how many GPM is needed

[Fixastuff]

38gpm

 

[LD1]

The one hydraulic-taxing implement I hope to get someday is a FEL-mounted auger. The potential to better control of hole placement and the ability to apply downward pressure is applealing versus that of using a PTO mounted post hole digger.

Digga, Premier Attachments, Danuser, BellTec, etc. all have models that will spin with relatively low gpm hydraulics, but they obviously produce lower torque to the auger, thus slower/ weaker auger cutting performance. The numerous variables such as soil composition, hole size and duration to drill will determine whether such performance is acceptable to the user. Short of hands-on experiance, I won't know if the juice is worth the squeeze.

My Kioti dealer told me that of the 17.9 gpm from the RX6620, about 8 gpm go to the steering circuit, with the balance (9.9 gpm) available to the rest of the hydraulic system. I hope that flow rate can produce acceptable results.

GPM is speed
PSI is torque.

So less GPM is just gonna make it run slower.

Most people I know augering with a skid loader are doing so at or near idle anyway. So I think even a big skid loader auger would be fine on a 10gpm tractor

 

[rScotty]

GPM is speed
PSI is torque.

So less GPM is just gonna make it run slower.

Most people I know augering with a skid loader are doing so at or near idle anyway. So I think even a big skid loader auger would be fine on a 10gpm tractor

I agree with that. It didn't take us long to learn that by running the auger really slow and lifting it a lot we actually end up spending less time with each hole. Most any 30 to 40 hp tractor running at a high idle can produce all the flow needed for running an auger slowly.

My guess - and it's just a guess - is that the only time you really need a lot of hydraulic flow in your compact tractor would be when running a front hydraulically powered snow blower on a tractor with a HST transmission and wanting to get the job done quickly.

In general, compact and utility tractors weren't designed for doing jobs fast. Some commercial machines are. But they start at double to triple the price of a compact tractor -and everything about them is proportionately expensive. They are nice though. We have one for backup. It works nicely & can do a lot of work quickly.

In this old timer's opinion, if you really want to enjoy your loader and remote hydraulics, look for a tractor with the best quality directional control valves. Loader manufacturers tend to use industrial standard control valves, which come in a wide range of quality and price. Most loaders and remotes use off-the-shelf commercial control valves. You can look up the prices on the internet.,

rScotty

 

[scootr]

Good stuff. I hadn't considered torque, PSI. My 773 Bobcat puts out 16 gpm at 3000 psi. It has a 70" bucket but it struggles with the 72" brush hog in thick material if I'm moving too fast. This machine is not the hi-flo model which puts out 27 gpm. I see most tractors in the 40-50hp range well under 16gpm but I don't know what the PSI is. Thanks for your replies.

 

[rScotty]

Good stuff. I hadn't considered torque, PSI. My 773 Bobcat puts out 16 gpm at 3000 psi. It has a 70" bucket but it struggles with the 72" brush hog in thick material if I'm moving too fast. This machine is not the hi-flo model which puts out 27 gpm. I see most tractors in the 40-50hp range well under 16gpm but I don't know what the PSI is. Thanks for your replies.

I hadn't considered a hydraulic brush hog. Most every tractor uses a three point mounted PTO powered brush hog. That way the operator is sitting above and in cleaner air and has the advantage of the 3pt hitch. For flow, I'd imagine that a brush hog would be like a snow blower in that it needs to have more flow at the standard 3000 psi pressure in order to get the blades spinning spinning fast enough to do the job.

Like your Bobcat, most modern tractors are also adjusted so that their hydraulics put out right around 3000 psi. There is a very large class of hydraulic implements that use that pressure.

Keep in mind that fluid power takes engine HP to make. And if engine HP stays the same and hydraulic pressure is raised, then flow rate has to go down.

Tractors didn't use to run 3000 psi pressure. A lot of tractor guys start dating the modern farm tractor in the 1960s - about when JD introduced the xx10 series of farm tractors that had standard features like remote hydraulics, power steering, gear ranges, power shifting, and sometimes 4wheel assist. But at that time typical tractor hydaulic pressure was in the 1200 to 1500 PSI range but flow rate was high

The next generation of XX20 JD tractors took us through the 1970s and hydraulic pressures almost doubled to that so that 2000 to 2350 psi became common. Now all fittings ad connectors better be specially made to be rated for hydraulic pressure. No more using forged plumbers fittings. At those pressures, plumbing fittings split and kill.
And since the pressure doubled, the flow rate at the same HP was either cut in half or required more tractor HP to run. Leaving less reserve throttle.

By the year 2000 many tractors were running commercial pressures around 3000 psi and most are still there today. To be able to run that much pressure at higher flow rates and still move the tractor around, tractor engines no longer run at the idle speeds common 50 years ago. Now they tend to be run at full rated RPM. Higher RPM has emissions advantages as well.

rScotty

 

[ptsg]

Good stuff. I hadn't considered torque, PSI. My 773 Bobcat puts out 16 gpm at 3000 psi. It has a 70" bucket but it struggles with the 72" brush hog in thick material if I'm moving too fast. This machine is not the hi-flo model which puts out 27 gpm. I see most tractors in the 40-50hp range well under 16gpm but I don't know what the PSI is. Thanks for your replies.

Pressure on most compacts is around 2500 to 2600 PSI. Some, smaller ones, run a bit less than that.

 

[LD1]

Good stuff. I hadn't considered torque, PSI. My 773 Bobcat puts out 16 gpm at 3000 psi. It has a 70" bucket but it struggles with the 72" brush hog in thick material if I'm moving too fast. This machine is not the hi-flo model which puts out 27 gpm. I see most tractors in the 40-50hp range well under 16gpm but I don't know what the PSI is. Thanks for your replies.

A brushhog needs speed. Speed is gpm.

A post hole digger needs torque. Torque is psi

 

[Hermio]

Understood but I don't know what I might run in the next 10-20 yrs.
I saw gpm from 7.5 to 16. Just wondering if there was a rule of thumb. Thanks

The implements that require the most flow are front-mounted bush hogs, snowblowers and the like. Most Bobcat-like loaders have enough hydraulic flow to run these implements. Most tractors do not. Look into what you might want to have down the road and see how much flow they need.

 

[auxhyd]

It's really a good idea to know what hydraulic attachments you might expect to operate. It's important to know the flow rating at a given pressure: Is it rated 9.8 gpm at 3000 psi or at 2500 psi or ...? If your attachment needs 9.8 gpm at 3000 psi but your tractor is only capable of 9.8 gpm at 2500 psi then your attachment may not do the work as intended.

As an example: For a hydraulic log splitter a high flow rate with low pressure will make the cylinder extend and retract fast without a load but as soon as you put a log in there it will slow way down and may not even split harder woods. With higher flow at working pressure the cylinder will extend and retract faster with or without a load (so you can split more wood!)

I notice Kubota's new tractor spec sheets don't even mention a pressure rating at all... maybe I've just spent too much time around hydraulic excavators.

A separate pump for power steering would be better in my opinion but probably not a big deal if you're not running a hydraulic motor while driving around... (when a hydraulic motor isn't under load, say like for a hydraulic brushcutter, as soon as the load is off the motor it becomes the path of least resistance, robbing flow from other circuits as the momentum from the weight of the heavy spinning blades keep the motor turning for a while.)

 

[Shenandoah MF1760]

My Massey has a flow of 12.1 gpm @ 2,320 psi, my Lane Shark requires 8.5-15.0 gpm (Standard Motor).

The Lane Shark is a FEL mounted Brush Cutter (think Bush Hog) the motor of which is strictly hydraulic, unlike a Bush Hog.

A 36" dia. FEL auger would need ~15 gpm but I can't fathom ever needing such a beast even if my tractor could handle it. a 15" dia FEL auger only needs ~5 gpm.

I'm unaware of anything else, maybe a snow blower (I'm in Texas, snow?) that needs such a continuous flow.

Cylinders need pressure, the amount of flow in their case just relates to speed of operation. As long as they have adequate pressure they'll get there eventually.