Kubota Backhoe powered from rear remotes of TYM

[myyaz33]

Ok, needing a little hydraulic help for my latest (partially finished) project. Just got the restoration done on my Kubota K-650 backhoe and I am finding that running off the PTO pump just doesn't cut it. Too slow with only 540rpm PTO speed so I am thinking that I can use the rear remotes on my TYM T273 to power the backhoe. I will provide as much as I know and hopefully someone can help me out.

The PTO pump is a Gresen Model TB-3 with the following stats;

Max 1500 PSI
Max 1800 RPM
1.46 GPM at 900 RPM
2.16 GPM at 1200 RPM
3.80 GPM at 1800 RPM

I am not sure of the valve specs on the backhoe. Hopefully I can get some pictures posted and be able to get it recognized.

The K-650 backhoe manaual states the following info;
Operating Pressure-
Digging 1,000psi , 6.9MPa
Swing 1,000psi , 6.9 MPa
Stabilizer Spread 42"-48" 1067-1219

My tractor is a TYM T273 and the hydraulic system should be around 2200psi and 5gpm.

I guess my question is; Taking into consideration that the max of the PTO pump was 3.8gpm & 1500PSI should I be worried about connecting to the rear remotes at 2200PSI & 5gpm? I know it is probably hard to tell without knowing the limits of the valves on the backhoe.

 

[Farmerford]

1,000 psi is a fairly low pressure limit for a modern backhoe, but I know nothing about yours, so we should accept that limit for planning. If it was ever operated with the 1500 psi Gresen pump and no damage occurred, then you might work with the higher pressure.

In either case, the 5gpm of your tractor system poses no problem. The worst case with volume will be that the valve and/or lines are so small that the fluid loses a lot of pressure (and energy) flowing through them. I doubt if the lines are smaller than 1/4" ID, and even if they are fairly long the pressure losses should not be too great.

However, the pressure at the backhoe valve and cylinders is a different matter. If those components are truly sized for 1,000 psi then a substantially higher pressure could burst hoses, crack valve bodies (very unlikely), bend cylinder shafts (more likely), and damage cylinder seals, as well as overload the structural components such as the boom and stick.

I am assuming that the BH valve does not have an integral relief valve. Of course, if it has one then you are protected, although that will also reduce the pressure in any downstream device such as the TPH.

If the tractor has a system relief valve (it probably does, between the pump and FEL) it will limit the pressure to say 2,200 psi when the backhoe is stalled against a load or the cylinder stops. You could adjust the system relief pressure down to 1,000 psi to protect the backhoe. Of course, that means your loader and three point hitch will lift about one-half as much as before.

If the FEL valve has a relief valve, and if the FEL valve is upstream of the BH valve, then you could probably more easily reduce the FEL relief valve setting. It will protect the backhoe as well, but it will also reduce the operating pressure of the FEL and any other downstream device (TPH?).

You could do this. Put a single in-line relief valve in the line from the tractor system (the out port on your remote?) to the in port of the BH valve, with the excess flow teed into the other line between the BH valve and the other remote port. Set that relief at 1000 psi. That always protects the BH. Then, if you need to use the FEL or TPH while the BH is attached, but you need full 2200psi system pressure, close the remote valve, which takes the BH and its relief valve out of the tractor system until you again need the BH.


The only solution that does not reduce pressure for the other devices in the system (FEL, TPH) and does not require manipulation of the remote valve is to install adjustable relief valves in the work ports of the BH valve. Many sectional control valves come with or have provision for these work port reliefs, but I suspect yours does not. Work port reliefs do not protect the BH valve itself from excess pressure, but I suspect the 1000 psi limit results from the design of the structural components (boom, etc) or cylinders more than the valve.

You can accomplish the same thing by installing cushion valves in each circuit on the backhoe. But will take four of them at about $100 each(boom, stick, bucket, stabilizers) plus the cutting of each hose and installation of hose ends compatible with the cushion valve. A cushion valve (also called a dual crossover relief valve) is just a type of relief valve that protects both work circuits and exhausts excess flow to the other circuit to reduce cavitation (that's not really your problem). That seems like a lot of money and effort if you can live with the previous suggestion of a single relief in the BH inlet circuit.

Or, depending on your affection for the BH, you might just turn the tractor's system relief valve (it almost surely has one) down to about 1500 psi and see if that compromise protects the BH while allowing the TPH and FEL to function acceptably. If the stick begins to bow when you crowd hard against a stump, stop and return to step one.

Good luck.

 

[myyaz33]

Thanks FarmerFord for the great info today as well as the info you provided some time back on the PTO pump. I am going to read this post a few more times so I get it right. I just wanted to attach a picture of 2 of the valves (stabilizer valves not pictured). Can you tell if it has an integral relief valve?

Also on my rear remotes, I have a lever under the seat that makes them work (Left-Neutral-Right) If it is not in the neutral position then the 3pt doesn't work. It is very easy to bump the lever with my feet! So my understanding is that if I don't have the integral relief valve and I go with the single in-line relief valve method, I wouldn't necessarily have to close the in-line valve, I could just return the lever under the seat to neutral? This should give me back full pressure for FEL and 3PH.

 

[myyaz33]

Any suggestions on an in-line valve? Not sure what I am really looking for as well as how to plumb it as far as where the tee goes to the return line. Am going to Surplus Center tomorrow to get the parts.

Also can someone explain 1-way vs 2-way when it comes to quick couplers? I am guessing the remotes are 2-way on my tractor?

 

[aczlan]

a "one way" remote is powered on one direction (like a jack made for a car) whereas a "two way" remote can power up OR down (like a bucket dump cylinder). most newer tractors have "two way" remotes, they will have two quick connects on the back of the tractor. you should be able to hook your BH into the two ports (remember which line is which) and hold the lever for the remotes open with a bungie cord. if everything runs backwards, move the lever the other way.

Aaron Z

 

[Reg]

Ok, needing a little hydraulic help for my latest (partially finished) project. Just got the restoration done on my Kubota K-650 backhoe and I am finding that running off the PTO pump just doesn't cut it. Too slow with only 540rpm PTO speed so I am thinking that I can use the rear remotes on my TYM T273 to power the backhoe. I will provide as much as I know and hopefully someone can help me out.

The PTO pump is a Gresen Model TB-3 with the following stats;

Max 1500 PSI
Max 1800 RPM
1.46 GPM at 900 RPM
2.16 GPM at 1200 RPM
3.80 GPM at 1800 RPM

I am not sure of the valve specs on the backhoe. Hopefully I can get some pictures posted and be able to get it recognized.

The K-650 backhoe manaual states the following info;
Operating Pressure-
Digging 1,000psi , 6.9MPa
Swing 1,000psi , 6.9 MPa
Stabilizer Spread 42"-48" 1067-1219

My tractor is a TYM T273 and the hydraulic system should be around 2200psi and 5gpm.

I guess my question is; Taking into consideration that the max of the PTO pump was 3.8gpm & 1500PSI should I be worried about connecting to the rear remotes at 2200PSI & 5gpm? I know it is probably hard to tell without knowing the limits of the valves on the backhoe.

Assuming there is a relief valve in the hoe - why not ?
Since you have the hoe manual, perhaps your first step should be to find it's pressure relief valve and what pressure that is set to.

 

[myyaz33]

Assuming there is a relief valve in the hoe - why not ?
Since you have the hoe manual, perhaps your first step should be to find it's pressure relief valve and what pressure that is set to.

Nothing in the manual about a relief valve. Probably safe say there isn't one. Going to try to get the parts to do an adjustable in-line valve tomorrow. Hope Surplus Center will have patience with me!

 

[Farmerford]

Attached is my sketch of what I think you need. I am guessing a bit because I don't have a complete diagram of your system, but this might be helpful.]

Items 2404 and 6804 are from Discount Hydraulic Hose (on the net); Surplus Center does not show them in their catalog. The Prince relief valve is the only 1000 psi valve shown in the Surplus Center catalog. It is an "inline" valve, meaning it has three ports. But by leaving the "out" port blocked with the pipe plug that should come with the valve, you can turn it into a tee valve. Connect the "in" port on the relief valve to the pressure line from the pump ("in" on the right hand BH valve) and the relief port on the valve to the "out" port tee on the forward BH valve block.

I am not sure of the sizes of fittings and hoses, so you will need to measure what you have. Finally, I can't tell clearly from the picture how the valves are plumbed. The right hand valve appears to receive pressure from the pumb. I am just guessing that the forward valve (with its "back" to the picture) has its "out" port connected to the tank/reservoir through the remote valve.

Good Luck.

 

[myyaz33]

FarmerFord, I really appreciate your assistance on this. The sketch is indeed helpful however I got to thinking yesterday about the bigger picture as far as rear remote hydraulics go. I ended up walking away from Surplus Center with an Eaton 3 spool valve. I said to myself this should allow more possibilities like Top-N-Tilt etc...

So, here are my new plans..

1. Mount the new Eaton valve in a convenient location and connect direct to rear remotes which are on a valve of their own. The remotes are powered by either moving the valve lever to the left which puts pressure in the left rear remote or moving the lever to the right and the right rear remote has pressure. My question here is can damage occur if I set the system up to have the pressure from the left rear remote and I accidentally move the lever to the right side thus putting pressure on what should be the return side?

2. How do you adjust the pressure on this new valve? Can different reliefs be set for each spool? What are the screw adjustments for? Why don't these things come with manuals for hydraulic dummies?

 

[Farmerford]

Nice valve.

Not sure I understand how you plan to plumb the valve, so I can't answer your first question.

The three screws on the top of the valve probably secure the lift checks, which keep a load from falling if the pump pressure is less than the pressure created in the line by the load. They do not affect relief pressure, and are not adjustable.


The relief valve is probably under the hex nut plug at the corner of the valve. The relief pressure is probably adjusted by loosening the lock nut and then screwing the hex nut plug in or out. The catalog says the relief is adjustable and preset at 2000 psi. In many cases, the plug can only be screwed in or out a few turns before it either bottoms out (when screwing in to increase pressure) or it leaks because the o-ring is exposed (when screwing out to reduce pressure). If on this type of valve you want to change the relief pressure very much from the factory setting (say from 2000 psi to 1000 psi) you have to change the relief valve spring that is behind the plug. If they did not give you any instructions, perhaps you can find them on line.