Converting 670 rake to hydraulic drive flow control valve qu

I am in the process of converting my deere 670 rake from ground drive to hydraulic drive. I changed the yoke on the drive shaft running from the drive wheels to the gearbox so the shaft will go onto an orbit motor salvaged from a 200 series bean head which I am mounting to the frame just above the left drive wheel. I was just going to change the speed with the turtle/rabbit control on the scv, but am thinking a flow control valve plumbed onto the rake will give greater control of the speed. My question is do I need to plumb the excess flow port on the valve into the return line from the orbit motor or can I just leave it plugged? The rake will be used behind a 4020 so closed center hydraulics. I also am curious if anyone thinks I would be able to run this setup with my 51 A if it was necessary? Thank in advance for all the help
 
Shouldn't you have asked advice before starting the project?
Those motors create a lot of heat.
I would say your A won't have hyd capacity or cooling capacity.
 
The size of the motor and the hydraulic capacity of the tractor will dictate how much power you can transmit. For example, 15 gpm at 1500 psi gives about 13 hp using the HP=GPM*PSI/1714 equation. I'm guessing that 15 gpm would be about the max for a 4020 but could be wrong. You would need a motor of the proper size to get the power and speed you want. If the motor is too small and runs too fast you can cut down the flow rate but that in turn will reduce the power capacity. It all depends on how much power it takes to run the rake and how much flow and pressure is available from the tractor.

If you use a flow control valve on the rake keep in mind that the entire flow from the tractor is still raised to the pressure required to run the motor, even if it is running at partial speed. The oil not being routed to the motor loses its energy in the form of heat as it passes from high to low pressure through the valve. From the tractor's perspective there would be no difference between slow and fast speeds (assuming the pressure at the motor is the same) since it doesn't care where the oil is going once it leaves the tractor's SCV. It would just know it is being asked to deliver a fixed flow at the developed pressure. And, the flow control valve itself will add pressure drop in the circuit, probably around 100 psi, thus cutting down the usable power you have available. On the other hand, adjusting the flow rate on the tractor will cause the closed center pump to only deliver what is required to run the motor at the chosen speed. You would also be pushing less oil through the quick couplers and hoses which will further reduce pressure drop and heat generation. Either way you'll want to monitor your oil temperature since these older tractors didn't have a lot of reserve hydraulic cooling capacity.
 
Here's a parts photo of the flow control valve that JD hyd drive side delivery rake utilized.
mvphoto24517.gif
 
Thank Jim that's the kind of help I needed,
the port with the T shows me that excess
flow is tapped into the return line. That
is the way I will plumb mine. What model of
rake did you find that valve under? Yes I
realize the valves make a lot of heat and
it's probably not the greatest set up.
However it is the most economical way I
could come up with to make ground speed and
rake speed independent from one another so
I don't have to fight it plugging and
dragging in heavy hay. So thanks for the
other advice/criticism but I will continue
this experiment as the budget doesn't allow
for a new rake and I believe in adapting
and making work what I already have
whenever possible.
 

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