What determines hydraulics capability?

[jim_wilson]

Thanks for all the info everybody. This has helped me get a better understanding. To answer your question qqq - I really like my BX23. As a first time tractor owner I don't really have anything to compare it against capability wise except for a Terramite that I rented a few years ago. From what I remember the Terramite had higher overall capacities ( it is a bigger tractor) but the BX23 just seems like a higher overall quality piece of equipment to me. I bought the BX23 because I wanted something relatively small ( I only have a 1/2 acre lot) but I needed a loader and I needed a backhoe and the BX23 and the Massey GC2310TLB were the only subCUT tractors that fit the bill. I bought mine just before Woods came out with it's hoe for the subCUT's so the New Holland and the John Deere got ruled out. I looked at both the Massey and the BX23 a lot before finally deciding on the Kubota. Honestly to me it was almost a tossup between the two tractors - they both have their strong points. The two biggest things I noticed on the Kubota that I liked vs. the Massey was the replaceable teeth on the backhoe bucket on the BX23 and the better turn around on the seat on the Kubota. The Massey seat was a big pain in the butt to figure out how to spin around and their hoe bucket had welded on teeth. I wanted replaceable teeth in case I ever broke one. I live in northeast MA and ended up buying the tractor at Chappell tractor in Milford NH. The final price was $16,400 delivered including higher capacity alternator, 50 hour service kit, bar tires filled with rimguard, and 12" bucket. I checked about 4 or 5 dealers and Chappell was second best on the price. The only price that was better was a dealer out in NY or PA that would have shipped the tractor up to me with same options for about $500 less. I work with a couple of people who have bought at Chappell and had good things to say about them and I figured that $500 is not a huge amount more to spend over the best price considering I was buying from the dealer I liked the best and was closest to me to boot. If you want the pricing info I got I can PM that to you if it helps your decision making and you are in the New England area.
I have put about 25 hours on the BX23 since getting it a couple of weeks ago and have to say overall it is pretty strong little tractor. The two things I have noticed ( and this was the reason for asking about hydraulic capabilities) that bug me about the BX23 is 1) when using the backhoe I find that often I can't move multiple cylinders at the same time - I have gotten pretty good with the hoe and when using it if I try to say move the bucket at the same time I am moving the dipperstick cylinder only one of the cylinders will appear to move at once. For the most part the hoe has pretty good power - the only thing that seems to give it a problem is when I do stuff like try to rip out say 1.5" and bigger roots near the stump - this I have to work at but that is too be expected, and 2) the other thing I could wish for better performance on is the lift capability of the FEL. I have tried to move some pretty big rocks with the FEL and have been doing a lot of digging with it and more power would be good. There have been a number of threads here on tractorpoint about BX's moving really big rocks - and if you look at the pictures that have been posted those rocks are the same approximate size as the ones I have tried to lift and couldn't. I have discovered that you can MOVE darn large rocks if you can get them into the FEL bucket but you cannot straight lift them off the ground. Some of this may be because I am still not putting the engine at max revs since I am still within the 50 hour breakin period. So these two problems - plus the fact that I have pretty much been a hot rodder since I got into motor vehicles got my mind working and wondering whether the capabilities of the BX23 could be improved some by a little tweaking. Your answers seem to suggest that my issue with the backhoe might be solved by a higher GPM pump and the FEL lift problem might be solved by some slightly bigger cylinders on the FEL arms. None of this of course is something that I would do to the tractor while it was under warranty but it is a nice mental exercise to think about for down the road.

 

[rswyan]

Jim,

I have a B2910 with a BL4690B backhoe (which uses an Eaton PTO pump supplied by Kubota) - if I'm running at 1500 -2000 rpm I can easily stall one (or more) cylinders if I actuate another cylinder on a separate valve (haven't tried it at a higher RPM) For instance, if I'm crowding the dipperstick in and curling the bucket - AND I start to raise the boom - the dipper and the bucket stall - or vice-versa. To some degree this is dependant on the how far the boom (or any control) lever is pushed in.

And on that matter, in my opinion, part of what makes the backhoe controls so touchy is the amount of return spring pressure one is pushing against - it would be nice if someone could design a valve that had a larger "sweet spot" that provided a more gradual difference in the amount of flow that was being passed - it doesn't seem like it is a linear progression - more like a Gaussian curve. Lighter valve return springs might do that - but perhaps it's a safety issue.

An additional complication on my set up is that the PTO pump is designed for a max input rpm of 2750 (which ain't never gonna happen hooked to the PTO of my tractor) and rated at around 23 GPM. Since I can only run the pump at max of 540 RPM on my rear PTO, the actual pump output would only be around 4.5 GPM at max PTO speed - this is actually less than the hydraulic output of the tractor, if it had a rear hydraulic hookup on it. /forums/images/graemlins/confused.gif

Why Kubota chose to go this way (rather than making the PTO pump an option - along with rear hydraulics an option instead of the PTO pump) and why they chose a pump with input rating of 2750 RPM, is beyond me. Just seems stupid and an unecessary cost.

 

[OkieG]

<font color="blue"> AND I start to raise the boom - the dipper and the bucket stall - or vice-versa. </font>
My JD BH does the same thing, but I don't think it's a "stall", per se. I believe some functions are designed to blend, others are prioritized. No matter how much more flow you have, I don't think this would be any different. Don't know for sure, just my opinion.

<font color="blue"> the PTO pump is designed for a max input rpm of 2750 </font>
That is interesting, and doesn't seem to make much sense. I believe some of the bigger tractors have a PTO speed of 1000 or so...some even have both 540 and 1000. The midPTO on my tractor runs at 3100rpm, but that would be an odd place to install a PTO pump.

OkieG

 

[jim_wilson]

It is good to hear I guess that other people experience the same limitations with their backhoes as I have seen - IE not being able to move multiple cylinders at the same time. Since I don't have experience with lots of other machines I was not sure if this was a limitation of the BX23 or whether it was common with all backhoes.

 

[Henro]

Jim,

I have no BX backhoe experience, but on my B2910 with BL4690A backhoe I can move multiple cylinders. But it seems like some over ride others, so feathering the control valves is necessary. This becomes easier with experience.

Also, some control valves have flow restrictors on the output ports, so those functions are designed to work slower for safety. I don't off hand remember which, but I think boom swing is one.

I could be wrong, but I think you should be able to take you backhoe on the BX and move the bucket in a horizontal or vertical figure 8 if you are good. Not a boxey one, but a smooth curved figure 8.

Someone correct me if I am wrong. I am pretty sure I can do that with my backhoe...but never tried it so I don't know for sure... /forums/images/graemlins/blush.gif

 

[JerryG]

If you have two cylinders activated, the one with the least resistance will be the one that moves first.

 

[Henro]

JerryG,

That is most certainly true.

But when you feather the valves you get pressure drop across the valves...so you can essentially shift flow to a cylinder that has more "power needs" in my experience, and still cause both to move together, even though if both control valves were full open, only the cylinder feeling the least resistance would actually move...

The hydraulic systems sees the load on the cylinders and added to that is the pressure drop across the control valves...so fully opening the valve to the cylinder that has the most resistance to movement, while just slightly opening the control valve to the cylinder that has the least resistance to movement, can result in a balance situation under which both cylinders will move, rather than one hogging all the fluid.

That is my experience anyway... /forums/images/graemlins/smile.gif

 

[JerryG]

Bill,
That is right. If you feather a valve, you do not have full flow to both. Thus, being able to control the work rate of each cylinder.

 

[MMM]

"This is only true if you want to go as the same speed as a smaller cylinder with a lighter load. If you have the pressure you can lift the same load with almost any hp motor and pump as long as you have time for the volumn (flow) to fill the cylinder."

Yep, I'm aware of that. But not many of us wish our loader's cycle time was slower. Didn't quite have time to explain to Jim that I upgraded from farm loader to industrial one and tried it with tractor's 14gpm (yawn). I ended up installing the 23gpm crank driven front pump that came with loader- and IT costs hp. I can almost stall engine lifting 3/4yd bucketfull if rpms aren't up when using foot throttle. I don't know how much hp the internal pump consumes unloaded (except for 3gpm steering), but I can tell the difference in load and fuel use after upgrade. I imagine a pto pump for bigger cyls would be same result, if it actually put out more flow. (ie rswyan pto pump dilemna).