Hydraulics Question(s)?

[radioman]

Use foot throttle to increase rpm (pump flow) when you demand more flow for simultaneous operation of two or more cylinders.....

No foot throttle on the BX's. you need to turn around and move the throttle. BTW, the BX's say when you use hydraulics or pto, you need to be at rated pto speed, the BX's is 3200 rpms which is nearly WOT. I don't use the rated engine speed for the power. I drop it down and use whatever conditions is needed. However I'd say using it at a lower speed, I do notice the issues more that you are describing.

When I am operating the backhoe, I notice that if I try to extend/retract the arm or swing the arm left/right (using the left handle), I seem to have the full power of the hydraulics. The same can be said when I try to curl the bucket or curl the arm (using the right handle). Full power and quick movement.

However, when I attempt to operate the backhoe with both handles, I end up noticing a severe "drop off" in the speed of the right handles operations. An perfect example:

I was digging a hole in the yard and was swinging the arm back and forth between the hole and the pile of dirt from the hole. I was trying to extend the arm and the bucket in one smooth motion, but was unable to do so. It seems as though the hydraulic power for both motions is not equally divided. Has anyone ever experienced this phenomena?
Is this something that I should be expecting given the small size of the tractor I am working with?
Is this a hydraulics deficiency? I have checked the fluid levels and it appears to be adequately filled. Perhaps there is something wrong with the cylinder? or the handle?

Any help with this would be greatly appreciated.

Yes this is to par with my BX24 as well. Nothing is wrong with the tractor, its the way its designed for a small sized tractor.

 

[J_J]

Many times what we think is common sense is just personal sense....:laughing:...

common sense is the sense that the community, "common-unity", agree on....

"common sense" can be determined with a poll.

But since polls are not allowed at this forum or "community", it will make common sense that we can not use common sense here....

...makes common sense??

I think we could make a new thread about "common sense"...but it would probably not make sense....

I am glad you are having fun, as the above crap did not make any SENSE.

You did not explain which log splitter would have the fastest cycle time, with zero load. Each having the same type pump and flow and same type valve. Which cyl will cycle the fastest, the 3 in cyl with a 24 in stroke or the 4 in cyl with a 24 in stroke.

 

[AKKAMAAN]

I am glad you are having fun, as the above crap did not make any SENSE.

You did not explain which log splitter would have the fastest cycle time, with zero load. Each having the same type pump and flow and same type valve. Which cyl will cycle the fastest, the 3 in cyl with a 24 in stroke or the 4 in cyl with a 24 in stroke.

I think Roy answered that so well, so I was sure it would make sense....

how ever, if these two difeerent sized cylinders are supplepied flow from the same pump, and feed parallel from the same wqork port, the one with the lowest load pressure will move first, and when it stalls, the one with higher load pressure will start moving. If we can ignore the minor impact from difference in mechanical friction, difference in cylinder size have no matter.
My example also applies if the two different cylinders are provided flow from two parallel spool valves that are metered identcally..

If the two different cyls are provided flow from two different but identical pumps, your "common sense" applies, the smaller will move faster as long as no flow is diverted in CV or PRV...
If two diff

 

[HydroTek]

What a long winded way to say the oil will follow the path of least resistance ..LOL

The OP was asking why his hoe was slow when operating two functions at the same time. This is normal to have this speed drop, if your valve does not have regeneration, many small hoes do not use regenerative valves.
.

 

[AKKAMAAN]

What a long winded way to say the oil will follow the path of least resistance ..LOL

The OP was asking why his hoe was slow when operating two functions at the same time. This is normal to have this speed drop, if your valve does not have regeneration, many small hoes do not use regenerative valves.
.

Sure know what OP asked for, but another member "widened" the task....
In the quoted blue part below, he tried to explain his problem, the red part shows his five (5 ?-marks) different questions...

I just purchased a Kubota BX25 for doing small jobs around my yard. In my "feeling out" of the equipment, I have noticed that there appears to be a power deficiency in the backhoe implement. Hopefully, someone will shed some light on this for me.

When I am operating the backhoe, I notice that if I try to extend/retract the arm or swing the arm left/right (using the left handle), I seem to have the full power of the hydraulics. The same can be said when I try to curl the bucket or curl the arm (using the right handle). Full power and quick movement.

However, when I attempt to operate the backhoe with both handles, I end up noticing a severe "drop off" in the speed of the right handles operations. An perfect example:

I was digging a hole in the yard and was swinging the arm back and forth between the hole and the pile of dirt from the hole. I was trying to extend the arm and the bucket in one smooth motion, but was unable to do so. It seems as though the hydraulic power for both motions is not equally divided. Has anyone ever experienced this phenomena?
Is this something that I should be expecting given the small size of the tractor I am working with?
Is this a hydraulics deficiency? I have checked the fluid levels and it appears to be adequately filled. Perhaps there is something wrong with the cylinder? or the handle?

Regeneration is interesting.....just so with do not high-jack this thread, why don't you HydroTek, copy and past my questions below into a new thread, and lets talk regeneration there...:thumbsup:

I re-quote part of your post here...

...This is normal to have this speed drop, if your valve does not have regeneration, many small hoes do not use regenerative valves.

1> I assume the valves with regeneration you refer to, is the control valve, or??

2> So what big hoes use "regeneration valves"??

3> What kind of regeneration valves?

4> Used on which hydraulic actuators/functions?

 

[wdchyd]

What a long winded way to say the oil will follow the path of least resistance ..LOL

The OP was asking why his hoe was slow when operating two functions at the same time. This is normal to have this speed drop, if your valve does not have regeneration, many small hoes do not use regenerative valves.
.

Are you and Akkamaan talking about "Series Center" valves (not tandem center) where the exhaust flow from an upstream valve spool is diverted internally to the next spool in-line to accomplish both circuits to operate at the same time..??

IIRC , I have this on my Kubota on the FEL controls to allow both lift & tilt to operate efficiently simultaneously and independently, when using the FEL control I can Lift & Tilt perfectly every time......

I don't remember if it's on the BH control valve (didn't get the schematics with it)

 

[AKKAMAAN]

Are you and Akkamaan talking about "Series Center" valves (not tandem center) where the exhaust flow from an upstream valve spool is diverted internally to the next spool in-line to accomplish both circuits to operate at the same time..??

IIRC , I have this on my Kubota on the FEL controls to allow both lift & tilt to operate efficiently simultaneously and independently, when using the FEL control I can Lift & Tilt perfectly every time......

I don't remember if it's on the BH control valve (didn't get the schematics with it)

Hi Bill!

I can see/read/hear many different definitions of tandem valve, parallel valve, open center valve...some do not even mention tandem valve as a type of valve...I think, not sure, that tandem valve is a term coming from the solenoid valve technology...anyway, it seems not be a strict standard of control valve terms that I can find....maybe someone else have a SAE standard document, or ISO standrad for valve symbols....:confused2:

I am assuming a regular multiple spool control valve, open center to tank in neutral, that have a parallel power core that diverts flow and pressure into each work port on all spools...like on this schematic...

This is how "all" boom and stick crane applications is served when they have a regular fixed displacement pump in an open center system...

A tandem valve setup, priorities upstream control valves over down streams ones, still pump flow goes through the open center in neutral....
Tandem valves do not allow simultaneous operation of cylinders since upstream valve cuts flow from a downstream valve

See page V7 on this Prince stack valve, it explains difference between parallel and tandem...

edit:
I have never seen an application where one cylinders exhaust/return flow, become power flow for a down stream cylinder, but I cant say it couldn't be one. That would connect the cylinders in series....would be interesting to see that schematic....
It have been seen on "synchronized" motors though...

 

[wdchyd]

edit:
I have never seen an application where one cylinders exhaust/return flow, become power flow for a down stream cylinder, but I cant say it couldn't be one. That would connect the cylinders in series....would be interesting to see that schematic....
It have been seen on "synchronized" motors though...

Actually they've been doing this in mobile hydraulics for years......the outside of the valves look the same, hard to tell tandem from series apart....

Here's a look at Gresen SP valves.....


....scan down to the SSK......these have been around for a long time........(notice they are "pressure additive"....sound familiar- ei: some of our PB discussions).......these special cores internally are available from many manufacturers.....

It allows for the exhaust from one spool to power the next spool that is used inline.......

 

[wdchyd]

Having trouble with the link.....

 

[AKKAMAAN]

Actually they've been doing this in mobile hydraulics for years......the outside of the valves look the same, hard to tell tandem from series apart....

Here's a look at Gresen SP valves.....


....scan down to the SSK......these have been around for a long time........(notice they are "pressure additive"....sound familiar- ei: some of our PB discussions).......these special cores internally are available from many manufacturers.....

It allows for the exhaust from one spool to power the next spool that is used inline.......

Thanks Bill!

Yes, that would be considered a type of "regeneration", similar to having two single spool valves plumbed in series with out power beyond.

This SSK valve, can not be applicable on two functions that both require high pressure to operate, since load pressures will be additive to a pressure higher than PRV setting.

Also if one cylinders stalls, the other one stalls too.

I assume each function can be operated individually.

SSK is only available/possible in a two spool configuration.
How will the rest of the back hoe functions be operated?
Another CV off a second pump, or another CV power beyond?
Power beyond will limit the possibility of simultaneous operation of other functions....

This SSK valve must be designed for a special, but common, "low budget" application??!!

It is also not designed the same as a regular "tandem valve". Should we still call it a tandem valve?

I'd like to see a schematic on an entire back hoe system with that setup....