Jerky project cylinder action
- Thread starter yarg
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J_J
Super Star Member
- Joined
- Sep 6, 2003
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- 18,952
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
If the pump can put out 20 GPM's, and your cyl valve is only passing about 3 GPM's to the cyl, at full stroke, how much fluid is passing through the relief.
The intent here is to show that it is not about the pressure.
2 in bore
1 in shaft
3000 psi pump
If you adjust the relief valve down to 1500 psi, you can still lift about 9,425 lbs
I don't think you will be lifting anything close to that weight.
If those hyd motors are 1500 psi motors, then you need to set the hyd motor valve relief at about 1450 psi. That is solely to protect the motor.
The motor valve relief valve will set the max relief for any valve downstreal. The fluid then flows to the ram valve, where the ram relief valve can be set anywhere below the main relief valve. Some reliefs can be set from 500 psi to 3000 psi.
Another point here is that if the hyd motors are using all the pump flow, there is none left for the ram.
The two spool motor valve has priority.
The intent here is to show that it is not about the pressure.
2 in bore
1 in shaft
3000 psi pump
If you adjust the relief valve down to 1500 psi, you can still lift about 9,425 lbs
I don't think you will be lifting anything close to that weight.
If those hyd motors are 1500 psi motors, then you need to set the hyd motor valve relief at about 1450 psi. That is solely to protect the motor.
The motor valve relief valve will set the max relief for any valve downstreal. The fluid then flows to the ram valve, where the ram relief valve can be set anywhere below the main relief valve. Some reliefs can be set from 500 psi to 3000 psi.
Another point here is that if the hyd motors are using all the pump flow, there is none left for the ram.
The two spool motor valve has priority.
Yes, JJ,
I have all of that. I have the motor spool valves set at their lowest, 1500 PSI setting therefore the rest of the circuit is protected pressure. The down stream valve for the ram is going to get a 500-1500psi adjustable relief that I will set just high enough for the load on the ram, when the ram is full and during the filling excess oil can then go through this relief valve to the tank. This should not overload the pressure and engine HP from the pump? The pump is rated up to 2300 PSI and 23 or 25 GPM max? I got it from Surplus center like much of the other parts.
I never want to use the ram at the same time as the motors so that is not a factor. The last thing I want is to have pipe in the ground and have someone activate the mast ram
Bad ju ju. So I put an integrated lock on the ram when fully vertical.
I am looking at needing about 1200 ponds of force to lift or lower the mast so 500 PSI will be more than enough?
Gray
I have all of that. I have the motor spool valves set at their lowest, 1500 PSI setting therefore the rest of the circuit is protected pressure. The down stream valve for the ram is going to get a 500-1500psi adjustable relief that I will set just high enough for the load on the ram, when the ram is full and during the filling excess oil can then go through this relief valve to the tank. This should not overload the pressure and engine HP from the pump? The pump is rated up to 2300 PSI and 23 or 25 GPM max? I got it from Surplus center like much of the other parts.
I never want to use the ram at the same time as the motors so that is not a factor. The last thing I want is to have pipe in the ground and have someone activate the mast ram
Bad ju ju. So I put an integrated lock on the ram when fully vertical. I am looking at needing about 1200 ponds of force to lift or lower the mast so 500 PSI will be more than enough?
Gray
bigdeano
Platinum Member
j-j,
This must be a quiz. OK. yarg, no cheating by looking at my answers, LOL
1. Not very much, too many variables to give a number. Seal drag, pressure drop in pipes, valves, etc.
2. Whatever pressure the relief valve is set at. If there's no relief valve, whatever pressure it takes to break the weakest part or stall the prime mover.
3. To protect the pump and other system components from excessive pressure.
How'd I do
Darn, I was too slow typing.
This must be a quiz. OK. yarg, no cheating by looking at my answers, LOL
1. Not very much, too many variables to give a number. Seal drag, pressure drop in pipes, valves, etc.
2. Whatever pressure the relief valve is set at. If there's no relief valve, whatever pressure it takes to break the weakest part or stall the prime mover.
3. To protect the pump and other system components from excessive pressure.
How'd I do
Darn, I was too slow typing.
bigdeano,
I think you aced it! Better answers than mine but the same concepts. I said in the beginning that I am a beginner and it shows but I am a quick study most often? I am not as much a technician in my terms but I do get the ideas.
My biggest confussion is on the proportioning valve option. If the excess flow is or is not subject to a pressure relief valve in such a unit? No matter whether I go to such a modification or not, I would like to know----the learner in me. I am not ashamed of learning from anyone who offers information. Healthy for me.
I think you aced it! Better answers than mine but the same concepts. I said in the beginning that I am a beginner and it shows but I am a quick study most often? I am not as much a technician in my terms but I do get the ideas.
My biggest confussion is on the proportioning valve option. If the excess flow is or is not subject to a pressure relief valve in such a unit? No matter whether I go to such a modification or not, I would like to know----the learner in me. I am not ashamed of learning from anyone who offers information. Healthy for me.
bigdeano
Platinum Member
By having the motor running yarg is limiting the pressure available to the ram to the back pressure developed by the motor. If the motor was under load there would be more pressure available to the ram.
bigdeano
Platinum Member
Technically, the excess flow does go thru a relief valve, but the pressure of that valve is controlled by the flow in the controlled flow port. The flow out the excess flow port has to be restricted to develop pressure for the controlled flow port, otherwise all the flow would just go to the tank, if that's where it's hooked to.
The excess flow port can be used to power another circuit as well.
Last edited:
Mace Canute
Elite Member
I think the problem may be more about flow and (lack of) flow capacity then "pressure".
yarg, what happens when you extend and retract the lift cylinder at both full throttle and at an idle with the lift control valve at maximum both ways and also the same test "feathering" the lift control valve?
yarg, what happens when you extend and retract the lift cylinder at both full throttle and at an idle with the lift control valve at maximum both ways and also the same test "feathering" the lift control valve?
OK,, so what you are explaining is that this sort of valve has it's own relief built in? Then you would have anything back of that valve at the pressure of that relief and that means that for any of the excess flow to get through the valve, it would have to be at that pressure?
So a proportioning valve does split the flow between a working port and a return port but the pressure upstream of both will be subject to the relief of the built in portion of this valve? This makes sense as from one written discription, it seamed that there would be high pressure upstream of the working port and into the actuated device but no pressure upstream of the flow through port. This did not make sense to me as in my mind, any upstream pressure must be present to the working port load and the overflow port.
Did I explain it right? Quiz two for me, or maybe five?
So a proportioning valve does split the flow between a working port and a return port but the pressure upstream of both will be subject to the relief of the built in portion of this valve? This makes sense as from one written discription, it seamed that there would be high pressure upstream of the working port and into the actuated device but no pressure upstream of the flow through port. This did not make sense to me as in my mind, any upstream pressure must be present to the working port load and the overflow port.
Did I explain it right? Quiz two for me, or maybe five?
MC,
Well, no matter the throttle point the engine is stalled. The valve would just bearly be able to handle the flow at high RPM and the pressure at any speed is such that it would reguire HP to work because the ram volume is so small that it fills or looks full to the flow as soon as you trigger it.
Feathering is almost impossible. The only way I could get good action was running a motor ( taking most of the flow away to the tank ) while valving the ram. In taking most of the flow away, I could throttle the flow to a lower pressure than the spool relief valve. Given this info. I decided that my first attempt at a change is to get the low pressure relief and a needle for flow control?
Well, no matter the throttle point the engine is stalled. The valve would just bearly be able to handle the flow at high RPM and the pressure at any speed is such that it would reguire HP to work because the ram volume is so small that it fills or looks full to the flow as soon as you trigger it.
Feathering is almost impossible. The only way I could get good action was running a motor ( taking most of the flow away to the tank ) while valving the ram. In taking most of the flow away, I could throttle the flow to a lower pressure than the spool relief valve. Given this info. I decided that my first attempt at a change is to get the low pressure relief and a needle for flow control?
