right side of the tower. I will modify the tower access cover, cutting out a u-shaped area so that pipe can stick out there.
So now there will be two quick disconnects in the vicinity of the right side footrest: a lower outer one that will be pressure supply, and a upper inner one that will be low pressure return. With the loader attached, you will just hook up two hoses to the new loader valve. One supply and one return. With the loader detached, you will have to hook up a loop back hose from the supply qd directly to the return qd. So it'll be a little bit like a PTO valve: either the loader valve needs to be hooked up or the loop back hose needs to be hooked up to give that high pressure flow a way to make it back to the tank.
If you forget to hook up that loop back hose, then all of the pressure side fluid will have to make its way through the TCVs pressure relief valve back to tank. It seems like it would be pretty hard to get the tractor to start in that condition, and if it happens while the tractor's running, I think it's going to make a loud unpleasant squealing noise! But there should be minimal if any risk of damage or injury in either case.
The high pressure side's pressure relief will now be controlled either by the setting on the TCV or the setting on the loader valve, whichever is lower. I'll have to tweak the TCV's main pressure relief upward a little bit if I find that my bucket tilt-back force is too weak for my satisfaction. I'm confident that every other function should have plenty of strength at 2100 PSI.
Half inch NPT pipe and fittings are plenty strong for the return side, since it will never see more than about 20 PSI under any circumstances.
For the supply side, I'll come out of the TCV with a short hose just for vibration damping purposes, and from there run half inch NPT pipe. Half inch black iron pipe is good for at least 5,000 PSI or thereabout. The weak point is the off-the-shelf iron fittings which are only good for about 300 psi. But I've picked up some heavy carbon steel NPT fittings that are good for 4,000 PSI. So I'll run standard 1/2 pipe and use those heavy fittings.
I'll route the lines under the foot rest but above the loader cross member.
By using the steel pipe, it has enough strength and structure all of its own to support the free-floating quick disconnect without having to manufacture a bracket to attach it to. On the return side l'll manufacture a bracket that will bolt to the tower and hold onto the pipe/disconnect, because otherwise I'd be asking the aluminum filter housing to support that weight and torque and vibration. And that's not going to hold up long term.
It's not all done yet. But I now have a clear vision for where it's going and it's nothing but the process of finishing it up. I'm starting to get excited!
