open/closed hydraulics on grain cart joystick manifiold block - The Combine Forum
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post #1 of 7 (permalink) Old 04-04-2018, 11:39 AM Thread Starter
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open/closed hydraulics on grain cart joystick manifiold block

i'm trying to wrap my head around these picture below.

this is the Joystick controlled manifold block off a Brent 2096 grain cart. connect 2 hoses to tractor to supply/return oil. all cylinders are connected to this block and oil flow is directed by5 electric 3 position valves. Assuming all new tractors that would pull this beast, are closed centre, what's the purpose of the 2 open centre valves for spout rotate and auger tilt only? Manual says to set flow for 8GPM max. How does th system build pressure to do work when valves 1-2-or3 are activated, if the flow is bypassing through valves 4 and 5 to return?

from left to right valves
1. slide gate
2. auger fold
3 spout tilt
4. spout rotate
5. auger tilt

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post #2 of 7 (permalink) Old 04-04-2018, 02:28 PM
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I think the best bet is to actually call up Brent/Unverferth and discuss the hydraulic joystick system with them, same if you have any inkling of trying to run the actual cart with a hydraulic motor ( I see that unit uses mechanical drive off the main mechanical drive system for the bottom drag auger ) . I know when we bought a cart a couple of years ago and was only after the single auger system regardless, they were really helpful at the factory in explaining which hydraulic motor they offered would best suit our tractors hydraulic capacity and also how their system was redesigned now with a valve block that prevented the motor from accidentally being run backwards. The local dealer was clueless, that was soon to be seen.

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post #3 of 7 (permalink) Old 04-04-2018, 03:49 PM
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It could be that one of the closed-center valves opens in conjunction with the open-center valve. This could allow for less flow to those circuits (bypassing some/most of the flow) without too high of hydraulic pressure building up. And sometimes the flow is too low to properly signal the pump without circulating some of the flow. My sprayer's valve block has something similar on it, probably for the same reasons.
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post #4 of 7 (permalink) Old 04-04-2018, 03:50 PM
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I believe that the "open center" they are talking about refers to those specific spools. Often motor spools are "open Center" to wind down as the oil flows through the open center of the spool.
perhaps they use this open center so if the auger touches something it will turn or fold.
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post #5 of 7 (permalink) Old 04-04-2018, 08:15 PM
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My thoughts without actually looking at the diagram, is that you have a constant flow from the tractor at 8gpm. If the valves were all closed centre on the block, when nothing is being used, the oil would have no where to go, and you would have your pump putting out pressure with no flow. The open centre valve would allow oil to constantly be moving through the block, and also have a ready supply for when you use the joystick. The fact that it your tractor is all closed centre is somewhat irrelevant, as in this case, the tractor is only really a pump as the SCV will be locked in detent.

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post #6 of 7 (permalink) Old 04-05-2018, 12:42 AM
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Did you notice that the pilot check valves are on the back side of the open center circuits?
I've seen similar items in other systems where you either have to have back pressure in order for them to open or a minimum pressure to open.
I wonder if these check valves turn your open center valves into something similar to closed center??.
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post #7 of 7 (permalink) Old 04-05-2018, 03:56 PM
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See if you can get the manufacturer to supply you with a schematic and a BOM. This will benefit you in the long haul. Without at least an accurate schematic you will be guessing until someone takes the valves and manifold and reverse engineers it.
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