I'm looking at an adjustable flow control valve with an adjustable relief valve that has the statement, For this model, the excess flow port must (must is underlined) be connected to tank. I'm trying to get my mind around why this statement is made by the mfgr. It would seem that if the travel valve relieves around 2100 PSI one could set the relief on the adjustable flow control with relief valve slightly higher and run the EX port to the travel valve, and not directly back to the tank as the mfgr states.
When you don't provide all the details of what you are trying to accomplish, it makes it difficult to give proper answers.
ASSUMING that it is your intention to install an aftermarket Flow Control Valve on your Case garden tractor instead of purchasing a factory unit, then you don't need a FCV with a relief valve. The pump is already protected by the OEM rear PTO kit because the pump's flow goes directly to the PTO before it comes to the FCV. The purpose of the FCV is to bleed off oil flow coming from the PTO valve and send it directly to the reservoir instead of allowing it to go through the travel valve. If you were to plumb the EX port back to the travel valve's IN port, then you would defeat the purpose behind the FCV.
In the Technical Library/Service Manuals/Hydraulic Section, you will find a manual there that shows colour diagrams depicting the oil flow in a tractor equipped with the rear PTO Kit and the Flow Control Kit. The manufacturer of that valve has no idea how their product will be utilized but they have to anticipate what the end user will do and provide warnings. Choose a FCV that has 1/2" ports and will flow at least 10 GPM but no more than 20 GPM. The closer you get to the 10 GPM mark, the better your control will be over the tractor's drive motor.
If your question has to do with Power Steering, then a FCV is not the way to go. What you need is a "Priority Valve" that can be adjusted from 0 to 4 GPM. Those are two totally different valves.
Well, you did a pretty good job answering my question considering I didn't give much information. I was assuming a FCV and a priority valve served the same purpose. I now have a better understanding of the difference, thank you.
Yes, my question centers around power steering. I was looking at a pump with a priority flow divider vs another method, and I'm still weighing options. The priority valve option is attractive because the flow is adjustable, where it looks like the pump with that option is set.
Just a couple of additional questions. Do I need a separate relief valve for the PS cylinder when I use a separate adjustable priority valve? Don't you wish I knew what ta hell I'm doing?
Some steering pumps have a built-in relief valve. If you already own one, then find out who made it along with the model number so you can contact them directly to get the specs on it. Companies often have an engineering department that will speak with you. Different pumps require differing amounts of oil flow coming in to them so that they work seamlessly. You want just enough oil flow to get that seamless operation and no more because the more you prioritize for the steering, the less that is available for the rear PTO and the travel motor. If you can get away with a mere 2 GPM for the steering, so much the better.
The steering pump must also be sized for the cylinder selected. As an example, a member built an articulated tractor and used two cylinders to bend the tractor in the middle. He complained about how slow the steering was along with the high number of rotations of the steering wheel that were required. I told him to remove one of the steering cylinders and try the tractor. Doing so cut the number of rotations in half and vastly improved the reaction to his input. Steering pumps come in many sizes and if you go to the Tech LIbrary/Service Manuals/Learning about hydraulics/Power Steering Units for Small Vehicles Manual - Danfoss......that manual can show you the Danfoss line of steering pumps.
I have studied the flows in the technical section, as well as the Danfoss info. My tractor has no PTO, nor any other use for hydraulics except travel and PS. I have a Hydraguide (Parker) 4 port steering unit, but the ID number is close (but different) than the numbers on the Parker website. I'm still trying to determine what I have with this unit through a Parker distributor.
I also have a Yanmar "all in one" power assist unit that takes 1.5 GPM and relieves at around 1200 PSI. It looks like I can drive this from the stock Ingersoll steering gear. I am looking at a Prince SP priority flow divider pump with a 1.5 GPM cartridge that relieves at 1300 PSI at the priority port. (slightly higher than the steering cylinder) Because my source of power runs at <1800 RPM I'm looking at a pump rated at 2500 PSI with a 15.4 GPM @t 2000 RPM, -1.5 GPM for priority port, or 13.9 GPM @ 2000 RPM. With my high end RPM probably closer to 1600 RPM I'm estimating the GPM to be in the 12+ range, a flow that compensates for my low top end RPM for a little higher speed, and a flow that 1/2" tubing can readily handle.
If I'm on the wrong track here I'd appreciate commments. I only want to buy the pump once, and I want to be safe. I'm most appreciative of the hydraulics 101 tutorial from you and others as I try to build this right.
Assuming that wide open throttle will be 1600 RPM, that pump will deliver 13.02 GPM at 0 PSI. If you prioritize 2 GPM of that flow for the PS pump, then you still have 11.02 GPM for the drive motor. There will be a slight increase in ground speed as a result but nothing dramatic. The 1/2" tubing will have no problems flowing that much oil without creating excess heat.
This is a large pump physically. Normally, Case and Ingersoll used the AA type of pump because of its diminutive size. The area where the pump goes seems large until you install the steering shaft, the travel lever, the lift lever and the PTO control lever. Back in the 60's, Case used the A type pump, which is what this Prince pump is. However, this pump measures nearly 7 inches in length. By comparison, the stock pump is a mere 4 inches in length. The working pressure of 2500 PSI is fine and so is the max RPM rating of 3000.
Prior to ordering that pump, you will have to speak with whomever makes the steering pump and tell them about this Prince pump. I don't see any reason why you cannot up the priority flow from 1.5 to 2 GPM for Yanmar unit but if you have to leave the stock Case steering shaft in place to use that unit, then I visualize problems with the length of the pump. I think that you would be better off having a steering pump mounted well above where the pump sits and if you have to use right angle fittings to get the hoses running off to one side, then that would be the way to go. Going to an electric clutch so that you can delete the PTO lever would also be in your best interests room-wise.
I really appreciate the feedback, it is extremely helpful. At almost 7" long this is a large pump, and with the stock steering shaft in place this would be an issue at the stock 48" wheelbase. Because I'm using a 4 cyl water cooled power unit for power, I have stretched the tractor to 60" Also, to avoid the wiener look I am putting 20x8-10 tires/wheels on the front and 31x15.5-15 tires/wheels on the rear. The front axle/spindles are more stout as well, in that the power unit complete weighs around 475#. The upshot is that I have room for the pump, including room to remove if necessary with the stock steering in place.
The Yanmar "all in one" power steering assist has everything contained on the cylinder.
The 1200" relief valve is built into the unit, and there is a "drag link" that would go from the IR steering quadrant to the cylinder. This power steering assist unit is sized for 1.5 GPM.
You had mentioned 2 GPM flow to the Yanmar unit for steering. If the specs for this unit are 1.5 GPM wouldn't I be safe sizing the pump priority cartridge at 1.5 GPM? Is there a down side to sizing this pump cartridge at 2 GPM? If the Yanmar unit is set to relieve at 1200 PSI +/- 100 PSI, am I safe in sizing the priority relief on the pump at either 1350 PSI or 1400 PSI? (just over the cylinder relief pressure so the cylinder relieves first)
I enjoy thinking through the hydraulics on this thing, but I obviously have a lot to learn. Thanks for your insite.
At the moment, the Yanmar unit isn't lighting my fire.
My biggest concern is with where this unit will mount. It looks BIG and space on these tractors is minimal. If you go with a Danfoss unit, you do away with the steering shaft, quadrant gear and drag link. The steering pump mounts directly below the dashboard. Two hoses go forward to the steering cylinder. One hose brings fluid to the pump and another hose provides a way for that fluid to get back to the reservoir. The cylinder gets anchored to the outside of the tractor frame and the rod end pushes/pulls on the kingpin/spindle unit. Very simple, very compact and it frees up a lot of space in an area that is crucial to you. Whether your tractor was originally fitted with a Kohler K or an Onan twin, the weight of those engines does not exceed 120 LBS. You are installing a water cooled 4 banger which will add 350 plus pounds to the tractor. Much of that weight will end up on the front axle. Moving to the 10 inch tires will increase the size of the contact patch and that increases the amount of resistance the tires will have to turning. Keep in mind that the OEM steering components were all sized to the original weight of the tractor and to the expected usage.
When Case developed the 600 Series loader tractors, the only steering component they used from the garden tractors was the steering wheel. The front axle, drag link, tie rod, quadrant, spindles, bearings and rims are all specific to the 600's because all of them are beefed up considerably. Yes, I read your post and I know that you believe that you have this covered but now is the time to make sure you get it right the first time out of the box because redoing it is costly, time-consuming and discouraging. If you intend to use the Yanmar unit, then I would suggest that you change the steering quadrant to the one used in the 600's and go up one size in the tubing used for the drag link and tie rod. I think that using Heim ends on those rods would also be advisable. If Yanmar says their steering unit works fine with a 1.5 GPM oil supply, then you can spec the pump that way. I just want you to be sure that you have decided on the Yanmar unit before you order the pump because most other full-time power steering units require more than 2 GPM to work flawlessly.
It's too bad that Case never worked with Ertl or any other manufacturer of scale models, to produce garden tractor models so you could stretch one of them to see what the end result would look like. Going from a 48" WB to a 60" WB is a substantial change to the appearance of the tractor.
You do raise points to ponder, and I appreciate that before I do something that will require rework.
As for the steering, I do have a Hydraguide HGF08 (similar configuration to the Danfoss) and I am still trying to find additional operating data. I did just find that it flows 1.71 GPM (for two handwheel turns/second) with an operating pressure of 1800 PSI. I would then need to find a cylinder, but your point is well taken on the size issue of the Yanmar, and the ability of doing away with the OEM quadrant and steering shaft. They are pretty light duty for this use. As you pointed out, I'm trying to make these decisions before I order the pump. They change the pump configuration greatly on the fixed cartridge priority flow and relief setting.
My friend has made Cad drawings, and the stretch from 48" wheelbase to 60" wheelbase actually looks to be proportioned pretty well, especially with the larger wheels and tires. It almost has the look of a small vintage airport tug.
Grummy started all this. A friend and I saw him at a show with a Case GT that had the frame dropped 6" just in front of the seat and we were hooked. I have done the same thing, which may well be helping with the proportions being pleasing to the eye. He has been helpful for parts, pieces, ideas, and information as well.
Once the decisions are all made and I get on with serious fabrication I'll start a string and post progress pics. I'm committed to do it, I just want to get it right before I get going. I hate rework.
Your insite and suggestions are excellent and greatly appreciated, thank you. I will continue to ask questions as I proceed.
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