There is no questuon the main PRV will unload at max system pressure. If it did not normal operstions woild fry the pump in short order. The PRV in the loader valve will do the same.
Depends on the cylinder design. A true displacement type SA cylinder has no internal seal,only one port, and dies not have a brearher. Different animal than a DA cylinder being used in a SA application.
I don't understand where the tank return would be installed referring to the schematic that I created and posted above (#21) and again below. The oil is returning from where? As the pump starts to dead head when the piston reaches the end of its travel, the only way to relieve that pressure is to allow the valve to return to neutral or for the PRV to open.
Pressurized oil is returning from the unused remote coupler so it is not dead headed during retract.
So like this? When the valve is out of the neutral position 3b (in this example) is directed to the tank so why would there be pressure in the line to 3b?
You have diagrammed extend which works fine.
Wouldn't pressure be required from 3a as I've shown in order to retract the piston and raise the wings? See the cylinder in the photo below. I'm assuming that pressure is acting on the backside of the piston thereby driving the piston to the retracted position. I would also assume that this cylinder doesn't need a spring since the weight of the wings will extend the cylinder if there's no pressure at the inlet port of the cylinder.
No. Thats fundamentally wrong.
This is really confusing.
Look at the wing cylinder when the wing is down. The piston is fully extended. To raise the wing, the piston has to be retracted. Based on the location of the inlet port to the cylinder, I'm not following your logic.
Those cylinders are an odd construction. Ordinarily the hose would go to the base end which is plugged. My guess is if you look at a component breakdown you will find there is no internal piston and seal. Oil entering the top travels down to the base end around the rod and the resulting pressure against the base of the rod forces the rod out. Its a displacement cylinder like I pictured above and can be fed from either port. Kind of clever.This is really confusing.
View attachment 149271
Here are the cylinders on the folding cutter. There are two 810-150C cylinders, one for each wing, and one 850-217C for the center deck. I've added the schematics from the part manual for the RC3712.
Funnily enough, last summer after I had finished cutting around my place, I raised the wings but the tractor and cutter were on a slight incline (left to right). I had to push one of the wings over the vertical position in order to get that one wing back on the ground.
Ford 6700 tractor that I owned could have had that type valve but I never looked for it due to my 6700 have a cab obscuring sight of the valve body & the fact the single acting cylinders lowered rake wheels with no problems.
Its a stock Red Lion DA cylinder plumbed for a SA application. They used the rod rather than base end to make it pull rather than push..
