Hydraulic flow numbers

[grsthegreat]

i thought about getting a front mount for my system, but not enough fence post to justify the expense. my post hole digger rear 3 point system spends most of its life on the rack in the shop. but i sure would love a reverse function.

 

[Gregster613]

Some hydraulic systems have only a single pump. In my case, a 2022 TYM T-25, a single pump partitions total flow into steering and implement flows. Presumably when there is no demand on the steering system, more flow is available for the implement hydraulics. I understand that earlier versions used two pumps.

YoungElder, I'm not exactly clear on this subject but I'd tend to agree with you. My 273 has one main pump that provides both the steering and hydraulic pressure; thus I'd "assume" that if stationary and not using the steering, one would have "full flow" of the pump to power implements. But, that's just my guess and is not stated as a fact!

 

[JCoastie]

Plan finally came together.
Out with the old:

In with the new

So much easier!

 

[Smokeydog]

Sweat set up! I want one too.

 

[oldnslo]

Some hydraulic systems have only a single pump. In my case, a 2022 TYM T-25, a single pump partitions total flow into steering and implement flows. Presumably when there is no demand on the steering system, more flow is available for the implement hydraulics. I understand that earlier versions used two pumps.

Young
The answer to your question is that It depends on how the system is designed.
With a single gear pump priority flow diverter for steering System making the flow available for implements is a complicated and expensive design so doubtful is an option on smaller tractors.

Larger tractors with variable volume pumps it is an option.

 

[SPYDERLK]

Finally may have found something regarding torque and flow, and if I am reading it correctly, the above statement is incorrect in this case.


View attachment 826252


Direct from Digga Drilling Augers for Skid Steer Loaders

This is probably with the hyd fluid fully warmed. The fluid is thus thinner allowing more bypass/leakage in the motor and preventing building good high pressure across the motor. You should be able to get near the full ~2300 ft-lb torque at the lower flows when the fluid is cool and thick. Itll be quite strong for a little while!

 

[dstig1]

They're changing both pressure and flow in those tables, which makes it look like flow has an effect on torque. But you can find any text book on hydraulics to tell you what affects motor torque.

I think you are misreading the table. While it may appear to be one where you read across the rows, when you think about it, the first pair of columns and the second pair are independent of each other. One shows flow vs rpm and the other pair shows torque vs pressure. I say this since the 2 pairs do not have the same number of entries and it also just makes sense. I will submit that the table is just poorly formatted...

 

[JCoastie]

I will submit that the table is just poorly formatted...

yeah, it's misleading for the uninformed like myself. The line shading makes it seem like speed and torque are related, and in this case, they aren't.

 

[rScotty]

I think you are misreading the table. While it may appear to be one where you read across the rows, when you think about it, the first pair of columns and the second pair are independent of each other. One shows flow vs rpm and the other pair shows torque vs pressure. I say this since the 2 pairs do not have the same number of entries and it also just makes sense. I will submit that the table is just poorly formatted...

I think that is the right interpretation on the chart. It is poorly done. But follow some figures and and the 2DSS appears to have a larger internal piston area (and volume) than the 1DSS. That makes sense.
And the chart shows that the smaller motor can match the torque of the larger up to a certain point by increasing pressure. That also makes sense.

On an earlier question about how the flow is divided up, it varies with the model.
Our old 1982 Yanmar had hydrostatic power steering and a single hydraulic pump for everything. The pump fed a min. absolute plus proportional flow divider so that whatever the engine rpm and hence hydraulic flow, a certain amount always went to the PS. Then all extra flow over that was available to the FEL or 3pt or remotes. Simple and elegant.

Our Kubota does it the other way. No diversion, just uses separate pumps for everything, including Power Steering, HST, and accessories.

Glad it's working for you, and that looks like some mighty find dirt you have there. Wish ours was as good.
rScotty

 

[Smokeydog]

Sweat set up! I want one too.

Could you stall the auger when digging?

 

[SPYDERLK]

With either given motor the lowering of torque with that motor as flow decreases is because flow has to supply both motor motion and leakage through the motor. If there were no leakage both of the motors would deliver their characteristic Torque -- ~1200 vs 1900ft-lb@ the 2500PSI relief setting on most tractors -- regardless of flow. The big motor would run slower of course because its larger displacement requires proportionately more flow for each revolution. In the ideal/no leakage situation the flow strictly causes the revolution, and the resistance to the revolution (load) causes the pressure. Thus the Torque you can apply is limited to tractor relief pressure acting on the motor displacement. If you were pumping grease yould see each motor run at constant speed with increasing load. Pressure would rise accordingly and the motor would suddenly stop when you reached your tractor relief pressure. The motor T would still be almost the same, but no motion. Just a bunch of grease flowing through a relief - the only place it can go since it cant leak past the motor element.

In our real world there is leakage. At any given fluid pressure across a motor (or pump) it is proportional to the fluid viscosity and the motor size. Even though leak paths are as small as feasible some flow is always wasted and this waste increases as the fluid thins out as the system warms up. The big motor is going to leak more. When fully heated there may be enough leakage past the motor elements to tax the self leaking and delivery capabilities of a fully warmed small tractor hyd pump. The pressure from the pump cannot rise to its full relief pressure while supplying both leak and displacement flow. Thus this "slip" effectively limits Torque below what you would achieve with a bigger delivery pump. --- But that potential for T is there. Just do your high T work right away while the fluid is cool and thick.