[AT] Hydraulic flow question?

[Thomas Martin]

That's the problem, the relief valve should adjacent to the return to the tank!
Otherwise the pressure relief valve is not protecting the actuation circuits.
I'm surprised the valve housing is not marked with P for pressure & T for tank.

Tom
> On 11 October 2019 at 12:00 Carl Gogol <cgogol1971 at gmail.com> wrote:
> 
> 
> James,
> The circuit is simple.  It is a three spool mono block open center valve.
> It is good for about 20 GPM and the tractor's pump is about 12 GPM>
> High pressure oil from pump is first going through the valve's pressure
> relief valve; 
> 1-  next in line is the motor control spool, a 4-way with detents with oil
> returning to its companion port.  
> 2- Oil then flows to a 4-way port to ram #1. power extend, gravity return
> both on one of the spool's ports.  I'm not sure it is needed but this
> spool's companion port is never-the less connected to the return flow line.
> I used it on a similar mower and don't remember if this connection was
> required.  Don't see how it hurts even if it is unnecessary.
> 3- second ram is identical to #2 above but downstream from #2.
> 4- Finally oil is returned to the reservoir
> Carl
> Manlius, NY
> 
> -----Original Message-----
> From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of James Peck
> Sent: Thursday, October 10, 2019 11:18 AM
> To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
> Subject: Re: [AT] Hydraulic flow question?
> 
> I believe some hydraulic valves use orifices to limit spool speed. Can you
> sketch the circuit for us?
> 
> [Carl Gogol] I just finished replacing a triple valve on my International
> 140 that controls a side mount Alamo (triumph) sickle bar mower.  I did it
> because I had the valve and the motor control on the "new" valve would
> reverse the
> motor where the original would not.  This is handy when the mower jams.   
> The problem I created is the two controls for the hydraulic rams for
> positioning the cutter bar are connected with ¼" hoses but the valve's ports
> are all ½', -- but so were the original valve's.  
> Problem - just moving one of the control's levers for a ram will stall the
> tractor if opened all or most of the way.  
> One solution - Limit the movement of the ram spools in some manner like
> using a spacer to limit spool travel.
> Question - Is there a more hydraulicy correct way -  the original valve did
> not suffer this issue.  BTW- system is open center.
> Carl
> Manlius, NY
> 
> Humm- I wonder if the valve's high pressure bypass is not working or set too
> high?
> 
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