BX25 FEL CYLINDER ENHANCEMENT

[Artisan]

I know little about hydraulics. The BX25 is a lil pit bull but the FEL
lift acts more like a poodle. I know I can bump up the pressure but would
it not be wiser to simply make larger cylinders that fit in that holes made
to OE dimensions?

The OD of the BX25 FEL Lift cylinders, (the bore?) is 1.85" and the
rod or the shaft OD is .985". If I use 1850 Lbs (max stock psi) for pressure that
gives me 4973 Lbs Push and 3563 Pull. If I keep the same shaft size
and go to a 2.5" Bore (I think the bore is the cyl OD) that changes
dramatically to 9081 Push and 7671 Pull.

"IF" a guy were responsible, and low and slow is always mandatory and
if a guy does not get silly using the very left or right side and full power
possibily tweaking the FEL does this sound viable?

 

[wrooster]

If I keep the same shaft size
and go to a 2.5" Bore (I think the bore is the cyl OD) that changes
dramatically to 9081 Push and 7671 Pull.

"IF" a guy were responsible, and low and slow is always mandatory and
if a guy does not get silly using the very left or right side and full power
possibily tweaking the FEL does this sound viable?

It will work BUT:
1) Operation will be slower. You have increased the volumetric capacity of the cylinder but have not increased the flow rate of the pump. Accordingly, extension and retraction will take longer.
2) The stress on the FEL's structural elements will increase. Whether this results in deformation or outright failure depends what type of static load you carry, and what type of dynamic load is presented while in motion over uneven terrain.
3) Overturning moment will increase with higher FEL loads -- both pitch and roll. You will need additional ballast at the TPH, and far more caution when maneuvering with a heavy load in the bucket.
4) Front axle lifespan will be reduced accordingly.
5) Tire sidewall stress will be increased accordingly.

Notwithstanding the above, there are a multitude of valid reasons that the smart folks at Kubota selected the cylinder diameter and therefore the attendant lift force. Engineering is about compromise and balance -- when you get these wrong things break, operation/repairs get costly, and/or personal injury results.

Wrooster

 

[Artisan]

10-4 and Thank YOU!

 

[oldnslo]

Another possibility is to change the lift angle of the main cylinders. Lowering the rear of the lift cylinders will provide increased lift capacity but decrease lift height. I believe there is a current thread about a M7040 that comes from the factory with this option.

You have to do some geometry to calculate the load capacity change by moving the pivot point 2" or what ever distance you would choose.

Picture of the two Bransons shows this. Tractors are the same frame size but look at the distance between the rear mast pivot and the rear cylinder mount.

 

[Artisan]

Noted: Thank You oldnslo!

 

[radioman]

yes - bigger bore will give you more "power" within same hydraulic pressure in exchange for slower speeds. They do this all the time with wood splitters. Either you want fast cycle time or the need to push through big, twisty, knotty, tough wood (just forget the 2 stage pump for a moment here just for argument stakes)

 

[swick1]

I would proceed with extreme caution, but I would still proceed...

I think raising system pressure to 2250psi would be pretty safe and it would improve backhoe performance.

That's 25% more pressure

 

[J_J]

I know little about hydraulics. The BX25 is a lil pit bull but the FEL
lift acts more like a poodle. I know I can bump up the pressure but would
it not be wiser to simply make larger cylinders that fit in that holes made
to OE dimensions?

The OD of the BX25 FEL Lift cylinders, (the bore?) is 1.85" and the
rod or the shaft OD is .985". If I use 1850 Lbs (max stock psi) for pressure that
gives me 4973 Lbs Push and 3563 Pull. If I keep the same shaft size
and go to a 2.5" Bore (I think the bore is the cyl OD) that changes
dramatically to 9081 Push and 7671 Pull.

"IF" a guy were responsible, and low and slow is always mandatory and
if a guy does not get silly using the very left or right side and full power
possibily tweaking the FEL does this sound viable?

I am thinking here that you figured the extended and retract force with the cyl pushing at 90 degrees. That is usually not the case with tractors. Also, you add the force from two cyl. The force you compute will be at the cyl pin connection. The mechanical advantage or disadvantage is then added.

Most tractor cyl are pushing at an angle and this has to be taken into account.

You can increase the pressure, or go to larger cyl, taking into account strength of the metal and weight transfer IE, more weight on the back.

The manufacturer has probably inserted a safety or reliability factor in the loads for the tractor. You don't raise max loads every time, so you will have more force for that extra load that you did not have before.

Lots of machines are tweaked out, and some do well and others not.

 

[case245]

i have a 7040 its called the power and hieght position lower hole 500 ib more lift cap upper hole 500ib less lift cap 15 more inches of hieght as far as lifting with bx 600 ib max been there done that the bx s are to light there are lawn mowers after all

 

[Zebrafive]

I think on the size cylinder you have the wall will be in the 3/16" range, so subract 3/8" from the O.D. for the bore. So your bore will be approximately 1.475. If you go to a 1.75 bore that's almost a 20% increase. I think 2.5 inch is way to big for that size tractor. As others have said, cycle times will be reduced in exchange for greater lifting force.

The older JD 640 loader had two mount holes for the lift cylinders. They were more inline (on the same horizonal line) than one higher and lower, there were cautions that the greater lift capacity could damage certain tractor models and not to change to the other mount hole. New models of this loader eliminated the extra mount hole.I am not sure if they had problems with tractors being damaged, they were no longer being marketed for certain models, or just a cost cutting measure.