hydraulic circuit review ... again .... please
hydraulic circuit review ... again .... please
(OP)
So .... I took all your advice ... did a bunch more reading and came up with a revised hydraulic circuit.
Just a quick review .... I am building a simple lift. The main section of the lift is a recycled electric forklift. I have stripped the mast of everything except the main lift cylinder ... simple single acting ) gravity down. I am also using the pump/motor.
I have included a N.O. dump valve so I can start the unit "unloaded". I will also tie it into the e-stop circuit to ed-engergize the unit ( even if something unexpected like the contactor welding on ).
I have included a "load check" so the unit will not "drop" when the pump is coming up to pressure.
On the lowering side, I have included a N.C. valve so I can stop the unit if the e-stop is actuated ( it would take a while for the flow valve to slow then stop the unit).
I have also included flow control valve on the raise and lower circuits. I want to get rid of the "jerk" when starting and stopping the lift.
So, can you guys review it again and see how I did this time?
Thanks so much again ..... Mike
Just a quick review .... I am building a simple lift. The main section of the lift is a recycled electric forklift. I have stripped the mast of everything except the main lift cylinder ... simple single acting ) gravity down. I am also using the pump/motor.
I have included a N.O. dump valve so I can start the unit "unloaded". I will also tie it into the e-stop circuit to ed-engergize the unit ( even if something unexpected like the contactor welding on ).
I have included a "load check" so the unit will not "drop" when the pump is coming up to pressure.
On the lowering side, I have included a N.C. valve so I can stop the unit if the e-stop is actuated ( it would take a while for the flow valve to slow then stop the unit).
I have also included flow control valve on the raise and lower circuits. I want to get rid of the "jerk" when starting and stopping the lift.
So, can you guys review it again and see how I did this time?
Thanks so much again ..... Mike





RE: hydraulic circuit review ... again .... please
Ted
RE: hydraulic circuit review ... again .... please
I thought increasing the flow from 0 to 8 gmp will get rid of the bump. Same on the way down.
Am I correct?
Thanks ..... Mike
RE: hydraulic circuit review ... again .... please
Ted
RE: hydraulic circuit review ... again .... please
I just don't have a good understanding of how the flow valve works.
From what I read .... and please correct me if I am wrong .. the CF and EX side of the valve somehow balance pressure ( or at least this is what I took from the literature ). So if the CF side is "taking" 2 gpm at 1000 psi then the EX side will flow 6 gpm at 1000 psi ( assuming a total flow of 8 gpm). I might be very wrong on this!
My thinking is that if I close the flow valve completely then does the EX side of the valve not build up "full pressure" ... or would closing the CF flow to zero put all the flow to EX with no pressure build up?
I guess the only other argument for the N.O. dump valve on the lift side is to instantly stop and ed-energize the system. I am actually planning to motorize these mechanical flow valves so they cycle from 0 to full(10) when starting the lift and then full to say 1 gmp just before landing ... then to zero after landing. It will take 5 seconds to take the flow valve from full to zero. The dump valve will be instant and the load check will hold the lift at its position.
I know this sounds a bit nuts but I can do this with a simple $50 linear actuator and three limit switches ... the mechanical flow valves are about $100.
A few years back I was asked (I do instrumentation / control panels for a living ... along with being a machinist) I was asked to get rid of the bounce in a lift .... it was a simple hydraulic lift standing up nuclear fuel bundles. I simply bought two proportional hydraulic valves, set up a few prox. switches and ran everything off a PLC.
It worked awesome! But I spend about $5K doing the job. I did a bit of searching .... the cheapest proportional valves I found were about $400 each with a $600 board to drive them. Say $500 in a cheap PLC, $500 for software .... I would estimate $2500 plus in parts ... then I need to program it.
Anyway, a lot of money for a "home" project. Maybe one day when I feel rich I will upgrade to this but for now I want a simple and safe lift.
Thanks so much again .... I truly appreciate all your comments and advice!
Mike
RE: hydraulic circuit review ... again .... please
http://www.brand-hyd.com/
Ted
RE: hydraulic circuit review ... again .... please
I am planning on using a FC51 1/2" ... this should give me good flow control between 2 and 6 ( zero to 10 scale ).
My original idea was to have a true mechanical system. I was going to trip these flow valves with a linkage or cable. Started designing it ... nightmare. Without my full shop in operation, it would be very hard to set up correctly.
I then got the idea of a simple ( and cheap ... $50 ) linear actuator to pull and push this flow valve controlling the speed of the lift.
Limit switches are cheap ..... $2 each on ebay.
I realize again this may seem a bit odd but it is only for a "home" system .... not to be used by anyone but myself.
Thanks .... Mike
RE: hydraulic circuit review ... again .... please
RE: hydraulic circuit review ... again .... please
Maybe the pressure would be so little it would not be needed?
Thanks .... Mike
RE: hydraulic circuit review ... again .... please
How do you plan on lowering the lift? Will the hydraulic pump still be running, or switched off?
If it is off, and you are just dumping the cylinder to tank, then you don't need the check valve anyway....
RE: hydraulic circuit review ... again .... please
Mike