% ofe torque to dedicate to hydraulics?

[Groo]

I've been looking at a couple old pieces of equipment that don't come with hydraulics, and am planning to add hydraulics if I purchase.

What % of engine torque should I devote to hydraulics?

Is there a rule of thumb for something like that?
Dad just ordered a Yanmar yt359. looking at combined flow (implement and steering) and pressure vs. engine torque, the hydraulics on that machine use about 1/3 of available torque at peak pressure.

Is that the general rule? how much variation from segment to segment?
1 machine I am considering is an old AG loader. would I stick to 1/3? or should I go higher? maybe 1/2?
Does pump style matter?

 

[bigdeano]

Would depend on what you're going to use it for. I would check hyd specs on new machines that have similar uses to what you want to do. Did the old loader have all the hydraulics removed?

 

[Fallon]

Completely dependent on what you are trying to do. My L4060 has 40hp at the flywheel if I recall. 10gpm (generous) @ 2,500gpm = 14hp. There is another 5gpm or something for steering. A datapoint for you to use, but not comprehensive.

 

[Dave M7040]

I've been looking at a couple old pieces of equipment that don't come with hydraulics, and am planning to add hydraulics if I purchase.

What % of engine torque should I devote to hydraulics?

Is there a rule of thumb for something like that?
Dad just ordered a Yanmar yt359. looking at combined flow (implement and steering) and pressure vs. engine torque, the hydraulics on that machine use about 1/3 of available torque at peak pressure.

Is that the general rule? how much variation from segment to segment?
1 machine I am considering is an old AG loader. would I stick to 1/3? or should I go higher? maybe 1/2?
Does pump style matter?

Your question does not reflect that your need of engine power for a hydraulic pump will be momentary. With an open center hydraulic system, it is only when the loader is lifting that you need hydraulic power and that is for a few seconds.

When you are lifting the loader arms you are usually stationary so the need for engine power is not occurring at the same time.

A simple gear pump is all you need. Drive it off the front engine pulley using a shaft and flex coupler.

The gear pumps are rated in c.c.'s of displacement per revolution. Engine speed, say 2,000 rpm x a pump with 20 c.c.'s per revolution yields a flow rate.

Pump style is a function of price and durability. A farm tractor will not need sophisticated hydraulics so buy based upon price.

Hydraulic reservoir size and return filter size are all discussed in many places on line. Do not buy a FEL valve with a high flow rating like 25 gpm. If you have a pump whose flow is max 10 gpm flowing through a 25 gpm valve means you loose the ability to effect fine movements with your loader.

With old loaders some were designed for much lower pressures than today's tractors. To compensate, the sizes of the cylinders were increased. If you start feeding old low pressure rated cylinders with new high pressure oil, for a short time you will be amazed at the strength of the old loader but then things will be ripped apart and broken.

Dave M7040

 

[Groo]

with fixed displacement hydraulics (like a gear pump); if you only partially open a valve, what doesn't go to the cylinder has to go over the main relief; so full hydraulic pump torque will be demanded fairly often.

ps. miss typed in the original post. The piece of equipment I am currently looking strongest at is an old ag crawler. There is a partial loader for it (probably need new cylinders and a bunch of other work as well), but has never been installed on the machine. It is made to have a front pump bolted in front. I am also looking at old tractors that don't have or only have minimal hydraulics.

I would probably design around 2500 or 3000 psi hydraulics since that is what most modern implaments are rated for.

 

[bigdeano]

with fixed displacement hydraulics (like a gear pump); if you only partially open a valve, what doesn't go to the cylinder has to go over the main relief; so full hydraulic pump torque will be demanded fairly often.

This usually isn't correct, unless the valve is defective. What doesn't go to the cylinder goes to the tank, not thru the pressure relief. The pressure only goes high enough to move the cylinder.

 

[Dave M7040]

I am with bigdeano on the operation of the Open center system.

The relief valve only opens when the cylinders are at the end of their stroke or are lifting their maximum rated load.

The unused or unneeded oil flows at low pressure to the tank.

If you have every used a log splitter, you have had a steady demonstration of the need for engine power during the cycle of the splitter.

It is only when the pressure builds that the need for engine power rises dramatically and the exhaust note rises. Otherwise, the engine is loafing.

That is why I make the point that the need for engine power to drive an open center pump is only a small portion of the overall engine run time.

Dave M7040

 

[4570Man]

The relief valve doesn’t open unless you dead head a cylinder or attempt to lift max load. If that’s not what’s happening it’s not working properly. Lots of people don’t understand the difference in flow and pressure. Or other simple physics for that matter such as a pulley in a winch. My wood splitter would still work and develop the max tonnage with a .5 GPM pump driven with a hand drill as long as it reaches the pressure it currently operates at. It’s just going to take forever. You could hook a firehose to it and it’ll be blazing fast but nowhere near as strong as it currently is.

 

[Groo]

I have worked with 3 types of open center valves. Parker p70, vg35eh and Danfoss pvg 100. They all send system pressure up to the relief when a fraction of the supplied flow is sent to a cylinder., either because it is a low flow work section or only slightly open.

 

[bigdeano]

I have worked with 3 types of open center valves. Parker p70, vg35eh and Danfoss pvg 100. They all send system pressure up to the relief when a fraction of the supplied flow is sent to a cylinder., either because it is a low flow work section or only slightly open.

That's interesting. I know some do that, but didn't know if it was on purpose or not. My Vickers CM11 valves don't do that. Seems better to not have the pressure spike and load the engine down. Load check valves make sure the load can't drop if the valve has them.